Tc-99m tetrofosmin tomography after nitrate administration in patients with ischemic left ventricular dysfunction: Relation to metabolic imaging by PET

Methods and Results. Thirty-six patients with chronic myocardial infarction and LV dysfunction (ejection fraction, 35% +/- 6%) underwent resting technetium 99m tetrofosmin single photon emission computed tomography (SPECT) imaging under control conditions (baseline) and after sublingual administration of 10 mg isosorbide dinitrate. Within 1 week, all patients underwent metabolic PET imaging with fluorine 18-fluorodeoxyglucose. Tetrofosmin uptake and metabolic activity were measured in 13 segments/patient. Regional LV function was assessed in corresponding segments by echocardiograpby. On baseline tetrofosmin imaging, 53 (40%) of the 131 akinetic or dyskinetic segments had reduced (<55% of peak activity) tracer uptake. Of these segments, 14 (26%) showed enhanced tetrofosmin uptake after nitrate administration ( :10% vs baseline) and the remaining 38 (74%) did not change. The sensitivity and specificity of baseline tetrofosmin SPECT for detecting preserved metabolic activity were 69% and 86%, respectively. After nitrate administration, the sensitivity was higher (81%, P < .05 vs baseline) whereas the specificity was not different (86%, P = not significant). Concordance between tetrofosmin SPECT and PET in differentiating viable and necrotic myocardium was observed in 94 (72%) of the 131 akinetic or dyskinetic segments at baseline (K = 0.35) and in 108 segments (82%) after nitrate administration (K = 0.53).

Background. In patients with ischemic left ventricular (LV) dysfunction, myocardial perfusion imaging after nitrate administration may improve the identification of dysfunctional but viable myocardium. This study was designed to assess the relationship between tetrofosmin uptake after nitrate administration and metabolic activity as assessed by positron emission tomography (PET) in patients with ischemic LV dysfunction.