1357803 - Apical hypertrophic cardiomyopathy of the right ventricle associated with mixed pulmonary stenosis

A 31-year-old man was referred to our hospital due to exertional dyspnea and palpitations. Cardiac exam was notable for a systolic murmur over the pulmonic area. Electrocardiogram showed sinus rhythm with signs of systolic overload and right ventricular hypertrophy.

Diagnostic Techniques and Their Most Important Findings:

Due to the suspicion of pulmonary stenosis, a magnetic resonance angiogram (MRA) was ordered to evaluate intracardiac anatomy as well as biventricular function and valvular function. The MRA sequences 3D turbo-flash and True FISP were used for sequential segmental analysis, which was notable for hypertrophy of the right ventricle (RV), predominantly in the mid and apical portions of its free wall, and global hyperkinesia with a decreased end-systolic volume and increased ejection fraction (EF) of 79%. The left ventricle also presented hypertrophy, mainly in the septal and apical segments, with global hyperkinesia, and an EF of 75%. T1 and T2 mapping was notable for increased extracellular volume fraction (33%). The RV outflow tract presented increased acceleration of the infundibular portion of the jet secondary to a muscular ring, pulmonary valve was tricuspid with decreased area (1.9 cm), and a supravalvular membrane with a functional diameter of 7 mm; the valve also presented mild regurgitation. Additionally, the main pulmonary arterial trunk, and its left and right branches were dilated accompanied by mild pericardial effusion. 

It is important to note that the predominance of the hypertrophy in the basal and apical segments could suggest Yamaguchi syndrome, a diagnosis that is often missed due to a characteristically poor acoustic window on echocardiogram, highlighting the importance of MRA in this disease. Finally, it is notable that the significant fibrosis measured in the patient is associated with a poor prognosis. Maron et al. reported that fibrosis of more than 20% of the left ventricular mass increased the risk of sudden cardiac death (SCD), with current guidelines establishing 15% as an intermediate risk. However, these cutoff points have not been as extensively studied in subtypes such as the present case, with predominantly right apical hypertrophy.

Learning Points from this Case:

Apical hypertrophic cardiomyopathy of the RV is a rare subtype that must be suspected when the RV free wall has a width of more than 5 mm without a cause that justifies this response. Additionally, when associated with other congenital heart defects, such as the present case, a detailed evaluation of intracardiac anatomy and function must be realized, as it can establish whether the fibrosis and hypertrophy is secondary to an abnormality or primary, like in the present case.