Dr. M. A. SOFI MD; FRCP (London); FRCPEdin; FRCSEdin

Myocarditis is an inflammatory disease of the myocardium with a wide range of clinical presentations, from subtle to devastating International occurrence  A population study in Finland found that, in a study of more than 670,000 healthy young male military recruits, 98 cases had myocarditis mimicking myocardial ischemia, 1 case presented as sudden death, and 9 cases presented as recent-onset dilated cardiomyopathy  A Japanese 20-year series of 377,841 autopsies found idiopathic, nonspecific, interstitial, or viral myocarditis in only 0.11% of individuals Race-, sex-, and age-related demographics  No particular race predilection is noted for myocarditis except for peripartum cardiomyopathy (a specific form of myocarditis that appears to have a higher incidence in patients of African descent).  The incidence of myocarditis is similar between males and females, although young males are particularly susceptible

Toxins  Drugs, including ethanol, anthracyclines and some other forms of chemotherapy, and antipsychotics, e.g. clozapine, also some designer drugs such as mephedrone Physical agents  Electric shock, hyperpyrexia, and radiation Immunologic  Allergic (acetazolamide amitriptyline)  Rejection after a heart transplant  Autoantigens (scleroderma, systemic lupus erythematosus, sarcoidosis, systemic vasculitis such as Churg- Strauss syndrome, and Wegener's granulomatosis, Kawasaki disease)  Toxins (arsenic, toxic shock syndrome toxin, carbon monoxide, or snake venom)  Heavy metals (copper or iron) Causes: A large number of causes of myocarditis have been identified, but often a cause cannot be found. Worldwide, however, the most common cause is Chagas' disease

Infection  Viral (adenovirus, parvovirus B19, coxsackie virus, HIV, enterovirus, rubella virus, polio virus, cytomegalovirus, human herpesvirus 6 and possibly hepatitis C)  Bacterial (Brucella, Corynebacterium diphtheriae, gonococcus, Haemophilus influenzae, Actinomyces, Tropheryma whipplei, Vibrio cholerae, Borrelia burgdorferi, leptospirosis, and Rickettsia)  Fungal (Aspergillus)  Parasitic (ascaris, Echinococcus granulosus, Paragonimus westermani, schistosoma, Taenia solium, Trichinella spiralis, visceral larva migrans, and Wuchereria bancrofti)  Protozoan (Trypanosoma cruzi causing Chagas diseasea nd Toxoplasma gondii  Bacterial myocarditis is rare in patients without immunodeficiency. Causes:

 Mild symptoms of chest pain (in concurrent pericarditis), fever, sweats, chills, dyspnea  In viral myocarditis: Recent history (≤1-2 wk) of flulike symptoms of fevers, arthralgias, and malaise or pharyngitis, tonsillitis, or upper respiratory tract infection  Palpitations, syncope, or sudden cardiac death due to underlying ventricular arrhythmias or atrioventricular block (especially in giant cell myocarditis)  Heart failure Signs and symptoms Myocarditis usually manifests in an otherwise healthy person and can result in rapidly progressive (and often fatal) heart failure and arrhythmia. Patients with myocarditis have a clinical history of acute decompensation of heart failure, but they have no other underlying cardiac dysfunction or have low cardiac risk

Specific findings in special cases are as follows:  Sarcoid myocarditis: Lymphadenopathy, also with arrhythmias, sarcoid involvement in other organs (up to 70%)  Acute rheumatic fever: Usually affects heart in 50-90%; associated signs, such as erythema marginatum, polyarthralgia, chorea, subcutaneous nodules (Jones criteria)  Hypersensitive/eosinop hilic myocarditis: Pruritic maculopapular rash and history of using offending drug  Giant cell myocarditis: Sustained ventricular tachycardia in rapidly progressive heart failure  Peripartum cardiomyopathy - Heart failure developing in the last month of pregnancy or within 5 months following delivery Diagnosis: The diagnosis of acute myocarditis is usually presumptive. Because many cases of myocarditis are not clinically obvious, a high degree of suspicion is required. Patients with myocarditis usually present with signs and symptoms of acute decompensation of heart failure (eg, tachycardia, gallop, mitral regurgitation, edema) and, in those with concomitant pericarditis, with pericardial friction rub.

Testing  Laboratory studies use to evaluate suspected myocarditis may include the following:  CBC  ESR (and that of other acute phase reactants [eg, C-reactive protein]  Rheumatologic screening  Cardiac enzyme (eg, creatine kinase or cardiac troponins)  Serum viral antibody titers  Viral genome testing in endomyocardial biopsy  Electrocardiography Imaging studies  The following imaging studies may be used with suspected myocarditis:  Echocardiography: To exclude other causes of heart failure (eg, amyloidosis or valvular or congenital causes) and to evaluate degree of cardiac dysfunction  Antimyosin scintigraphy: To identify myocardial inflammation  Cardiac angiography: To rule out IHD as cause of new-onset heart failure  Gadolinium-enhanced MRI: To assess extent of inflammation and cellular edema; nonspecific Diagnostic work up

Procedures  Endomyocardial biopsy is the standard tool for diagnosing myocarditis. However, the use of routine endomyocardial biopsy in establishing the diagnosis of myocarditis rarely is helpful clinically, since histologic diagnosis seldom has an impact on therapeutic strategies, unless giant cell myocarditis is suspected Management  In improving cardiac hemodynamics in heart failure, as well as providing supportive therapy, with the hope of prolonging survival Pharmacotherapy  Medications used in the management of myocarditis include the following:  Vasodilators (eg, nitroglycerin, sodium nitroprusside)  Angiotensin-converting enzyme inhibitors (eg, enalapril)  Diuretics (eg, furosemide)  Anticoagulation may be advisable as a preventive measure  Antiarrhythmics can be used cautiously, although most antiarrhythmic drugs have negative inotropic effects that may aggravate heart failure  Inotropic drugs (eg, dobutamine, milrinone) may be necessary for severe decompensation, although they are highly arrhythmogenic

Nonpharmacotherapy Supportive care in patients with myocarditis includes the following:  Hemodynamic and cardiac monitoring  Administration of supplemental oxygen  Fluid management Surgical option Surgical intervention in myocarditis may include the following:  Temporary transvenous pacing for complete heart block  Cardiac transplantation  Extreme cases:  Ventricular assist device or percutaneous circulatory support  left ventricular assistive devices (LVADs) and extracorporeal membrane oxygenation