What are the diagnostic criteria for dilated cardiomyopathy?

Diagnostic Criteria for Dilated Cardiomyopathy

Dilated cardiomyopathy is diagnosed when left ventricular or biventricular systolic dysfunction (LVEF <45%) with or without dilatation is present, and abnormal loading conditions (such as hypertension or valvular disease) and coronary artery disease have been excluded as the cause. 1, 2

Core Diagnostic Requirements

The diagnosis requires three essential components to be present simultaneously 2:

• Systolic dysfunction: LVEF <45% 1
• Ventricular dilatation (when present): LV end-diastolic volumes or diameters >2 standard deviations from normal according to normograms (Z scores >2 SD) corrected for body surface area and age, or body surface area and gender 1
• Exclusion of secondary causes: No abnormal loading conditions (hypertension, valvular disease) or coronary artery disease sufficient to cause the observed dysfunction 1, 2, 3

Important Diagnostic Nuance

DCM can present with systolic dysfunction (LVEF <45%) WITHOUT dilatation, and this should still be diagnosed as DCM if secondary causes are excluded. 1 This represents an important evolution in diagnostic criteria, as the traditional definition requiring dilatation was overly restrictive and could miss early disease 3.

Mandatory Diagnostic Workup

Initial Imaging Assessment

Comprehensive echocardiography is mandatory and must include: 1

• LVEF measurement and LV dimensions
• Global longitudinal strain (GLS) assessment
• Right ventricular function quantification
• Valvular function assessment (particularly secondary mitral and tricuspid regurgitation)
• Diastolic function parameters
• Left atrial size
• 3D imaging when available

A focused cardiac ultrasound exam using handheld devices can only raise suspicion and must always be followed by comprehensive echocardiography. 1

Excluding Coronary Artery Disease

One of the following three modalities must be used to exclude significant coronary disease: 1

• Cardiac CT: Highly valuable for excluding significant epicardial coronary artery disease with excellent spatial resolution 1
• Radionuclide imaging: Allows assessment of myocardial perfusion and is particularly useful for distinguishing DCM from ischemic cardiomyopathy 1
• Cardiovascular magnetic resonance (CMR): Can exclude ischemic component of LV dysfunction and provides superior myocardial tissue characterization 1

Advanced Tissue Characterization

CMR should be considered when: 1

• Echocardiographic data is suboptimal, borderline, or doubtful
• Specific etiologies need to be identified (sarcoidosis, post-myocarditis)
• Prognostic information is needed (presence and extent of myocardial fibrosis, scarring, or late gadolinium enhancement)

CMR detects myocardial edema, scarring, fibrosis, infiltration, and iron overload, providing unique non-invasive information for underlying diagnosis and prognosis 1, 4.

Diagnostic Criteria for Familial DCM Screening

For first-degree relatives of DCM patients, screening should begin at age 10 years with echocardiography and 12-lead ECG. 1

Screening intervals: 1

• Every 2-3 years if cardiovascular tests are normal
• Annually if minor abnormalities are detected
• Consider stopping at age 60-65 years, though this depends on family history

Imaging criteria for relatives include: 1

• Major criteria: LVEF reduction and LV dilatation
• Minor criteria: Abnormal regional wall motion in the absence of conduction defects, or non-ischemic late gadolinium enhancement on CMR

Common Diagnostic Pitfalls

Avoid these errors: 1, 2, 3

• Diagnosing DCM without excluding coronary disease—this is a mandatory exclusion criterion
• Missing early DCM by requiring dilatation—systolic dysfunction alone (LVEF <45%) without dilatation qualifies for diagnosis
• Relying on focused ultrasound exams without comprehensive echocardiography
• Failing to assess right ventricular function, which has major prognostic implications 1
• Not screening first-degree relatives in familial cases, as 30-50% of DCM is genetic 2

Prognostic Markers to Document

The following parameters predict cardiovascular death and hospitalization and should be systematically assessed: 1

• LV dilatation and contractile function (major prognosticators)
• Left atrial enlargement
• Right ventricular dilatation and contractile dysfunction
• LV global longitudinal strain
• Secondary mitral regurgitation severity 1