Background: Previous studies have shown an association between day-to-day variability of heart rate (HR) and cardiovascular (CV) events in general population. This association is unknown in coronary artery disease (CAD) patients with optimal medical therapy.
Purpose: To study HR and HR variability dynamics at home before the occurrence of CV events.
Methods: A total of 160 angiographically documented CAD patients from ARTEMIS study were guided into 2-years home- based exercise intervention and 44 patients (age 61±5 years, BMI 29±4, LVEF 66±7% and maximal exercise capacity 161±43 W) were willing to measure R-R intervals on a weekly basis at home during the follow-up. Eleven out of 44 patients had a new onset of ACS (n7), cardiac death (n=1), new onset of arrhythmia needing hospitalization (n=2), or stroke (n=1) during the follow-up. Day-to-day HR and HR variability (SDANN) were analyzed prospectively from weekly home measurements for 8 weeks preceding the CV event or from corresponding period without the event. Home measurements were performed in controlled conditions including 3 min beat-to-beat R-R intervals recordings in sitting and supine positions.
Results: There were no differences in the mean HR or SDANN analyzed over 8 weeks between the groups, e.g. the mean R-R interval at sitting position was 1000±138 vs. 1020±156 ms and SDANN 38±12 vs. 39±14 ms (p=ns for both) for patients without and with the new onset of event, respectively. During the 8-week period preceding the CV event, the day-to-day variability of mean R-R intervals was larger in patients with the new onset of event compared to patient without the event in the supine (87±19 vs. 62±7 ms, p=0.009) and sitting positions (93±24 vs. 65±7 ms, p=0.013), respectively. The day-to-day variability of SDANN did not differ between the groups, e.g. 12±6 vs 15±8 ms in patients without and with a new onset of event in the sitting position, respectively. There were no differences in age, BMI, LVEF or exercise capacity between the groups.
Conclusions: These data show that day-to-day variability of HR increases before the onset of CV events suggesting to a more unstable hemodynamic balance preceding these events. If confirmed in a large sample size, home HR measurement may become a simple and useful method for providing information on the risk of imminent CV event in patients with stable CAD.