Abstract 2016: Myocardial Internal Strain Fraction Predicts Volume Response in Patients with Cardiac Resynchronization Therapy
Background: Reduction of left ventricular (LV) end-systolic volume (ESV), “reverse remodeling”, is regarded as a relevant and objective improvement by cardiac resynchronization therapy (CRT), but prediction of reverse remodeling is still problematic. We investigated whether a high internal strain fraction (ISF, reflecting the part of total systolic strain that is lost internally due to simultaneous stretch and shortening due to dyssynchrony) predicts reverse remodeling.
Methods: MRI tagging images were acquired in CRT candidates with Ischemic (ICM, n=9) and Dilated Cardiomyopathy (DCM, n=11) and in healthy volunteers (C, n=9). From circumferential strain tracings in 160 LV regions mechanical activation time (Mact) was determined as the delay between 20 and 90 percentile of time to first peak of shortening and ISF as the amount of stretch divided by the amount of shortening. Acute hemodynamic effect of CRT was determined from the %change in LV dP/dtmax.
Results: The figure⇓ shows tracings of strain in 160 regions in a DCM and an ICM heart, positive strains indicating stretch. ISF was significantly larger in DCM than in ICM (58±22% vs. 30±19%) while ISF was almost absent in C: 2±1%. Six months of CRT increased ejection fraction (by 9.8±6.2%) and decreased LVESV in DCM (by 30±15%, both p<0.05), but not in ICM (1.2±6.3% and 5±12%, respectively). Mact was equally increased in ICM and DCM (300±65ms and 290±45ms) as compared to C (120±30ms). Also, %increase in LVdP/dtmax upon CRT was similar in ICM and DCM (30±15% and 27±13%, respectively).
Conclusions: Internal strain fraction reveals new functional properties of the LV wall and may improve predicting outcome of CRT.