All are the true regarding hyperophic obstructive cardiomyopathy, except:
**Core Concept**
Hyperophic obstructive cardiomyopathy (HOCM) is a genetic disorder characterized by abnormal thickening of the heart muscle, specifically the septum, which can lead to impaired cardiac function and potential obstruction of blood flow. This condition is often inherited in an autosomal dominant pattern and can be associated with various genetic mutations.
**Why the Correct Answer is Right**
The correct answer is D. In HOCM, the thickened septum can cause dynamic left ventricular outflow tract obstruction, leading to symptoms such as chest pain, shortness of breath, and syncope. The pathophysiology involves an interplay between the thickened septum and the mitral valve, which can lead to mitral regurgitation. The left ventricular cavity is often small and nondilated, and the ejection fraction may be normal or even increased.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because HOCM is often associated with a characteristic "hypertrophied" or "dysplastic" appearance of the septum on echocardiography.
**Option B:** Incorrect because the left ventricular cavity is often small and nondilated in HOCM, in contrast to dilated cardiomyopathy.
**Option C:** Incorrect because HOCM is a genetic disorder that can be inherited in an autosomal dominant pattern, and genetic mutations are often identified.
**Clinical Pearl / High-Yield Fact**
A key clinical feature of HOCM is the presence of a "hypertrophied" or "dysplastic" appearance of the septum on echocardiography, which can be a useful diagnostic clue. Additionally, HOCM can be associated with other cardiac conditions, such as mitral valve prolapse and arrhythmias.
**Correct Answer:** D