Peak of nocturnal blood pressure surge in seconds is associated with left ventricular mass index in obstructive sleep apnea patients

Background: Nocturnal blood pressure (BP) surge in seconds (sec-surge), which is characterized as acute transient BP elevation over several tens of seconds, could be a predictor of target organ damage and trigger cardiovascular events. Sec-surges are induced by sleep apnea (SA) or sympathetic nerve activity. However, it is not clear that the severity of sec-surge is different between sec-surges induced by SA (apnea/hypopnea detected by polysomnography (PSG) or oxygen desaturation) and those induced by non-SA factors (rapid eye movement, micro arousal, etc.). Furthermore, it is also not clear whether the sec-surge increases the cardiac overload. Methods and Results: Firstly, we assessed the sec-surge severity between sec-surges induced by SA and those induced by non-SA factors by comparing the sec-surge variables. Secondly, we assessed the association between sec-surges and left ventricular hypertrophy (LVH) independently of conventional BP variables. We assessed these points with 41 patients (mean age 63.2 ± 12.6 years, 29% female) who underwent full PSG, beat-by-beat (BbB) BP, and cuff-oscillometric BP measurement during the night. All patients were included for the analysis comparing sec-surge severity between inducing factors (SA and non-SA factors). There were no significant differences in the number of sec-surges/night, the peak of sec-surges defined as the maximum systolic BP in each sec-surge, and the amplitude of sec-surges defined as peak of sec-surge minus start point systolic BP in each sec-surge between SA-related sec-surges and non-SA-related sec-surges (19.5 ± 26.0 vs. 16.4 ± 29.8 events/night; 148.2 ± 18.5 vs. 149.3 ± 19.2 mm Hg; and 26.0 ± 4.3 vs. 25.8 ± 5.7 mm Hg, respectively). Eighteen subjects who had inspection results of cardiac magnetic resonance imaging out of the 41 patients (mean age 65.0 ± 12.5 years, 33% female) were included for the analysis assessing the association between sec-surges and LVH. The peak of sec-surge was significantly and strongly correlated with left ventricular mass index (LVMI) (r = 0.607, p < .01). As a result of multiple regression analysis (n = 18), the peak of sec-surge was significantly and strongly associated with the LVMI (standardized β = 0.62, p = .02), compared with the mean nocturnal SBPs measured by oscillometric method (standardized β = -0.04, p = .87). Conclusions: This study suggests that peak of sec-surge could be a better predictor of LVH compared to parameters derived from regular nocturnal oscillometric SBP.