K. Kim1, P. Frank2, W. Toppen3, S. Barajas Nuno1, L. Mukdad1, P. Benharash1,4 1David Geffen School Of Medicine, University Of California At Los Angeles,Los Angeles, CA, USA 2University Of California – Los Angeles,Anesthesiology,Los Angeles, CA, USA 3University Of California – Los Angeles,Medicine,Los Angeles, CA, USA 4University Of California – Los Angeles,Cardiac Surgery,Los Angeles, CA, USA
Introduction: Postoperative atrial fibrillation (POAF) is the most common complication following cardiac surgery and is associated with increased morbidity and mortality. Successful reduction of POAF by administration of beta-blockers suggests that sympathetic activity is a significant driver of atrial fibrillation following cardiac surgery. Due to practical difficulties of measuring cardiac autonomic tone, surrogate markers using ECG have been developed and validated. Given the putative impact of sympathetic tone in POAF, we hypothesized that shortening of RR and QT intervals would precede the onset of POAF.
Methods: Telemetric ECG data were collected for adult patients without a history of atrial arrhythmias undergoing coronary artery bypass or valve operations at our institution from February to May 2016. Patients were grouped into POAF or non-POAF categories based on in-hospital telemetry results. A custom LabView® program was created to determine RR and QT intervals adjusted for heart rate. Resulting values were continuously recorded and plotted on a Poincaré plot, demonstrating short (SD1) and long-term (SD2) variability and their ratio, SD1/SD2 indicative of sympatho-vagal balance. Telemetry data was analyzed for up to 48 hours postoperatively for non-POAF patients or until the occurrence of POAF for others. With baseline values defined as the first hour of un-paced, postoperative ECG, patients were compared using an unpaired two tailed, Student’s T-test.
Results: After exclusion for poor signal quality and pacing, a total of 20 patient data sets were analyzed hourly (10 POAF, 10 non-POAF). The groups were similar in demographics including age, incidence of hypertension, diabetes, heart failure, and cerebrovascular disease. Compared to baseline, SD1/SD2 did not show a statistically significant difference (Figure) in the POAF and non-POAF groups (%Δ = 69.7±184.9% vs. 12.7±24.7%, p=0.48). No significant trends were observed when comparing normalized QT intervals (POAF: 1.5±11.3% vs. non-POAF: -8.7±7.5%, p=0.15)
Conclusion: In this study, changes in heart rate variability and QT interval parameters were not predictive of the onset of postoperative atrial fibrillation. Although previous studies have shown ARI and HRV parameters to vary predictably with changes in sympathetic tone, surface ECG markers may not have the ability to accurately detect such changes. POAF may be a complex process and may have other driving factors. Due to the large fluctuations in QT and heart rate variability parameters, our findings warrant further investigation in a larger patient cohort.
