Changes in the Electrocardiogram Induced by Coronary Artery Bypass Grafting

ECG recordings of coronary artery bypass grafting (CABG) surgery patients have been collected: number of patients 20 (men 95%, age 64.4 +/- 8.4), records duration 10-15 minutes. The number of bypasses for each individual is from 1 to 4 (40% of the patients are with 4). ECG recordings are pre- and post-surgery, from 2 to 10 days after intervention. All parameters were measured on an average P-QRS-T interval in order to avoid accidental events or noise. QRS amplitude, T-wave amplitude and ST elevation did not change, comparing pre- vs. post-stages. T-wave alternans (TWA) showed a clear upward trend (p=0.080) in the post-stage, and QRS-T angle in the frontal plane showed a clear downward trend (p=0.070) in the post-stage, although both have no statistical significance. Significant increase (p=0.0010) in the post-stage was obtained for the heart rate (HR). Four patients had negative T-waves in lead V2 in both pre- and post-stages, highly correlated with the number of TWA episodes: 5 +/- 2.4 episodes per person with negative T-waves, vs. 2.9 +/- 3.2 episodes in those with positive T-waves. The observed increase in TWA and HR during the early postoperative period suggests that this period could be a more vulnerable one regarding cardiac complications.