Exercise capacity of the patients after cardiac surgery with special reference to left atrium incision

Abstract

Abstract Background Chronotropic incompetence (CI) is sometimes observed during exercise in patients who underwent cardiac surgery, however, little is known which factors affect to the incidence of CI and exercise capacity of those patients. Purpose We hypothesized that the incidence of CI is higher in patients with left atrium incision (LAI) as compared with those without LAI, which is caused by impairment of cardiac sympathetic nerves by LAI. The purpose of this study is to elucidate whether LAI causes CI, and if so, to analyze which factor determine the exercise capacity of the patients with LAI. Methods We performed cardiopulmonary exercise testing in total 157 patients who had undergone elective cardiac operation (46 patients with LAI, 111 patients without LAI). We analyzed chronotropic response index (CRI), parameters of exercise capacity, echocardiography, and blood hemoglobin concentration (Hb). Results The value of CRI was significantly reduced in the patients with LAI as compared with those without LAI (0.24±0.22 vs. 0.45±0.17, respectively, p<0.001). Exercise capacity such as peak oxygen uptake (peak VO2), anaerobic threshold showed no significant difference between two groups. In patients with LAI, peak VO2 showed significant correlations between peak oxygen pulse (peak VO2/HR; r=0.34, p<0.05), Hb (r=0.43, p<0.005) and left atrium dimension (LAD) measured by echocardiography (r=-0.56, p<0.001). Conclusions The present study demonstrated that higher incidence of CI was observed in patients with LAI as compared with those without LAI. Moreover, peak VO2 of patients with LAI showed significant correlations with peak VO2/HR, Hb and LAD. These results suggest that 1) LAI may impairs cardiac sympathetic nerves and causes CI, 2) peak VO2/HR and its component Hb are important factors which determine exercise capacity of patients with CI, 3) LAD which indicates left atrial function may also affect exercise capacity of patients with CI.