Background: Ventricular pressure and volume overload may induce hemodynamically important ventricular interactions mediated by the thick interventricular septum. The purpose of this study was to determine whether analogous hemodynamically manifest atrial interactions occur across the thinner interatrial septum. Methods: Right atrial (RA) and left atrial (LA) pressures were measured with micromanometer-tipped catheters before and after atrial pressure and volume overload elicited by sequential right ventricular (RV), RA, and septal ischemia induced in nine open-chest dogs. Results: Following RV ischemia, RA pressure increased 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 descent. 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 were enhanced, as reflected in an augmented A wave and X descent. Despite persistent RA ischemia, the RA A wave and X descent increased. Conclusions: These findings demonstrate interatrial transmission of pressure and waveform changes that may influence hemodynamic evaluation and cardiac function.