What are the factors that can influence the accuracy of the ECG during exercise testing to diagnose obstructive CAD?
Resting ECG abnormalities such as left ventricular hypertrophy, left bundle branch block, ventricular-paced rhythm, or any resting ST-segment depression of 0.5 mm can all influence the accuracy of the ECG during exercise testing to diagnose obstructive CAD. Certain medications, such as digitalis, can also cause false positive ischemic ECG changes. Anti-ischemic therapies can reduce heart rate and myocardial workload, leading to false negative findings when the test is used to diagnose SIHD. It is therefore important to withhold beta-blocker therapy for 24 to 48 hours before testing, and ensure that the patient has an interpretable ECG (defined as a normal 12-lead ECG or one with minimal resting ST-T-wave abnormalities of less than 0.5 mm).  