Which pharmacological stress is optimal? A technique-dependent choice.

Reasons for using pharmacological stress as a substitute for physical exercise may vary. In the nuclear cardiology laboratory, patients generally perform physical exercise on treadmill or bicycle. Pharmacological stress is used in selected patients who are incapable of performing adequate physical exercise because of orthopedic, neurologic, peripheral vascular, or other medical problems.1 On the other hand, in the echocardiography laboratory, the performance of physical exercise in conjunction with two-dimensional echocardiography is a challenging task, and an alternative mode of nonphysical stress may be preferred in most patients.2.3 The first pharmaceutical to be employed for simulating cardiac stress was intravenously administered dipyridamole.4 Dipyridamole has been used in combination with Tl scintigraphy for more than a decade. Recently, new agents for pharmacological stress have been introduced -adenosines and dobutamine.6,7 The technology of radionuclide imaging and echocardiography has evolved considerably in recent years. Although planar radionuclide imaging remains an adequate imaging modality, single-photon emission computerized tomography (SPECT), which enables more precise detection of disease in specific coronary arteries, is now used widely. The new 9'9Tc-labeled imaging agents, such as Sestamibi, now ensure consistently goodquality SPECT images.8,9 Similar to radionuclide images, echocardiographic images are now often acquired on dedicated minicomputers. Selected digitized cardiac cycles can be displayed as an endless loop, analogous to cine display of radionuclide ventriculography, for analysis of regional wall motion. Because of considerable technical difficulties with physical exercise on supine bicycle, stress two-dimensional echocardiography is increasingly per-