TMT is exercise ECG and observation of patient during a graded stress. In males in the ages 30 and above with a normal ECG it gives a good information about the exercise tolerance and ECG changes during the exercise which increases the product of heart rate and blood pressure. This product called the double product increases the oxygen demand of heart.
If the ECG remains normal at peak exercise and at the predicted maximal heart rate for the age the chance of having a significant block in a major coronary artery is very low. The predictive value of the test increases if the person doing TMT remains asymptomatic and has a normal BP response and clinical examination immediately after exercise remains normal. A positive TMT has to be interpreted along with the total clinical picture and other risk factors (like diabetes, high lipids, family history, obesity, smoking etc). If the result is not clear other non invasive tests like Stress echocardiography or stress thallium give more physiological information. These functional tests do not show the status of coronary arteries and are positive if the blocks are significant (more than 50% luminal obstruction). Insignificant blocks, which can cause sudden problems like - if the obstructing plaques are vulnerable can not be diagnosed by stress tests. Diagnosis of vulnerable plaques is a challenge and lot of work is going on in this direction. The future promises to have sensitive specialised tests to diagnose the vulnerable patients and vulnerable mild obstructions. To keep risk factors of coronary artery disease in check, which you seem to know very well, helps in keeping the coronary arteries with minimal age related obstructions from progressing to catastrophic events.