The value of P dispersion on predicting atrial fibrillation after coronary artery bypass surgery: effect of magnesium on P dispersion.

BACKGROUND: AF is a frequent arrhythmia complicating CABG, and it is well known that dispersion and prolongation of P wave increases the risk of AF. The aim of this study was to investigate the effect of magnesium (Mg) treatment on P-wave duration and dispersion in patients undergoing CABG.

METHOD: The study included 148 consecutive patients (33 women, 115 men; mean age 62.1 +/- 7.0 years) undergoing CABG who were randomly allocated to two groups. Group A consisted of 93 patients to whom 1.5 g daily MgSO(4) infusion was applied the day before surgery, just after operation, and 4 days following surgery, and group B consisted of 55 control patients. From the preoperative and postoperative fourth day, 12-lead ECG recordings, duration of the P waves, and P-wave dispersions were calculated.

RESULTS: There were no differences between the two groups with regard to age, sex, and blood Mg level. Comparison of the baseline and day 4 ECG measurements showed no difference as far as heart rates, duration of PQ, and QRS intervals were concerned. AF developed in 2 (2%) cases in group A and in 20 (36%) cases in group B (P < 0.001). There was no difference between the two groups when average basal P max, P min, P dispersion, and day 4 P min values were compared. In group A, fourth day P max (94.3 +/- 11.8 vs 101.0 +/- 13.2 ms; P = 0.0025) and P dispersion (38.2 +/- 9.2 vs 44.9 +/- 10.9 ms; P = 0.0002 ) were significantly lower as compared to group B. Comparing the patients who developed AF, and who did not, no difference was detected with regard to baseline P max, P min, P dispersion, and day 4 P min. Day 4 P max (95.1 +/- 11.8 vs 106.4 +/- 14.0 ms, P = 0.0015) and P dispersion (38.9 +/- 8.8 vs 50.7 +/- 13.0 ms, P = 0.001) of patients who developed AF were significantly higher. Baseline Mg levels were similar in patients who developed AF, and who did not, but the day 4 Mg level was significantly lower in AF group (2.0 +/- 0.23 vs 2.15 +/- 0.26 mg/dL, P < 0.001).

CONCLUSION: Perioperative Mg treatment reduces P dispersion and the risk of developing AF in patients undergoing CABG.