HEMODYNAMIC-EFFECTS OF ATRIAL INTERACTION

Background: Ventricular pressure and volume overload may induce hemody namically important ventricular interactions mediated by the thick int erventricular septum. The purpose of this study was to determine wheth er analogous hemodynamically manifest atrial interactions occur across the thinner interatrial septum.Methods: Right atrial (RA) and left at rial (LA) pressures. were measured with micromanometer-tipped catheter s before and after atrial pressure and volume overload elicited by seq uential right ventricular (RV), RA, and septal ischemia induced in nin e open-chest dogs. Results: Following RV ischemia, RA pressure increas ed and RA contraction and relaxation were enhanced, as indicated by an augmented A wave and X descent. Despite decreased LV diastolic size, LA pressure increased, with similar increases in its A wave and X desc ent. RA ischemia depressed RA contraction and relaxation, resulting in diminished A wave and X descent. Parallel changes occurred in the LA waveform. Following septal ischemia, LA contraction and relaxation wer e enhanced, as reflected in an augmented A wave and X descent. Despite persistent RA ischemia, the RA A wave and X descent increased. Conclu sions: These fingings demonstrate interatrial transmission of pressure and waveform changes that may influence hemodynamic evaluation and ca rdiac function.