P2480Pulmonary function is an independent determinant for chronotropic incompetence during exercise in patients with chronic heart failure

Abstract

Background: Chronotropic incompetence during exercise has been known to deteriorate exercise tolerance and clinical outcomes in patients with chronic heart failure (CHF). Chronotropic incompetence reportedly enhances autonomic imbalance and is generally assessed by chronotropic index (CI) obtained from cardiopulmonary exercise test, and then CI of <0.6 is a strong predictor for all-cause mortality in these patients. On the other hand, pulmonary dysfunction has also been documented to decrease event-free survival rate. Although the effect of respiratory modulation on autonomic system has been documented, it is still unclear whether pulmonary dysfunction aggravates chronotropic incompetence during exercise. We investigated the relationship between pulmonary function and chronotropic incompetence and clarify the determinants for chronotropic incompetence in CHF patients. Methods: We studied 266 patients with compensated CHF (58±13 years, 207 males and 59 females) who received cardiac rehabilitation during hospitalization and after hospital discharge. The patients who received thoracic surgery within the past three months or had chronic respiratory diseases were excluded from this study. We obtained body mass index, etiology of heart failure, medications, heart rate, blood pressure, left ventricular ejection fraction and plasma brain natriuretic peptide as clinical characteristics. We also measured forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) as a pulmonary function using spirometer two months after the discharge. To assess a chronotropic incompetence, we monitored heart rate (HR) response during symptom-limited cardiopulmonary exercise test and calculated a chronotropic index (CI) with following equation: (peak HR - rest HR) / (220 - age - rest HR). CI of <0.6 was defined as a chronotropic incompetence. To identify the determinants for chronotropic incompetence, we performed correlation analysis and multivariate logistic regression analysis using clinical characteristics and pulmonary function as independent variables. We also analyzed receiver operating characteristic (ROC) curve of independent determinants for chronotropic incompetence. Results: One-hundred and nineteen patients among the studied patients showed CI of <0.6. There were significant positive correlations of CI with FVC (r=0.370, P<0.001) and FEV1 (r=0.345, P<0.001), although no significant correlations were observed between CI and clinical characteristics. Multivariate logistic regression analysis detected the FVC as a significant independent determinant for chronotropic incompetence (OR: 0.342, 95% CI: 0.209-0.560, P<0.001). Result of the ROC curve analysis is shown in Figure. The area under the ROC curve of FVC for chronotropic incompetence was 0.689 (95% CI: 0.625-0.753, P<0.001). Conclusion: Pulmonary function was an independent determinant for chronotropic incompetence during exercise in patients with CHF.