Exercise Echocardiography vs Exercise SPECT Testing

To the Editor: Dr Fleischmann and colleagues¹ review selected literature to compare the diagnostic performance of exercise echocardiography (ECHO) and single-photon emission computed tomography (SPECT) in the diagnosis of coronary artery disease (CAD). However, of the 44 listed articles, the 6 directly comparing exercise ECHO and exercise SPECT were published prior to 1995. Articles appearing in the literature since then are not discussed. O'Keefe et al,² in their review of more than 75 published studies involving more than 7000 patients, also compared noninvasive cardiac exercise imaging modalities. They found that exercise SPECT was more sensitive than exercise ECHO for detecting CAD, localizing it to the proper artery distribution and correctly identifying the presence of multivessel CAD. The use of pharmacological stress agents, including adenosine, dipyridamole, and dobutamine, provided similar diagnostic accuracy in conjunction with SPECT scintigraphy and were all more accurate then dobutamine ECHO. They also found that clinical specificity was comparably high with adenosine SPECT, dipyridamole ECHO, and exercise ECHO. A review by Bonow³ stresses that SPECT provides greater sensitivity in detecting the presence and severity of physiologically significant CAD and the identification of dysfunctional, but viable, myocardium.