Coronary Artery Bypass Grafting Is Associated with a Significant Worsening of QT Dynamicity and Heart Rate Variability

Abstract

Background: Imbalance in autonomic nervous system and impaired myocardial repolarization has been shown to increase the risk for arrhythmias in patients with coronary artery disease. This study evaluated the effects of coronary artery bypass grafting (CABG) on heart rate variability and QT interval dynamicity in subjects with coronary artery disease undergoing elective CABG surgery. Methods: The study group consisted of 68 consecutive patients (mean age ±SD: 61 ± 9 years) with coronary artery disease who underwent elective CABG. Twenty-four-hour Holter monitoring was performed 2–5 days before cardiac surgery and was repeated 10 days after CABG. ELATEC holter software was used to calculate heart rate variability and QT dynamicity parameters. All subjects had a complete history, laboratory examination and transthoracic echocardiography. Results: All patients had beta-blocking agent medication pre- and postoperatively. Standard deviation of all NN intervals for a selected time period, square root of the mean of the sum of the squares of differences between adjacent RR intervals, the proportion of differences in successive NN intervals greater than 50 ms, normalized low-frequency power, and normalized high-frequency power were significantly decreased after CABG surgery, whereas low-frequency/high-frequency ratio was significantly increased after CABG. QT/RR slopes over 24 h were significantly increased after CABG surgery for QT end and QT apex (QTapex/RR: 0.16 ± 0.13 vs. 0.28 ± 0.19, p < 0.001; QTend/RR: 0.18 ± 0.13 vs. 0.36 ± 0.23, p < 0.001). Conclusion: This prospective study showed for the first time that CABG was associated with a significant worsening of heart rate variability and QT dynamicity parameters in the postoperative period.

Heart rate variability measures poorly predict atrial fibrillation after off-pump coronary artery bypass grafting

“…CABG surgery is associated with increased autonomic instability of the heart, leading to unpredictable cardiac responses during and after surgery [9][10][11]. A balance between sympathetic and parasympathetic systems results in the normal variation in heart rate (HR).…”

The Importance of Histopathological Findings in Saphenous Vein Grafts

“…Coronary-artery bypass grafting is associated with greater freedom from repeat revascularization for patients with ischemic heart disease [2]. Human aortocoronary grafts may be compromised postoperatively or due to early thrombosis or fibrointimal hyperplasia.…”

Comparative study of short-term cardiovascular autonomic control in cardiac surgery patients who underwent coronary artery bypass grafting or correction of valvular heart disease

“…14,15 Changes in the autonomic control of the heart, associated with CABG, lead to unpredictable cardiovascular events during and after surgery. 16,17 In particular, the increased HF% and peak point correlation dimension before CABG are associated with postoperative atrial fibrillation. 18 These statements are not confirmed by our findings on short-term follow-up in the present study.…”