What are the risks of exercise testing? What are the contraindications?

Although exercise testing is generally considered a safe procedure, acute myocardial infarction and death have been reported (up to 10 per 10,000 tests performed in some studies). The risk is greater in the post-MI patient and in those being evaluated for malignant ventricular arrhythmias. The rate of sudden cardiac death during exercise has ranged from zero to as high as 5% per 100,000 tests performed. Guidelines for exercise testing for North America have now been made available. In patients recovering from acute myocardial infarction, a low level exercise test before discharge helps identify those patients at high risk for future cardiac events. In addition to being a source of reassurance to the patient and his/her family, the test may also provide guidelines for an exercise programme and resumption of work and normal sexual activities.

The sensitivity ranges from a low of 40% for single vessel coronary artery disease to up to 90% for angiographically severe three vessel disease, with a mean sensitivity of 66%. The specificity of the test is ~85% when at least 0.1mV horizontal or downsloping ST-segment depression are used as markers of ischaemia. In patients with a positive exercise test, an ischaemic threshold less than 70% of the patient’s age predicted maximum heart rate is indicative of severe disease.

Various drugs may affect interpretation of the exercise test either because of haemodynamic alterations in the myocardial response to exercise or because the drug has direct electrophysiologic effects that can affect the interpretation of the electrocardiogram. The decision to stop medications prior to an exercise test depends on the drug and the reasons for using it. Some institutions withhold beta blockers for 48 hours prior to exercise testing if there is doubt about the diagnosis of coronary artery disease.