Exercise-based cardiac rehabilitation is associated with a normalization of the heart rate performance curve deflection.

The heart rate (HR) rises with increased power output, whereby in most healthy individuals, the slope of HR levels off with higher intensity. This corresponds to a downward deflection of the heart rate performance curve (HRPC). Conversely, in patients after myocardial infarction, an upward HRPC deflection is frequently observed that is especially pronounced in patients with compromised left ventricular ejection fraction. To investigate whether regular endurance training during cardiac rehabilitation might normalize HRPC, data of 128 male patients were analyzed. All patients performed three exercise tests: at baseline, after 6 weeks, and after 1 year. Ninety-six patients exercised regularly according to guidelines for 1 year (training group, TG), and 32 stopped after 6 weeks (control group, CG). Similarly, upward-deflected HRPCs were observed at baseline and after 6 weeks in both groups. After 1 year, TG patients had less upward-deflected HRPCs compared with CG ones, corresponding to a partial normalization. Greater changes in HRPC deflection were associated with larger improvements in cardiorespiratory fitness. Our results might indicate improved myocardial function due to long-term rehabilitation. Further, HRPC alterations over time should be considered when prescribing exercise intensities using a target HR, as deflection flattening might render the intensity of corresponding exercise insufficient.

Effects of high-intensity interval training on platelet function in cardiac rehabilitation: a randomised controlled trial.

OBJECTIVE: To compare effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) on platelet function in patients undergoing cardiac rehabilitation, as hyper-reactive platelets are involved in atherogenesis and atherothrombosis. METHODS: In this single-centre parallel group randomised controlled trial, male patients after an acute coronary syndrome under dual antiplatelet therapy performed MICT or HIIT+MICT for 12 weeks. Main outcome was platelet reactivity measured by the half-maximal concentration (EC50) of platelet agonist thrombin receptor-activating peptide-6 (TRAP-6) in terms of P-selectin expression. EC50 was determined at baseline, after 6 and 12 weeks, each time at physical rest and on exertion. RESULTS: 82 patients were randomised to MICT or HIIT+MICT. Mean (95% CI) baseline EC50values at physical rest were 6.7 µM (6.3 µM to 7.0 µM) TRAP-6. After 6/12 weeks, 36/33 MICT and 34/28 HIIT+MICT patients were examined. HIIT+MICT patients had 0.9 µM (0.4 µM to 1.4 µM)/0.5 µM (-0.1 µM to 1.0 µM) higher EC50values than MICT ones, and the propensity of their platelets to form aggregates with monocytes was significantly lower after 12 weeks. Short-term strenuous physical exertion was generally associated with platelet activation and an EC50reduction of 0.7 µM (0.6 µM to 0.8 µM). HIIT+MICT patients tended to be fitter after 12 weeks. No serious harms were observed. CONCLUSIONS: Including HIIT in cardiac rehabilitation seems to confer additional benefits compared with MICT alone, which should be confirmed in clinical trials with hard endpoints. Exertion-induced platelet activation and hyper-reactivity occur despite dual antiplatelet therapy. TRIAL REGISTRATION NUMBER: NCT02930330; Results.