Echocardiographic Features of the Right Heart in Sleep-Disordered Breathing The Framingham Heart Study

Abstract

The effect of sleep-disordered breathing (SDB) on right heart structure and function is controversial. Studies of patients referred for evaluation of possible sleep apnea have yielded conflicting results, and the impact of SDB on the right heart has not been investigated in the general population. We examined the echocardiographic features of subjects with SDB at the Framingham Heart Study site of the Sleep Heart Health Study. Of 1,001 polysomnography subjects, 90 with SDB defined as a respiratory disturbance index (RDI) score > 90th percentile (mean RDI = 42) were compared with 90 low-RDI subjects (mean RDI = 5) matched for age, sex, and body mass index. Right heart measurements, made without knowledge of clinical status, were compared between groups. The majority of the subjects were male (74%). After multivariable adjustment, right ventricle (RV) wall thickness was significantly greater (p = 0.005) in subjects with SDB (0.78 ± 0.02 cm) than in the low-RDI subjects (0.68 ± 0.02 cm). Right atrial dimensions, RV dimensions, and RV systolic function were not found to be significantly different between subjects with SDB and the low-RDI subjects. We conclude that in this community-based study of SDB and right heart echocardiographic features, RV wall thickness was increased in subjects with SDB. Whether the RV hypertrophy observed in persons with SDB is associated with increased morbidity and mortality remains unknown. Keywords: cohort study; echocardiography; epidemiology; obesity; right ventricle; sleep-disordered breathing Numerous cross-sectional studies have demonstrated an association between obstructive sleep apnea and coronary heart disease (1, 2), stroke (3, 4), and sudden death (5). Pulmonary hypertension and right heart failure have also been observed in patients presenting with severe obstructive sleep apnea syndrome, although the relation of more modest degrees of sleep-disordered breathing (SDB) to alterations in right heart structure and function in the general population is unknown. The paucity of data regarding right heart structure and function in SDB is likely related to several factors. SDB has been underrecognized in clinical practice, even though the prevalence of SDB in middle-aged adults is estimated to be 9% for women and 24% for men (6). In addition, the right ventricle is more challenging to assess both qualitatively and quantitatively than the left ventricle (7). The few studies that have examined the right heart in SDB have been limited by design issues and sleep laboratory referral bias (8-19). Hence, it is not surprising that prior studies have differed as to whether SDB is associated with altered right heart morphology and function.