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 Catheterisation / Coronary Angiography
Cardiac catheterisation 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.

Classification Of Heart Disease
Based on the results of the diagnostic tests performed, doctors usually classify a patient’s heart condition based on how severe his symptoms are. The most commonly used classification system in this respect is the New York Heart Association’s Functional Classification, which places patients into one of four categories depending on the extent to which their cardiac problems limit their capacity for physical activity.

Class Nature of Symptoms
I No symptoms and no limitations on ordinary physical activities
II Mild symptoms, with slight limitations on ordinary activities. Patient is comfortable at rest.
III Symptoms are sufficiently serious to place marked constraints on ordinary physical activities as well as on less strenuous activities. Patient is comfortable only at rest.
IV Symptoms impose severe limitations on patient’s daily activities. Patient experiences symptoms even while at rest.