Persistent Shift in Principal Strain Angles and Postsurgical Decline in Left Ventricular Ejection Fraction in Patients With Primary Mitral Regurgitation.

BACKGROUND

The double helical direction of myocardial fibers allows for left ventricular (LV) twist. This led to the hypothesis that principal strain angles determine LV functional recovery after mitral valve repair in patients with primary mitral regurgitation (PMR).

METHODS

Controls (n=52) and patients with PMR with regurgitant volume defined as mild (<30 mL, n=16), moderate (30-50 mL, n=38), and severe (50 mL, n=55) had cardiac magnetic resonance with tissue tagging and 3-dimensional analysis. Fifty-four patients with PMR had presurgery and 6 (n=46), 12 (n=44), and 24 (n=25) month studies. Longitudinal, circumferential, and maximal shortening were computed along with principal strain angles (circumferential, longitudinal, and radial directions) at base, mid, and distal LV levels.

RESULTS

LV ejection fraction did not differ in mild, moderate, and severe PMR with similar increases in mid LV 3-dimensional radius-to-wall thickness and decrease in LV mass to volume and sphericity index versus controls. Radial longitudinal shear strain and LV mid and distal LV circumferential and longitudinal angles increased in all groups with PMR. Postsurgery LV end-diastolic volume, LV end-diastolic mass to volume and 3-dimensional radius-to-wall thickness returned to normal at 6, 12, and 24 months; however, mid LV circumferential, longitudinal, and maximal shortening decreased below normal. LV circumferential and longitudinal angles and LV sphericity index did not change from presurgery whereas LV ejection fraction post surgery correlated with decrease in LV twist at 6, 12, and 24 months.

CONCLUSIONS

Changes in principle strain angles occur early in PMR. The extent to which they persist after surgery may underlie the decrease in LV ejection fraction.