Prevalence, Genetics, and Imaging Characteristics of Patients with Mitral Valve Prolapse and Arrhythmogenic Right Ventricular Cardiomyopathy

This study reveals that mitral valve prolapse (MVP) is prevalent in 14% of arrhythmogenic right ventricular cardiomyopathy (ARVC) patients, is strongly associated with *PKP2* mutations, and presents with distinct features such as increased left ventricular mass and wall motion abnormalities rather than the typical arrhythmic MVP characteristics like annular disjunction.

The Gist

Imagine the heart as a busy, two-room house. The Right Ventricular Cardiomyopathy (ARVC) part of this study is like a problem with the foundation and walls of the right room. Over time, the strong muscle walls of this room get replaced by fatty, scar-like tissue, making the room weak and prone to electrical short-circuits (arrhythmias) that can stop the heart.

Mitral Valve Prolapse (MVP) is like a faulty door in the left room. The door (the valve) doesn't close tightly; instead, it flops backward a little bit when the house is pressurized. Usually, doctors think of this as a minor issue, but sometimes it can also cause electrical storms.

This paper asks a simple question: What happens when a patient has both a shaky foundation in the right room AND a floppy door in the left room?

Here is what the researchers found, explained simply:

1. The "Double Trouble" is More Common Than You Think

The researchers looked at 111 patients with the "shaky foundation" (ARVC). They found that 14% of them also had the "floppy door" (MVP). This is much higher than the rate of floppy doors in the general population, suggesting that these two problems might be linked by the same underlying cause, rather than just happening to occur together by chance.

2. The Genetic "Blueprint" Error

Think of your genes as the blueprint for building the heart. The study found that in patients with both conditions, the blueprint was almost always missing a specific instruction for a protein called PKP2.

• The Metaphor: Imagine PKP2 is the "glue" that holds the heart cells together. In these patients, the glue is defective.
• The Finding: About 83% of the patients with both conditions had a mutation in this specific "glue" gene. This suggests that when the glue fails, it doesn't just weaken the right room's walls; it also causes the door in the left room to become floppy.

3. The Door is Different Here

Usually, a dangerous "floppy door" (arrhythmic MVP) looks like a double-door that is sagging and has a gap in the frame (called annular disjunction).

• The Surprise: In these ARVC patients, the door was not the typical dangerous type.
  • They rarely had the double-door sagging.
  • They rarely had the gap in the frame.
  • Instead, the door was usually just the back part (posterior leaflet) that was floppy.
• The Takeaway: The "floppy door" in these patients doesn't look like the classic dangerous kind seen in regular MVP patients.

4. The Left Room is Also Struggling

Even though the "shaky foundation" (ARVC) is famous for attacking the right room, this study found that in patients with the floppy door, the left room was also showing signs of trouble.

• Thick Walls: The left room's walls were significantly thicker (higher mass) than in ARVC patients without a floppy door.
• Weak Spots: The left room had more areas where the muscle wasn't moving correctly.
• The Metaphor: It's as if the defective "glue" (PKP2) is causing the left room to try to compensate by bulking up its walls, but those walls are actually becoming stiff and weak in spots. This is a sign of a broader disease affecting the whole house, not just the right side.

5. The Danger Level

The study checked if having both conditions made the heart more likely to stop (cardiac arrest).

• The Result: About 20% of the "double trouble" patients had a cardiac arrest, compared to 16% of those with just the shaky foundation.
• The Nuance: While the number is slightly higher, the difference wasn't massive. However, the "double trouble" group did have more frequent electrical glitches (sustained ventricular tachycardia) than the group with just the foundation issue.

Summary

This paper tells us that when a patient has a specific genetic "glue" defect (PKP2), it often causes two things at once: a weak right side of the heart and a floppy valve on the left side.

Unlike the classic "dangerous floppy door" we usually see, this specific type of floppy door comes with a thickened, struggling left side of the heart. The researchers conclude that we need to look at the whole heart, not just the right side, when treating these patients, because the "glue" problem seems to be affecting the entire structure.

Technical Summary

Problem Statement
While Mitral Valve Prolapse (MVP) and Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) are distinct clinical entities, their co-existence has historically been documented only in isolated case reports. Consequently, the genetic and phenotypic characteristics of patients with concomitant ARVC and MVP remain poorly understood. Specifically, it is unclear whether the presence of MVP in ARVC patients represents a coincidental finding or a manifestation of a shared underlying genetic substrate, and how this combination influences left ventricular (LV) involvement and arrhythmic risk.

Methodology
This retrospective cohort study analyzed 111 patients with a definite diagnosis of ARVC, confirmed via the 2010 revised Task Force Criteria, medical record review, and targeted arrhythmia/cardiomyopathy gene panels. The study population was drawn from the University of California, San Francisco (UCSF) electronic medical records and Cardiovascular Genetics Center Database between 2015 and 2025.

• Diagnosis of MVP: MVP was diagnosed via echocardiography and Cardiac Magnetic Resonance (CMR) as mitral leaflet displacement >2 mm above the annular plane in systole. Patients with displacement ≤2 mm were classified as having "borderline MVP."
• Genetic Analysis: Genetic variant information was collected from clinical whole exome sequencing panels. The study focused on desmosomal genes (e.g., PKP2, DSP, DSG2) and non-desmosomal genes.
• Imaging Assessment: Two-dimensional echocardiography and CMR were used to assess valve morphology (bileaflet vs. single leaflet, presence of Mitral Annular Disjunction [MAD]), regurgitation severity, and ventricular function. CMR specifically evaluated RV and LV wall motion abnormalities, ejection fractions, volumes, late gadolinium enhancement (LGE), and diffuse fatty infiltration.
• Statistical Analysis: Continuous variables were compared using t-tests, and categorical variables were compared using Fisher's Exact Test. Significance was set at p < 0.05.

Key Contributions and Results

• Prevalence: The study identified MVP or borderline MVP in 14% (n=15) of the ARVC cohort, a rate significantly higher than the 2.5% prevalence in the general population.
• Genetic Profile: Among the 69 ARVC patients with identified genetic variants, PKP2 mutations were highly prevalent (64% overall). Notably, among the MVP subgroup with genetic data, PKP2 variants (pathogenic or variants of uncertain significance) were found in 83% (5/6) of cases.
• Valve Morphology: Unlike typical "arrhythmic MVP" which often features bileaflet involvement and MAD, the MVPs in this ARVC cohort were predominantly posterior prolapse (73%) with single-leaflet involvement. Crucially, none of the patients exhibited mitral annular disjunction (MAD).
• Left Ventricular Involvement: ARVC patients with MVP demonstrated significantly higher LV mass indexed to body surface area (93 g/m² vs. 75 g/m², p = 0.02) and a higher prevalence of LV wall motion abnormalities (27% vs. 5%, p = 0.02) compared to ARVC patients without valve abnormalities.
• Arrhythmic Outcomes: Cardiac arrest occurred in 20% of the MVP group versus 16% of the non-MVP group. While the MVP group had a lower prevalence of premature ventricular contractions, they exhibited a higher rate of non-sustained and sustained ventricular tachycardia compared to the non-MVP group.
• Imaging Findings: The MVP group showed a higher prevalence of diffuse fatty infiltration in the RV (40% vs. 14%, p = 0.02) and LV compared to the non-MVP group.

Significance and Claims
The authors claim this study provides the first comprehensive overview of the genetic, clinical, and imaging characteristics of concomitant MVP and ARVC. The primary significance lies in the identification of a strong association between PKP2 genetic variation and the co-occurrence of MVP and ARVC, suggesting a shared desmosomal dysfunction rather than a coincidental finding.

The paper posits that the phenotype of MVP in ARVC patients differs from classic arrhythmic MVP; specifically, the absence of MAD and bileaflet involvement, coupled with the presence of increased LV mass and wall motion abnormalities, points toward a diffuse myopathic process characteristic of arrhythmogenic left-sided cardiomyopathy. The authors conclude that MVP is a prevalent finding in ARVC, particularly in PKP2 carriers, and that these features may serve as markers for increased LV involvement and arrhythmic risk, warranting further investigation into risk stratification. However, the authors remain modest regarding causal inference due to the retrospective nature of the study and the small sample size of the concomitant group.