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Decreased Exercise Capacity in HCM Patients With OSA | Journal Scan
Study Questions:
Does sleep-disordered breathing (SDB) lower peak oxygen consumption during stress testing in patients with hypertrophic cardiomyopathy (HCM)?
Methods:
Participants were recruited from a single center between January 2008 and December 2009 into this cross-sectional observational study. HCM was diagnosed by clinical, electrocardiographic, and echo features of HCM. SDB was diagnosed by overnight oximetry, defined as ≥4% drop in oxygen desaturation from baseline. Oxygen desaturation index (ODI) was defined as total number of desaturations divided by time in hours. Significant SDB was defined as ODI ≥10. Symptom-limited exercise stress testing with oxygen consumption was performed with an accelerated Naughton protocol. Cardiopulmonary testing and overnight oximetry were done within 30 days of each other.
Results:
A total of 198 patients were enrolled out of all 453 (44%) HCM patients seen during the specified period. Study subjects had similar clinical characteristics compared to all HCM patients seen. The average age was 53 ± 16 years old and 48% were women. Of the enrolled, 64 (32%) had SDB. Patients with SDB had decreased peak oxygen consumption compared to those without SDB (16 vs. 21 mlO2/kg/min; p < 0.001). SDB remained significantly associated with peak oxygen consumption after accounting for confounding clinical variables (p < 0.001) including age, sex, body mass index, atrial fibrillation, and coronary artery disease.
Conclusions:
The authors concluded that SDB in HCM is independently associated with worse exercise performance. Since SDB is potentially modifiable, an effective strategy to improve exercise tolerance in this population may include treatment of SDB.
Perspective:
The capacity to exercise to peak levels is among the strongest predictors of cardiovascular risk among both normal and cardiovascular disease populations. These findings are useful in context of the 70% of New York Heart Association class I HCM patients who have abnormal peak oxygen consumption, and may help to generate more hypotheses. A randomized trial will be needed to address whether treatment of SDB improves exercise tolerance in this HCM population. A final note on the tool used to diagnose SDB: The authors explain the use of overnight oximetry over standard polysomnography due to its lower cost and practical use on top of reported correlation between ODI and apnea-hypopnea index.
Keywords: Cardiomyopathy, Hypertrophic, Sleep Wake Disorders, Sleep Apnea Syndromes, Exercise Test, Exercise Tolerance, Oximetry, Oxygen Consumption, Oxygen, Cross-Sectional Studies, Heart Failure
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