NOCTURNAL HYPOXIA INDEXES ARE ASSOCIATED WITH LEFT VENTRICULAR REMODELING AND DIASTOLIC DYSFUNCTION IN OBSTRUCTIVE SLEEP APNEA PATIENTS

Abstract

Objective: Echocardiography features of obstructive sleep apnea (OSA) are heart derangements as higher left ventricular mass index (LVMI) and left ventricular end-diastolic diameter, lower left ventricular ejection fraction (LVEF), and impaired diastolic function. The apnea/hypopnea index (AHI), the parameter currently used to define diagnosis and severity of OSA, poorly predicts cardiovascular damage, cardiovascular events, and mortality. Thus, we aimed to assess, if, in addition to AHI, other polygraphic indices of OSA presence and severity might serve as better predictors of echocardiographic cardiac remodeling. Design and method: We enrolled two cohorts of subjects referred for suspected OSA to the outpatient facilities of the IRCCS Istituto Auxologico Italiano, Milano, and of the Clinica Medica 3, Padova. All patients underwent home sleep apnea testing and echocardiography. Based on the AHI the cohort was divided into no-OSA (AHI<15 events/hour) and moderate-severe OSA (AHI> = 15 events/hour). A stepwise multiple regression analysis was used to identify the covariates among age, gender, body mass index, past medical history, and polygrapic variables, independently associated to four echocardiographic variables, e.g., LVMI, LVEF, left ventricular end-diastolic volume (LVEDV), early and late ventricular filling velocity ratio (E/A). Results: We recruited 162 patients and found that compared to patients with no-OSA, those with moderate-severe OSA showed higher LV remodeling [LVEDV 48.4±11.5 ml/m2 vs. 54.1±14.0 ml/m2, respectively, p = 0.005] and lower LVEF (65.3±5.8 % vs. 61.6±7.8%, respectively, p = 0.002), whereas we could not find any difference in LVMI and E/A. At multivariate linear regression analysis, the only polygraphic independent predictor of LVEDV was the percentage of time with SatO2 < 90% (↓ = 0.262), whereas, the independent predictors of E/A were AHI (↓ = -0.379) and oxygen desaturation index (↓ = -0.422). None of the polygraphic variables was associated to LVMI and LVEF at multivariate linear regression analysis. Conclusions: Our study shows that nocturnal hypoxia-related indexes were associated with left ventricular remodeling and diastolic dysfunction in OSA patients. If confirmed in future studies with a wider sample of patients included, these results support the adoption of hypoxia indexes in the evaluation of OSA patients, particularly those at a greater cardiovascular risk.