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Abnormal Systolic Strain Overestimates Myocardial Non-Viability In Patients With Ischemic Mitral Regurgitation
Ashley E. Morgan1, Yue Zhang2, Mehrzad Tartibi2, Samantha Goldburg3, Jiwon J. Kim3, Thanh D. Nguyen3, Liang Ge2, Jonathan W. Weinsaft3, Mark B. Ratcliffe4.
1UCSF East Bay, Oakland, CA, USA, 2Northern California Institute for Research and Education, San Francisco, CA, USA, 3Weill-Cornell Medical College, New York, NY, USA, 4San Francisco VA Medical Center, San Francisco, CA, USA.

Objective: Ischemic mitral regurgitation (IMR) recurs in 32% of patients after mitral repair, due to continued left ventricular (LV) remodeling and leaflet tethering. Accurate measurement of predictors of remodeling, including myocardial viability, is therefore critically important. Abnormal LV strain (hypo and a-kinesis) may be a surrogate for viability, but this has not been validated in patients with IMR. We compared abnormal systolic strain with viability measured with late gadolinium enhancement (LGE) MRI to test the hypothesis that abnormal strain overestimates the number of non-viable LV segments. Methods: Nine patients with >mild IMR (average severity moderate) on echocardiography were prospectively enrolled. Cardiac MRI with CINE, LGE, regadenoson stress perfusion, and tagged strain (CSPAMM) sequences was performed. Each LV was divided into 17 AHA segments, for a total of 153 segments analyzed. Ischemia and infarction (stress perfusion and LGE) were visually scored by a cardiologist with expertise in cardiac MRI. End-systolic circumferential strain was analyzed with custom software [Figure 1]. Strain > -9 was set as the cutoff for abnormal segments, based on published values from normal patients. Strain and LGE were compared segmentally using paired t-tests; p<0.05 was considered significant. Results: In non-viable segments (transmural infarction on LGE), average strain was -0.27, compared to -9.3 in viable segments, p<0.01. Strain was abnormal in 13/15 non-viable segments (86%). However, 55/137 (40%) of viable segments also had strain >-9, predominantly due to stress ischemia (40/55, 73%). In viable but ischemic segments, average strain was -8.9, compared to -11.1 in viable well-perfused segments, p = .02. Of viable segments, 19% were severely hypokinetic (strain >-5), and 6% were akinetic (strain >-1). Conclusions: End-systolic strain overestimates the number of non-viable myocardial segments when compared to the validated measure of transmural infarction on LGE MRI. Viable myocardium manifests abnormal end-systolic strain in the presence of stress ischemia. Further studies will investigate reverse remodeling after reperfusion in these patients, with the goal of developing a predictive model for successful treatment of IMR.


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