Chapter 17: Evaluation of Patients with Known Coronary Artery Disease

INTRODUCTION

In the last 40 years, there has been a dramatic decline in cardiovascular mortality. Over the past decade alone, the rate of death attributable to cardiovascular disease has decreased by 30%.¹ This trend is credited primarily to the development and implementation of effective treatment strategies including medical therapy, interventions such as coronary artery bypass graft surgery (CABG) and percutaneous coronary interventions (PCIs), and successful treatment for acute myocardial infarction (MI). The decision to undergo myocardial perfusion imaging (MPI) evaluation following the diagnosis of ischemic heart disease is an important one, particularly in asymptomatic patients. This chapter will evaluate the role of stress MPI in patients with known CAD in a variety of settings, including medical therapy, postinterventions, and following MI.

MYOCARDIAL PERFUSION IMAGING AND CHRONIC ISCHEMIC HEART DISEASE

Indications for Stress Myocardial Perfusion Imaging

Stress testing is an important tool in the longitudinal assessment of patients with known coronary disease, especially when there is a change in the frequency or pattern of symptoms. However, several factors may preclude the use of exercise tolerance testing (ETT) without imaging to make management decisions, as discussed in Chapters 8 and 26. The American College of Cardiology/American Heart Association (ACC/AHA) guidelines for ETT strongly recommend an imaging study as part of the evaluation in patients unable to exercise and in those with baseline EGG abnormalities (pre-excitation, paced ventricular rhythm, ≥1 mm resting ST-segment depression, and complete left bundle branch block [LBBB]).² The use of digoxin, presence of left ventricular hypertrophy (LVH), or any resting ST-segment depression decreases the specificity of exercise testing while sensitivity may remain unaffected.² Importantly, several other subsets of patients benefit incrementally with the use of radionuclide imaging, including patients with previous MI and/or coronary revascularization procedures (CABG or PCI), patients with prior angiography demonstrating significant disease (where identification of the lesion causing myocardial ischemia is important), individuals with high risk for future events (e.g., diabetics), and patients with a previous positive MPI.^2–6

Timing of Imaging of Follow-Up in Patients with Stable Coronary Artery Disease

Many patients with CAD undergo stress MPI for postinterventional assessment. Stress MPI is indicated as part of initial risk assessment and/or prior to planning PCI or CABG. It is also performed during follow-up after revascularization (PCI or CABG) or modification of medical therapy.

The role of stress MPI in stable CAD is linked to an effort to identify individuals at higher or lower risk for future cardiac events. Unless cardiac catheterization is indicated, patients with known CAD who present with changing symptoms suggestive of ischemia should likely first undergo stress imaging, to assess the risk of future events.² Furthermore, localization of ischemia, identification of extent and severity of ischemic burden, and assessment of left ventricular performance are desirable for most patients who are being evaluated for intervention or titration of medical ...