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Reverse Redistribution on Exercise-Redistribution ²⁰¹Tl SPECT in Chronic Ischemic Dysfunction: Predictive of Functional Outcome After Revascularization?

¹ Division of Nuclear Medicine, Cliniques Universitaires St-Luc, Université Catholique de Louvain, Brussels, Belgium
² Division of Cardiology, Cliniques Universitaires St-Luc, Université Catholique de Louvain, Brussels, Belgium
³ Department of Nuclear Medicine, Mont-Godinne University Hospital, Université Catholique de Louvain, Yvoir, Belgium

This study analyzed the incidence and clinical significance of reverse redistribution (RR) on stress-redistribution ²⁰¹Tl 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 ²⁰¹Tl 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 10% decrease in ²⁰¹Tl uptake on the circumferential profiles. The left ventricle was divided in 16 segments for ²⁰¹Tl 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 1 grade, among which 8 (13%) displayed RR on ²⁰¹Tl 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 ²⁰¹Tl uptake of >54%, the accuracy of ²⁰¹Tl 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 ²⁰¹Tl 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.

Key Words: reverse redistribution • stress-redistribution-reinjection ²⁰¹Tl SPECT • chronic left ventricular dysfunction • myocardial viability