Aim: To compare the predictive value of thallium-201 single photon emission computed tomography (SPECT) scintigraphy (Sci) and low-dose dobutamine echocardiography (Dob) in predicting late recovery of dysfunctioning myocardium in patients with recent, uncomplicated myocardial infarction (MI).
Methods and results: 19 patients (18 male, aged 58+/-8 years) with recent MI and ejection fraction <50% (35.5+/-8.3%) underwent 5-15 microg/kg per min Dob, rest-redistribution Sci and coronary angiography, respectively, 14+/-6, 16+/-7 and 17+/-5 days after MI. On an eleven-segment ventricular model devised to compare Dob and Sci segment by segment, each dysfunctioning ventricular segment was considered viable if it showed recovery of mechanical function at the echocardiographic follow-up, performed 6.3+/-1.5 months after revascularization (five PTCA, five GABG) or medical therapy. Among the 104 dysfunctioning segments, of which 26 (25%) showed recovery at follow-up, Dob and Sci gave a concordant response in 50 (48%, k = 0.13), correctly predicting the recovery (or not) of function in 42. Forty-two of 54 discordant responses were due to segments judged viable only by Sci and which had no recovery at follow-up (of these 37 were akinetic or severely hypokinetic at baseline). At the segment-by-segment analysis, the sensitivity, specificity, and accuracy in predicting recovery of function at follow-up were, respectively, 69, 88 and 84% for Dob as against 88, 36 and 49% for Sci (P<0.001 for both specificity and accuracy, P=NS for sensitivity).
Conclusion: In patients with recent MI, the specificity of Dob in the detection of myocardium capable of late mechanical recovery is significantly higher with respect to Sci, whereas sensitivity is slightly, not significantly higher for the latter. It is conceivable that Sci detects viable myocardium even if it is transmurally limited to epicardial layers in segments with severely impaired mechanical function in which viability will not affect late recovery of function.