The role of P wave duration as a predictor of postoperative atrial arrhythmias.

Atrial fibrillation (AF) and flutter (AFI) occur frequently after aortocoronary bypass grafting. To identify patients at highest risk, we observed 99 patients undergoing aortocoronary bypass surgery. P wave duration was measured on a three-channel ECG. An intra-atrial conduction defect (IACD), defined by conventional criteria as a single standard lead P wave greater than 110 msec, was present in 42 patients. We also identified IACDs by measuring the total P wave duration (TPWD) from the simultaneous three-channel recording of the standard leads (IACD-TPWD). Sustained AF-AFI, less than one hour, occurred in 29/99 patients. Of the 29 patients with AF-AF1, 24 had IACD-TPWD. The mean total P wave duration of patients with and without AF-AFI was 126 msec and 116 msec, respectively (P less than .001). The mean P wave duration measured conventionally (ECG lead 2) was 114 msec in the patients with AF/-AFI and 110 msec in patients without AF/-AFI. An isoelectric interval (IEI), derived by subtracting the ECG lead 2 P wave duration from the total P wave duration measured from three simultaneous limb leads, for patients without AF-AFI was 5.9 msec vs 12.4 msec for patients with AF-AFI (P less than 0.001). Of the patients with IACD-TPWD, 24/64 (38 percent) had AF-AFIRM; of the patients without IACD-TPWD, 5/35 (14 percent) had AF-AFI (P less than .05). The mean ages, number of bypass grafts, preoperative propranolol dose and prevalence of digoxin use presence of IACD-TPWD is a sensitive but non-specific predictor of AF-AFI after bypass surgery, and a prolonged IEI enhances the specificity.