This study demonstrates that assessment of regional and global strain at 1.5 h after reperfusion therapy correlates with size and transmural extent of myocardial infarction as determined by contrast-enhanced MRI. The novel global strain parameter is a valuable predictor of the total extent of myocardial infarction and may therefore be an important clinical tool for risk stratification in the acute phase of myocardial infarction.

Background-Peak

Background-Normal left ventricular myocardium demonstrates distinct spikes in the velocity trace before and after left ventricular ejection. We tested the hypothesis that the preejection and postejection velocity spikes reflect early systolic shortening and late systolic lengthening that are interrupted by mitral and aortic valve closure, respectively. Methods and Results-In 11 anesthetized dogs, timing of valve closure was determined by pressure variables; left ventricular dimensions were determined by sonomicrometry. Myocardial shortening started 20Ϯ10 ms (meanϮSD; PϽ0.001) before mitral valve closure and was interrupted at the time of mitral valve closure (time difference, 4Ϯ7 ms). Similarly, myocardial lengthening started 31Ϯ15 ms (PϽ0.001) before aortic valve closure and was interrupted at the time of aortic valve closure (time difference, 0Ϯ3 ms). Prevention of mitral (nϭ4) and aortic (nϭ4) valve closure by stenting the valves abolished the preejection and postejection velocity spikes, respectively. Echocardiographic measurements of patients (nϭ15) with severe mitral regurgitation showed that the preejection velocity spike was reduced after prosthetic valve replacement (43Ϯ25 versus 32Ϯ15 mm/s; Pϭ0.036), indicating that preejection shortening was larger with a leaking valve. Similarly, late systolic lengthening was reduced in patients (nϭ15) with severe aortic regurgitation after prosthetic valve replacement; minimum postejection velocity spike was increased from Ϫ32Ϯ11 to Ϫ17Ϯ11 mm/s; Pϭ0.0003). Asynchronous onset of contraction/ relaxation and atrioventricular interaction were investigated as alternative mechanisms of the velocity spikes in dogs and patient groups but were found implausible. Conclusions-This