Nejm 2009;360:1526; 200;343:1388

Cause:

• Arrythmias: ectopic atrial and permanent junctional reentrant tachycardias, reversible cardiomyopathy if ablate focus (R. Fletcher 1/00)
• Collagen vascular causes including SLE, polyarteritis nodosa, endocardial fibroelastosis (occasionally seen in children due to a treatable inherited carnitine deficiency—Nejm 1981;305:385), sarcoid, carcinoid (last two may be restrictive and/or congestive)
• Deficiencies: hypophosphatemia from antacid binding, reversible (Ann IM 1978;89:867); thiamine (beriberi), selenium, carnitine
• Endocrine: thyrotoxicosis (Nejm 1982;307:1165) and hypothyroidism; pheochromocytoma (Nejm 1987;316:793); homocystinuria, hypocalcemia
• Lymphocytic myocarditis (Nejm 1997;336:1860)
• Idiopathic (<50%)
• Infectious from any severe bacteremia, eg, meningococcal, diphtheria, mycoplasma (Ann IM 1977;86:544); viral including CMV, influenza, echo, coxsackie B, yellow fever, mumps, polio, rubella, HIV (Nejm 1998;339:1093); parasites including toxoplasma, Chagas' disease
• Ischemic
• Genetic neurologic/myopathic causes (30%) including Friedreich's ataxia; dyskalemic myopathies; muscular dystrophies including limb girdle, Emery-Dreifuss (Ann IM 1993;119:900), and myotonic; Refsum's disease; familial sarcomere protein gene mutations (Nejm 2000;343:1688) and other autosomal dominant genetic causes affecting cellular function (Nejm 1999;341:1715; 1996;335:1224)
• Peripartum (Nejm 2001;344:1567, 1629); onset 1 mo prior or up to 6 mo postpartum w variable outcomes but usually some residual dysfunction
• Toxic agents like alcohol (Ann IM 1974;80:293; Nejm 1972;287:677), daunorubicin (Daunomycin) and bleomycin, cobalt in beer (Ann IM 1969;70:277), arsenic (Antiarrhythmics); lead, cocaine, mercury, carbon monoxide, phenothiazines; most reversible except chemotherapy drugs.

Pathophys:Dilation of both ventricles; mural thrombi

Idiopathic type prevalence = 36/100 000 (Circ 1989;80:564): blacks/whites = 2.5/1; males/females = 25/1.

Sx:CHF sx's; muscle weakness in alcoholic type since 83% have skeletal myopathy as well (Ann IM 1994;120:529)

Si:Atrial fibrillation and other supraventricular arrhythmias; S₃ gallop (Ann IM 1969;71:545); CHF si's

(Nejm 2000;342:1077) Often chronic and indolent; in alcoholic type, it can rapidly resolve with abstinence. Postpartum type has best prognosis (90% 5-yr survival); idiopathic, ischemic, daunorubicin, and infiltratives types = 50% 5-yr mortality; HIV type, 25% 3-yr mortality

Systemic emboli from mural thrombi and Afib

r/o hypertrophic (IHSS); "hibernating myocardium," ie, ischemic myocardopathy reversible w revascularization (Nejm 1998;339:173); andRESTRICTIVE MYOCARDIOPATHIES(Nejm 1997;336:267): amyloid, hemachromatosis, familial, idiopathic, endomyocardial fibrosis, eosinophilic cardiomyopathy, sarcoid, Gaucher's, Fabry's, and Hurler's disease; and "stress stunning", transient myocardopthy seen in grieving widows w dramatic T changes (Nejm 2005;352:534)

Lab:

Noninv:EKG may show Afib (20%), cloven T waves especially in alcoholic type (Ann IM 1969;71:545), arrhythmias, blocks, Q waves, or LVH. Echocardiogram most helpful, EF <45%

Path:Endocardial bx (Nejm 1982;307:732) in peripartum and all types to dx infiltrative disease; not helpful in dilated types, IHSS, Wilson's disease, etc (complete list—Ann IM 1982;97:885; Nejm 1983;308:12); but does not correlate well with clinical findings or prognosis (Nejm 1985;312:885)

Rx:

Preventive: screen 1st-degree relatives where prevalence = 15% (Ann IM 2005;143:108)

Anticoagulate acutely and chronically; prednisone rx even when inflammatory by bx is no help (Nejm 1989;321:1061) or even w additional immunosuppressive drugs (Nejm 1995;333:269); perhaps human growth hormone 4 IU sc qod (Nejm 1996;334:809, 856); transplantation

of CHF using vasodilators

of ventricular arrythmias: improve EF w digoxin, ACEIs, -blockers, amiodarone (Mayo Clin Proc 1998;73:430), implantable cardioverter/defibrillator prolongs life in non-ischemic type (Nejm 2004;350:2152)