Unfavorable effects of sleep-disordered breathing (SDB) in heart failure (HF) are mainly mediated by impaired sympathetic activity. However, few data are available on SDB and cardiac adrenergic impairment evaluated at myocardial level. The aim of the present study was to assess the relationship between SDB, cardiac sympathetic innervation and prognosis in HF patients.
Ninety-four patients (66.1±9.8 years) with systolic HF (median left ventricular ejection fraction 32±7%) underwent nocturnal cardiorespiratory monitoring to assess presence and type of SDB by Apnea/Hypopnea Index (AHI), and 123I-MIBG myocardial scintigraphy to calculate heart-to-mediastinum (H/M) ratios and 123I-MIBG washout rate. Patients were prospectively followed for 29±18 months for the combined endpoint of cardiovascular death and HF hospitalization.
Of 94 patients, 72 (77%) showed SDB and, compared to non-SDB, had significantly reduced early (1.67±0.22 vs. 1.77±0.13; p<0.02) and late (1.50±0.22 vs. 1.61±0.23; p<0.04) H/M ratios. At multiple linear regression analysis, early and late H/M ratios remained independent predictors of AHI (=-0.749; p<0.001; =-0.830; p=0.001, respectively). Similarly, AHI was the only predictor of early (=-0.643; p<0.001) and late (=-0.453; p<0.002) H/M ratios. Patients with AHI above the median showed significantly higher event rates and worse survival compared to patients with AHI below the median (35% vs. 9%, respectively; p<0.01). Similarly, patients with moderate to severe disorder showed significantly increased incidence of the combined endpoint and worse survival compared to patients with mild or no disorder (35% vs. 11.7%; p<0.01). Adding SDB variables to the already known prognostic role of 123I-MIBG imaging, we observed an incremental prognostic discrimination with the worst survival in patients with both SDB and H/M impairment.
Patients with systolic HF and SDB show more impaired cardiac adrenergic innervation and more adverse prognosis compared to HF patients without SDB.