Pharmacologic stress testing was initially developed as an alternative to dynamic exercise. Presently, most imaging laboratories primarily use either vasodilators or synthetic catecholamines. These can be administered intravenously to evaluate coronary flow reserve, which can overcome the problem of low-level exercise stress testing, which by itself can fail not only to detect the presence of coronary artery disease (CAD) but also to provide appropriate prognostic risk stratification. There has always been a relatively significant segment of the cardiac referral population who have been unable to perform maximal dynamic exercise stress testing. During the past decade, the portion of patients studied with pharmacologic stress agents has grown from a small percentage to as high as 30% to 50% in some major imaging centers. This article will review some of the considerations that impact the choice of which pharmacologic agent would be most appropriate for specific clinical presentations or situations. This will involve knowledge of specific contraindications and adverse reactions that may occur, as well as the type of information that would be important to the referring physician. I will review some of the basic physiologic comparisons among the different perfusion agents and compare their diagnostic utility. Finally, a clinical study involving direct comparison of vasodilators in a single population group will be discussed.
Physiologic Comparisons
It is important to understand the basic cardiovascular effects of the different pharmacologic stress agents. They can be divided into two groups: coronary vasodilators and synthetic catecholamines. The former will reduce coronary vascular resistance directly and thereby increase coronary blood flow. In contrast, synthetic catecholamines increase the heart rate and blood pressure, thereby mimicking the effects of dynamic exercise. Both types of agents significantly increase coronary blood From the