Unraveling Marfan hearts: ultrastructural evidence for myocardial remodeling and cardiomyopathy
Authors: Deleeuw V , D'hulst S , Demolder A , Steijns F , Renard M , De Rycke R , Van Dorpe J , Muino-Mosquera L , Francois K , Benke K , Szabolcs Z , Sips P , De Backer J 
Published: October 2024

Abstract

Background
Despite improved life expectancy for patients with Marfan syndrome (MFS), significant morbidity and mortality persist. Although primarily attributed to aortic dissection and rupture, recent studies highlight the emerging role of arrhythmias and heart failure as additional contributors to morbidity and mortality in MFS. While severe valvular heart disease is an established cause of heart failure, there is a growing recognition of primary cardiomyopathy in patients with MFS. The mechanisms underlying cardiomyopathy in MFS remain poorly understood.

Purpose
This study aimed to reveal insights into the ultrastructural myocardial architecture in patients with MFS, thereby elucidating the role of cardiomyopathy in MFS.

Methods
This study enrolled 44 patients who underwent cardiac surgery at 2 centers (Marfan syndrome patients n=27 (MFS), ascending thoracic aortic aneurysm repair patients n=5 (non-MFS), patients post-orthotopic heart transplant n=12 (controls)). Myocardial biopsy samples were subjected to histopathological analysis using transmission electron microscopy and conventional histology.

Results
Conventional histological analysis revealed subtle abnormalities in the cardiomyocyte morphology of MFS patients, compared to non-MFS and controls. Overall, a slight increase in interstitial fibrosis and mild myocyte hypertrophy were observed in MFS patients. Ultrastructural examination of both MFS and non-MFS patients revealed significant structural remodeling and degenerative changes in the myocardium. These changes included: extensive myofibril lysis, compromised cell membrane integrity and nuclear chromatin condensation. Degenerative lesions were often accompanied by cytoplasmic debris, lysosomal residual bodies, autophagic vacuoles, and severe mitochondrial pathology. Dense accumulation of glycogen granules and lipofuscin was evident in areas of focal myofibril lysis. Notably, only MFS patients exhibited recruitment of granulocytes, including mast cells, eosinophils and neutrophils. A subset of MFS patients displayed advanced stages of myocardial degeneration. However, these changes did not correlate with clinical myocardial failure.

Conclusions
To the best of our knowledge, this study represents the first evidence of ultrastructural changes in the myocardium of patients with MFS. Our data indicate various degenerative changes in the myocardial architecture, including structural and metabolic myocardial remodeling, along with inflammatory cell infiltration. We believe that our findings of ultrastructural lesions reflect the complexity of myocardial disease in MFS and emphasize the importance of careful surveillance for cardiomyopathy in MFS patients. Further studies are warranted to confirm whether the observed granulocyte influx is specific to MFS and to clarify its role in MFS myocardial disease pathophysiology.Graphical abstract