High-Yield Pearls

• Titin (TTN) mutations are the single most common genetic cause (~25% familial, ~18% sporadic). Always screen family members.
• Alcohol causes >10% of HF in the US; abstinence can partially or fully reverse the cardiomyopathy.
• Distinguish from ischemic CMP with coronary angiography — this is mandatory before labeling DCM "idiopathic."
• Peripartum DCM: onset in last month of pregnancy or within 5 months postpartum; bromocriptine has shown benefit in some trials.

• The LVOT murmur behaves oppositely to aortic stenosis: it increases with Valsalva/standing (↓ preload) and decreases with squatting/handgrip (↑ preload/afterload).
• Mavacamten (cardiac myosin inhibitor, FDA-approved 2022) is a major therapeutic advance: it directly reduces LV contractility and LVOT gradient without the hemodynamic risks of disopyramide.
• SCD can be the first manifestation — HCM is the leading cause of sudden death in athletes under 35.
• Avoid nitrates, diuretics (excess), vasodilators, and digoxin in HOCM — all worsen LVOTO by reducing preload/afterload or increasing contractility.

• The most critical DDx is constrictive pericarditis — differentiated by pericardial thickness on CT/MRI, hemodynamic equalization vs. discordance, and tissue Doppler (preserved e' in CP, reduced in RCM).
• ATTR amyloidosis is the most prevalent form of RCM overall and is increasingly diagnosed in elderly patients; tafamidis significantly reduces mortality and HF hospitalization.
• Endomyocardial biopsy is often definitive (Congo red stain for amyloid, Prussian blue for hemochromatosis).
• Endomyocardial fibrosis is the most common RCM worldwide (tropical Africa); Löffler endocarditis is the non-tropical eosinophilic counterpart.