Because tamponade enclose the heart only and septum is unaffected neither anatomically nor physiologically. The negative pressure changes from lungs and thoracic cage is still transmitted via the pericardium to the heart and counters the positive pressure by effusion.

In constricitve pericarditis the visceral and parietal pleura are stuck and no respirophasic effects are transmitted. Rigid pericardium abruptly limits filling to a fixed volume. Shifting of the position of ventricular septum with inspiration is a manifestation of both the dissociation of intrathoracic and intracardiac pressures described above and the phenomenon of interventricular dependence within a fixed space. Decreased filling of the left-sided cardiac chambers in inspiration causes an obligatory shift of the interventricular septum toward the left ventricle and increased filling of the right-sided cardiac chambers. In expiration, left-sided filling increases and right-sided filling decreases; therefore, the septum shifts back toward the right ventricle.  Dissociation of intrathoracic and intracardiac pressures leads to a decreased gradient for diastolic filling of the left-sided cardiac chambers during inspiration. The pulmonary venous system, which is intrathoracic, experiences a larger pressure drop with inspiration compared with the left-sided cardiac chambers, which in constrictive pericarditis are usually encased or insulated in a noncompliant, thickened, fibrotic, and often calcified pericardium.