Novel High-Resolution and Wireless Continuous Smart ECG Monitoring Improves Postoperative Atrial Fibrillation Recognition and Reveals Preceding Subtle Cardiac Autonomic Modulation Changes

Objectives: Postoperative atrial fibrillation (poAF) is a common complication after cardiac surgery. One of the important triggers is seemingly deranged cardiac autonomic modulation (CAM) which can be determined by methods of heart rate variability (HRV). The aim of this study was twofold: to determine if novel wireless ECG monitoring using smart technologies improves poAF detection and to define the levels of CAM before poAF onset.

Methods: We determined ECG (sub)intervals, and nonlinear heart-rate variability parameters from 20-minute high-resolution ECG recordings on the day before surgery and on 2nd, 3rd, and 5th postoperative day in 52 patients undergoing elective coronary artery bypass grafting, aortic valve replacement, or both combined. In addition, novel SAVVY ECG wireless device was attached to all patients from preoperative up to 5th postoperative day to detect any poAF episodes. Statistical analysis included Student´s unpaired t-test, Mann–Whitney U-test, Kolmogorov Smirnov test and chi-squared test. p < 0.05 was considered significant.

Results: ECG was able to detect poAF in 9 patients, whereas SAVVY ECG detected it in 13 patients. Patients who developed poAF (n = 13) constituted the AF group and the remaining 34 the no-AF group. Patients of AF group were moderately older (72.9 ± 8.7 vs. 68.3 ± 7.5 years; p = 0.08) and had longer ventilatory support (14.3 ± 6.1 vs. 10.4 ± 5.3 hours; p = 0.024). P-wave difference (i.e., P-wave duration postoperative − P-wave at baseline) was higher (−27 ± 27 vs. −5 ± 23 ms; p = 0.030) and postoperative PQ interval was longer (204 ± 61 vs. 162 ± 47 ms; p = 0.048) in AF group. Postoperative detrended fluctuation analysis (DFA) α1 (0.7 ± 0.3 vs. 1.1 ± 0.4; p = 0.015) was lower in AF group. DFAα1 and DFAα2 differences were higher in AF group (−0.3 ± 0.2 vs. 0.04 ± 0.4; p = 0.030 and −0.2 ± 0.4 vs. 0.1 ± 0.3; p = 0.037, respectively).

Conclusions: Novel continuous monitoring with single-lead wireless ECG sensor detects about 30% more AF episodes than conventional rhythm monitoring. AF patients tended to be older with longer ventilatory support and had also longer PQ interval. Non-linear HRV DFAα1 in DFAα2 indicated deranged CAM before poAF onset and might aid poAF prediction in the future.