The artial signal averaged electrocardiogram has been used to detect
patients at risk for paroxysmal atrial fibrillation but not yet for
paroxysmal supraventricular tachycardia. The P-wave-triggered
signal-averaged electrocardiogram, during sinus rhythm, was obtained
from 97 subjects divided in groups as follows: 30 controls (Group C), 38
patients with documented paroxysmal atrial fibrillation (Group A) and 29
with documented paroxysmal supraventricular tachycardia (Group B). The
atrial duration, root mean square of last 20 and 30 ms and the P-QRS
segment 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 <
0.00 1) in Group C (113.4 +/- 8) than in Group A (138.5 +/- 23.8) and
Group B (134.3 +/- 14.3). The root mean square (muV) of last 20 ms was
significantly 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
significantly 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
that (a) atrial late potentials could be useful not only for detecting
patients at risk for paroxysmal atrial fibrillation but for paroxysmal
supraventricular tachycardia as well (b) P-QRS segment might be used for
distinguishing paroxysmal atrial fibrillation from paroxysmal
supraventricular tachycardia signal averaging
