Invasive Tests
Nuclear Imaging
These tests involve injecting radioactive substances known
as radionuclides (for instance, thallium) into the patient’s
bloodstream. As the radioactive substances flow through
the patient’s cardiovascular system, scans and computer-generated
images are taken to detect how well the heart’s
chambers are working, how good blood supply to the heart
is, and whether or not any heart muscle has been damaged
by a heart attack.
Nuclear imaging may be combined with an exercise stress
test to augment the accuracy of the results obtained.
In such cases, the radioactive substances injected into
the patient are mapped both at the peak of exercise and
at rest so as to identify areas where the coronary arteries
are narrowed, as well as the extent and severity of the
patient’s blood flow abnormalities.
Cardiac Catheterization / Coronary
Angiography
Cardiac catheterization is commonly performed before invasive
procedures such as “balloon” angioplasty in
order to determine the type and extent of surgery required.
A catheter in the form of a thin plastic tube is inserted
into an artery or vein in one of the patient’s limbs
and directed into the chambers of his heart and the coronary
arteries. Once the catheter is in position, the blood
pressure, oxygen content of the blood, and pumping ability
of the heart can be assessed.
The catheter may also be used to inject a dye into the
coronary arteries. As the dye flows through these arteries,
X-rays are taken (coronary angiography). The dye shows
up as white lines on the X-rays, with disruption or narrowing
of the lines indicating areas where the coronary arteries
are obstructed.
Trans-Oesophageal Echocardiography
Unlike conventional echocardiography which is non-invasive,
in trans-oesophageal echocardiography, a special instrument
is inserted into the patient’s throat and passed
down his oesophagus (the tube connecting the mouth to
the stomach). As part of the oesophagus lies close to
the heart, the images captured by the instrument are able
to give a very clear picture of the heart’s structure.
Blood Tests
Certain substances such as creatinine kinase and troponin
are released into the bloodstream when the heart is damaged
during a heart attack. Their concentrations peak after
a specific period of time from the initial moment of heart
attack. Blood tests to detect the presence of these substances
are useful in helping doctors to estimate the time of,
or to confirm the occurrence of a heart attack. They also
help in the detection of any injury which may have been
caused to heart muscle due to a heart attack. |
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