Patients with asymptomatic severe mitral regurgitation already have abnormal left ventricular myocardial sarcomeric ultrastructural characteristics.

Authors

Yuanjia Zhu, Seung Hyun Lee, Avi Gupta, Catherine A Wu, Jinsuh Jung, Akshay Venkatesh, Sidarth Ethiraj, Charles J Stark, Chris Huynh, Matthew D Vergel, Shin Yajima, Y Joseph Woo

Published in

JTCVS open. Volume 32. Pages 101821. Epub May 04, 2026.

Abstract

Mitral valve (MV) surgery remains a class I recommendation for patients with symptomatic severe primary mitral regurgitation (PMR). For asymptomatic patients with severe PMR and preserved left ventricular (LV) function without atrial fibrillation, pulmonary hypertension, or significant left atrial enlargement, surgical treatment is not currently recommended. However, the nature and extent of LV myocardial ultrastructural alterations in patients who are asymptomatic remain unclear.
Twelve patients with severe PMR were enrolled in this study, 8 of whom were symptomatic and 4 asymptomatic. Three donor hearts were used as controls. LV biopsies were obtained and processed for transmission electron microscopy. Transmission electron microscopy images were acquired from 600× to 25,000× magnification. Quantitative analysis was performed using the ImageJ software. Statistical comparisons were made using a linear mixed-effects model to account for repeated measurements within individuals. Post-hoc pairwise comparisons were conducted using Bonferroni correction. Statistical significance was defined as P < .05. This study was approved by the institutional review board.
Qualitatively, myofibrillar disarray, reduced cytoplasmic reserve, and mitochondrial derangement were observed in patients with severe PMR, regardless of presence of symptoms, compared with controls. Quantitatively, the sarcomere length was greater in control patients (1.65 ± 0.23 μm) compared with those who were symptomatic (1.31 ± 0.34 μm, P = .049). The mitochondria area was also larger in control patients (0.35 ± 0.19 μm²) than in patients who were symptomatic (0.27 ± 0.14 μm², P = .33). The mitochondria cristae thickness was greater in control patients (0.05 ± 0.01 μm) compared with patients who were symptomatic (0.02 ± 0.003 μm, P < .001) and asymptomatic (0.02 ± 0.03 μm, P < .001). Similarly, the mitochondrial major-to-minor axis ratio was greater in control patients (1.86 ± 0.93) than in patients who were symptomatic (1.65 ± 0.52, P = .044) and asymptomatic (1.50 ± 0.46, P = .003).
In patients with severe asymptomatic PMR and preserved LV function without atrial fibrillation, pulmonary hypertension, or significant left atrial enlargement, ultrastructural alterations of the LV myocardium are already evident and comparable with those observed in severe symptomatic PMR. These findings suggest that early surgical intervention in patients who are asymptomatic with severe PMR may help prevent further adverse remodeling and potentially improve clinical outcomes.

PMID:
42604190
Bibliographic data and abstract were imported from PubMed on 16 Aug 2026.

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