Absolute value of the difference of Tl-201 uptake between redistribution and rest is a specific marker of myocardial viability.

Although Tl-201 rest redistribution SPECT is widely used to assess myocardial viability, there is no agreement on the best prognostic marker of left ventricle contraction improvement after revascularization. More recent data suggest that not only rest or redistribution uptake but also reverse redistribution patterns may serve to indicate the viability of myocardium. The aim of this study was to define criteria (which include reversibility and reverse redistribution) for viability testing and prediction of functional outcome in Tl-201 rest redistribution SPECT. Twenty-five patients with left ventricle dyssynergy were studied before and after revascularization with Tl-201 SPECT and echocardiography. Perfusion and contractility was assessed in a 16-segment model of the left ventricle. Out of 400 left ventricular segments, contraction disturbances of various degree of intensity (hypokinesis, akinesis and dyskinesis) were found by echocardiography in 107 segments. Revascularization was performed in 97 segments. In 57% of the segments, improvement of contraction was observed after PTCA or CABG. Perfusion was analysed in the segments between segments with and without contraction improvement. In discriminant analysis, only the modulus of difference between rest and redistribution study > or = 10% was the common parameter for hypo-, a- and dyskinetic segments to predict the functional recovery of left ventricle (LV) with the specificity of 93% and sensitivity of 78%. The modulus of segmental quantitative difference between redistribution and rest image is a new parameter adding specificity to Tl-201 rest redistribution SPECT in prediction of recovery of left ventricle function.