Post-training changes in the distance/heart rate ratio in patients undergone cardiovascular surgery

BACKGROUND: Exercise-based cardiac rehabilitation (CR) leads to an improvement in clinical outcomes.The distance/heart rate ratio,measured immediately after a 6-minute walk test (6MWT), has not been evaluatedin patients undergone CR after cardiovascular surgery. METHODS: This retrospective study included patients, who had undergone coronary artery bypass grafting (CABG), valve surgery with or without CABG, surgery of the ascending aorta with or without CABG, or Bentall procedure. They had completed a formal program of CR following hospital discharge and had performed a 6MWT before and after CR. RESULTS: Changes in the distancewalked(259.1±70.8 versus 429.4±88.5;p<0.001) were associated to subjective improvement in post-exercise fatigue (4.3±1.7 versus 1.1±0.7 meters;p<0.001) and dyspnea (5.4±1.6 versus 1.7±0.7;p<0.001), decreased systolic blood pressure(133.9 ±14.3 versus 128.4±9.3 mmHg;p<0.01), reduced heart rate (99.1±12.7 versus 91.7±11.7 beats per minute;p<0.001), increased distance/heart rate ratio (0.4±0.1 versus 0.8±0.2 meters/ beats per minute;p<0.001)and, enhancedoxy-hemoglobin saturation (96.6±2.0 versus 98.0±3.9;p<0.05). CONCLUSIONS: Findings from the present study highlight the clinical benefits of CR in a patient population undergone cardiac surgery. In particular, longer distance walked associated to changes in the heart rate response to exercise did lead to an enhancement in the distance/heart rate ratio.