Apical hypertrophic cardiomyopathy

Apical hypertrophic cardiomyopathy (AHCM or ApHCM), also known as Yamaguchi syndrome, is a rare form of hypertrophic cardiomyopathy which usually involves the apex of the left ventricle, rarely involves the right ventricular apex, or involves both apices.

Epidemiology

Historically, this condition was thought to be confined to the Japanese population but it is also found in other populations. Of all hypertrophic cardiomyopathy patients in Japan the prevalence of apical hypertrophic cardiomyopathy was 15-25% (cf. US ~3%).

Clinical presentation

Over half of patients with apical hypertrophic cardiomyopathy are thought to be asymptomatic but the most common presenting symptom is chest pain, followed by palpitations, dyspnea and syncope. It may also manifest as morbid events such as atrial fibrillation, myocardial infarction, embolic events, ventricular fibrillation and/or congestive heart failure.

ECG

• left ventricular hypertrophy
• giant (>10 mm in amplitude), negative T waves ¹²
  • most pronounced in the mid to lateral precordial (V4-5) leads
  • may correlate with severity of apical hypertrophy ¹³

Pathology

Genetics

It is frequently sporadic. An autosomal dominant inheritance has been reported in a few families where a sarcoma gene mutation (E101K mutation in the alpha-cardiac actin gene) has been identified ¹.

Classification

Some publications divide this into 3 subtypes:

• pure focal: considered most common
• pure diffuse
• mixed

Radiographic features

A "spade-like" configuration, or ace-of-spades sign, of the left ventricle is the classic appearance ⁶.

Treatment and prognosis

Compared with other variants of HCM, the prognosis of apical hypertrophic cardiomyopathy is relatively benign. The overall mortality rate of AHCM patients has been reported ~10.5% and cardiovascular mortality ~1.9% after a follow-up of 13.6 ± 8.3 years ¹.

History and etymology

The syndrome and its echocardiographic appearances were first described in 1979 by H Yamaguchi.

Differential diagnosis

Possible differential considerations include

• left ventricular non-compaction ⁴