Abstract 12705: Mechanisms of Decreased Exercise Capacity with Sleep Disordered Breathing in Hypertrophic Cardiomyopathy
BACKGROUND: Mechanisms of decreased exercise capacity in patient with hypertrophic cardiomyopathy (HCM) are not well understood. One potential mechanism is sleep disordered breathing (SDB) - a treatable and highly prevalent disorder in patients with HCM. We previously reported that peak oxygen consumption (pkVO2, an accurate and reproducible measure of cardiopulmonary fitness) is decreased in HCM patients with SDB, yet the mechanisms behind this association were not previously explored.
METHODS: Overnight oximetry, cardiopulmonary exercise testing, and echocardiographic studies were performed in consecutive HCM patients. SDB was considered present if oxygen desaturation index (ODI, number of ≥4% desaturations per hour) was ≥10. RESULTS: A total of 198 HCM patients were included (age 53±16 years; 122 male) of whom 32% fulfilled the SDB diagnosis. SDB patients had decreased pkVO2 compared to those without SDB (16 vs 21 mlO2/kg/min; p<0.001). SDB remained significantly associated with pkVO2 after accounting for all clinical variables (Model 1, p<0.001) including age, gender, body mass index, atrial fibrillation, and coronary artery disease. This association was weakened (Model 2, p=0.071) by the inclusion of the following echocardiographical variables: diastolic dysfunction, left atrial size, and right ventricular systolic pressure. LV ejection fraction or LV outflow gradient did not have a significant effect on the SDB-pkVO2 association.
CONCLUSIONS: HCM patients with SDB have worse exercise tolerance in part because SDB may be promoting diastolic dysfunction, pulmonary hypertension, and increased left atrial size. Whether screening and treatment of SDB improves these pathophysiological mechanisms needs to be further studied, especially because SDB could be a novel reversible therapeutic target for improvement of functional tolerance in often young HCM patients.
- © 2012 by American Heart Association, Inc.