Cardiomyopathies for USMLE Step 3

Here are key facts for USMLE Step 2 & COMLEX-USA Level 3 from the Cardiomyopathies tutorial, as well as points of interest at the end of this document that are not directly addressed in this tutorial but should help you prepare for the boards. See the tutorial notes for further details and relevant links. 1. Management mirrors heart failure with reduced EF (HFrEF):

• Initiate ACE inhibitors or ARBs
• Add beta-blockers (carvedilol, bisoprolol, or metoprolol succinate)
• Use loop diuretics for volume overload
• Add spironolactone or eplerenone in patients with NYHA class II–IV symptoms
• Add SGLT2 inhibitors (e.g., dapagliflozin) for added mortality benefit

2. ICD placement is indicated if LVEF remains <35% after at least 3 months of optimized medical therapy. 3. Cardiac resynchronization therapy (CRT) is indicated for patients with LVEF <35%, QRS >150 ms, and NYHA class II–IV. 4. Heart transplant or LVAD is considered in patients with end-stage disease not responding to medical therapy. 5. Avoid NSAIDs and calcium channel blockers (except amlodipine) as they may worsen outcomes. 1. First-line treatment is beta-blockers to reduce myocardial oxygen demand and improve filling. 2. Verapamil is an alternative if beta-blockers are contraindicated. 3. Avoid vasodilators, diuretics, and nitrates, which reduce preload and worsen obstruction. 4. ICD placement is indicated for patients with:

• Family history of sudden cardiac death
• LV wall thickness >30 mm
• Unexplained syncope
• Non-sustained VT on Holter
• Abnormal blood pressure response to exercise

5. Surgical septal myectomy or alcohol septal ablation is used for symptomatic patients with significant obstruction despite medical therapy. 6. Counsel all patients to avoid competitive sports and dehydration. 1. Treatment depends on the underlying cause:

• Amyloidosis: Tafamidis (for transthyretin type), chemotherapy (for AL type)
• Hemochromatosis: Phlebotomy or deferoxamine
• Sarcoidosis: Glucocorticoids for active inflammation

2. Diuretics are used cautiously, as patients are often preload dependent. 3. Atrial fibrillation is common and should be treated with rate/rhythm control and anticoagulation as appropriate. 4. Differentiation from constrictive pericarditis is essential: constrictive pericarditis is potentially curable with pericardiectomy. 1. Treat with activity restriction, especially avoidance of competitive sports. 2. Use ICD for prevention of sudden cardiac death in patients with sustained VT or syncope. 3. Consider antiarrhythmic medications (e.g., sotalol, amiodarone) in symptomatic patients. 1. Chagas cardiomyopathy should be suspected in Latin American immigrants with heart failure. 2. Alcohol-induced cardiomyopathy improves with cessation but may require full heart failure therapy. 3. Patients with doxorubicin-induced cardiomyopathy may benefit from early EF monitoring and dexrazoxane prophylaxis in high-risk cases. 4. Treat peripartum cardiomyopathy with standard heart failure meds (except ACE inhibitors if breastfeeding). 1. Regularly reassess risk factors for sudden cardiac death to determine ICD eligibility. 2. Monitor for progression to systolic dysfunction (burned-out HCM), which alters treatment approach. 3. Use Holter monitoring to assess for non-sustained VT or arrhythmias in symptomatic or high-risk patients. 1. Endomyocardial biopsy is indicated when diagnosis is unclear or for suspected infiltrative disease. 2. Amyloidosis may be suspected with symptoms of carpal tunnel, proteinuria, and unexplained heart failure. 3. If constrictive pericarditis is suspected, look for pericardial thickening, respiratory variation in mitral inflow, and calcification on imaging. 1. Family screening and genetic counseling are appropriate, especially for first-degree relatives. 2. Regular ECGs and imaging are used to monitor for progression and arrhythmias.

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Below is information not explicitly contained within the tutorial but important for USMLE & COMLEX 3. 1. Cardiac MRI helps differentiate ischemic from non-ischemic cardiomyopathy and detect fibrosis. 2. SGLT2 inhibitors (e.g., dapagliflozin, empagliflozin) have shown mortality benefit even in non-diabetic HFrEF. 1. Dual-chamber pacing may be considered in patients with HCM and bradyarrhythmias or as a second-line therapy in those who are poor candidates for surgery. 2. Genetic testing is encouraged for definitive diagnosis and family screening. 1. Pulmonary hypertension may develop due to chronic elevated filling pressures and is associated with poor prognosis. 2. RCM often presents late; consider palliative approaches in advanced disease when transplant is not an option. 1. In patients with new-onset heart failure, always determine if the underlying cause is ischemic, valvular, or cardiomyopathic, as management paths differ. 2. Step 3 cases frequently involve patients with comorbidities (diabetes, CKD, cancer treatment history), requiring modification of standard algorithms.