Atrial T(Ta) wave and atrial gradient in patients with A-V block.
The P and the Ta waves of two patient groups with A-V block were magnified with a direct-current amplifier and recorded at a high paper speed. In Group A patients (those without serious cardiovascular complications except A-V block) the P and the Ta waves were recorded in the opposite direction in every lead and there was a linear relationship between the amplitude of the P and the Ta waves. The atrial gradient was nearly zero. There existed a positive correlation between the P + Ta time and the P-P interval. In Group B patients (those with serious cardiovascular complications besides A-V block) there were significant differences in the Ta wave from Group A with respect to form, polarity, amplitude, duration, and the relationship between the Ta and the P waves. The atrial gradient was markedly large. Careful attention should be paid to the deviation of the PQ segment caused by the Ta wave in daily ECG's to detect atrial abnormalities. The Ta wave extends into the ST segment and, while describing the deviation of the ST segment, the influence of the Ta wave should be kept in mind.