Interatrial conduction and STa in experimental atrial damage

Right (RA) and left atrial (LA) damage was produced with a subepicardial infiltration of 96 degrees alcohol in two groups of dogs. In six other dogs the left or right portion of the interatrial band was also injured. Conventional ECG and supplementary unipolar leads were recorded using photographic and direct inscription polygraphs at paper speeds of 50 and 100 mm/sec. Control, immediate postinjury and late tracings were obtained. A-V block was provoked to determine QTac. Slowing of heart rate and slight widening of the P wave and P-R interval were observed with both types of atrial damage. In four cases low right atrial rhythm was detected: two showed anatomo-histological sinus node involvement in right atrial injury. Qp waves were registered over the left precordium with necrosis of both sides, but were more frequent with RA damage. Damage of the left portion of the interatrial band delayed left atrial activation and split P waves in the precordial leads. Damage of the RA distorts the initial vectors, magnifying the left ones and simulating LA enlargement. The Qp registered on the RA is also detected by surface leads. Contrary distorted LA depolarization increases the RA vector and delays the left, ones, giving rise to greater asynchronsim and bimodal P waves.