What is the clinical evidence from this study?

Study design: Observational. Population: Mitral valve prolapse (MVP) with mitral annular disjunction (MAD) (n=54). Intervention: Mitral valve prolapse with mitral annular disjunction (MVP-MAD) vs. Mitral regurgitation without MAD (MR-NoMAD) and normal CMR (NoMR-NoMAD). Primary outcome: Basal segments myocardial extracellular volume (ECVsyn) (p=<0.001).

March 1, 2021Open Access

Myocardial extracellular volume by T1 mapping: a new marker of arrhythmia in mitral valve prolapse

Q: What are the key findings of this study?

Patients with mitral valve prolapse and mitral annular disjunction had significantly higher myocardial extracellular volume compared to controls (30% vs 24%, p<0.001), indicating increased interstitial fibrosis.

Key Result

Patients with mitral valve prolapse and mitral annular disjunction had significantly higher myocardial extracellular volume compared to controls (30% vs 24%, p<0.001), indicating increased interstitial fibrosis.

Study Design

Type

Observational (n=54)

Multicenter

Structured PICO

Does myocardial extracellular volume (ECVsyn) by T1 mapping correlate with mitral annular disjunction severity and identify arrhythmic risk in patients with mitral valve prolapse?

Population

54 patients, including 30 with bileaflet mitral valve prolapse and mitral annular disjunction (MVP-MAD), 14 with mitral regurgitation but no MAD (MR-NoMAD), and 10 with normal CMR (NoMR-NoMAD). Mean age 50, 43% female.

Intervention

Cardiovascular magnetic resonance (CMR) with assessment of MAD length, late gadolinium enhancement (LGE), and basal segments myocardial extracellular volume (ECVsyn) by T1 mapping

Comparator

Patients with mitral regurgitation but no MAD (MR-NoMAD) and patients with normal CMR (NoMR-NoMAD)

Outcome

Relationship between MAD severity and myocardial interstitial fibrosis (ECVsyn) at the LV base, and association between severity of interstitial fibrosis and occurrence of ventricular arrhythmic events (OHCA)surrogate

Myocardial extracellular volume (ECVsyn) by T1 mapping is increased in patients with mitral valve prolapse and mitral annular disjunction, correlating with disjunction length and identifying patients at high risk for out-of-hospital cardiac arrest even without late gadolinium enhancement.

Main Result

Absolute Event Rate: 30% vs 24%

p-value: p=<0.001

Limitations

Observational, retrospective study with a limited number of patients.
Likely selection bias toward higher arrhythmic risk.
Routine evaluation of fibrosis in the papillary muscles area was not part of the analysis.
Mitral regurgitation severity was not systematically evaluated during CMR examinations.
No histologic confirmation of interstitial or replacement fibrosis could be obtained.
Patients underwent CMR examination in two different scanners.

Abstract

OBJECTIVES: We aimed to evaluate the relationship between mitral annular disjunction (MAD) severity and myocardial interstitial fibrosis at the left ventricular (LV) base in patients with mitral valve prolapse (MVP), and to assess the association between severity of interstitial fibrosis and the occurrence of ventricular arrhythmic events. BACKGROUND: In MVP, MAD has been associated with myocardial replacement fibrosis and arrhythmia, but the importance of interstitial fibrosis remains unknown. METHODS: In this retrospective study, 30 patients with MVP and MAD (MVP-MAD) underwent cardiovascular magnetic resonance (CMR) with assessment of MAD length, late gadolinium enhancement (LGE), and basal segments myocardial extracellular volume (ECVsyn). The control group included 14 patients with mitral regurgitation (MR) but no MAD (MR-NoMAD) and 10 patients with normal CMR (NoMR-NoMAD). Fifteen MVP-MAD patients underwent 24 h-Holter monitoring. RESULTS: LGE was observed in 47% of MVP-MAD patients and was absent in all controls. ECVsyn was higher in MVP-MAD (30 ± 3% vs 24 ± 3% MR-NoMAD, p < 0.001 and vs 24 ± 2% NoMR-NoMAD, p < 0.001), even in MVP-MAD patients without LGE (29 ± 3% vs 24 ± 3%, p < 0.001 and vs 24 ± 2%, p < 0.001, respectively). MAD length correlated with ECVsyn (rho = 0.61, p < 0.001), but not with LGE extent. Four patients had history of out-of-hospital cardiac arrest; LGE and ECVsyn were equally performant to identify those high-risk patients, area under the receiver operating characteristic (ROC) curve 0.81 vs 0.83, p = 0.84). Among patients with Holter, 87% had complex ventricular arrhythmia. ECVsyn was above the cut-off value in all while only 53% had LGE. CONCLUSION: Increase in ECVsyn, a marker of interstitial fibrosis, occurs in MVP-MAD even in the absence of LGE, and was correlated with MAD length and increased risk of out-of-hospital cardiac arrest. ECV should be includedin the CMR examination of MVP patients in an effort to better assess fibrous remodelling as it may provide additional value beyond the assessment of LGE in the arrhythmic risk stratification.

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