Abstract 15324: Exercise Acutely Exacerbates Derangement Of Cardiac Energy Metabolism In Hypertrophic Cardiomyopathy, a 31 Phosphorus Magnetic Resonance Study at 3 Telsa
Introduction: Hypertrophic cardiomyopathy (HCM) affects up to 1 in 500 of the population and is the commonest cause of sudden death in the younger population. However, its pathophysiology and mechanisms of progression are not fully understood. The underlying sarcomere mutations increase the energy cost of contraction, and impaired resting energetics (i.e. phosphocreatine/adenosine triphosphate, PCr/ATP, as measured by 31Phosphorus MR Spectroscopy, 31P MRS) has been documented in genetically modified animal models and in patients with HCM.Hypothesis: Our hypothesis is that the high incidence of exercise-related death in HCM may be explained by an acute impairment of myocardial energetics. As a proof-of-principle study, we examined whether cardiac energetics are further impaired during exercise in HCM.
Methods: Cardiac 31P MRS (3T Siemens Trio, 3D-CSI, 8 min spectra) was performed in 35 age and gender matched HCM patients and 20 normal controls at rest and during 8 minutes of steady leg exercise while lying prone with 2.5 kg weights attached to both legs.
Results: During exercise, the cardiac rate-pressure product rose by 72% in HCM and by 77% in normal (p=0.90). Resting PCr/ATP was lower in HCM, 1.70±0.38 (2.14± 0.37 in normal, p<0.05). During exercise in HCM, there was a significant further drop in PCr/ATP to 1.56±0.31 (p<0.05), while PCr/ATP remained unchanged in controls at 2.17±0.27. The change of PCr/ATP during exercise in HCM (-0.14±0.34) was significantly different (p<0.05) from the change in controls (+0.05±0.27). Figure 1 shows examples of rest and stress spectra.
Conclusion: During exercise, the pre-existing energetic deficit in HCM is further exacerbated. This may lead to acute derangement of energy-dependent ion homeostasis, triggering Ca++ overload and ventricular arrhythmias. Our findings offer a possible explanation for the high incidence of exercise-related death in HCM and suggest that treatments that optimize energetics may be protective.
- © 2011 by American Heart Association, Inc.