Anti-ischemic therapy and myocardial ischemia shown by single photon emission computed tomography imaging.

Shown by Single Photon Emission Computed Tomography Imaging To the Editor: O‘Rourke and colleagues1 describe a case of resolution of stress-induced myocardial ischemia during aggressive medical therapy demonstrated by single photon emission computed tomography (SPECT) imaging. They conclude that a 1-year period of aggressive medical treatment led to this favorable result in a patient, who initially had typical angina pectoris and a 80% mid-left anterior descending coronary artery stenosis. We do not agree with their interpretation, and we think that the effect demonstrated on SPECT imaging can be shown within hours after the administration of effective antianginal therapy with -blockers,2 calcium antagonists, or nitrates.3 Sensitivity for the detection of stress-induced myocardial ischemia by SPECT imaging depends on several factors, including the administration of anti-ischemic medications, non–flow-limiting coronary stenoses, overlap circulation, “balanced” hypoperfusion or hypoperfusion in segments with attenuation, and collateral circulation.4 Antianginal therapy can abolish the effects of pharmacological stress with consecutive “false-negative” SPECT imaging results. Therefore, serial testing using pharmacological stress with dipyridamole or adenosine is not appropriate to assess the adequacy of medical therapy.5