ATRIAL LATE POTENTIALS - PAROXYSMAL SUPRAVENTRICULAR TACHYCARDIA VERSUS PAROXYSMAL ATRIAL-FIBRILLATION

The artial signal averaged electrocardiogram has been used to detect p atients at risk for paroxysmal atrial fibrillation but not yet for par oxysmal supraventricular tachycardia. The P-wave-triggered signal-aver aged electrocardiogram, during sinus rhythm, was obtained from 97 subj ects divided in groups as follows: 30 controls (Group C), 38 patients with documented paroxysmal atrial fibrillation (Group A) and 29 with d ocumented paroxysmal supraventricular tachycardia (Group B). The atria l duration, root mean square of last 20 and 30 ms and the P-QRS segmen t were measured. Atrial late potentials were considered to exist when: atrial duration was > 120 ms and root mean square of last 20 ms were < 3.5 muV. The atrial duration (ms) was significantly shorter (P < 0.0 0 1) in Group C (113.4 +/- 8) than in Group A (138.5 +/- 23.8) and Gro up B (134.3 +/- 14.3). The root mean square (muV) of last 20 ms was si gnificantly higher (P < 0.001) in Group C (5.2 +/- 2.5) than in Group A (2.5 +/- 1.3) and Group B (3.1 +/- 1.8). Atrial late potentials were present in 3/30 controls, 32/38 of Group A cases and 23/29 of Group B . The specificity and sensitivity were, respectively: 0.90, 0.84, for Group A, and 0.90, 0.79 for Group B. The P-QRS segment (ms) was signif icantly shorter (P < 0.01) in Group B (12.5 +/- 9.4) than in Group C ( 32.5 +/- 16.9) and Group A (20.5 +/- 13.4). These findings suggest tha t (a) atrial late potentials could be useful not only for detecting pa tients at risk for paroxysmal atrial fibrillation but for paroxysmal s upraventricular tachycardia as well (b) P-QRS segment might be used fo r distinguishing paroxysmal atrial fibrillation from paroxysmal suprav entricular tachycardia signal averaging.