Final answer:
Flattening of the interventricular septum in diastole is an echocardiographic finding associated with pulmonary hypertension. It occurs due to increased pressure in the right ventricle that bulges the septum into the opposite chamber, visible as a flat septum on the echocardiogram during diastole.
Step-by-step explanation:
A two-dimensional echocardiographic finding associated with pulmonary hypertension is flattening of the interventricular septum in diastole. The interventricular septum is the wall that separates the left and right ventricles of the heart. During diastole, the ventricles relax and fill with blood. Pulmonary hypertension leads to increased pressure in the pulmonary artery, resulting in the right ventricle facing abnormally high resistance to blood flow. This excessive pressure in the right ventricle can cause the septum to bulge into the left ventricle, creating a flat appearance on an echocardiogram. This finding reflects the deviation from the normal convex shape of the septum during diastole, indicating strain or overload in the right heart structures, often due to pulmonary hypertension.