Interstitial Fibrosis and Arrhythmic Mitral Valve Prolapse: Unravelling Sex-Based Differences
Background:
Interstitial fibrosis as quantified by cardiac magnetic resonance (CMR) has been demonstrated in arrhythmic mitral valve prolapse (MVP), a condition with known female predominance. However, prior studies included only MVP cases with significant mitral regurgitation (MR) or mitral annular disjunction (MAD). We sought to evaluate the association between interstitial fibrosis and complex ventricular ectopy (ComVE) in MVPs unselected for MAD or severe MR, and to investigate the contribution of sex to this association.
Methods:
We performed contrast CMR in consecutive individuals with MVP between 2020 and 2022. Extracellular volume fraction (ECV%), a surrogate marker for interstitial fibrosis, was quantified using T 1 mapping. Replacement fibrosis was assessed using late gadolinium enhancement (LGE). ComVE, defined as frequent premature ventricular contractions and/or non-sustained/sustained ventricular tachycardia (VT), was detected using ambulatory ECG monitoring.
Results:
We identified 59 MVP cases without severe MR (49% women, 80% with mild or less MR) and available ECV% measurement. Among these, 23 (39%) had ComVE, including a case of aborted ventricular fibrillation (VF) and one with sudden arrhythmic death, both females. Global ECV% was significantly greater in ComVE versus non-ComVE (31%[27-33] vs 27%[23-30], p=0.002). In MVP-ComVE, higher segmental ECV% was not limited to the inferolateral/inferior LV wall, but was also demonstrated in atypical segments including the anterior/anterolateral wall (p<0.05). The association between ComVE and ECV% was driven by female sex (32%[30-33] vs 28%[26-30], p=0.003 in females; 31%[25-33] vs 26%[23-30], p=0.22 in males). ECV% remained independently associated with an increased risk of ComVE, including VT/VF, after adjustment for cardiovascular risk factors, MAD, and LGE (p<0.01).
Conclusion:
In MVP without significant MR, interstitial fibrosis by CMR is associated with an increased risk of ComVE, suggesting a primary myopathic process. The stronger association between interstitial fibrosis and ComVE in females may explain why severe arrhythmic complications are more prevalent among women.
Insights
Interstitial fibrosis detected by cardiac MRI is linked to ventricular arrhythmias in mitral valve prolapse (MVP). This association is stronger in women, potentially explaining higher rates of severe arrhythmias in females with MVP.
Area of Science:
- Cardiology
- Medical Imaging
- Pathology
Background:
- Mitral valve prolapse (MVP) is associated with arrhythmias, particularly in women.
- Previous studies on interstitial fibrosis in MVP focused on cases with significant mitral regurgitation or mitral annular disjunction.
- The current study investigates interstitial fibrosis and complex ventricular ectopy (ComVE) in a broader MVP population.
Approach:
- Contrast cardiac magnetic resonance (CMR) was used to assess interstitial fibrosis via extracellular volume fraction (ECV%) and late gadolinium enhancement (LGE).
- ComVE was identified using ambulatory ECG monitoring.
- The study included 59 MVP cases unselected for mitral regurgitation severity or mitral annular disjunction.
Key Points:
- Interstitial fibrosis (higher ECV%) was significantly associated with ComVE in MVP patients.
- The association between fibrosis and ComVE was predominantly observed in female patients.
- Higher segmental ECV% was found in various LV segments, not just the typical inferolateral/inferior walls.
Conclusions:
- Cardiac MRI-quantified interstitial fibrosis is linked to an increased risk of ComVE in MVP patients without significant mitral regurgitation.
- The findings suggest a primary myopathic process contributing to arrhythmias in MVP.
- The stronger association in females may explain the higher prevalence of severe arrhythmic complications in women with MVP.
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