Shifting the Balance: Mitochondrial Heteroplasmy as a Driver of Cardiac Disease.

Mitochondrial heteroplasmy represents a fundamental determinant of mitochondrial function and disease, yet its consequences vary across different tissues. Although mitotic tissues possess mechanisms, such as cell division and mitochondrial turnover, to dilute or remove deleterious variants, postmitotic tissues lack this renewal capacity and are disproportionately vulnerable. Neuromuscular and neurodegenerative disorders have illustrated the impact of heteroplasmic mutations, but the (postmitotic) heart remains underexplored. Current reliance on blood-derived samples provides only an indirect view of cardiac heteroplasmy, highlighting the need for alternative approaches, such as endomyocardial biopsies and human induced pluripotent stem cell-derived cardiomyocytes. Expanding cardiac-focused research is essential for identification, clarifying pathogenesis, improving risk stratification, and guiding patient monitoring. Emerging therapies, including mitochondrial transplantation and mitochondrial-targeted DNA editing, demonstrate potential to modulate heteroplasmy and restore equilibrium. Integrating these strategies with precision medicine will be vital for addressing tissue-specific vulnerabilities. Ultimately, bridging the gap in cardiac heteroplasmy research will be critical for translating basic mitochondrial biology into meaningful clinical advances.