Relationship between native papillary muscle T1 time and severity of functional mitral regurgitation in patients with non-ischemic dilated cardiomyopathy

Background: Functional mitral regurgitation is one of the severe complications of non-ischemic dilated cardiomyopathy (DCM). Non-contrast native T-1 mapping has emerged as a non-invasive method to evaluate myocardial fibrosis. We sought to evaluate the potential relationship between papillary muscle T-1 time and mitral regurgitation in DCM patients. Methods: Forty DCM patients (55 +/- 13 years) and 20 healthy adult control subjects (54 +/- 13 years) were studied. Native T-1 mapping was performed using a slice interleaved T-1 mapping sequence (STONE) which enables acquisition of 5 slices in the short-axis plane within a 90 s free-breathing scan. We measured papillary muscle diameter, length and shortening. DCM patients were allocated into 2 groups based on the presence or absence of functional mitral regurgitation. Results: Papillary muscle T-1 time was significantly elevated in DCM patients with mitral regurgitation (n = 22) in comparison to those without mitral regurgitation (n = 18) (anterior papillary muscle: 1127 +/- 36 msec vs 1063 +/- 16 msec, p < 0.05; posterior papillary muscle: 1124 +/- 30 msec vs 1062 +/- 19 msec, p < 0.05), but LV T-1 time was similar (1129 +/- 38 msec vs 1134 +/- 58 msec, p = 0.93). Multivariate linear regression analysis showed that papillary muscle native T-1 time (beta = 0.10, 95 % CI: 0.05-0.17, p < 0.05) is significantly correlated with mitral regurgitant fraction. Elevated papillary muscle T-1 time was associated with larger diameter, longer length and decreased papillary muscle shortening (all p values < 0.05). Conclusions: In DCM, papillary muscle native T-1 time is significantly elevated and related to mitral regurgitant fraction.