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Studies on the p wave of atrial septal defect by high speed magnified electro cardiography


, : Studies on the p wave of atrial septal defect by high speed magnified electro cardiography. Shikoku Acta Medica 37(1): 69-81

Qualitative and quantitative observations on the P waves of the magnified high-speed ECG were performed in 106 patients with the ostium secundum type of atrial septal defect (ASD). Various parameters of the P wave were compared with hemodynamic data from cardiac catheterization and with left atrial dimension (LAD) from echocardiographic method. Biphasic P waves in lead V1 were observed in 79 cases (74.5%) with ASD and those in lead III in 56 cases (52.8%). Entirely negative P waves in lead V1 were observed in 3 cases (2.8%) with ASD and those in lead III in 8 cases (7.6%). The amplitudes of P waves in lead V2.5 and V6 showed significant positive correlations with various parameters, such as right ventricular systolic and mean pressures, pulmonary to systemic flow ratio (Qp/Qs), left to right shunt ratio (Qp-Qs/Qp), pulmonary artery systolic and mean pressures, which reflected the right ventricular pressure overload and the amplitudes of the negative phase of the P wave in lead V1 and V2 showed positive correlations with pulmonary mean capillary pressure (PCW). Positive correlations were observed between the upstroke time of the P wave in lead I and II and Qp/Qs and were observed between the duration of the P wave in lead II and PCW. Following the operation of ASD, there were significant decreases in the positive phase amplitude of the P wave in lead II, in the positive phase amplitude and duration of the biphasic P waves in lead V1 and in the P initial force in lead V1. There were significant increases in the negative phase duration of the biphasic P waves in lead V1 and in the degree of left deviation of the mean frontal P axis. These changes in the various parameters of the P wave could be a good index of the correction of ASD. Left axis deviation of the P wave suggested a relative overload of left atrium compared with right atrium after the surgical operation. There was no significant difference on Macruz index between ASD and normal group. Macruz index of < 1.0, diagnosed as having right atrial volume overload, were observed in only 4 (3.8%) of 106 cases. There was no significant difference on LAD measured on echocardiogram between ASD and the normal group. The ratio of LAD to body surface area (LAD/BSA) was significantly increased in ASD compared with the normal group. There was a significant positive correlation between LAD and age in ASD. There was no significant difference between LAD values before or after the operation of ASD. The magnified high-speed ECG apparently was useful for the detailed observation of the P wave and for the evaluation of the atrial overload in ASD.

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