MYOCARDITIS

Myocarditis, i.e. the inflammation, necrosis or cytolysis of the myocardium, is a common cause of CCF and arrhythmias in children, occasionally leading to sudden unexplained death.

Etiology: Viral infections are predominant causes of myocarditis, apart other infections, connective tissue disorders and toxins (Table 17.31). Viral myocarditis may develop either due to direct viral injury or as abnormal immune response to persistent viral infection.

Clinically, myocarditis usually presents with acute CCF, shock or arrhythmia, though few cases have a gradual course leading to dilated cardiomyopathy. History of preceding viral illness or signs of causative illness, e.g. rash or arthritis may be present.

Important clinical indicators include—(a) sudden unexplained hypotension/shock, (b) CCF refractory to usual therapy, and (c) cardiac signs, e.g. muffled heart sounds, gallop rhythm, arrhythmia and pansystolic

TABLE 17.31: Causes of myocarditis

• Infections

- Viruses: Varicella, mumps, Coxsackie V

- Bacterial: Diphtheria, Typhoid, Leptospirosis

- Gram -ve sepsis (acute toxic myocarditis)

- Parasites: Toxoplasmosis, Schistosomiasis

- Fungal: Actinomycosis, histoplasmosis

- Rickettsiae: Psittacosis

• Connective tissue disorders

- Rheumatic fever

- Rheumatoid arthritis

- Others: SLE, Kawasaki disease

[*] Toxins

- Drugs: Adriamycin, iron overload

- Radiotherapy

- Snake bite/scorpion sting

• Miscellaneous

- Nutritional: Beri-beri

- IEMs: Hurler syndrome, Pompe's disease

- Hematological: Sickle cell disease

- Neuromuscular: Friedreich ataxia, DMD

DMD: Duchenne muscular dystrophy; IEM: Inborn errors of metabolism

murmur due to dilatation of the valvular annulus and mitral incompetence.

Diagnosis is supported by—(a) abnormal ECG finding, e.g. low QRS voltage, ST segment/T wave changes, and prolonged QTc interval; (b) biochemical evidence of myocardial injury, e.g.

Management of acute myocarditis aims towards its complications, e.g. CCF and shock, with—(a) bed rest and restricted activity, (b) oxygen or ventilatory support, (c) diuretics, and (d) inotropic agents, e.g. dopamine or dobutamine, to improve myocardial contractility.

Digitalization should be either avoided or done with half of the usual doses, as myocardium in these cases may be hypersensitive to digoxin with risk of arrhythmia.

Specific treatment is indicated in selected cases, e.g. prednisolone in rheumatic fever or IV immunoglobulins in Kawasaki disease, etc. Role of IVIG or corticosteroids in viral myocarditis is controversial.

Prognosis: Recovery depends on the cause and severity of myocardial injury. Important complications include-

(a) arrhythmias. Which may cause sudden death and

(b) cardiomyopathy-a long-term sequel.

17.9.2