100 QUESTIONS IN CARDIOLOGY

15 What are the risks of exercise testing? What

are the contraindications?

Joseph F Malouf

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.^1

Table 15.1 lists absolute and relative contraindications to

exercise testing. 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 electro-

physiologic effects that can affect the interpretation of the electro-

cardiogram. The decision to stop medications prior to an exercise

test depends on the drug and the reasons for using it. Some insti-

tutions withhold beta blockers for 48 hours prior to exercise

testing if there is doubt about the diagnosis of coronary artery

disease.