The functional rs1049434 polymorphism (T1470A; Asp490Glu) affects MCT1-mediated lactate transport and substrate utilization, but its clinical relevance in sarcomere-related hypertrophic cardiomyopathy (HCM) remains poorly defined.<h4>Methods</h4>We studied 56 carriers of pathogenic or likely pathogenic sarcomeric variants examined in a familial HCM program. The gene discussed is SLC16A1; the disease is hypertrophic cardiomyopathy.