AHCM is frequently sporadic; however, a few families have been reported with autosomal dominant inheritance[3].
A sarcoma gene mutation (E101K mutation in the alpha-cardiac actin
gene) has been identified in these families. A family history is more
common in patients with asymmetric septal hypertrophy than with AHCM.
Morphologically AHCM is divided into 3 types: pure focal, pure diffuse
and mixed, of which pure focal is most common[4].
However in clinical practice this sub-classification is not widely
accepted and its clinical relevance is unknown. Others have divided AHCM
into two groups, based on whether they had isolated asymmetric apical
hypertrophy (pure AHCM) or had co-existent hypertrophy of the
interventricular septum (mixed AHCM)[5].
The diagnostic criteria for AHCM included demonstration of asymmetric
LV hypertrophy, confined predominantly to the LV apex, with an apical
wall thickness ≥ 15 mm and a ratio of maximal apical to posterior wall
thickness ≥ 1.5 mm, based on an echocardiogram or magnetic resonance
imaging (MRI)[5].
The mean age of presentation of AHCM is 41.4 ± 14.5 years and is most commonly seen in males[5].
About 54% of patients with AHCM are symptomatic and the most common
presenting symptom is chest pain, followed by palpitations, dyspnea and
syncope[5].
AHCM may also manifest as morbid events such as atrial fibrillation,
myocardial infarction, embolic events, ventricular fibrillation and
congestive heart failure[5].
Other complications of AHCM include apical aneurysm and cardiac arrest.
Physical findings of an audible/palpable fourth heart sound and a new
murmur are common[5]. Our patient was asymptomatic, with no family history and had no physical findings.
The
most frequent ECG findings are negative T-waves in the precordial leads
which are found in 93% of patients, followed by LV hypertrophy in 65%
of patients[5]. Negative T-waves with a depth > 10 mm are found in 47% of patients with AHCM[5].
The ECG in our patient showed LV hypertrophy and negative T-waves with a
maximum depth of 7 mm. TTE shows hypertrophy of the LV apex and is the
initial diagnostic tool for AHCM. When the baseline images are
suboptimal, a contrast echocardiogram is useful in establishing the
diagnosis[6]. On contrast ventriculography AHCM shows a distinctive LV “spade-like” configuration[5].
On single photon emission computed tomography (SPECT) myocardial
perfusion imaging findings of resting “solar polar” map pattern and
reduced flow reserve of the apex are the characteristics of AHCM[7].
Multislice spiral computed tomography can also be used to diagnose
AHCM; besides diagnosis it provides information on cardiac anatomy,
function and coronary arteries[8]. Cardiac MRI is also a valuable tool for diagnosing patients with inconclusive echocardiography and SPECT findings[9]. Although the initial diagnostic test for AHCM is most commonly TTE, the best diagnostic tool is considered to be cardiac MRI.
AHCM may mimic other conditions, including apical cardiac tumors[10], LV apical thrombus[11], isolated ventricular non-compaction[12], endomyocardial fibrosis (EMF)[13] and coronary artery disease[14] (Table 1). Chest pain in a patient with AHCM can be mistaken for ischemia from coronary artery disease[14]. Frequently these patients undergo a nuclear scan for abnormal ECG[15].
The majority of the patients with AHCM who suffer myocardial infarction
have an apical infarct, and in these patients wall motion abnormalities
varies from apical aneurysm to apical hyopokinesis[5]. Some patients may have asymptomatic apical infarction[5]. Hence, in clinical practice, an apical aneurysm may sometimes be seen with AHCM in asymptomatic patients.
Isolated ventricular non-compaction may be differentiated
from AHCM by high resolution images of the heart obtained by cardiac
MRI[12]. An echocardiogram with contrast can be used to differentiate AHCM from a LV apical mass (thrombus or tumor)[11].
A LV angiogram shows apical obliteration during both systole and
diastole in EMF, whereas in AHCM apical obliteration occurs only in
systole and also there is an absence of significant ventricular
hypertrophy in EMF patients[13].
In symptomatic patients with AHCM, verapamil, beta-blockers and antiarrhythmic agents are used[5]. Verapamil and beta-blockers are found to be beneficial in improving the symptoms in AHCM patients[16,17]. Amiodarone and procainamide are used in the treatment of atrial fibrillation and ventricular arrhythmias[18].
An implantable cardioverter defibrillator (ICD) is recommended for high
risk HCM patients with (1) previous cardiac arrest or sustained
episodes of ventricular tachycardia; (2) syncope; (3) a family history
of sudden death; or (4) episodes of non-sustained ventricular
tachycardia on serial Holter monitoring[19]. ICD has been was used in AHCM patients with cardiac arrest and non-sustained ventricular tachycardia[17].
Unlike
other variants of HCM, the prognosis of AHCM is relatively benign. The
overall mortality rate of AHCM patients was 10.5% and cardiovascular
mortality was 1.9% after a follow-up of 13.6 ± 8.3 years[5].
Sudden death and cardiovascular events occur more commonly in patients
with asymmetric septal hypertrophy than in those with AHCM[20]. A large LV end diastolic dimension may predict cardiac events in AHCM patients[21]. Some AHCM patients may develop sudden life-threatening complications, hence close follow-up of these patients is recommended[5].
