INTRODUCTION

Among patients who undergo stress testing to determine the diagnosis or prognosis of coronary artery disease, symptom-limited treadmill or bicycle exercise is the preferred form of stress for those who can attain an adequate level of exercise (defined as ≥85 of their predicted maximal heart rate) because it provides the most information concerning exercise capacity, patient symptoms, cardiovascular function, and the hemodynamic response during usual forms of activity [1,2]. The inability to perform an exercise test is in itself a negative prognostic factor in patients with coronary artery disease. (See "Selecting the optimal cardiac stress test" and "Stress testing to determine prognosis and management of patients with known or suspected coronary heart disease", section on 'Advantages of exercise stress'.)

While exercise electrocardiographic (ECG) testing is recommended for patients who are able to exercise, this technique requires the absence of baseline ECG abnormalities that could interfere with interpretation of the test (table 1). Two such abnormalities are complete left bundle branch block (LBBB) and a paced ventricular rhythm, which are also associated with a high rate of false positive or uninterpretable tests in patients undergoing exercise stress. The 2002 American College of Cardiology/American Heart Association (ACC/AHA) guidelines on exercise testing concluded that there is NO level of ST segment depression that confers diagnostic significance during exercise ECG testing in patients with LBBB [1,2]. (See "Exercise ECG testing: Performing the test and interpreting the ECG results".)

Options for stress testing in patients with LBBB or paced ventricular rhythm are discussed here. The role of coronary CT angiography (CCTA) using multidetector row computed tomography (MDCT) in the evaluation of patients with LBBB is discussed separately. (See "Noninvasive coronary imaging with cardiac computed tomography and cardiovascular magnetic resonance", section on 'Other uses'.)

LEFT BUNDLE BRANCH BLOCK

Exercise and pharmacologic stress radionuclide myocardial perfusion imaging (rMPI) and exercise and pharmacologic stress echocardiography have been evaluated in patients with LBBB. The goals of exercise testing in patients with LBBB include assessing for evidence of coronary heart disease (CHD); assessing the extent, severity, and location of CHD if present; and evidence of myocardial viability patients with LBBB and heart failure.

Exercise rMPI — Left bundle branch block can interfere with exercise rMPI. Among patients who undergo exercise rMPI, LBBB is associated with transient positive defects in the anteroseptal and septal regions in the absence of a lesion within the left anterior descending coronary artery (LAD) in approximately 10 to 20 percent of cases [3-7]. Thus, there is a high rate of false positive tests when exercise rMPI is performed in patients with LBBB.