AXIAL CORRELATES OF PV1 IN LEFT ATRIAL ENLARGEMENT AND RELATION TO INTRAATRIAL BLOCK

In conclusion, a P-terminal force in V1 > -0.04 mV·s, a widely reported sign of LA enlargement, may be biphasic (+-) or monophasic (-), a consideration that was never specifically investigated before. Among 51 patients with echocardiographic LA enlargement, 28 had an abnormal P-terminal force, which was (+-) in 22 and had a mean frontal P axis of 41 °, significantly more horizontal than 25 patients without a Pterminal force with a P axis of 54 ° (p < 0.01). Only 6 P-terminal forces were (-) with a P axis of 58.3°; p <0.05 versus (+-) P-terminal force. Seventeen of 29 patients with IAB had an abnormal P-terminal force, with a trend toward a more horizontal P axis versus the P axis in those without P-terminal force. There-fore, in patients with LA enlargement, spatial vector forces other than those attributable to LA enlargement itself affect electrocardiographic sensitivity and the configuration of PV1. © 1994.