How to Perform Auscultation for Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) can be effectively assessed through auscultation, focusing on the presence of a fourth heart sound and specific cardiac murmurs. Normally, the fourth heart sound is not audible and is also referred to as the atrial sound. It occurs during late ventricular diastole, just before the first heart sound. In patients with HCM, this sound becomes detectable due to impaired ventricular relaxation and increased reliance on atrial contraction to fill the stiff, hypertrophied ventricle. The presence of a fourth heart sound is a key clinical clue in diagnosing this condition.

Identifying Characteristic Heart Murmurs in HCM

One of the hallmark findings in HCM is a harsh, crescendo-decrescendo systolic murmur caused by left ventricular outflow tract obstruction. This murmur is typically best heard at the left sternal border, specifically between the third and fourth intercostal spaces. It is often described as a "dynamic" murmur, meaning its intensity can change with various physiological maneuvers, such as squatting or standing, which alter preload and afterload.

Murmurs Related to Mitral Valve Dysfunction

In addition to the classic outflow tract murmur, patients may also exhibit a systolic murmur at the cardiac apex. This is often due to systolic anterior motion (SAM) of the mitral valve, which occurs when the hypertrophied ventricular septum disrupts normal mitral valve function during ventricular contraction. This phenomenon mimics the auscultatory findings of mitral regurgitation and further supports the diagnosis of hypertrophic cardiomyopathy.

Enhancing Diagnostic Accuracy Through Auscultation

Proper auscultation technique is essential for identifying the subtle yet significant findings associated with HCM. Clinicians should carefully listen to heart sounds in different patient positions and during various phases of respiration to detect changes in murmur intensity. Understanding the unique acoustic features of HCM allows for earlier recognition and improved patient management, especially in high-risk populations.