Abstract 19403: Deterioration of Cardiac Performance and Dysfunction of Sympathetic Activity Affects Respiratory Instability in Chronic Heart Failure: Non-invasive and Simple Quantitative Assessment of Respiratory Stability

Abstract

Background: Cardiac sympathetic activity, in general assessed by 123I-meta-iodobenzylguanidine cardiac scintigraphy (mIBG-s), has been shown to be a critical indicator to predict morbidity and mortality associated with chronic heart failure (HF). We herein hypothesized that nocturnal respiratory stability, which has been suggested to be impaired by autonomic dysfunction, may be correlated with sympathetic nerve activity in advanced HF. To test this hypothesis, we developed respiratory stability index (RSI), which is calculated by computer-based non-invasive measurements. Methods: Fifteen patients with chronic HF under intensive medical treatments including maximized beta-blocker therapy were enrolled. All patients echocardiographically displayed their ejection fraction (EF) less than 35%. Nocturnal respiratory signals were serially collected by the under-pillow sensor to evaluate the respiratory spectrum during asleep. RSI was calculated from average of the reciprocal of the standard deviation of respiratory spectral ranges (Figure). Results: RSI was successfully and reproducibly evaluated in all cohorts with an average value being 44±21. mIBG-s-based values to indicate sympathetic activity, such as heart-to-mediastinum ratio (HMR) or wash-out rate, showed abnormality in all cohorts. Of note, the RSI was strongly correlated with HMR (ρ=0.83, p<0.01) or wash-out rate (ρ=-0.87, p<0.01). In addition, RSI was significantly correlated with standard indicator of HF such as plasma brain natriuretic peptide level (ρ=-0.59, p<0.05), EF (ρ=0.73, p<0.05) or pulmonary capillary wedge pressure assessed by right heart catheter study (ρ=-0.70, p<0.05). Conclusions: RSI showed a significant correlation with degree of autonomic dysfunction assessed by mIBG-s in advanced HF of chronic stage. This non-invasive method might enable serial evaluation to predict cardiac events even in patients on home healthcare, though further validation is required.