Heart Rate Recovery Velocity in Cardiac Disease

Abstract

Introduction Rate of recovery of heart rate between 10 and 20 seconds following orthostatic challenge (HRR10-20) is a risk factor for all-cause mortality. Furthermore, both cardiac rehabilitation and completeness of coronary revascularisation have been shown to improve prognosis of patients with cardiovascular disease. We aim to determine if, by assessing HRR10-20 in patients who have undergone complete coronary revascularisation in comparison with those who have had incomplete revascularisation, we can determine which patients are at greatest risk of future cardiovascular events. We will also evaluate HRR10-20 before, during and after cardiac rehabilitation to determine if this known risk factor for all-cause mortality is a modifiable risk factor in cardiac disease.

Methods Between July 2019 until March 2020 cross sectional and longitudinal assessment of the same patient groups were carried out as a case-control study. Patients aged >18 years of age who had percutaneous coronary intervention, coronary artery bypass surgery, transcatheter aortic valve implantation or surgical aortic valve replacement were enrolled at the beginning of phase 2 of cardiac rehabilitation. A cross-sectional comparison was made initially between those who had undergone complete coronary revascularisation and those with incomplete revascularisation. Thereafter, a longitudinal assessment was made comparing those who completed a cardiac rehabilitation programme and those who did not.

Assessment of HRR10-20 was performed at the beginning of rehabilitation, at 6-weeks, and again at 12-weeks. During active stand, real time heart rate, blood pressure and ECG recordings were taken via non-invasive digital photoplethysmography (Finometer, Finapres Medical systems, Arnhem, The Netherlands).

Statistical analysis was performed using GraphPad Prism 9.0.2. Pearson?s correlation coefficient was used to determine the relationship between HRR10-20 and incomplete versus complete revascularisation, and was also used to determine the relationship between change in HRR10-20 from baseline to 12 weeks and upon completion of the rehabilitation programme. Student?s T test used to determine statistical significance of the difference between the two independent groups (p <0.05 was considered statistically significant).

Results Participants (n= 53) were recruited, 37 of whom had undergone complete revascularisation, while 16 had not. Following initial recruitment, 16 participants elected not to participate in the cardiac rehabilitation stage of the study. The remaining participants (n=37) underwent further assessment in regards to cardiac rehabilitation response. Of these, 25 participated in cardiac rehabilitation versus 12 who did not.

HRR10-20 was impaired in the incomplete revascularisation group (-3 ? 0.60) compared to the completed revascularisation group (-6.56 ? 0.52) (p<0.0001). Completeness of revascularisation was strongly associated with HRR10-20 (Pearson?s correlation coefficient 0.529; p <0.0001).

Completion of cardiac rehabilitation also correlated with improvement of HRR10-20 from baseline to 12 weeks (r=0.6104 p<0.0001). Through the 6 week and 12-week time periods, differences in HRR10-20 were noted between the two groups. At the 6-week time point the group who participated in cardiac rehabilitation improved their HRR10-20 to -5.74?1.91, while the non-rehab group disimproved to 1.85?0.77 (p<0.0001). This pattern was repeated at the 12-week interval, with the rehab group maintaining a marginal improvement of -6.33?2.32, and the non-rehab group deteriorating further to 4.05?1.27 (p<0.0001).

HRR10-20 in the non-rehab group deteriorated between week 0 and week 6 by 5.94 (p<0.0001), and between week 6 and 3 months by 2.2 (p=0.004).

Conclusions This study shows a significant correlation between both revascularisation status and completion of cardiac rehabilitation with improved autonomic function as measured with HRR10-20. Impaired autonomic function in the incomplete revascularisation group may be due to residual baseline ischaemia. Augmentation of autonomic function following cardiac rehabilitation may explain in part how cardiac rehabilitation improves prognosis. Furthermore HRR10-20 may be a modifiable risk factor in high-risk secondary prevention patients. The main limitation is the limited sample size; the trend observed of improved autonomic function through rehabilitation was in comparison to a group who, through not completing rehabilitation, had a deterioration in autonomic function. The trend of actual improvement in autonomic function may be significant in a larger cohort.