Pharmacological Stress Agents for Radionuclide Myocardial Perfusion Imaging

For patients unable to exercise or in some circumstances where it is undesirable or unsafe,pharmacological stress is an excellent alternative.

Patients with the following are suitable for pharmacological stress testing:

a) Poor physical conditioning; limiting non-cardiac symptoms (e.g. atigue) Left bundle branch block (false-positive exercise perfusion scans)

b) Peripheral arterial disease; lung disease Spinal injuries; amputations; or orthopedic problems (e.g. low back pain)

Pharmacological Stress Agents
There are two classes.

The vasodilators include adenosine and dipyridamole. These increase myocardial perfusion and lead to a relative reduction in perfusion in territories supplied by obstructed vessels. These regional variations are not normally associated with ischaemia because they are not accompanied by an increase in myocardial oxygen demand.

The synthetic catecholamines include dobutamine and arbutamine. These also increase myocardial perfusion but less than the vasodilators and they also increase myocardial oxygen demand by increasing cardiac contractility and heart rate. They are therefore, more likely to provoke ischaemia.