EFFECTS OF ACUTE VOLUME CHANGES ON P-WAVE CHARACTERISTICS - CORRELATION WITH ECHOCARDIOGRAPHIC FINDINGS IN HEALTHY-MEN

Introduction: This study was performed to determine the effect on the P wave of different hemodynamic loads to the heart. Methods and Result s: Signal-averaged P wave ECG and atrial echocardiographic measurement s were obtained from eight healthy male volunteers at rest and after i nfusion of 1000 mt of plasma expander (Haemaccel(R)) over 15 minutes. These measurements were repeated 24 hours later at rest and after 0.8 mg of nitroglycerin given sublingually. The effect of positional chang es was also studied. At rest the amplitude of the P wave and the time of the maximal the P wave amplitude were reproducible, Sitting increas ed heart rate variability; no significant changes of the P wave were f ound. Volume overload decreased the heart rate and increased the atria l size on echocardiography with changes in lead V-1 (earlier appearanc e of the first positive deflection). Nitroglycerin administration incr eased heart rate and decreased the echocardiographic size of the atria , the latter not reaching statistical significance. Administration of nitroglycerin induced P wave amplitude rise in leads I and II, The max imal power in fast Fourier transformation for calculated orthogonal le ads X and Y increased as well. Conclusions: Amplitude behavior in lead s I, II and V-1 appears to correlate with load conditions, particularl y with volume redistribution. In healthy men subtle changes in the P w ave morphology after volume changes can be detected by the signal-aver aged EGG. Application of these findings in patients following acute ch anges in circulation needs further investigation.