Quantification of Left Ventricular Interstitial Fibrosis in Asymptomatic Chronic Primary Degenerative Mitral Regurgitation
Background—The optimum timing of surgery in asymptomatic patients with chronic severe primary degenerative mitral regurgitation (MR) remains controversial and further markers are needed to improve decision-making. There are limited data that wall stress is increased in MR and may result in ventricular fibrosis. We investigated the hypothesis that chronic volume overload in MR is a stimulus for myocardial fibrosis using T1-mapping CMR.
Methods and Results—A cross-sectional study of 35 patients (age 60 ± 14 years) with asymptomatic moderate and severe primary degenerative MR (mean EROA 0.45 ± 0.25cm2) with no class I indication for surgery were compared to age and gender controls. Subjects were studied with cardiopulmonary exercise testing, echocardiography and cardiac MRI. Longitudinal and circumferential myocardial deformation was reduced with MR, when LV ejection fraction (EF) (67 ± 10%) and NT pro-BNP (126 [76-428] ng/L) were within the normal range. Myocardial extracellular volume (ECV) was increased (0.32 ± 0.07 vs. 0.25 ± 0.02, p<0.01) and was associated with increased LV end-systolic volume index (LVESVi r = 0.62, p<0.01), left atrial volume (LAVi r = 0.41, p<0.05) but lower LV ejection fraction (LVEF r = -0.60, p<0.01), longitudinal function (MAPSE r = -0.46, p<0.01), and peak VO2 max (-0.51, p<0.05). In a multivariable regression model LVESVi and LAVi were independent predictors of ECV (r2 = 0.42, p<0.01).
Conclusions—Patients with asymptomatic MR demonstrate a spectrum of myocardial fibrosis associated with reduced myocardial deformation and reduced exercise capacity. Future work is warranted to investigate whether LV fibrosis affects clinical outcomes.
- extracellular volume
- mitral valve regurgitation
- cardiovascular magnetic resonance imaging
- myocardial fibrosis
- Received May 2, 2014.
- Accepted August 11, 2014.