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

Perfusion scintigraphy provides important information regarding the presenc e of viable tissue after myocardial infarction. Defects of moderate severit y, however, may represent viable myocardium, necrotic tissue or a mixture o f 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 th ose obtained with stress echocardiography (SE). Twenty-five patients with a cute myocardial infarction were studied. Gated SPET myocardial perfusion im aging was performed 60 min after the injection of technetium-99m tetrofosmi n (925 MBq) at rest using a triple-headed camera equipped with focussing co llimators (Cardiofocal). Two consecutive acquisitions were performed accord ing to a "fast" gated SPET protocol (3x20 stops, 9 s/stop, 64x64 pixel matr ix, 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 mu g kg(-1) min(-1) dobutamine. The severity of regional dy sfunction, wall thickening severity (WTsev), was assessed and quantified us ing a method based on circumferential profile analysis. SE was performed at rest and during infusion of 5 and 10 mu g kg(-1) min(-1) dobutamine. Two p atients could not be analysed because of disturbing gastro-intestinal activ ity on the perfusion study. Under dobutamine 11 patients presented a signif icant change in WTsev (three showed normalisation, five an improvement and three a deterioration), while in 12 patients the WTsev score remained uncha nged. The overall concordance between LDD gated SPET and SE was 83%. In pat ients with per fusion defects of moderate severity the concordance was 90% (9/10). It may be concluded that functional changes in infarcted areas indu ced by dobutamine can be detected with gated SPET. Good agreement was obser ved between LDD gated SPET and SE for the identification of inotropic reser ve in infarcted areas.