Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy in the Elderly.

BACKGROUND: Hypertrophic obstructive cardiomyopathy is a genetic disorder treated with septal reduction therapy, either alcohol septal ablation or septal myectomy (SM). Historically older patients have been presumed to be poor candidates for SM and thus referred directly for alcohol septal ablation in some centers. We reviewed our experience with SM in older patients. METHODS: We identified 100 patients at our institution who underwent SM for hypertrophic obstructive cardiomyopathy from 2015 to 2020. Demographic and clinical characteristics and outcomes of patients 65 years or older were compared with patients younger than 65. RESULTS: Sixty-five patients were in the <65 group and 35 patients in the ≥65 group. Both groups had similar preoperative peak stress left ventricular outflow tract gradients (129 mm Hg vs 110 mm Hg, P < .001). Most patients in both groups had moderate to severe mitral regurgitation on preoperative stress echocardiography. The elderly group was more likely to have coronary artery bypass graft as a concomitant procedure (37% vs 8%, P < .001). Only 1 death occurred in the series secondary to a pulmonary embolism. At the 30-day follow-up on stress echocardiography, peak stress gradients were normal in both groups (21 and 20 mm Hg, respectively; P < .001), and 88% of all patients had trace to mild mitral regurgitation. CONCLUSIONS: Properly selected older patients can safely undergo SM with excellent outcomes similar to younger patients. Relief of left ventricular outflow tract obstruction and correction of mitral regurgitation are reliably achieved in both groups. Advanced age should not be a strict criteria for selecting septal reduction therapy approach.

Single-cell imaging and transcriptomic analyses of endogenous cardiomyocyte dedifferentiation and cycling.

While it is recognized that there are low levels of new cardiomyocyte (CM) formation throughout life, the source of these new CM generates much debate. One hypothesis is that these new CMs arise from the proliferation of existing CMs potentially after dedifferentiation although direct evidence for this is lacking. Here we explore the mechanisms responsible for CM renewal in vivo using multi-reporter transgenic mouse models featuring efficient adult CM (ACM) genetic cell fate mapping and real-time cardiomyocyte lineage and dedifferentiation reporting. Our results demonstrate that non-myocytes (e.g., cardiac progenitor cells) contribute negligibly to new ACM formation at baseline or after cardiac injury. In contrast, we found a significant increase in dedifferentiated, cycling CMs in post-infarct hearts. ACM cell cycling was enhanced within the dedifferentiated CM population. Single-nucleus transcriptomic analysis demonstrated that CMs identified with dedifferentiation reporters had significant down-regulation in gene networks for cardiac hypertrophy, contractile, and electrical function, with shifts in metabolic pathways, but up-regulation in signaling pathways and gene sets for active cell cycle, proliferation, and cell survival. The results demonstrate that dedifferentiation may be an important prerequisite for CM proliferation and explain the limited but measurable cardiac myogenesis seen after myocardial infarction (MI).