Observations on the interatrial pressure gradients in man.

It was possible to calculate pressure gradients across the interatrial septum in several cases of congenital heart disease. Gradients in cases of interatrial septal defect are similar to those found in animals with artificially produced defects. The data are used to form a rounded picture of the hemodynamics of interatrial septal defect. In pulmonic stenosis with interatrial communication, reversal of the usual left-to-right gradient may occur only during atrial systole. Under these circumstances it is often possible to distinguish a patent foramen ovale with competent valve from an interatrial septal defect. ATRIAL hemodynamics have been extensively studied in animals'-7 with or without interatrial communications. Despite the widespread use of right heart catheterization, there is still a paucity of such information in man. During routine right heart catheterization of several patients with congenital heart disease, passage of the catheter through inter-atrial communications made it possible to record pressure pulses from both atria. An analysis of these curves, insofar as it provides information on atrial hemodynamics in man, forms the basis of this report. METHODS The data consisted of atrial pressure pulses from 14 cases with congenital interatrial communications. Seven of these sets of curves were unsuitable for detailed analysis because of artefacts or large respiratory variations. However, the data from these discarded cases lend themselves to the same interpretation as the seven analyzed in detail. The atrial pressure curves were recorded from each atrium in quick succession, using the Sanborn capacitance manometer (fig. 1). A simultaneously recorded electrocardiogram (lead II) served as a time reference. The patients were supine and breathing quietly. The zero level was 5 cm. dorsad to the angle of Louis. Blood samples were obtained in each case from both atria. The presence and magnitude of right-to-left shunting of blood in the atria were (H-218). 527 determined by comparing the oxygen content of left atrial or systemic arterial blood with that of pulmonary venous blood. Where the latter was not available, 95 per cent saturation was assumed. Left-to-right shunting of blood in the atria was indicated by the high oxygen content of right atrial blood relative to caval blood. The pressure pulses and blood samples from other chambers and vessels were used to complete the hemodynamic picture and to arrive at a final diagnosis. The pressure differences between the left and right atrial curves during several heart cycles were determined for each 0.04 second, using the summit of …