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How to Find BIockages without
Angiography?
"REALISTIC GEOMETRIC
CARTOGRAPHIC IMAGING”
Coronary artery blockages, till
now, could not be measured by
any tests except angiography,
which is not only expensive but
also exposes the patient to a
number of risks and
complications. Moreover,
angiography needs an admission
and now being use by most of the
hospitals to compel patients to
undertake next procedures like
Bypass surgery or Angioplasty.
Good news for heart patients is
that in the near future they
will be able to find and measure
the blockages without
angiography, through a Hungarian
developed investigation called
Realistic Geometric Cartographic
Imaging (RGCI).
RGCI can be done at the bedside
of the patients, It takes
roughly 20 minutes from start to
finish. The procedure is done
using few disposable electrodes.
Complex parameters are obtained
using high precision data
accusation system. Pressure,
volume, time of blood flow are
collectively obtained by
simultaneously recorded
electrocardiography (ECG),
phonocardiography (sound of the
heart), non-Invasive continuous
blood pressure and trans
thoracic bio-impedance. The
acquired parameters are then
mapped against a mathematical
model and cartogram is obtained,
which is a collective
behavioural pattern of the heart
and its circulation status.
Doctor gets a complete
heomodynamic picture of the
heart, as well as the location
and severity of coronary artery
disease and relative oxygen
demand of the heart. This can
help the doctor in taking
appropriate decision regarding
management of the patient.
RGC Imaging can detect coronary
tube blockages as low as 20%, it
is having a sensitivity and
specificity of more than 92%
which according to the experts
is good enough for non-invasive
test. This procedure can be used
to substitute costly, dangerous
and not so accurate procedures
for accessing the coronary heart
disease (i.e. Angiography). It
is also used in the management
of critically ill patients since
its a bedside procedure.
Scientific papers were presented
at the 8th European Congress of
Intensive Care Medicines,
Athens, Greece 1995; 12th
International Congress "The New
Frontiers of Arrythmia" Italy
1993; 3rd International
Conference on Impedance
Cardiography, Domdovan, Hungry
1997; 4th Asia Pacific symposium
on Electro-physiology, New Delhi
1997. Recently papers was
presented by Manipal Heart
FoundaUon, Bangalore during the
50th Scientific Session of
Cardiological Society of India,
December 1998.
The authenticity of RGCI has
been established in the last 10
years. The technique is being
studied extensively in many part
of Europe and India. The added
advantage of RGCI is that people
with minimum blockages can also
detect their blockages by this
procedure, allowing them to
prevent heart disease in future.
==============================================================
Angiograms and Ultrasound Are
Not Accurate to Measure Profound
Improvement Following Chelation
by Elmer M. Cranton, M.D.
It is hard to
believe but scientifically
proven less than 7 percent
increase in the interior
diameter of a diseased blood
vessel will double the flow of
blood.
Angiograms and ultrasound
imaging are only accurate to
within approximately 20 percent
and cannot measure such small
changes.
Blood is only about half
liquid. The other half is
composed of red and white blood
cells. These cells rub along
blood vessel walls and move much
more slowly than more fluid
blood in the center of an
artery. This makes blood highly
viscous and sticky close to the
arterial wall. Because the
distance relative to blood cells
between the outer wall and the
center of a vessel is much less
in small blood vessels, a small
increase in the internal opening
will result in a very large
increase in the flow of blood.
Blood flow past plaques is
turbulent, causing even more
resistance to flow. In diseased
arteries with plaque, an even
smaller increase (less than 6
percent) can double the flow of
blood and totally relieve
symptoms.
The liquid and cell-free
portion of blood is more viscous
than water because of its high
protein content. Cell-free
plasma is about 1-˝ times as
viscous as water. When blood
cells are added, the viscosity
increases to more than 3 times
that of water.
The cross sectional area in the
opening in a blood vessel
decreases exponentially with a
decrease in diameter. An artery
of half the diameter has only
one fourth the cross sectional
area.
Combining all of these factors
together,
as proven
by Poiseuille’ Law,
doubling the diameter of the
internal channel results in a
16-fold increase in the flow of
blood (assuming no change in
blood pressure or length). Put
another way, a smooth healthy
blood vessel will carry twice as
much blood if the interior
increases less than 7% in
diameter. A blood vessel with
plaque and has turbulent flow
and a mere 5 percent or less
increase in diameter of the
internal opening will double the
flow of blood.
Angiograms and ultrasound
imaging are only accurate to
within approximately 20 percent.
Even if repeated an hour later
on the same patient using the
same technique, the reading can
vary by as much as 20 percent.
That explains why patients
whose symptoms have improved
dramatically following chelation
therapy often do not show a
significant change in reading on
followup angiogram. For the same
reason, calcium scores on
followup ultra-fast,
electron-beam, CT scan (EBCT)
are also not a reliable way to
measure benefit following
chelation therapy.
It is a waste of time, a waste
of money, and can involve
unnecessary risk to do follow-up
angiograms merely to document
improvement from EDTA chelation
therapy. The proof of the
pudding is in the eating. If
symptoms improve it is logical
to assume that blood flow has
increased. If that benefit can
be retained by periodic
maintenance chelation treatments
with
the most
effective nutritional
supplements,
much can be achieved without
surgery, stents or other
potentially dangerous
procedures.
References
http://www.answers.com/topic/poiseuille-s-law
http://hyperphysics.phy-astr.gsu.edu/hbase/ppois.html
http://www.cvphysiology.com/Hemodynamics/H003.htm
================================================================
Bangalore team's invention gets
FDA approval
Our
Bureau
Bangalore, July 21, A MEDICAL
diagnostic device invented by a
Bangalore research team has
become the first such hi-tech
Indian tool to win the US FDA
approval for its clinical use in
the US and certification from
the EU.The device, called
Haemotron, is non-invasive and
uses 3D mapping technology or 3D
cardiovascular cartography
(3D-CCG) to measure the heart's
functions and blood flow. The
painless 3D-CCG technique takes
barely 20 minutes and gives a
comprehensive picture of the
heart and any of its
abnormalities in early stages,
according to its inventors.
The
Haemotron, developed over six
years and in use for two years,
has been invented by Dr Rajah
Vijaykumar, Chief Scientific
Officer, and his biomedical
engineering team at the Centre
for Advanced Research &
Development (CARD) in Bangalore.
Costing around Rs 35 lakh, it is
manufactured by Scalene
Cybernetics in India and Austin
Systems, Inc, US, and ASKIT kft
in Europe.
According to a
panel of doctors at a press
conference, the 3D CCG way costs
Rs 3,500 each and can detect
cardiovascular blocks very early
at even 10 per cent of the
blocks, compared to angiograms
that are effective in cases with
more than 40 per cent of blocks
and are three to four times
costlier. Prevention of heart
attacks could begin five years
earlier than with other tests.
Source: The Hindu Business Line
(http://www.blonnet.com/2003/07/22/stories/2003072201051700.htm)
========================================================================
Cardiovascular
Cartography: The Message Is The
Medium
Cardiovascular Cartography [CCG],
a new non-invasive tool with a
systemic approach for
interpreting haemodynamics, is
based on modelling and
simulation techniques. Its
clinical application is keyed to
diagnoses, estimation of
prognosis, and modification of
therapeutic modalities —
especially in coronary artery
disease [CAD].
Dr G N Shirbur, Dr S S Sibia, Dr
N T Murlimohan & Dr Rajasimha
Measure what is measurable, and
make measurable what is not so.
-- Galileo
The prevalence of CAD in India
is of the highest magnitude. It
has been confirmed by several
studies.1 It is also
a construct that requires mass
screening not only to detect
anomalies, but also follow-up
and strategy for cost-effective
treatment.
The technique, which is simple,
easy-to-perform, and painless,
can be repeated as many times as
may be required. Its sensitivity
and specificity have no less
been assessed and validated in a
blind study with angiographic
findings in confirmed CAD
patients.2 Our
experience with about 1,900
patients screened
contemplatively, so far, with
angiograms, echocardiography,
stress ECG and clinical
assessment, has shown detection
of CAD, with a mean accuracy of
well over 90%.
There has been a great deal of
misunderstanding or balderdash
in the popular media about this
technique. This explains why we
need to set the record straight.
We are the actual users.
Inaddition, our [benefited]
patients and we stand by its
capabilities. More so, because
the technique which was studied
by a group of researchers with
utmost scientific diligence and
fidelity, not to speak of
painstaking precision, has been
acquiesced to with the stamp of
authority, what with results
presented in scientific forums
in Europe and India.
We wish to briefly elaborate the
functional theory behind
cardiovascular cartography. In
simple terms, the technique
makes scientific sense and uses
a very advanced method of
modelling and simulation with a
24 parameter kinetic model.
Historically, kinetic models
were built to assess
continuously changing non-linear
dynamics of large scale data in
the field of electronic warfare,
weather prediction, and nuclear
physics. Its application in the
cardiovascular domain was, in
the first place, discovered by
Kumar and co-workers.
Basic Theory — Get it Right
The cardiovascular system
functions as a closed loop
dynamic fluid mechanics system
based on pressure, volume, time
and flow principles which occur
independently and
simultaneously. In other words,
it is non-linear. The efficacy,
or any deviation, in its
functions for assessment
purposes requires measurement of
various haemodynamic parameters
responsible for a dynamic event
of the heart. This is called the
cardiac cycle — a
product of non-linear
physiological activity occurring
in unit time.
The measurement of pressure, and
volume, can be executed by
methods like Doppler or radio
nuclear studies, but flow
measurement is possible only by
way of Transthoracic
Bio-Impedance [TBI]. The
clinical use of TBI has been in
vogue for more than 30 years. It
was first formulated by Kubicek3
and only recently by Gomory.4
The usage of pulsatile changes
that occur due to flow of blood
is a function of TBI. TBI
produces signals [curves] that
are precisely time-related to
other physiological curves like
ECG, PCG etc., The signals
produced are due to the
electromechanical activity of
the blood flow. The CCG
integrates the measured and
derived parameters from these
curves, and the first derivative5,
[dz/dt, which is similar to dp/dt
curve] of the modulated curves.
The numerical values of the
individual beat, or cycle, of
systolic time interval and
diastolic filling phase are
derived from this specific.
In like manner, the vertical
lines plotted are used to
compute the pre-ejection [PEP],
ventricular ejection time [VET],
and QS2 intervals
[electromechanical systole/See
Fig. 1]. With the amplitude
modulations of TBI synchronous
with pumping of blood in the
heart and proportional to the
amount of blood pumped out, the
modulations are practically
equivalent to stroke volume
— an absolute value
proportionate to the duration of
systole, flow velocity and the
resistance of blood, that
depends on haematocrit6,7
Thus, the value of stroke volume
can be calculated from the
measurable, modulated curve as
well as its proportions related
to the amount of fluid in the
thorax and the volume of the
connective tissues of the
thoracic cavity with Kubicek
formula2, and
corrected to body habitus. From
the measurable data of these
four recorded signals, the heart
rate and the amount of blood
pushed out by the heart per beat
can be calculated, along with
the cardiac output.6,7,8
Furthermore, with the knowledge
of the various systolic time
intervals and the pressure
values measured, the remaining/
derived haemodynamic parameters
can be obtained for every beat.
Principles
of Cardiovascular Cartography
The 3-D mathematical modelling
and simulation using high-speed
computation enables non-linear
haemodynamic parameters of a
patient to be mapped against the
mathematical model of the
cardiovascular system. Using
neural network computing, a
predictive model of the patient
is created. The measured
haemodynamic behaviour is
superimposed on the predictive
model. The resultant dynamic
deviation is represented in a
form called cardiovascular
cartogram. The resultant
deviation difference is
distributed as pressure zone,
volume zone, time zone and flow
zone, in a clockwise direction
on the cartogram [Fig. 2]. The
K-Scale on the cartogram is an
independent scale. It has
positivity and negativity
elements and indicates the
deviation difference, aside from
reflecting a physiological,
pathological or compensatory
phenomenon to assessing the
efficacy and function/s of the
cardiovascular system.
The pattern of change that
occurs in the flow zone of the
cartogram [contractility,
acceleration, after-load,
ventricular depolarisation to
peak ejection delays] is
obviously related to the
anterioseptal regions of the
myocardium. The pattern of
change in the volume zone [rate
pressure product, stroke volume,
cardiac output, and pre-load]
is, thus, related to
inferioseptal regions of the
myocardium and the time zone;
intracycle timings, and LV
ejection rate are related to the
lateral regions of the
myocardium. In an ICU setting,
it is these factors that we try
to correct — especially in
situations where there is
myocardial infarction in the
respective regions...
The Vertical Acceleration
Detector [VAD] is a special
device that picks up subsonic
waves that are transmitted from
the heart to the chest wall. It
is similar to the seismic waves
that get transmitted from deep
inside the earth to the surface
during a quake. The VAD picks up
subsonic signals throughout the
cardiac cycle. This includes
every component of the first and
second heart sounds, just as
much as specialised spectrum
analysis and digital signal
processing enable us to detect
and extract micro variations in
the subsonic activity during
early-, mid- and late-diastolic
[passive] filling phase.
The second component of the
second heart sound is of prime
importance in cardiovascular
cartography because it signifies
the onset of diastole. The
turbulence in flow is
differentiated and extracted
during a period when there is
maximal coronary flow: a
parameter that is used to detect
primary presence of coronary
obstruction. The power and
frequency signifies the regions
from which these signals
originated. It is correlated
with zonal [pressure, volume,
time and flow] behaviour to
obtain a three-dimensional array
of information that is suitable
for image reconstruction.
The first part of reconstruction
is to identify the ischaemic
zones and reconstruct the
regions on the short axis slices
of the LV muscle mass [Fig. 3].
This enables one to identify the
major vessel supplying the
region. The appropriate site of
the lesions embedded on the
realistic geometry coronary
model also helps us to get the
realistic geometric
reconstruction of the most
probable location of coronary
occlusion.9,10 [Fig.
4]. {Note: These are
microsecond events that have
been studied. There are no
parallel methods available, at
present, for detecting
non-invasively CAD
[positive/negative], with this
aggregate}.
The vast amount of data acquired
during a cardiovascular
cartography study enables us in
computing other vital
information. Some of the
important information that will
have diagnostic, management and
prognostic value are: regional
myocardial blood flow, coronary
flow reserve, global cardiac
efficiency, arterial compliance
[specially in diabetics], ANS
predominance, besides pre-load,
contractility, and after-load.
CCG Test Protocols and
Procedure for CAD Detection
Following strict protocol, in
our opinion, will ensure best
results. Unlike many other test
procedures for CAD detection,
where linear changes in
unilateral function like
electrical conduction pattern in
stress ECG or material uptake in
stress thallium are ratified,
CCG is based on non-linear
dynamics of blood flow. Drugs,
for example, alter cardiac
haemodynamics and maintain a
forced balance.
The Protocol We Use and
Recommend
·
The patient should abstain from
all drugs that alter cardiac
haemodynamics for a period of 12
hours prior to the test. We have
found that there is no
significant change in the test
results between a 12-hour
avoidance or a longer period. [Note:
CCG is based on relative beat to
beat changes, and not on
absolute values. If drugs do not
interfere with the relative
changes, this is sufficient]
·
Alcohol plays an important role,
mainly as a diuretic. The
patient should abstain from
alcohol for a period of 24 hours
prior to the test
·
Patients should abstain from all
types of stimulants like coffee,
tea and other soft drinks for a
period of 12 hours prior to the
test
·
The patient should generally be
fasting [A light breakfast, or a
glass of milk and some biscuits,
two to three hours prior to the
test do not alter test results]
·
It is important that the patient
should empty his/her bladder and
be relaxed during the entire
test procedure. Test results
will be inconclusive in
non-co-operative patients
The patient is wired to the CCG
system with meticulous care.
Generating electrodes should not
be interchanged with measuring
[or, pick-up] electrodes. VAD
should be placed at a site where
the second heart sound is of
maximum amplitude [this will
need some practice]. The bed
used should be at 180 degrees;
any inclination will alter the
pre-load and result in an error.
The test is performed in two
phases: the first phase in
supine position following the
above protocol, and the second
phase during the same sitting by
creating a vasodilator response
and altering the coronary flow
reserve [CFR] that is severely
decompensated at rest in case of
certain types and severity of
coronary occlusion [NYHA Class
III-IV]. In certain cases, where
there is a large by-lane flow
[collateral flow], the CFR will
be near-normal [4~5:1], but will
start to get effected after
induction of reactive hyperaemia,
usually by the administration of
a coronary vasodilator, where a
steal phenomena is induced
secondary to pre-stenotic
vasodilatation.
To exactly understand the second
phase of the cardiovascular
cartography study, one has to
have adequate knowledge of
coronary circulation, factors
governing coronary flow,
dominion of auto-regulation,
resistance, large and small
vessel pathophysiology, type of
stenosis [rigid, dynamic etc.,]
and coronary artery steal. It
is, however, beyond the scope of
this article to discuss all
these factors. For the purpose
of understanding, we will only
discuss a few of the important
ones.
Dynamic Coronary Artery
Stenosis

If coronary lesions were hard
and geometrically fixed,
physical activity would be
proportional to the maximal
luminal area reduction or
coronary blood flow. It would
also explain most of the signs
and symptoms of coronary artery
disease. Yet, anatomical studies
indicate that most human
coronary stenosis contain at
least some normal wall segment.11,12
A normal epicardial coronary
artery vasoconstriction will
decrease the luminal area, but
this will have no significant
effect on either flow or
pressure across the vessel.13
On the other hand, for a truly
circumferential stenosis, liable
to change its size and shape,
vasoconstriction will have no
influence on its cross-sectional
area or stenotic haemodynamic
severity. For diffuse smooth
muscle stenosis and eccentric
stenosis, alteration in smooth
muscle tone will have
significant, physiologically
important effects on the
cross-sectional area, possibly
causing rest or exertional
angina.
Large vs Small Vessels
The large and the small coronary
arteries respond differently to
the same vasoactive substances.
Table 1 shows the physiological
and biochemical characteristics
of small and large coronary
arteries.14
For example, in whole_animal and
isolated_heart preparations, the
small vessel vasodilatation with
nitroglycerine was found to last
only 20 to 30 seconds, whereas
the larger coronary arteries
remained dilated for up to 10
minutes.15 The
differences in response to
vasoconstrictors between the
large and the small coronary
arteries have not been
extensively studied.
Stenotic Modulation
Rigid stenosis is where there is
a geometrically fixed stenosis,
the arterial wall is rigid, and
the luminal area cannot change.
Regardless of the degree of
stenosis, decreasing distal
resistance always increases
flow, while increasing distal
resistance always decreases it.
With mild underlying rigid
stenosis, decreasing distal
resistance leads to a large flow
increase, while with a severe
rigid stenosis decreasing distal
resistance results in a greatly
attenuated flow increase. Thus,
a patient with mild rigid
stenosis can perform substantial
physical exercise such as
running etc., whereas a patient
with severe rigid stenosis can
only perform light work such as
climbing stairs.
In case of a dynamic stenosis,
where vasoconstriction,
perfusion pressure and distal
resistance, can each alter
luminal areas, interaction[s]
among vasoconstriction,
perfusion pressure and distal
resistance can occur.
Correspondingly, altering distal
resistance changes the luminal
area; decreasing distal
resistance decreases the luminal
area; and, increasing distal
resistance increases the luminal
area. Also, proximal coronary
artery vasoconstriction can
decrease the vessel size. For
example, in mild underlying
dynamic stenosis, proximal
coronary artery vasoconstriction
would decrease the luminal area,
and the decreasing distal
resistance would further
decrease the luminal area.
Additionally, due to such a
definitive decrease in luminal
area, the coronary blood flow
increase would be less than the
response observed for rigid
stenosis. This patient will only
achieve light to moderate work
levels, such as jogging. For
severe dynamic stenosis,
proximal coronary artery
vasoconstriction would decrease
the luminal area, whereas
decreasing distal resistance
would further decrease the
luminal area. This may cause a
paradoxically small flow
decrease as compared to rigid
stenosis response. Thus, in a
patient with severe dynamic
stenosis maximal physical
activity will be severely
decreased and an imbalance in
myocardial oxygen demand and
coronary blood flow will occur
at rest. These patients will
also experience rest angina
without any physical exertion.
Table
1.
Physiological and biochemical
characteristics of large and
small coronary arteries.
Characteristics
|
Large |
Small |
|
Autoregulation
Reactive hyperaemia
Ischaemia
Passive distension
Total resistance [%]
Adenosine
Hypoxia
KCN
Mitochondria
Succinic dehydrogenase
|
No
Slight constriction
Constriction
Yes
5-20
Constriction
No Dilation
No Dilation
10/unit
1 |
Yes
Dilation
Dilation
Yes
95-80
Dilation
Dilation
Dilation
23/unit
2.6 |
Induction
of reactive hyperaemia by
administering vasodilators like
nitrates is essential in
performing the cardiovascular
cartographic study because it is
important to achieve arterial
modulation of stenosis as some
types of coronary artery disease
may go undetected. Modulating
and creating a coronary artery
steal can unmask some of the
disease regions not severely
altered under basal conditions.
There are two potential types of
coronary artery steals that can
occur. Both require stenosis in
the large coronary arteries.
Type I steal involves only
one coronary artery and is
caused by a redistribution of
flow between the endocardium and
epicardium. As maybe known,
subendocardium is subjected to
greater stress and, thus, needs
a higher blood flow. In the
presence of a proximal stenosis,
the epicardial vessels maybe
maximally vasodilated even under
resting flow conditions. Distal
coronary arteriolar vasodilators
result in a greater pressure
decrease across the stenosis,
resulting in a decrease in
distal coronary pressure. This
pressure decrease can cause a
decrease in flow to the
subendocardium. It also
partially explains why
ST-segment elevation is observed
on stress ECG test.
The Type II steal
involves a decrease in
collateral blood flow, aside
from an alteration of the
coronary flow reserve [CFR].
With the gradual obstruction of
a coronary vessel, collateral
vessels develop from the other
[donor] coronary vessels.
Collaterals are thin-walled
anastomotic connections that
exist between coronary arteries
without an intervening capillary
bed. They are anatomically
present from early life in the
form of native collaterals, but
mature only if a need for
additional coronary flow exists
in certain region/s of the
heart.
These collateral vessels supply
blood flow to the myocardium
normally perfused by the
diseased [recipient] vessel. The
collateral blood flow maybe
adequate to maintain the resting
energy requirements of the
myocardium. However, the
collateral circulation is
insufficient to meet the needs
of the myocardium during periods
of physiological stress. In such
a vista, distal coronary
arteriolar vasodilatation has
been reported to shunt blood
flow away from the diseased
vessel [coronary artery steal].
Consequently, these vessels do
not prevent the development of
ischaemic changes in stress ECG
or abnormalities of ventricular
contraction and performance.
Coronary artery steal only
occurs in the presence of
proximal resistance in the donor
circulation. Steal does not
occur without stenosis in the
proximal recipient artery. For a
proximal rigid stenosis in the
recipient circulation, coronary
steal is due solely to the
decrease in collateral blood
flow. Likewise, the magnitude of
flow reduction in a rigid
stenosis is directly related to
the decrease in collateral blood
flow. In contrast, for a dynamic
stenosis in the recipient
circulation, coronary steal is
due primarily to a decrease in
flow through the diseased
vessel. Thus, in dynamic
stenosis the largest decrease in
flow occurs through the native
coronary vessel — a self-steal
phenomenon.
During the second phase of
cardiovascular cartographic
studies, the patient is
administered 10 mg sub-lingual
nitroglycerine. It is advisable
to wait till the patient's
systolic blood pressure drops by
about 10 to 15 mm Hg. The test
is now repeated and another
1,024 beats are acquired and
processed. Table 2 gives the
outcome of a typical
cardiovascular cartographic
study during pre- and
post-nitrate studies and their
interpretation.
What You can Get out of CCG
?
Table 2.
Cardiovascular Cartographic
Study: Outcome and
Interpretation
|
Sudy Mode |
Results |
|
Basal study
|
+
|
-
|
+
|
- |
|
Nitrate enhanced study
|
- |
+ |
+ |
- |
|
Interpretation
|
Type I coronary
steal syndrom
|
Type II coronary
steal syndrom
|
No steal syndrom
|
Normal
No evidence of flow
limiting lesions |
|
|
Mild endothelial
dysfunction |
Endothelial
dysfunction |
Severe endothelial
dysfunction |
|
|
|
Small vessels
compliant
|
Small vessels
non-compliant
|
Small vessels
non-compliant |
|
|
|
Ř CAD positive with dynamic
stenosis
|
Ř CAD positive
with rigid stenosis
|
Ř CAD positive with critical
stenosis
|
Ř Normal Study |
The CCG indicates CAD lesions,
LV functions, LV contractility,
LV stroke work, cardiac reserve
systemic vascular resistance,
arterial compliance, global
myocardial blood flow, regional
myocardial blood flow, pulmonary
capillary wedge presence and
pulmonary pathology. The other
clinical applications of CCG are
post-MI rehabilitation,
pacemaker programming, ICU
monitoring and CCF follow-up,16
ventricular arrhythmias, and
EPS. There are no `gold
standards' to assess the global,
or regional, blood flow but our
assessment with expectations
with coronary angiography,
echocardiographic abnormalities
and stress thallium, seems to be
correlating well.
It will, therefore, be a good
guide for clinicians for
diagnoses, prognostication and
modification of therapy
depending on haemodynamic
behaviours that are obtained
non-invasively. CCG can also be
of help in non-cardiac problems
such as pre-operative evaluation
of non-cardiac surgery, during
haemodialysis, spinal
anaesthesia during TURP
[Transurethral Resection of
Prostrate], and critical care
monitoring of septicaemia: to
name a few.
Conclusion
Cardiovascular cartography is a
technique that is keyed to
studying physiological
[functional] effects that are
secondary to an anatomical
[structural] cause.
Its technology is complex, and
difficult to understand, but
with a little effort and
open-minded approach, it should
fall into place. Contrary to
popular belief, CCG does not
replace coronary angiography,
but it gives a clear perspective
of the underlying problems,
haemodynamic behaviour and
circulatory status, thus
complementing coronary
angiography by enabling the
interventional cardiologist to
be prepared to expect the
unexpected.
Considering its simplicity,
non-invasiveness, unambiguous
interpretation and, of course,
the cost, we should look at CCG
as the future modality of mass
screening of any population for
cardiovascular disorders —
especially coronary artery
disease.
Acknowledgments
The authors wish to acknowledge
the contributions of early
researchers of TBI viz., Dr W
Kubicek and Dr Gomory; Dr R V
Kumar and his team for
discovering the technique of
mathematical modelling and
simulation of the cardiovascular
Reference
|
1.
Enas A Enas et al.
Prevalence of Coronary
Artery Disease in Asian
Indians, Am J Cardiol
1992;70:945-949.
2.
Ravi Kishore et al.
Cardiovascular Cartography Ś
A New Tool to Detect and
Assess Coronary Artery
Disease, Ind Heart J 1999,
Vol.50.pp 719.
3.
Kubicek W, Patterson R P et
al.
Impedance Cardiography as a
Non- Invasive Method of
Monitoring Cardiac Functions
and other Parameters of the
Cardiovascular System.
Annals New York Academy of
Sciences, 1970, 724-732.
4.
Gomory A, Horvaty S. et al.
Possibility of Impedance
Cardiography in Clinical
Practice. Hungerica 1990,
19,
21-34.
5.
Lababidi et al. The First
Derivative Thoracic
Impedance Cardiogram.
Circulation, 1970, 41:651.
6.
Fuller H D, The Validity of
Cardiac Output Measurements
by
Thoracic Impedance: A
Meta-analysis. Clin Invst
Med, 1992, 15-103-112.
7.
Pikette B, Beul J C.
Validity of Cardiac Output
by Compute Averaged
Impedance Cardiography and
Comparison with
Thermodilution
Determination. Am J Cardiol,
1992, 69-1354-1358.
8.
Paul Pianosi et al.
Comparison of Impedance
Cardiography with Indirect
Factor [CO2] Method of
Measuring Cardiac Output in
Healthy Children During
Exercise. Am J Cardiology,
1996, 77:745-749.
9.
Chandra S. et al. Realistic
Geometry Cartographic
Imaging in Evaluating
Patients with Coronary
Artery
Disease during Pre- and
Post-intervention
Phase. Euro Heart J. 1999,
20:309.
10.
Coleman T G, Mathematical
Analysis of Cardiovascular
Function. IEEE Transaction
on Biomedical Engineering
Vol.32, No.4.1985.
11.
Freudenberg H, Lichtlen P R.
The Normal Wall Segment in
Coronary Stenosis. A
Postmortem study. Z Kardiol
1981; 70:863-9.
12.
Vladover Z, Edwards J E.
Pathology Coronary
Atherosclerosis.
Prog. Cardiovasc. Dis, 1971;
114:256-74.
13.
Brown B G. Coronary
Vasospasm: Observation
Linking the Clinical
Spectrum of Ischaemic Heart
Disease to the Dynamic
Pathology of
Coronary Atherosclerosis.
Arch Inter Med, 1981;
41:716-22.
14.
Winburg M M. Proximal and
Distal Coronary Arteries.
In: Samtamore W P, Bove A A
[Eds]. Coronary Artery
Disease: Aetiology;
Haemodynamic
Consequences; Drug Therapy;
Clinical Implications,
Baltimore Urban and
Schwarzenberg, 1982;63-77.
15.
Cohen M V, Kisk E S.
Differential Response of
Large and Small Coronary
Arteries to Nitroglycerin
and Angiotensin:
Autoregulation and
Tachyphylasis Ś Circ Res
1973; 33:445-533.
16.
Hubbard, W W et al. The Use
of Impedance Cardiography in
Heart Failure. Int J
Cardiology 1986,12:71.
Top |
|
[First Published: BioMed,
August 2000 ] |
Dr G N Shirbur - Simha Heart
Foundation/Mysore
Dr S S Sibia - Sibia Medical
Centre/Ludhiana
Dr N T Murlimohan
Dr. Ambedkar Medical College &
Hospital/Bangalore
===========================================================
RGCI DETECTS BLOCKS YEARS BEFORE
HEART ATTACK
Ludhiana: 19 Feb,
2000: India’s seventh
Cardiovascular Cardiographic
Imaging System (CVC) was
installed today at Sibia Medical
Centre, Ludhiana. This new
non-invasive technique to detect
Coronary Heart Disease in the
form of Realistic Geometric
Cartographic Imaging (RGCI)
brings a new diagnostic
advantage for chest pain
patients for complete
evaluation. It will help doctors
monitor and diagnose heart
problems even in early stage
making timely
protective
treatment possible. RGCI is an
advanced technique based on 3D
mathematical modeling and
simulation, that accurately
informs of the probable location
and severity of flow limiting
lesions in heart’s blood vessels
and its oxygen demand / supply
with the help of measurement of
heart muscle blood flow.
This
equipment works on the
principals of Integration of
time related physiological
curves derived out of
transthoracic Bioimpedance,
Electrocardiography and subsonic
thoracis transverse waves to
detect various cardiac
parameters relating to pressure,
volume, time and flow. A team of
experts from Delhi, Bangalore
and Mysore visited the city and
addressed the leading
cardiologists and physicians on
this occasion where
Dr.L.S.Chawla founder Vice
Chancellor of Baba Farid
University of Health Sciences
was the chief Guest. Dr Rajah
Vijay Kumar, Chairman Centre for
Artificial Intelligence and Non
Linear Studies, Bangalore and
co-inventor of RGCI explained
that doctors prefer to gain
maximum accurate information
about the cardiovascular system
non-invasively. In invasive
techniques catheters have to be
inserted to know the status of
coronary vessels and risks of
injury, rupture, infection and
radiation always exist. If the
doctors get accurate data about
heart functions without
inserting any equipment, it
would minimise the risk and
simplify the process. This new
technique does exactly that and
could be repeated any number of
times without any harm.
The
new noninvasive system uses skin
electrodes and sensors that
acquire and monitor the data in
just 30 minutes. RGCI is
providing continuous accurate
data about any changes in
haemodynamics such as the heart
rate, stroke volume, cardiac
output and other 24 parameters.
Dr.G.N.Shirbur a leading
cardiologist from Simha Heart
Foundation, Mysore added that
RGCI is the only technique that
takes into consideration upto
twenty four parameters and can
be applied on a patient at rest
with total safety and no pain or
difficulty. This highly
sensitive and accurate test
detects flow limiting lesions
even as little as 20 percentage
with over ninety percent
accuracy while other existing
tests like angiography detect
only above 40 percent and TMT
becomes positive
only
above 60 percentage
blocks in heart’s blood vessels.
This sensitivity helps early
detection, prevention and
treatment of Coronary
Artery Disease
which kills almost eight lacs
Indians every year that is about
90 Indians every hour and more
than three million worldwide.
For the undiagnosed victims
delay can be costly or even
fatal. RGCI is the only non
invasive system that can give an
accurate diagnosis even in acute
heart problems in more than
ninety percent patients.
Dr.Shirbur mentioned that this
low cost screening test should
be part of every master health
check up for all persons above
30 years of age and is specially
useful for persons at high risk
having diabetes, high blood
pressure, overweight, smokers,
alcoholics, high cholesterol and
persons with family history of
heart disease, sedentary and
stressful lifestyle, etc. Other
uses of RGCI include follow up
after angioplasty (ballooning,
stents etc) and bypass surgery.
It is also ideal for mass
screening of clients and staff
of institutions, corporates,
insurance companies etc. Special
tests like Nitrate enhanced,
stress cartography etc can also
be done with RGCI.
Dr.O.P.Aggarwal a senior
cardiologist from Bareilly who
is using RGCI for a long time
told that RGCI is the only
investigational tool in the
field of cardiology which does
not have any difference of
opinion. Contrary to that all
investigations including
angiography have differences of
opinion if placed before
different cardiologists. Furthur
he added all preoperative
patients must undergo RGCI which
in this case takes only 60
seconds to evaluate the safety
of anaesthesia and surgery in
the patient.Another doctor from
Bareilly, Dr.Ram Babu Aggarwal
ex-vice president Indian Medical
Association of Uttar Pradesh
said RGCI is also useful in
young children and chest
diseases and he stressed that
RGCI does not require any
admission for doing the test.
Dr.Sibia has a vision that such
equipment would be part of every
physician’s setup for early
diagnosis, follow up and the
selection of modalities of
treatment - medical or surgical
together with appropriate life
style modification.
==========================================================
THE HINDU
Date:27/07/2003 URL:
http://www.thehindu.com/2003/07/27/stories/2003072701460500.htm
Southern States
-
Karnataka-Bangalore
Machine
for 3D mapping of heart
developed
By
Our Special Correspondent
The Haemotron developed by the
Bangalore-based Heart and
Vascular Research Centre
Bangalore July 26. What
cardiologists are increasingly
depending on to diagnose heart
ailments is a "3D map" of that
vital organ.
Making this possible is the
Bangalore-based Heart and
Vascular Research Centre which
has designed a fourth-generation
Haemotron to do the mapping.
Cardiovascular 3D cartography
has become a new technique for
early detection of coronary
artery disease (CAD). A
cardiologist can also evaluate
the functional status of the
heart and the circulatory
system. Both are needed to plan
further treatment.
It
is a non-invasive procedure, and
the patient is "wired" to
Haemotron using 12 sterile
electrodes and a highly
sensitive transducer. The
recordings are made for 1,024
heartbeats while the patient is
lying down and repeated after a
drug that causes mild stress is
given. A high-speed computer
makes all calculation and prints
out the results. The entire
procedure takes six to 10
minutes.
The
cardiologist gets data that was
earlier not possible, through
non-invasive methods. The
records obtainable include
details such as the amount of
blood pumped for every beat of
the heart, pressure, volume and
time relationship, relative
oxygen demand, and the state of
the heart as a pump. These
parameters give the patient's
complete cardiac and circulatory
status.
The
3D maps of the heart have a
positive predictive accuracy of
98.28 per cent and a negative
accuracy of 82.16 per cent in
detecting heart disease.
Angiography measures the
quantity of blockages in the
heart but does not give other
causes for the reduced blood
flow. Blockages in the arteries
contribute to only 70 to 80 per
cent of the reasons for the
reduced blood flow.
Y.
Parameshwara, cardiologist and
winner of the B.C. Roy National
Award, who was present at the
launch-demonstration of
Haemotron, said the machine
helped in non-invasive and
painless mapping of the heart,
and was an important tool to
detect coronary heart disease
early.
==========================================================
CARDIOVASCULAR CARTOGRAPHY
Mass mapping of Cardiac Blood
Flow Non-invasively
Poster Presentation at - 7th
Punjab Science Congress,
Department of Human Genetics,
Guru Nanak Dev University,
Amritsar
Dr.Parneet Baring, PhD,
Dr.S.S.Sibia, MBBS, MD,
Dr.Harpreet Kaur Sibia, MBBS
Sibia, Medical Centre,
B/XIX-573, Civil Lines, Ludhiana
- 141001
Five
hundred suspected patients of
Coronary Artery Disease
underwent Cardiovascular
Cartography test done to assess
the haemodynamic parameters
including myocardial blood flow
prior to nutritional guidelines,
lifestyle modification and where
required other treatments. The
device is a new technique for
early detection of Coronary
Artery Disease and also for the
evaluation of functional status
of the heart and the circulatory
system (haemodynamics). The
information is safely obtained
in about 30 minutes without any
catheterization or radiation.
Some of the information obtained
was never possible,
non-invasively, earlier. CAD is
a progressive, often silent
killer and if left undetected at
its earlier stage, can lead to
Angina pectoris, Myocardial
infarction and sudden death.
Persons with high cholesterol,
blood pressure, diabetes,
obesity, smokers, sedentary
persons and those with a strong
family history of heart disease
can know about their disease
status in time and hence take
timely measures. Dietary
management and lifestyle
modifications are more effective
the earlier they are initiated.
Hence Cardiovascular Cartography
can play a major role in
controlling the rapidly
increasing incidence of Coronary
Artery Disease in Indians by
providing a cost effective mass
mapping test. The poster
provides details of the over
thirty parameters obtained by
Cardiovascular Cartography.
Keywords:
coronary artery disease,
Cardiovascular Cartography,
haemodynamic, myocardial blood
flow, nutritional guidelines,
lifestyle modification,
circulatory system,
catheterization, radiation,
non-invasive, CAD.
======================================================================
PRESS
RELEASE
RGCI DETECTS BLOCKS YEARS BEFORE
HEART ATTACK
Ludhiana: 19 Feb,
2000: India’s seventh
Cardiovascular Cardiographic
Imaging System (CVC) was
installed today at Sibia Medical
Centre, Ludhiana. This new
non-invasive technique to detect
Coronary Heart Disease in the
form of Realistic Geometric
Cartographic Imaging (RGCI)
brings a new diagnostic
advantage for chest pain
patients for complete
evaluation. It will help doctors
monitor and diagnose heart
problems even in early stage
making timely
protective
treatment possible. RGCI is an
advanced technique based on 3D
mathematical modeling and
simulation, that accurately
informs of the probable location
and severity of flow limiting
lesions in heart’s blood vessels
and its oxygen demand / supply
with the help of measurement of
heart muscle blood flow.
This
equipment works on the
principals of Integration of
time related physiological
curves derived out of
transthoracic Bioimpedance,
Electrocardiography and subsonic
thoracis transverse waves to
detect various cardiac
parameters relating to pressure,
volume, time and flow. A team of
experts from Delhi, Bangalore
and Mysore visited the city and
addressed the leading
cardiologists and physicians on
this occasion where
Dr.L.S.Chawla founder Vice
Chancellor of Baba Farid
University of Health Sciences
was the chief Guest. Dr Rajah
Vijay Kumar, Chairman Centre for
Artificial Intelligence and Non
Linear Studies, Bangalore and
co-inventor of RGCI explained
that doctors prefer to gain
maximum accurate information
about the cardiovascular system
non-invasively. In invasive
techniques catheters have to be
inserted to know the status of
coronary vessels and risks of
injury, rupture, infection and
radiation always exist. If the
doctors get accurate data about
heart functions without
inserting any equipment, it
would minimise the risk and
simplify the process. This new
technique does exactly that and
could be repeated any number of
times without any harm.
The
new noninvasive system uses skin
electrodes and sensors that
acquire and monitor the data in
just 30 minutes. RGCI is
providing continuous accurate
data about any changes in
haemodynamics such as the heart
rate, stroke volume, cardiac
output and other 24 parameters.
Dr.G.N.Shirbur a leading
cardiologist from Simha Heart
Foundation, Mysore added that
RGCI is the only technique that
takes into consideration upto
twenty four parameters and can
be applied on a patient at rest
with total safety and no pain or
difficulty. This highly
sensitive and accurate test
detects flow limiting lesions
even as little as 20 percentage
with over ninety percent
accuracy while other existing
tests like angiography detect
only above 40 percent and TMT
becomes positive
only
above 60 percentage
blocks in heart’s blood vessels.
This sensitivity helps early
detection, prevention and
treatment of Coronary
Artery Disease
which kills almost eight lacs
Indians every year that is about
90 Indians every hour and more
than three million worldwide.
For the undiagnosed victims
delay can be costly or even
fatal. RGCI is the only non
invasive system that can give an
accurate diagnosis even in acute
heart problems in more than
ninety percent patients.
Dr.Shirbur mentioned that this
low cost screening test should
be part of every master health
check up for all persons above
30 years of age and is specially
useful for persons at high risk
having diabetes, high blood
pressure, overweight, smokers,
alcoholics, high cholesterol and
persons with family history of
heart disease, sedentary and
stressful lifestyle, etc. Other
uses of RGCI include follow up
after angioplasty (ballooning,
stents etc) and bypass surgery.
It is also ideal for mass
screening of clients and staff
of institutions, corporates,
insurance companies etc. Special
tests like Nitrate enhanced,
stress cartography etc can also
be done with RGCI.
Dr.O.P.Aggarwal a senior
cardiologist from Bareilly who
is using RGCI for a long time
told that RGCI is the only
investigational tool in the
field of cardiology which does
not have any difference of
opinion. Contrary to that all
investigations including
angiography have differences of
opinion if placed before
different cardiologists. Furthur
he added all preoperative
patients must undergo RGCI which
in this case takes only 60
seconds to evaluate the safety
of anaesthesia and surgery in
the patient.Another doctor from
Bareilly, Dr.Ram Babu Aggarwal
ex-vice president Indian Medical
Association of Uttar Pradesh
said RGCI is also useful in
young children and chest
diseases and he stressed that
RGCI does not require any
admission for doing the test.
Dr.Sibia has a vision that such
equipment would be part of every
physician’s setup for early
diagnosis, follow up and the
selection of modalities of
treatment - medical or surgical
together with appropriate life
style modification.
======================================================================

3D-Cardiovascular Cartography: A
Novel Non-invasive
Technique for Coronary Screening
in Aircrew
by Gp
Capt GS Nayar (Retd) Former
Senior Advisor (Aviation
Medicine), IAF
Dr GN Shirbur Cardiologist,
Heart Care Foundation, Bangalore
Abstract
Cardiovascular screening to
exclude coronary artery disease
(CAD) forms a very important
part of any aircrew evaluation.
A routine ECG forms part of
initial evaluation for aircrew
duties. As the incidence of CAD
is age-related, repeat ECG
examination and even periodic
Bruce protocol stress test are
mandatory requirements by
certain Regulatory Agencies
including India. Routine use of
cardiac stress testing has been
controversial because of
inadequate specificity when
applied to an asymptomatic
population. At times further
invasive tests for delineation
of the coronary arteries become
necessary with avoidable stress
and even risk to life to the
apparently normal aircrew.
Availability of population
health data and increasing use
of computer applications in
medical database management have
made risk analysis and risk
stratification easier and more
reliable.
This paper discusses the use of
a truly non-invasive protocol
for routine coronary screening,
especially of aircrew. The first
part of the protocol involves
the use of a simple
computer-based algorithm
developed using the Framingham
study with various risk factors
including age, gender, family
history, smoking habit, body
mass index, blood pressure,
cholesterol and HDL levels. The
software predicts the coronary
risk of the individual based on
population data. The second part
of the protocol involves the use
of a novel new technique of 3-D
Cardiovascular Cartography (CCG).
This is based on 3-D
mathematical modeling and
simulation using high speed
computation enabling non-linear
haemodynamics to be evaluated
from beat-to-beat recording of
the cardiac cycle. The regional
coronary circulation is
displayed and a number of
physiological data of cardiac
functions are calculated. It is
recommended that the scope of
using these non-invasive methods
in routine cardiovascular
evaluation of the aircrew be
considered. The data obtained by
these techniques will also be
useful in aircrew maintenance
programmes based on preventive
cardiology.
Keywords: Aircrew evaluation,
coronary risk stratification,
coronary cartography, aircrew
maintenance
Flying an aero plane is an
occupation that demands repeated
successful demonstration of a
minimum standard of physical and
mental fitness by its operator.
The objective of the regulatory
authority will always be to rule
out even the remotest
possibility of a sudden
incapacitation of the pilot
while at the controls. The
medical regulations thus insist
on clauses to preclude such
events as epilepsy,
incapacitating angina, altered
consciousness or sudden death.
Cardiovascular Screening
Cardiovascular screening to
exclude coronary artery disease
(CAD) thus forms a very
important part of any aircrew
evaluation. A routine ECG forms
part of initial evaluation for
aircrew duties. As the incidence
of CAD is age-related, repeat
ECG examination and even
periodic Bruce protocol stress
test are mandatory requirements
by certain Regulatory Agencies
including India1. The following
are some of the important
considerations in this respect:
-
The resting ECG is an
insensitive tool for the
detection of pre-symptomatic
CAD although it identifies a
small number who have suffered
a silent myocardial infarction
(MI)2.
-
The risk of sudden death from
an unheralded heart attack
increases with age. Thus, when
compared to a man of 30 years,
the risk of sudden death from
acute MI increases 8 times at
40 years, 36 times at 50 years
and 100 times at 60 years.
Further, 50% of those dying
suddenly do so without
premonitory symptoms 3.
-
Sudden death is the initial
presentation in more than one
third of MI with up to 60% of
patients dying in the first
hour. Other initial symptoms
may include incapacitating
angina or altered
consciousness, both equally
dangerous when occurring
inside the cockpit
environment.
-
Aeromedical stresses such as
heat, hypoxia,
hyperventilation, and high Gz
manoeuvres may provoke
dysrhythmia or infarction in
individuals with pre-existing
coronary artery lesions4.
Exercise ECG is not a routine
mandatory requirement for
aircrew evaluation in the ICAO
ISARPs5 nor in the JAR6. The
positive predictive value of an
abnormal treadmill test for
significant CAD in men average
about 21%, with values ranging
from 5% to 46%, but in most
studies were less than 25%7. The
poor yield of exercise testing
due to the relatively low
prevalence of CAD in the healthy
aviator population must be
recognized.
While there is general agreement
that CAD is a disqualification
in the context of military
aviation, careful consideration
supported by detailed evaluation
is made mandatory in the case of
civil aircrew. Regulatory
authorities may often take the
easy option of denying licenses
to civil aircrew detected to
have CAD on routine testing. The
Federal Aviation Authority (FAA)
has an exceptional record of
granting medical waivers to
pilots with evidence of CAD
following painstaking evaluation
as can be seen from the figures
in Table 1.
Table 1. Medical certification
of pilots with CAD - FAA
(January 2001)
|
Event |
Type of License |
|
Class I |
Class II |
Class III |
|
Myocardial infarction |
299 |
323 |
2,819 |
|
Percutaneous transluminal
angioplasty |
354 |
278 |
2,233 |
|
One or more coronary stents
in the same time frame |
213 |
173 |
1,289 |
|
Coronary artery bypass
grafting |
256 |
295 |
3,197 |
|
Atherectomy |
51 |
10 |
227 |
Some of the newer tests for
coronary evaluation, though not
yet widely available, include
the following:
-
Imaging for coronary artery
calcification
-
Stress radionucleide imaging
-
Stress echocardiography
-
Non-invasive coronary
angiography, such as electron
beam computed tomography (EBCT),
magnetic resonance angiography
(MRA)
Coronary angiography is the
'gold test' which forms the
basis for evaluating whether a
lesion is Non-significant or
Significant depending on the
degree of occlusion of any
coronary artery as indicated in
Table 2.
Table 2. Criteria of severity of
CAD
|
Degree of severity |
Occlusion in any coronary
artery |
Aggregate of occlusion |
|
Minimal Coronary Artery
Disease (MCAD) |
< 40% |
< 120% |
|
Significant Coronary Artery
Disease (SCAD) |
> 40% |
> 120% |
The
prevalence of CAD in
asymptomatic military pilots is
reported to be extremely low
even though published figures
are not available for India.
Among the commercial aircrew and
private pilots, this prevalence
may be closer to that of the
general population. With the
treadmill stress test being made
mandatory among Indian civil
aircrew above the age of 35
years since over 5 years now, a
huge database must be available
for detailed analysis with a
view to review the practice and
give very valuable inputs to
other international regulatory
authorities. An abnormal
treadmill test continues to
generate a lot of anxiety among
the aircrew and many physicians
are unhappy to subject them to
further invasive procedures
knowing that the predictive
significance of the positive
treadmill test in an unselected
aviator population may be less
than 10% for angiographic
significant CAD8. Further, as
the treadmill tests are being
done outside the direct
supervision of the physicians of
the medical evaluation centres,
this policy needs to be reviewed
to ensure standardization of the
aircrew evaluation procedures.
Coronary Risk Stratification
A
suggestion gaining increasing
acceptance internationally is
the need for risk stratifying
the aviator population prior to
performing screening tests in
order to improve their
predictive value.
The
authors propose that this
suggestion be accepted at the
earliest and recommend the
following procedures:
-
History, physical examination,
laboratory investigations, etc
be utilized to assess the
classical CAD risk factors.
-
Use of simple computer-based
risk calculators can be used
to assess the risk factors
quickly and effectively.
-
An
example of such an approach
will be the use of a
Framingham risk index.
-
If
the risk index is above the
specified threshold, a graded
exercise test may be conducted
which will show a better
predictive value.
-
If
the stress test is positive,
other tests including coronary
angiography can be conducted
to establish the diagnosis.
Cardiovascular Cartography (CCG)
A
novel technique of 3-D
Cardiovascular Cartography (CCG)
has recently been developed by
Indian scientists. This is based
on 3-D mathematical modeling and
simulation using high speed
computation enabling non-linear
haemodynamics to be evaluated
from beat-to-beat recording of
the cardiac cycle9.
As
far as the patient and the
doctor are concerned the
technique is as simple as
recording an ECG but with a
little more elaborate and
precise preparation of the
patient. The equipment (Fig 1)
uses a vertical acceleration
detector that picks up subsonic
waves that are transmitted from
the heart to the chest wall
throughout the cardiac cycle.
The recordings of 1024 heart
beats include beat-to-beat
stroke volume, systolic time
intervals, flow turbulence and
arterial blood pressure. Using
specialised digital signal
processing and neural network
computing, a predictive model of
the individual is created and
the measured haemodynamic
behaviour is superimposed on the
predictive model. The resultant
deviation difference is
distributed as pressure zone,
volume zone, time zone and flow
zone in a clockwise direction on
the cardiovascular cartogram
(Fig 2). The regional coronary
circulation is also displayed
(Fig 3). CCG is scale
independent but has positivity
and negativity indicating the
deviation difference, reflecting
physiological, pathological or
compensatory phenomena and thus
assesses the efficacy and
function of the cardiovascular
system. A more detailed
description of the technique is
out of the scope of this
presentation.
CCG
is a novel non-invasive tool
with a systemic approach for
interpreting haemodynamics based
on modeling and simulation
techniques. Its clinical
application is oriented
especially to diagnosis,
estimation of prognosis and
modification of therapeutic
modalities in coronary artery
disease (CAD). Carefully
conducted studies have indicated
that CCG has a sensitivity of
91%, specificity of 92%,
positive predictive accuracy of
98% and negative predictive
accuracy of 75% (Table 3).
Table 3. Sensitivity and
specificity of CCG
|
|
Primary presence of
CAD |
Anterioseptal region
(LAD) |
Inferioseptal region
(RCA) |
Lateral region (LCX) |
|
Sensitivity |
91% |
83% |
80% |
72% |
|
Specificity |
92% |
76% |
74% |
80% |
|
PPA |
98 |
85% |
80% |
81% |
|
NPA |
75% |
74% |
74% |
70% |
|
Mean Accuracy |
91% |
81% |
78% |
75% |
The
CCG technique is adequately
sensitive and specific in the
detection of CAD even at a very
early stage of the disease. CCG
results compare favourably with
other available invasive and
non-invasive tests to detect CAD
and can be a low cost solution
for mass screening of a
population for early detection
of CAD.
Risk
Modification
One
of the significant advantages of
this combined system of CAD risk
stratification followed by
non-invasive CCG will be in the
field of primary prevention of
CAD. As the entire process
involves transparent and
easy-to-understand
presentations, the subject,
viz., aircrew in our context,
has total involvement in the
evaluation and gets full grasp
of the salient features of the
underlying mechanisms in the
development of CAD. This will
help in motivating the aircrew
on the preventive measures to
improve the clinical risk
profile through life style
management and other measures.
Conclusion
A
novel method of using
computer-aided risk analysis and
stratification followed by a
non-invasive process of CCG is
recommended to carry out
coronary screening among
aircrew. Prompt acceptance of
the findings and recommendations
on the part of the aircrew will
bring about a favourable shift
in their attitude towards
primary prevention of CAD. Early
identification of the risk
factors will help in improving
their health status with a
positive impact on air safety.
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