Low-dose dobutamine gated single-photon emission tomography: comparison with stress echocardiography

Abstract.

Perfusion scintigraphy provides important information regarding the presence of viable tissue after myocardial infarction. Defects of moderate severity, however, may represent viable myocardium, necrotic tissue or a mixture of both. In this study the presence or absence of inotropic response in the infarcted area was assessed by low-dose dobutamine tetrofosmin gated single-photon emission tomography (LDD gated SPET). Results were compared with those obtained with stress echocardiography (SE). Twenty-five patients with acute myocardial infarction were studied. Gated SPET myocardial perfusion imaging was performed 60 min after the injection of technetium-99m tetrofosmin (925 MBq) at rest using a triple-headed camera equipped with focussing collimators (Cardiofocal). Two consecutive acquisitions were performed according to a ”fast” gated SPET protocol (3×20 stops, 9 s/stop, 64×64 pixel matrix, zoom 1.23) with the subjects remaining in the same position. The first acquisition was obtained at rest; the second acquisition was obtained under infusion of 10 µg kg^–1 min^–1 dobutamine. The severity of regional dysfunction, wall thickening severity (WT_sev), was assessed and quantified using a method based on circumferential profile analysis. SE was performed at rest and during infusion of 5 and 10 µg kg^–1 min^–1 dobutamine. Two patients could not be analysed because of disturbing gastro-intestinal activity on the perfusion study. Under dobutamine 11 patients presented a significant change in WT_sev (three showed normalisation, five an improvement and three a deterioration), while in 12 patients the WT_sev score remained unchanged. The overall concordance between LDD gated SPET and SE was 83%. In patients with perfusion defects of moderate severity the concordance was 90% (9/10). It may be concluded that functional changes in infarcted areas induced by dobutamine can be detected with gated SPET. Good agreement was observed between LDD gated SPET and SE for the identification of inotropic reserve in infarcted areas.