AimsTo examine the relation between mitochondrial dysfunction and myocardial contractile and relaxation reserves in hypertrophic cardiomyopathy (HCM).Methods and resultsThirty HCM patients (LVEF ≥60%) underwent biventricular cardiac catheterization analysis both at rest and during atrial pacing as well as myocardial 99mTc-sestamibi scintigraphy at rest to calculate washout rate. Endomyocardial biopsy specimens were obtained for quantitative mRNA analysis and electron microscopy. The HCM patients were divided into two groups - group A: normal force-frequency relation and a pressure half-time (T1/2) of <30 ms (n = 15); group B: abnormal force-frequency relation or T1/2 of ≥30 ms (n = 15). The 99mTc- sestamibi washout rate was significantly correlated with T1/2 for all patients (r = 0.74, P < 0.01) and was also significantly greater in group B (29.2 ± 6.3%) than in group A (19.3 ± 3.1%). The abundance of mRNAs for mitochondrial electron transport-related enzymes was significantly higher in group A than in group B. Mitochondria showed a greater variation in size and were more disorganized in group B than in group A.
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