Stress testing
Many patents with coronary heart disease may have apparently normal rest ECG. So if you’re ECG is normal it does not completely exclude the possibility of pressure of significant block in your coronary arteries. If you have symptoms like exertional chest pain or breathlessness on mild to moderate exercise or suffering from easy fatiguibility, you should go for stress test to exclude the possibility of coronary heart disease. Any type of exercise results in an increase in myocardial (heart muscle) oxygen supply. This increase in oxygen need can only be met by coronary artery dilation or expansion. If you have significant block in any of your three coronary artery, the exercise induced increase in heart muscle oxygen consumption cannot be met due to presence of fixed block in coronary arteries. So during rest your ECG can remain normal and can indicate the abnormalities only during exercise, but in rest.
There are different ways to perform this test. But the Bruce treadmill test is the most popular one. During this test the patient is asked to walk fast or run on a treadmill and continuous ECG is recorded in a computer monitor. The test is continued as long as the ECG does not reveal any ischaemic change suggestive of block or target heart rate is achieved or the patient becomes fatigued.
Stress test is an excellent investigation for the diagnosis of coronary heart disease. This test is reported to have specificity of 77% for the detection of significant steno sis or block in any of your coronary arteries. If you are male and your stress test is positive for block then you can take it as 90% guarantee that you are having coronary artery disease. But in case of female this test is some times misleading and gives false positive result. If your stress test is positive, then doctor will advise you to undergo coronary angiogram. Stress test can tell you that probably you are having block but it can not tell you where are the blocks, how severe are the blocks and how many blocks you have. So stress test is the initial screening test but coronary angiogram is the final test for decision making.
Stress test is a noninvasive test and painless. Risk involved in this test is very little with a fatality of 1 in 10,000 patients. Preparation of the patient for this test is also simple. The patient is only advised not to take heavy meals 4 hours before testing. Patients undergoing diagnostic testing ideally should have beta blockers (e.g tenormin, tenoren, cardipro, betasec, betanol, tenoloc, inderal, indevar, adloc, carditab, propranol etc.) at least 24 hours before the test if possible. This test is also done after heart attack for further coronary risk stratification. If after heart attack this test becomes positive then it is a strong indication for coronary angiogram.
