What investigation protocol should a patient with dilated cardiomyopathy undergo?

A protocol for the investigation of dilated cardiomyopathy should aim to confirm the diagnosis, rule out treatable causes, prevent potential complications and determine prognosis. The following investigations are routinely used:

1. Echocardiography. Two-dimensional echocardiography is the major diagnostic test. Cardiac dimensions and systolic function are also of prognostic value, with an approximately 2-fold increase in relative risk of mortality for every 10% decline in ejection fraction.1 The presence of intracardiac thrombi, as well as poor systolic function itself, may be indications for anticoagulation.
2. Electrocardiography. Twelve-lead electrocardiography and Holter monitoring for arrhythmias should be performed. Occasionally a diagnosis of incessant tachycardia as a cause of the cardiomyopathy may be made. The signal averaged ECG may be a useful predictor of risk of sudden death and progressive heart failure and should be performed where available
3. Metabolic exercise testing is of prognostic value, particularly in advanced disease, and may guide referral for cardiac transplantation.
4. Screens for metabolic causes should routinely include liver function tests for unsuspected alcohol excess, thyroid function tests and iron studies including transferrin saturations. Further investigation (such as for sarcoid or amyloid) should be guided by history and examination.

Other tests may also be performed, but are not indicated in every case:

1. Coronary angiography should be performed in patients over the age of 40 years, or who have risk factors or symptoms or signs suggestive of coronary disease.
2. Coxsackie and adenoviral titres should be tested where there is a history of recent suspected myocarditis or recent viral illness, but the value of these in established cardiomyopathy is questionable.
3. Serology may be performed to detect the presence of markers of myocardial inflammation and myocyte damage.
4. Endomyocardial biopsy may have a role, but the risks and benefits are debated. What is, however, clear is that a tissue histological diagnosis provides important prognostic information which may (as in the case of sarcoidosis) have an impact on treatment.4 Biopsy may be recommended to exclude treatable causes such as sarcoidosis and giant cell myocarditis, if these are thought likely. In research centres, biopsy specimens may be analysed by immunohistochemical and molecular biological techniques to determine the presence or absence of low grade inflammation and viral persistence.

Frequency of follow up will depend on the severity of involvement at initial presentation. The course of the disease at early follow up is a useful indicator of long term prognosis with improvement or deterioration occurring in most cases within six months to one year of diagnosis.

The possibility that the patient’s cardiomyopathy may be familial should be explored by taking a detailed family history, but incomplete and age-related penetrance make family screening problematic. The decision to evaluate (usually first degree) relatives should be individualised, based on the extent of disease within a family, the levels of anxiety among patients and relatives, the presence of suggestive symptoms and the extent of local experience in the evaluation of dilated cardiomyopathy.