Chronotropic incompetence and survival in chronic heart failure

Failure of the heart rate to rise normally during an incremental exercise test is termed chronotropic incompetence (CI). It is common in patients with chronic heart failure (CHF), and we wanted to explore the relation between CI and outcome in unselected patients with CHF.

411 patients with left ventricular systolic dysfunction who underwent cardiopulmonary exercise testing (CPET) were included. CI was defined as a failure to achieve 80% of the maximum predicted heart rate (HR). A CI index was also calculated: (Peak HR-Rest HR)/(220-age-Rest HR)∗100. Cox regression was used to assess the univariate and multivariate relationship between variables and all-cause mortality. Survivors were followed for a median of 89months (IQR 62.8-98.6). The majority were male (81.4%) with a median age of 67years (IQR 60-73). A subgroup of 266 patients had NT-proBNP values.

CI was present in 42.3% of the population. The mean CI index was 65.7% (SD 41.3%). Patients without CI exercised for longer (510s) and had higher peak VO(2) values (21.1mL/kg/min) than those with CI (424 seconds and 18mL/kg/min). Only peak VO(2), age and β blocker use were independent prognostic variables. In the subset of patients with NT-proBNP available, Log[NT-proBNP] was the most powerful predictor of mortality followed by peak VO(2) and β blocker use.

Patients with CI had lower exercise time and peak VO(2). However CI was not a significant predictor of mortality in patients with CHF undergoing CPET.