Abstract 5914: The Prognostic Value of the Initial Heart Rate Increase during Progressive Exercise Testing in Heart Failure
The increase in heart rate during the first minute of a progressive exercise test (HR1) has been shown to be prognostically significant in a large cohort at risk for or diagnosed with cardiovascular disease. This issue, however, has not been specifically investigated in patients diagnosed with heart failure (HF). We assessed the hypothesis that HR1 would possess prognostic value in a large HF cohort. Three-hundred and ninety two subjects diagnosed with HF (207 ischemic/185 non-ischemic, 279 male/113 female, age: 57.2 ±13.2 years, ejection fraction: 33.4 ±12.5) underwent cardiopulmonary exercise testing. Two-hundred and thirty three subjects were prescribed a beta-blocking agent at the time of testing. The difference between resting HR and HR after the first minute of exercise was defined as HR1. Ventilatory efficiency (VE/VCO2 slope), the presence of oscillatory ventilation (EOV) and peak oxygen consumption (VO2) were also determined. Subjects were tracked for major cardiac events following exercise testing. There were 93 major cardiac events (82 deaths, 8 heart transplants, 3 left ventricular assist device implantations) during the 24.5 ±21.2 month tracking period (annual event rate: 10.5%). A HR1 threshold of >13 beats per minute was a significant univariate predictor of adverse events in the overall group (Hazard ratio: 6.5, 95% CI: 3.6–11.4, p<0.001) as well as the subgroup receiving a beta-blocking agent (Hazard ratio: 4.0, 95% CI: 1.9 – 8.1, p<0.001). Moreover, in a multivariate analysis, HR1 (>13, chi-square: 53.5, p<0.001), the VE/VCO2 slope (<34, residual chi-square: 18.0, p<0.001) and EOV (yes/no, residual chi-square: 7.3, p<0.007) were all significant predictors of major cardiac events while peak VO2 (>14 mlO2·kg−1·min−1, residual chi-square: 0.42, p=0.52) was not. Others have postulated that a greater HR1 reflects a more rapid withdrawal of parasympathetic stimulus during exercise and a higher vagal tone at rest. These results demonstrate HR1 during a progressive exercise test is prognostically valuable in patients with HF. Consideration of HR1 for prognostic purposes may therefore be warranted in patients with HF during both submaximal and maximal exercise testing.