Hypertrophic cardiomyopathy differential diagnosis

Editors-In-Chief: C. Michael Gibson, M.S., M.D. [mailto:mgibson@perfuse.org]

Overview
The diagnostic imaging modality of choice is echocardiography. There are multiple echocardiographic features that distinguish hypertrophic cardiomyopathy from other conditions that lead to myocardial hypertrophy. In hypertrophic cardiomyopathy, the left ventricle is not dilated, and there is no other condition that would account for the magnitude of hypertrophy. The hypertrophy is often asymmetric.

Differential Diagnosis
HCM must be distinguished from the following disorders:

Athlete's heart
Quite often, HCM can be mistaken for a condition known as athlete’s heart. Both involve growth of the myocardium, however the latter generally is not correlated with incidences of SCD. While HCM can be linked to family history, athlete’s heart arises purely as a function of intense exercise (usually at least an hour a day, everyday. Since the body is operating at high training levels, the heart adapts and grows in order to pump blood more efficiently. Stoppage of exercise for three months generally leads to a decrease in wall/septum thickness in those with athlete’s heart, whereas those with HCM exhibit no decline.

People with athlete’s heart do not exhibit an abnormally enlarged septum, and the growth of heart muscle at the septum and free ventricular wall is symmetrical. The asymmetrical growth seen in HCM results in a less-dilated left ventricle. This in turn leads to a smaller volume of blood leaving the heart with each beat.

The degree of left ventricular wall thickness

 * In athlete's heart the LVH is symmetric and less than or equal to 12 mm
 * Rarely the LV thickness can be 14-16 mm and this makes it difficult to distinguish from HOCM. Athletes who engage in strength training may develop this pattern, ahtletes who engage in endurance training do not.
 * If the degree of thickening is out of proportion to the type and intensity of exercise, this suggests HOCM

The pattern of left ventricular wall thickness

 * Athleste's heart is symmetric
 * HOCM is more often asymmetric, but may in some cases be symmetric

The left ventricular cavity size

 * HOCM has smaller LV cavitary dimensions

Anderson-Fabry disease
(X-linked deficiency of the lysosomal enzyme alphagalactosidase)