What is Dilated Cardiomyopathy
Dilated cardiomyopathy (DCM) is a heart muscle disease characterized by left ventricular dilatation and global or regional systolic dysfunction that cannot be explained by abnormal loading conditions (such as hypertension, valvular disease, or congenital heart disease) or coronary artery disease. 1
Core Definition and Diagnostic Criteria
DCM represents a spectrum of heterogeneous myocardial disorders where the ventricles become enlarged and the heart's pumping ability becomes impaired. 1 The traditional definition requires both ventricular dilation and systolic dysfunction, though this has been recognized as overly restrictive since left ventricular hypokinesis without dilation can be the initial presentation of DCM. 2
Key Distinguishing Features
The diagnosis specifically excludes conditions that can cause similar ventricular changes: 1
- Coronary artery disease sufficient to explain the dysfunction
- Primary valvular heart disease
- Hypertension
- Congenital heart disease
A critical pitfall: The term "nonischemic cardiomyopathy" is often used interchangeably with DCM in clinical practice, but this is imprecise—nonischemic cardiomyopathy can include conditions caused by volume or pressure overload that don't meet the conventional definition of DCM. 1
Epidemiology and Prevalence
DCM affects approximately 1 in 250 to 1 in 400 individuals in the general population. 1 This makes it one of the most common forms of cardiomyopathy and a leading cause of heart failure. 3
Etiology: Genetic and Acquired Causes
Genetic Component
Familial DCM accounts for 30-50% of all cases, with approximately 30-40% of these attributable to identifiable genetic causes. 1 Genetic mutations typically involve genes responsible for cytoskeletal, sarcomere, and nuclear envelope proteins. 4 Well-established genotype-phenotype correlations exist for specific gene variants including desmoplakin (DSP), filamin-C (FLNC), and laminin. 1
Acquired Causes
Secondary DCM can result from: 2, 3
- Viral myocarditis (with progression to DCM being a long-hypothesized mechanism) 5
- Toxins (particularly alcohol)
- Cancer treatment
- Endocrinopathies and metabolic diseases
- Pregnancy (peripartum cardiomyopathy)
- Tachyarrhythmias
- Immune-mediated diseases
Important consideration: 5-15% of patients with acquired DCM harbor a likely pathogenic or pathogenic gene variant, meaning the diagnostic approach must always consider both genetic and acquired factors simultaneously. 2
Clinical Spectrum and Phenotypic Variability
DCM encompasses a wide spectrum of presentations beyond overt disease: 1
- Early heart rhythm disorders without overt structural disease
- Isolated left ventricular dilation
- Isolated myocardial scar
- Hypokinetic non-dilated cardiomyopathy
This phenotypic heterogeneity reflects advances in cardiogenetics and deep phenotyping through advanced imaging with tissue characterization capabilities, which have enabled detection of subclinical forms of disease. 1
Clinical Manifestations
Patients typically present with systolic heart failure symptoms, though diastolic dysfunction develops as the disease progresses. 4 Clinical presentations can also include: 4
- Arrhythmias
- Thromboembolic events
- Cardiogenic shock
Prognosis and Disease Progression
Despite improvements in recent years, DCM remains associated with significant mortality—approximately 40% at 10 years—and is a leading cause of heart failure and premature death. 6, 7 Disease progression and prognosis are primarily driven by disease severity and the degree of reverse remodeling within the heart. 4
The worst prognosis occurs in patients with: 4
- Lowest ejection fractions
- Severe diastolic dysfunction
- Those progressing to terminal heart failure requiring left ventricular assist device implantation or heart transplantation
A major clinical challenge: Identifying which DCM patients are at risk of disease progression remains difficult, making it challenging to distinguish those who might benefit from early treatment and potentially experience improvement or remission. 1