DCM is the final common pathway of a number of cardiomyopathies; it is typically characterized by the enlargement and dilation either of the left ventricle (LV) or of both heart ventricles and by the impaired contractility of ventricles defined as left ventricular ejection fraction (LVEF) less than 40%.[1]

DCM can be classified either as primary DCM, when the pathological involvement is predominantly limited to the myocardium or as secondary DCM, when the ventricular dilation is the final stage of an extensive myocardial damage which can be associated with an extremely heterogeneous group of systemic affections from autoimmune, cytotoxic or metabolic diseases.

Epidemiology

The yearly incidence of DCM in children is 0.57 cases per 100000, it is higher in boys than in girls though (0.66 vs 0.47 cases per 100 000).[2]

In adults DCM affects more frequently men than women; its prevalence is 1:2500 with an incidence of 7 per 100 000.[3]

This data may not reflect the true prevalence though as many patients are asymptomatic and, therefore, remain undiagnosed despite LV dysfunction.

DCM is the third most common cause of heart failure after ischemia and valvular heart disease and the most frequent cause of heart transplantation.[4]

Etiology

Idiopathic DCM accounts for 50% of all cases but family screenings show that 30–50% of all idiopathic DCM cases are familial with autosomal-dominant inheritance as predominant pattern of transmission.[5,6] Nonetheless there can also be cases of X-linked, autosomal recessive and mitochondrial inheritance. DCM has been associated with mutations in genes for desmin (cytoskeletal), lamin C (nuclear membrane) or myosin (contractile proteins).

Non-familial DCM can be triggered by a variety of etiologies such as: inflammation, autoimmune and systemic disorders (including collagen vascular disorders), infection (viral or bacterial myocarditis), ischemic disease, hypertension, infiltrative processes (sarcoid, amyloid, haemochromatosis), chronic anemia, non-compaction cardiomyopathy, metabolic disorders (uremia, hypocalcemia, hypophosphatemia, thyrotoxicosis), toxins (alcohol, cocaine), chemotherapy (doxorubicin), peripartum cardiomyopathy, muscular dystrophies, auto-immune cross reactivity (e.g. late onset cardiomyopathy in Chagas disease) but also valvular heart disease and hypertension.[1-7]

Clinical features

In general, the symptoms are manifested once the disease has progressed to its end-stage and significant myocardial (interstitial) fibrosis has occurred. At this stage patients show the symptoms of a cardiac heart failure such as dyspnea, fatigue, angina, pulmonary congestion and low cardiac output. Patients may also have complications related to DCM, for instance arrhythmias (atrial fibrillation, supraventricular and ventricular arrhythmias) or thromboembolic events may occur.[6-8]

Treatment and Prognostic Stratification

The LVEF is the strongest predictor of the heart failure progression in DC patients, while the LV volume and mass are independently correlated with the mortality and morbidity.[5]

In patients with nonischemic DCM the presence of a mid-wall fibrosis with LGE-CMR imaging was found to give independent prognostic information even beyond LVEF.

An accurate quantification of all these parameters is essential not only for an adequate evaluation of patients but also for the monitoring of the disease progression and its response to different therapeutic agents. The main purpose of the DCM therapy is the treatment of the heart failure symptoms and the prevention of the disease progression and related complications. Medical therapy remains the mainstay in patients with DCM and heart failure.

For patients who have a LVEF of less than 30% and who suffer from the symptomatic heart failure for which they are receiving the best possible medical therapy, the use of implantable cardioverter-defibrillators is a class I indication, as outlined by the ACC/AHA guidelines.[7,8]

The presence of a mid-wall LGE predicts an inducible ventricular tachycardia and allows the stratification of patient’s risks and the selection of an ideal candidate for ICD.[5]