An ostium primum atrial septal defect (ASD) occurs when then atrial septum near the atrioventricular valves has a communication between the two atrium causing a left to right shunt. This rarely ...

If the left ventricle is noncompliant, and atrial contraction forces blood through the atrioventricular valves, a S4 is produced by the blood striking the left ventricle. CLINICAL PEARL ...