Heart Rate Variability-guided Training in Cardiac Rehabilitation

Background: Previous studies have reported that heart rate variability (HRV)-guided training is a better option for improving autonomic function and aerobic capacity (i.e., oxygen uptake and power output at second ventilatory threshold and maximal exercise) during a cardiopulmonary exercise test compared to predefined training in sedentary and physically active healthy people. Nevertheless, none of these previous studies have been carried out with coronary artery disease (CAD) patients.

Methods: A total of 23 patients with CAD were divided into HRV-guided training group (HRV-G; n = 11) and predefined training group (PRE-G; n = 12). All patients trained three days a week for eight weeks (18 sessions). Patients allocated in the PRED-G carried out a previously established cardiac rehabilitation programme, combining sessions of moderate and high intensity, while patients allocated in the HRV-G carried out sessions of moderate or high intensity on the basis of their daily HRV assessments. The weekly averaged and isolated parasympathetic-related HRV indices, heart rate recovery, resting heart rate, and aerobic capacity were assessed before and after of the training programme.

This study was a parallel-group, double-blind, randomised controlled trial. This study was approved by the ethical committee of the local University and was conducted conforming to the recommendations of the Declaration of Helsinki. Eligible patients were men and women with low-risk and age ≥ 18 years, who had experienced an acute myocardial infarction, angina pectoris, had undergone revascularisation (percutaneous transluminal coronary angioplasty or coronary artery bypass grafting) or coronary heart disease was documented by angiography, up to one year before to the enrolment in the study. Exclusion criteria included unstable angina, atrial fibrillation, cardiac implantable electronic devices, complex ventricular arrhythmias, uncontrolled hypertension, conditions limiting participation in exercise training and/or symptom-limited cardiopulmonary exercise test at pre-intervention. Before taking part in the study, patients were interviewed and signed a written informed consent. The patients were randomly allocated to a predefined training group (PRED-G; n = 12) or heart rate variability (HRV)-guided training group (HRV-G; n = 11).Before to start the study protocol, patients were instructed to properly carry out day-to-day HRV measurements. The study protocol was divided into two periods: a 2-week baseline period (BP) and a 6-week training period (TP). Before and after TP, baseline assessment week (PRE) and final assessment week (POST) were conducted, respectively. The variables/tests assessed/included in the assessment weeks were: cardiopulmonary exercise test, autonomic function, body composition, blood analysis, quality of life and dietary intake. Assessments were carried out in the same sequence and at the same period of the day. Patients and assessors recording the outcome measurements were blinded to the group allocations. Throughout the 6-week TP, patients allocated to PRED-G carried out a predefined training program, while patients that were assigned to HRV-G trained based on day-to-day HRV measurements.

Eligibility Criteria:
Inclusion Criteria:

* Patients who had experienced an acute myocardial infarction up to one year before to the enrolment in the study
* Patients who had experienced an angina pectoris up to one year before to the enrolment in the study
* Patients who had undergone revascularisation (percutaneous transluminal coronary angioplasty or coronary artery bypass grafting), up to one year before to the enrolment in the study
* Clinical diagnosis of coronary heart disease documented by angiography, up to one year before to the enrolment in the study

Exclusion Criteria:

* Unstable angina
* Atrial fibrillation
* Cardiac implantable electronic devices
* Complex ventricular arrhythmias
* Uncontrolled hypertension
* Conditions limiting participation in exercise training
* Symptom-limited cardiopulmonary exercise test at PRE