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Variability of myocardial perfusion defects assessed by thallium-201 scintigraphy in patients with coronary artery disease not amenable to angioplasty or bypass surgery

Daniel Burkhoff, MD, PhD^*, James W. Jones, MD, PhD and Lewis C. Becker, MD, FACC

^* Department of Medicine, Columbia University, New York City, New York, USA
Department of Surgery, University of Missouri, Columbia, Missouri, USA
Department of Medicine, The Johns Hopkins University, Baltimore, Maryland, USA

View larger version (18K): [in a new window]   Figure 1 Variability of test results was quantified by the variability index (VI), which was the mean value of the absolute change from baseline percent myocardial ischemia.

View larger version (20K): [in a new window]   Figure 2 (A) Scattergram showing baseline versus three-month percent ischemia for 60 subjects in the ATLANTIC study; solid line = line of regression; dashed line = line of identity. (B) Change in percent ischemia between baseline and three months as a function of baseline percent myocardial ischemia for the same subjects. The points scattered approximately equally above and below the horizontal line of 0 change with large variability. The dashed line shows the maximal possible reduction in ischemia for a given baseline value. See text for further details.

View larger version (44K): [in a new window]   Figure 3 Mean percent myocardial ischemia at baseline and follow-up at specified times (paired analysis) and mean absolute change in perfusion. Although it is evident that the mean change in perfusion is negligible at each time, the mean absolute change in perfusion amounts to 50% of the baseline value. Mean values ± SD are shown.

View larger version (15K): [in a new window]   Figure 4 Examples of percent myocardium with fixed and reversible perfusion defects, which varies as a function of time in medically treated subjects. (A) A subject with a variability index (VI) of 9.5 (refer to the equation in Methods), approximately equal to mean VI for the entire group of subjects. (B) A subject with a VI of 5.0, significantly less than the mean VI for the group. (C) A subject with a VI of 20, significantly greater than the mean VI for the group. Note that dramatic improvements (complete resolution) in the amount of ischemia were observed sometimes.

View larger version (27K): [in a new window]   Figure 5 (A) Results (mean ± SD) stratified according to percent baseline ischemia. Test variability, indexed by variability index (VI) (refer to the equation in Methods) increases as baseline ischemia increases, so that VI as a proportion of baseline ischemia decreases. (B) Baseline and 12-month follow-up thallium results from subjects who had transmyocardial laser revascularization (TMR) in the ATLANTIC study, stratified according to percent baseline ischemia. Although the data in B suggest TMR may improve myocardial perfusion in subjects with a greater amount of baseline ischemia, data from the ATLANTIC subjects in the continued maximal anti-anginal therapy (MEDs)-only group (C) exhibit the same trends. This suggests a "regression to the mean" phenomenon, as discussed in the text. The p values were derived from paired t tests.