Assessment of perfusion, function, and myocardial metabolism after infarction with a combination of low-dose dobutamine tetrofosmin gated SPECT perfusion scintigraphy and BMIPP SPECT imaging

Background, Tetrofosmin gated single photon emission computed tomography (S PECT) allows simultaneous assessment of regional myocardial perfusion, glob al and regional left ventricular function, and function at rest and during pharmacologic intervention, SPECT with fatty acid analogues, such as beta-m ethyl-iodophenyl-pentadecanoic acid (BMIPP), can be used to monitor metabol ic changes induced by myocardial ischemia. In this work, the results of bot h studies obtained in patients with recent myocardial infarction are integr ated. Methods. Twenty patients underwent tetrofosmin and BMIPP scintigraphy with a 3-head camera. Two consecutive tetrofosmin gated SPECT acquisitions were performed 60 minutes after administration of technetium-99m tetrofosmin (92 5 MBq) at rest (3 x 20 stops of 9 s; matrix 64 x 64 over 360 degrees. One a cquisition was made at rest, and the second was made during dobutamine infu sion (10 mu g/kg/min). Regional functional abnormalities were quantified an d expressed as wall thickening severity (WTsev) in arbitrary units. Left ve ntricular ejection fraction and volumes were assessed with the Cedars Sinai algorithm. BMIPP imaging started 20 minutes after iodine 123-BMIPP (150 MB q) administration at rest (3 x 32 stops of 60 s; matrix 64 x 64 over 360 de grees; medium energy collimators). Tracer uptake was scored according to a 25-segment model. Results. Sixteen of 18 patients had regional functional abnormalities at ba seline (average WTsev 13.7 units). The WTsev score at baseline correlated w ell with the degree of residual perfusion. During dobutamine infusion, WTse v did not change (from 23.4 to 23.6 units) in 5 patients; it decreased (fro m 16.1 to 5.9 units) in 11 patients; and it increased (from 13.0 to 22.3 un its) in 3 patients. An increase or decrease in WTsev during dobutamine infu sion was associated with the presence of a considerable amount of BMIPP mis matched myocardium, whereas no change in WTsev was preferentially associate d with a BMIPP matched pattern and perfusion defects with a higher severity score. Conclusion. Immediately after infarction, the severity of regional dysfunct ion at rest correlated well with the perfusion defect severity, Improvement in regional function during dobutamine administration is associated with l ess severe perfusion defects and a considerable amount of BMIPP mismatched myocardium, both suggesting viability.