Reverse redistribution on exercise-redistribution (201)Tl SPECT in chronic ischemic dysfunction: predictive of functional outcome after revascularization?

UNLABELLED

This study analyzed the incidence and clinical significance of reverse redistribution (RR) on stress-redistribution (201)Tl SPECT studies in patients with poor left ventricular function and tested the hypothesis that the RR phenomenon could be caused by artifacts.

METHODS

Seventy-three consecutive patients with chronic coronary artery disease and left ventricular dysfunction (ejection fraction, 36% +/- 12%) who underwent exercise-redistribution-reinjection (201)Tl SPECT before myocardial revascularization were included. Recovery of left ventricular systolic function was assessed with 2-dimensional echocardiography performed before and 5.5 +/- 2.5 mo after revascularization. RR was determined visually and confirmed quantitatively as a > or = 10% decrease in (201)Tl uptake on the circumferential profiles. The left ventricle was divided in 16 segments for (201)Tl uptake and wall motion analyses.

RESULTS

RR was present in 39 of 1,168 segments (3.3%) and in 18 of 73 patients (25%). Before revascularization, regional wall motion was normal in 26 of 39 RR segments (67%), hypokinetic in 7 of 39 (18%), and akinetic in 6 of 39 (15%). Eight percent of all dysfunctional segments (13/167) of RR patients presented RR. After revascularization, 60 of 167 dysfunctional segments (36%) improved function by > or = 1 grade, among which 8 (13%) displayed RR on (201)Tl SPECT before revascularization. Segments with RR improved function more frequently than those without RR (62% vs. 34%; P = 0.05). Using a threshold for segmental (201)Tl uptake of >54%, the accuracy of (201)Tl reinjection to detect functional improvement in RR segments after revascularization was 77% (10/13). Artifactually induced RR was also excluded in all but 1 case because no increased activity of the pixel used for normalization could be found on redistribution images relative to that of the stress images.

CONCLUSION

These data suggest that in patients with chronic left ventricular ischemic dysfunction, RR on exercise-redistribution (201)Tl SPECT is not an artifact and occurs rarely in normally functioning and in dysfunctional myocardium. In the latter, RR is frequently associated with myocardial viability as shown by functional recovery after revascularization. However, the presence or absence of RR in dysfunctional segments seems to be of little clinical relevance.