How should I investigate a patient with hypertrophic cardiomyopathy (HCM)?

The first step in the investigation of a patient with hypertrophic cardiomyopathy (HCM) is to establish the diagnosis and determine whether the case is sporadic or familial.

History
The investigation should begin with the taking of a detailed history. This should include the construction of a family tree with at least three generations.

The clinical examination
This should be aimed specifically at excluding other causes of hypertrophy such as aortic stenosis or hypertension.

Descriptive investigations
Electrocardiography. In the majority of patients, the 12-lead electrocardiogram (ECG) shows abnormalities such as voltage criteria for left ventricular hypertrophy (LVH), minor intraventricular conduction defects or bundle branch blocks. Only rarely (<5% of cases) is the ECG completely normal.

Echocardiography. The mainstay of diagnosis is the echocardiographic demonstration of left ventricular hypertrophy (LVH), with either the interventricular septum or the free wall measuring 15mm. A very detailed study by an experienced operator is often necessary as hypertrophy may involve any part of LV. It is important to note that for adults with family history of HCM, modified diagnostic criteria apply.

Investigations to identify risk factors of sudden death The recognised risk factors are family history of sudden deaths, recurrent syncope, non-sustained ventricular tachycardia and an abnormal blood pressure response during exercise. History of multiple sudden deaths in the family is an important risk factor.

• Ambulatory monitoring of all patients with a diagnosis of HCM is mandatory and this should be for at least 48 hours.
• Exercise electrocardiography is also mandatory. Patients with HCM should undergo a metabolic exercise test with frequent blood pressure monitoring (every minute during exercise and for 5 minutes during recovery). An abnormal BP response is an important non-invasive marker of risk. The peak oxygen consumption during the exercise also helps identify those with significant limitation of exercise capacity.
• Non-sustained ventricular tachycardia (5 beats rate of 120 beats) especially if repetitive, is also associated with increased risk of sudden death.

Additional investigations in patients with syncope
In these patients, additional investigations should be aimed at determining the mechanism.

• Repetitive Holter recordings should be made.
• Tilt table test and if necessary.
• Electrophysiological study to exclude accessory pathway.

Other investigations that may be useful but not mandatory
This includes electrophysiological studies and rarely a thallium scan for myocardial ischaemia. It is necessary to exclude significant coronary artery disease with a coronary angiogram in patients >40 years old, smokers or those with severe chest pain.