What is the diagnosis and treatment for a patient with suspected dilated cardiomyopathy?

Dilated Cardiomyopathy: Diagnosis and Treatment

Dilated cardiomyopathy requires a systematic diagnostic workup to identify specific etiologies, followed by aggressive guideline-directed medical therapy with ACE inhibitors/ARBs, beta-blockers, mineralocorticoid receptor antagonists, and SGLT2 inhibitors—a quadruple therapy regimen that can reduce mortality by up to 73% over 2 years. 1

Definition and Classification

Dilated cardiomyopathy is characterized by left ventricular or biventricular dilation and depressed myocardial performance in the absence of hypertension, valvular disease, congenital heart disease, or coronary artery disease sufficient to cause the dysfunction. 2 The prevalence ranges from 1:250 to 1:400 individuals in the general population, with familial DCM accounting for 30-50% of cases. 2

Diagnostic Approach

Initial Clinical Assessment

History taking should focus on:

• Duration and progression of dyspnea, orthopnea, paroxysmal nocturnal dyspnea, fatigue, and edema (symptoms >3 months with severe decompensation indicate less chance of recovery) 3
• Three-generational family history to identify familial DCM 3
• Exposure to cardiotoxins, alcohol, chemotherapy agents, and infections 2

Physical examination must document:

• Volume status: jugular venous pressure, peripheral edema, orthopnea 3
• Presence of S3 gallop (indicates poor prognosis) 3
• Orthostatic blood pressure changes 3

Laboratory and Imaging Investigations

Mandatory initial blood work includes: 3

• Complete blood count, comprehensive metabolic panel
• Fasting glucose and hemoglobin A1c
• Fasting lipid profile, liver function tests
• Thyroid-stimulating hormone
• BNP or NT-proBNP (for diagnosis and monitoring)
• Cardiac troponin

12-lead ECG should assess for left bundle branch block (LBBB), which indicates poor prognosis and potential cardiac resynchronization therapy candidacy. 3

2D echocardiography with Doppler is essential to assess: 3

• Left ventricular ejection fraction (LVEF)
• LV dimensions and wall thickness
• Right ventricular function
• Severity of mitral regurgitation
• Diastolic function parameters
• Global longitudinal strain (GLS)

Cardiac MRI should be performed for borderline echocardiographic data, tissue characterization, and assessment of myocardial fibrosis or scar. 3 This is particularly valuable for identifying specific etiologies like sarcoidosis, hemochromatosis, or inflammatory cardiomyopathy. 2

Endomyocardial biopsy is indicated when inflammation or infection is suspected based on clinical presentation and imaging findings. 4

Treatment Strategy

Pharmacological Management: Quadruple Therapy

All patients with DCM and reduced ejection fraction should receive four medication classes simultaneously: 1, 3

1. ACE inhibitors/ARBs or ARNI:

   • Start at low doses and uptitrate every 2 weeks to target or maximally tolerated doses 3
   • These agents significantly reduce mortality and morbidity 1

2. Beta-blockers:

   • Start at very low doses and uptitrate gradually to avoid initial decompensation 3
   • Essential for optimal neurohormonal antagonism 1

3. Mineralocorticoid receptor antagonists (MRAs):

   • Indicated in all symptomatic heart failure patients with LVEF ≤35% 3
   • Require close monitoring of potassium levels, especially in patients with chronic kidney disease 5

4. SGLT2 inhibitors:

   • Indicated in all heart failure with reduced ejection fraction patients regardless of diabetes status 3
   • Strongly recommended if eGFR is 30 to <90 mL/min/1.73 m² 5

Critical implementation point: Uptitrate medications in small increments to the recommended target dose or highest tolerated dose, with close monitoring of vital signs and laboratory parameters. 1 Elderly patients or those with chronic kidney disease require more frequent visits and laboratory monitoring during dose titration. 1

Device Therapy

Implantable cardioverter-defibrillator (ICD):

• Recommended for patients with hemodynamically unstable ventricular tachycardia or ventricular fibrillation 1
• Consider in patients with LVEF ≤35% and NYHA class II-III symptoms despite optimal medical therapy 3
• Should be considered in patients with confirmed disease-causing LMNA mutations and clinical risk factors 1

Cardiac resynchronization therapy (CRT):

• Indicated in patients with LVEF ≤35%, NYHA class II-IV symptoms, and LBBB with QRS ≥150 ms 3
• Should be considered in DCM patients with LBBB, especially when LBBB may be contributing to cardiomyopathy 1

Arrhythmia Management

Catheter ablation is recommended for bundle branch re-entry ventricular tachycardia refractory to medical therapy. 1

Amiodarone should be considered in patients with an ICD who experience recurrent appropriate shocks despite optimal device programming. 1 However, amiodarone alone should not be used to treat ventricular arrhythmias in DCM patients. 1

Advanced Heart Failure Management

Patients with nonobstructive DCM and advanced heart failure should be assessed for heart transplantation or mechanical circulatory support. 1 Continuous-flow left ventricular assist device therapy is reasonable as a bridge to heart transplantation in appropriate candidates. 1

Monitoring and Follow-Up

Clinical assessment every 3-6 months should include: 3

• Symptoms and functional capacity
• Volume status and vital signs
• Laboratory results (electrolytes, renal function)
• Repeat echocardiography at 3-6 months to assess response to therapy
• BNP monitoring to assess disease progression

Prognostic Indicators

Poor prognostic factors include: 1

• Severe LV and RV enlargement and dysfunction
• Persistent S3 gallop
• Moderate to severe mitral regurgitation
• Pulmonary hypertension
• Left bundle branch block
• Recurrent ventricular tachycardia
• Elevated BNP levels
• Peak oxygen consumption <10-12 mL·kg⁻¹·min⁻¹

Common Pitfalls

Underuse and underdosing of guideline-directed medical therapy is common, with less than one-quarter of eligible patients receiving all traditional medications (ACE inhibitor/ARB, beta-blocker, MRA) concurrently. 1 Clinicians must aggressively uptitrate all four medication classes to target doses rather than accepting suboptimal dosing.

Discontinue cardiac myosin inhibitors in patients with DCM who develop persistent systolic dysfunction (LVEF <50%). 1 It is also reasonable to discontinue previously indicated negative inotropic agents (verapamil, diltiazem, or disopyramide) in patients who develop systolic dysfunction. 1

Risk of contrast-induced nephropathy should be considered when performing coronary angiography in DCM patients with chronic kidney disease. 5