Let's get physical: Myocardial stress tests - A student's perspective

Abstract

Myocardial perfusion imaging is a routine study that helps determine whether blood flow to the heart muscle is normal or abnormal. There are 3 parts to myocardial imaging: a resting scan with a radioactive tracer, stressing of the myocardium, and a stress scan with a radioactive tracer. For the resting scan, a radioactive tracer is injected into the patient to obtain a set of images of the myocardium at rest. After the resting scan comes stressing of the myocardium. There are 2 different ways to stress the myocardium. The first is to have the patient exercise on a treadmill following a specific exercise protocol, and the second is to use a pharmacologic stressing agent if the patient cannot exercise. Pharmacologic stressing agents produce coronary artery vasodilation and increased myocardial blood flow. During exercise stress, the heart rate should preferably reach 85% of the maximum heart rate and the patient should be symptomatic or fatigued. The technologist injects the patient with the radioactive tracer at peak stress and then obtains a second set of images. Of the 2 different ways to stress the myocardium, physical stress is preferred to pharmacologic stress.