**Question:** Causes of wide fixed splitting of second heart sound include all except:

A. Pulmonary hypertension
B. Pulmonary edema
C. Pneumonia
D. Congenital heart disease

**Core Concept:**

The second heart sound (S2) is a result of closure of the mitral and tricuspid valves during diastole. Splitting of S2 indicates differential closure times of these valves due to various causes. A wide fixed splitting is seen in conditions where the closure of the mitral valve is delayed relative to the tricuspid valve.

**Why the Correct Answer is Right:**

The correct answer (D) is related to congenital heart diseases, which cause structural abnormalities in the heart and its surrounding vessels, leading to the delayed closure of the mitral valve. This would result in a fixed split second heart sound.

**Why Each Wrong Option is Incorrect:**

A. Pulmonary hypertension (A) results from increased vascular resistance in the pulmonary circulation and does not directly affect the timing of valve closure, making it unrelated to the fixed splitting of S2.
B. Pulmonary edema (B) is a consequence of fluid accumulation in the lungs, which does not affect the timing of valve closure and therefore is not the cause of fixed splitting of S2.
C. Pneumonia (C) is an infection affecting the lungs and does not directly influence the timing of valve closure, making it an incorrect answer.

**Clinical Pearl:**

Awareness of the underlying causes of fixed splitting of S2 allows for a better understanding of heart sounds and their significance in clinical diagnosis. Fixed splitting of S2 should prompt a thorough evaluation for congenital heart diseases in pediatric patients, while in adults, it may indicate valvular or coronary artery disease.