|
Each month we provide you with
a feature article. This article is authored by one of our
clinicians. Please direct all comments/questions to
info@cdaradiology.com.
Heart disease, Heart
Attacks, and Coronary CTA - Feature 0807
Coronary CTA is a breakthrough technology for testing for Heart
Disease. In order to understand the promise of Coronary CTA we will
review what Heart Disease is and how it is evaluated. Following this
we will discuss the role of Coronary CTA and explain why the
technology has caused a lot of excitement in the medical community.
Heart Disease is the number one cause of death in the United States.
Heart Disease, which is called Coronary Artery Disease by the
medical community, is caused by the buildup of cholesterol deposits
in the arteries that supply the heart with blood—the coronary
arteries. The buildup of cholesterol and related material in the
inside of the coronary arteries is called atherosclerosis.
As Coronary Artery Disease gets worse, atherosclerotic plaque
buildup can decrease blood flow to the heart and cause chest pain.
If a cholesterol deposit breaks open, it can block the coronary
artery supplying blood to the heart. The heart muscle downstream
from the blockage is starved of blood and in danger of dying. This
event is called a Heart Attack by the general public and Acute
Coronary Syndrome by the medical community. When heart muscle
becomes nonfunctional because of a Heart Attack, a person’s life is
in danger, and immediate medical attention is necessary.
Because Coronary Artery Disease is common, and the number one cause
of death, patients naturally want to know if they have the disease.
However, it is often difficult for doctors to answer to this simple
question. One reason for this is that until recently there has not
been a way to noninvasively look at the diseased structures--the
coronary arteries. Because of suboptimal diagnostic capabilities,
and the silent nature of the disease, many patients are unaware of
their heart disease--until they have a heart attack or sudden death.
Coronary Computed Tomography Angiography (Coronary CTA) is a new
medical technology which can directly look at the coronary arteries.
Because of this, it has the potential to transform the how
physicians diagnose Coronary Artery Disease, and dramatically
improve patients’ heart health. To understand where Cardiac CTA fits
in to medical testing for Coronary Artery Disease, it is helpful
understand other heart tests.
Because evaluating heart disease directly is difficult, doctors have
had to guess about the chance of having disease. For example, if you
know specific factors (such as age, cholesterol level, if the
disease runs in the family, and if the person smokes or is
diabetic,) you can estimate a rough probability of having Coronary
Artery Disease. This is called risk factor assessment. Risk factor
assessment may be very inaccurate for a specific individual. For
example, recent research has highlighted the poor accuracy of this
approach in women.
 If
you have an indication, such as chest pain, that you have coronary
artery disease, other tests may be performed. Stress tests evaluate
delivery of blood to the heart muscle, and therefore indirectly
evaluate narrowing in the coronary arteries. A stress test may be
done with just exercise and monitoring the heart. Or the stress test
may be augmented by nuclear medicine technology which evaluates
delivery of radioactivity to the heart muscle. While a stress test
can be valuable in certain situations, it is has important
limitations. It only detects advanced coronary artery disease, and
even then it is only moderately accurate. It is also expensive and
associated with a high radiation dose.
In the past when doctors had to look at the coronary arteries they
would perform an invasive procedure where they thread catheters into
the heart and inject dye. This is called invasive angiography and it
has two major advantages. It can treat blockages by opening them
with a balloon (angioplasty) or a metal cage (stent). And it shows
the best detail in the coronary arteries.
Angiography also has major disadvantages that arise from its
invasive nature: It is subject to complications, and it is very
expensive. Also invasive angiography is unable to see the coronary
artery in three dimensions and unable to see plaque that is in the
wall of the vessel. For these reasons, invasive angiography may
underestimate the extent of Coronary Artery Disease.
This brings us back to coronary CTA. CT scanning technology has just
recently advanced to the point that it could visualize the very
small coronary arteries, which are moving as the heart beats. Let’s
look at the advantages and disadvantages of Coronary CTA.
The major advantage of Coronary CTA is that you can directly image
the coronary arteries without invading the body. Another advantage
is that coronary CTA has excellent accuracy (over 97%) in excluding
the presence of disease. This means that if your coronary CTA scan
is negative, no significant disease is present, and no more tests
for Coronary Artery Disease are necessary. Coronary CTA is also less
expensive than nuclear medicine stress tests and much less expensive
than angiography.
A disadvantage of Coronary CTA is that it slightly overestimates
disease, resulting in only moderate accuracy (80%) in determining
disease severity. Therefore, if you have a high level of coronary
artery disease, other tests may be necessary to define the disease
severity. Like invasive angiography and nuclear medicine stress
testing, coronary CTA requires a radiation dose to the patient. The
current best technology delivers a radiation dose about half that of
a nuclear medicine stress test.
Coronary CTA is also highly technology dependent--it requires high
level CT technology to get an accurate test. It is always advisable
to seek out the best technology for your medical tests. This is even
more critical with coronary CTA. Dual source CT scanners are
currently the best technology. They are becoming more common and are
well worth seeking out if you are going to have a coronary CTA. The
older generation 64 slice CT scanner is less accurate and requires
drugs to slow the heart before the test.
In summary, we have discussed heart disease, the tests for heart
disease, and a new technology—Coronary CTA. Radiological Associates
of North Idaho is proud to employ the best technology and advanced
subspecialist expertise. We are at the forefront of a movement that
is improving diagnosis in the most important disease in United
States.
Author
Keith McKlendin, MD
Useful Links
Patient Information
top |
|
Feature Highlight
