When a remnant of the interventricular membranous septum is also present, the so-called membranous flap, it lies immediately on top of the atrioventricular bundle.
The funnel consisted of myocardium that formed a continuity between the right wall of the atrioventricular canal and the ventricular septum.
The membranous atrioventricular septum can itself also very rarely be deficient in isolation.
At this stage, the wider curved end of the baffle is brought down onto the remnant of the atrial septum between the atrioventricular valves.
The distinction between the two entities depends on whether the atrial septum walls off the left atrium from the atrioventricular junction.
The interatrial septum bulged to the left, contributing further to the huge right atrium.
The malaligned atrial septum was widely excised to reveal a small left atrium receiving the pulmonary venous orifices and a tiny atrial appendage.
The angiosarcoma, due to its invasive nature, required extensive resection, after which pericardial patches were needed to reconstruct the right atrium and the septum.
