What is the initial treatment for cardiomyopathy?

Initial Treatment for Cardiomyopathy

The initial treatment for cardiomyopathy depends critically on the specific type: for hypertrophic cardiomyopathy (HCM), beta-blockers or non-dihydropyridine calcium channel blockers are first-line; for dilated cardiomyopathy with reduced ejection fraction, guideline-directed medical therapy with ACE inhibitors/ARBs, beta-blockers, and mineralocorticoid receptor antagonists is recommended. 1

Hypertrophic Cardiomyopathy (HCM)

Obstructive HCM with Symptoms

• Start with beta-blockers as first-line therapy for patients with symptomatic obstructive HCM, titrating to achieve adequate heart rate control and symptom relief 1, 2
• Non-dihydropyridine calcium channel blockers (verapamil or diltiazem) are equally effective alternatives if beta-blockers are contraindicated or not tolerated, though they must be used cautiously in patients with severe outflow obstruction 1, 2
• Never combine beta-blockers with verapamil or diltiazem due to high risk of complete heart block 2

Nonobstructive HCM with Preserved Ejection Fraction

• Beta-blockers or non-dihydropyridine calcium channel blockers are recommended for patients with exertional angina or dyspnea 1
• Add oral diuretics cautiously when dyspnea persists despite beta-blockers or calcium channel blockers, using intermittent or low-dose therapy to avoid symptomatic hypotension 1
• ACE inhibitors and ARBs have uncertain benefit for symptom control in nonobstructive HCM; a randomized trial of 124 patients showed losartan provided no benefit on left ventricular mass, fibrosis, or functional class compared to placebo after 12 months 1, 3
• For younger patients (≤45 years) with mild phenotype and sarcomere variants, valsartan may slow adverse cardiac remodeling, though this represents emerging rather than established therapy 1

Critical Medications to Avoid in HCM

• Never use dihydropyridine calcium channel blockers (nifedipine, amlodipine) as they worsen outflow obstruction 2
• Avoid vasodilators including ACE inhibitors, ARBs, and nitroglycerin in patients with resting or provocable left ventricular outflow tract obstruction, as they reduce preload/afterload and can cause cardiovascular collapse 2
• Do not use digoxin for dyspnea in HCM patients without atrial fibrillation 2

Dilated Cardiomyopathy with Reduced Ejection Fraction

Guideline-Directed Medical Therapy (GDMT)

• Initiate ACE inhibitors or ARBs immediately to reduce sudden death and progressive heart failure, titrating to target doses achieved in clinical trials 1, 4
• Start beta-blockers concurrently as part of foundational therapy 1, 4
• Add mineralocorticoid receptor antagonists to the regimen 1, 4
• SGLT2 inhibitors are recommended for management of hyperglycemia in patients with diabetes and heart failure 1

The ATLAS trial demonstrated that high-dose lisinopril (32.5-35 mg daily) reduced the combined outcome of all-cause mortality and heart failure hospitalization by 15% compared to low-dose (2.5-5 mg daily), with a 24% reduction in heart failure hospitalization specifically 5. This underscores the importance of dose titration to target levels.

Dose Titration Strategy

• Titrate ACE inhibitors/ARBs to the maximum tolerated dose rather than stopping at low doses, as benefits are dose-dependent 6, 5
• Monitor renal function and serum potassium closely during titration, particularly when combining ACE inhibitors with ARBs or aldosterone antagonists 5

Cancer Therapy-Related Cardiomyopathy

Asymptomatic Patients with Reduced EF

• ARBs, ACE inhibitors, and beta-blockers are reasonable in asymptomatic patients with cancer therapy-related cardiomyopathy (EF <50%) to prevent progression to heart failure and improve cardiac function 1

Multidisciplinary Management

• Engage in multidisciplinary discussion involving the patient about risk-benefit ratio of cancer therapy interruption, discontinuation, or continuation 1

Atrial Fibrillation Management in Cardiomyopathy

Anticoagulation

• Direct-acting oral anticoagulants (DOACs) are first-line for all HCM patients with atrial fibrillation, regardless of CHA₂DS₂-VASc score 1, 4
• Vitamin K antagonists are second-line alternatives 1
• For dilated cardiomyopathy, anticoagulation decisions follow standard CHA₂DS₂-VASc scoring, with DOACs preferred over warfarin except in moderate/severe mitral stenosis or mechanical valves 4

Rate Control

• Beta-blockers, verapamil, or diltiazem are recommended for ventricular rate control in atrial fibrillation, with agent selection based on comorbidities 1, 2, 4
• Target resting heart rate <60-65 bpm in HCM patients 2

Common Pitfalls to Avoid

• Do not treat HCM patients like typical heart failure patients—standard heart failure therapies including vasodilators and aggressive diuresis can be harmful 2
• Do not withhold anticoagulation in HCM patients with atrial fibrillation based on low CHA₂DS₂-VASc scores, as guidelines mandate anticoagulation regardless of score 4
• Avoid under-dosing ACE inhibitors/ARBs in dilated cardiomyopathy; the survival and morbidity benefits are dose-dependent 6, 5
• Monitor for hypotension and hypovolemia when using diuretics in HCM, as excessive diuresis worsens outflow obstruction 2