Relationship between native papillary muscle T(1) 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 (β = 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.