What are the stratification data for risk from exercise tests in patients with angina? Which patterns of response warrant referral for angiography?

The best evidence available on these questions is found in the two studies that used the appropriate statistical techniques to find the risk markers that were independently and statistically associated with the time to cardiovascular events. Both studies were performed in large populations (>3000 patients with probable coronary disease) and had five year follow-up. The Veteran’s Affairs (VA) study was performed only in men and the risk factors identified were a history of congestive heart failure (CHF) or digoxin administration, an abnormal systolic blood pressure (SBP) response, limitation in exercise capacity, and ST depression.1 The DUKE study included both genders and has been reproduced in the VA as well as other populations. It includes exercise capacity, ST depression and whether or not angina occurred. The DUKE score has been included in all of the major guidelines in the form of a nomogram that calculates the estimated annual mortality due to cardiovascular events.

In general, an estimate more than 1 or 2% is high risk and should lead to a cardiac catheterisation that provides the “road map” for intervention. Certainly a clinical history consistent with congestive heart failure raises the annual mortality of any patient with angina and this is not considered in the DUKE score. Exercise capacity has been a consistent predictor of prognosis and disease severity. This is best measured in METs (multiples of basal oxygen consumption). In clinical practice this has been estimated from treadmill speed and grade but future studies may show the actual analysis of expired gases to be more accurate. Numerous studies have attempted to use equations to predict severe angiographic disease rather than prognosis but these have not been as well validated.