Diagnostic Electrocardiographic Sequences in Acute Pericarditis
Significance of PR Segment and PR Vector Changes
Diagnostic electrocardiographic patterns were analyzed in 50 consecutive patients who had unequivocal clinical evidence of acute pericarditis. Distributions of P and QRS, and of P-R segment, ST-segment and T wave changes were plotted by lead and by mean frontal vector (Â). Transient gross deviations of P-R segments, mainly in Stages 1 and/or 2, occurred in 41 patients (82%) and could produce an optical illusion of ST elevations when the J-points were actually on the baseline. Â P-R was close to 180° opposite to Â P and was not related to P wave or heart rate changes. In Stage 1, Â ST tended to be concordant with Â QRS and Â T. T wave inversions in Stage 3 produced an Â T which was distributed over an arc of 210° with no range of predilection.
Transient increase in magnitude of a normally oriented PR vector was consistent with the subepicardial atrial injury of acute pericarditis. It is the analogue of the classic Stage 1 ST-segment abnormalities of subepicardial ventricular injury and was equally as widespread in the electorcardiogram and almost as prevalent. P-R segment deviations were always depressions for leads of "epicardial" patterns. ST-segment deviations departed from the classic elevation pattern in 10 patients: 7 patients in whom ST was depressed in Lead III, 5 of whom had a horizontal QRS axis; and 3 patients in whom ST was depressed in aVL, two of whom had a vertical QRS axis. In Stage 3, the much wider range for Â T as compared with the relatively concentrated early injury vectors, Â P-R and Â ST, is ascribed to greater inhomogeneity of post-injury ventricular repolarization.
- Received March 26, 1973.
- Accepted April 26, 1973.
- © 1973 American Heart Association, Inc.