# Mechanism of Myocardial Fibrosis Induced by Mitral Valve Prolapse

> **NIH NIH R01** · MASSACHUSETTS GENERAL HOSPITAL · 2024 · $1,862,169

## Abstract

Mitral valve prolapse (MVP) affects 1 in 40 individuals and is complicated in 30-35% by ventricular arrhythmias
that increase risk for sudden cardiac death (SCD). Such arrhythmias are strongly associated with left ventricular
(LV) myocardial fibrosis, primarily localized to regions physically connected with the prolapsing valve. The
mechanism of such fibrosis is currently unknown and studies are limited by lack of an available model. Most
(80%) of patients with malignant ventricular arrhythmias and SCD have only mild to moderate MR lacking surgical
indications, a major gap in treatment and clinical guidelines. Recent publications from our group and others link
abnormal mechanics of the papillary muscle (PM) and inferobasal LV with co-localized fibrosis and risk of
arrhythmias. These data support the central hypothesis that MVP causes tension-induced LV fibrosis
leading to arrhythmic events. To test this, we have developed a surgical MVP model in sheep that uniquely
isolates the mechanical stimulus and consistently produced regional fibrosis in six previously normal hearts over
six months. We will probe mechanistic links between altered biomechanics, fibrosis, and arrhythmia in MVP.
Aim 1 hypothesis: MVP-induced forces on the subvalvular apparatus cause regionalized LV fibrosis. Ex
vivo, we confirmed increased systolic forces on the PMs in MVP that will be quantified with MVP in vivo.
Progression of fibrosis will be quantified in this model over 3, 6 and 9 months along with serial longitudinal
advanced parametric CMR imaging as used in patients. Controls will include comparable primary MR without
MVP (no fibrosis in 2 6-month pilots), sham surgery and normal hearts. This aim will link MVP-altered mechanical
forces to LV structural changes as a function of time. Aim 2 hypothesis: Increased stress activates a pro-
fibrogenic molecular switch through mechano-responsive signaling pathways. Our preliminary in vitro data
show that stretch alters purinergic-ATP signaling and increases collagen deposition. In MVP sheep tissues and
stretched cardiac fibroblasts, changes in stressed LV regions and cells will be identified at the single-cell level
that will test this and alternative mechanisms to reveal mechanically-induced cellular and molecular changes. In
sheep, we will compare valve-stressed and remote regions over time with those from normal and MR-only LVs;
and cross-reference changes in existing surgical biopsies from 40 patients with fibrotic and nonfibrotic zones.
This aim will link MVP-increased tension to regional fibrogenesis. Aim 3 will explore the hypothesis that MVP-
induced fibrosis predisposes to ventricular arrhythmias. In the MVP model and controls, rhythm will be
monitored and PM endocardial electrograms recorded invasively at baseline and with isoproterenol, measuring
repolarization markers of electrical instability and arrhythmic predisposition. This aim will link pathologic and
molecular findings from MVP-induced fibrosis to arrhythmic...

## Key facts

- **NIH application ID:** 10890967
- **Project number:** 1R01HL173930-01
- **Recipient organization:** MASSACHUSETTS GENERAL HOSPITAL
- **Principal Investigator:** ROBERT A LEVINE
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $1,862,169
- **Award type:** 1
- **Project period:** 2024-09-05 → 2028-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10890967

## Citation

> US National Institutes of Health, RePORTER application 10890967, Mechanism of Myocardial Fibrosis Induced by Mitral Valve Prolapse (1R01HL173930-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10890967. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*