Cyclic variation in myocardial gray level as a marker of viability in man: A videodensitometric study

Abstract

Experimental and human studies have shown that a preserved cyclic (diastolic-to-systolic) echoreflectivity variation, assessed by radiofrequency sampling of backscatter signal with non-commercially available prototypes, identifies viability in a myocardial segment with a resting dyssynergy. The objective of this study was to assess whether a videodensitometric analysis of myocardial gray level variation during cardiac cycle might identify viable but dyssynergic myocardium in a clinical setting. Thirty-four patients with a resting dyssynergy (akinesis in 26, marked hypokinesis in eight) in the septum and/or infero-posterior wall were evaluated by videodensitometry. All echo studies were performed with commercially available instruments in the long axis parasternal view, with quantitative analysis of gray levels performed off-line on digitized images. Segmental wall motion was assessed with a 16 segment model of the left ventricle, each scored from 1, normal, to 4, dyskinetic. A follow-up echo study was obtained in all patients > 4 weeks after successful revascularization (in 22 by angioplasty, in 12 by bypass surgery). Two groups of segments were identified: 18 viable segments (contractile improvement of 1 grade or more in resting function after revascularization); 16 necrotic segments (no contractile improvement in resting function after revascularization). The % cyclic variation was higher in viable vs necrotic segments (26 ± 16 vs 1 ± 13%, P < 0.01), in spite of similar % systolic thickening (5 ± 5 vs 4 ± 6%, P = ns) and end-diastolic thickness (10 ± 2 vs 10 ± 2 mm, P = ns). When individual patient analysis was performed, % cyclic variation was below the 95% confidence limits obtained from normal control regions (n = 34; % cyclic variation = 38 ± 14) in two out of 18 viable and in 14 out of 16 necrotic segments. A cut-off of ≥ 9.4% cyclic variations in a dyssynergic segment yielded 89% sensitivity and 88% specificity for predicting functional recovery following successful revascularization. In conclusion, viable dyssynergic myocardial segments show a cyclic gray level variation at rest, which can be detected by simple videodensitometric analysis, much less technologically demanding than radiofrequency backscatter evaluation.