Historical assessment of diphtheritic myocarditis from a hospital in northeastern Thailand

Background: Although there have been many descriptive studies of diphtheria from resource limited countries, descriptions of the natural history of diphtheritic myocarditis in patients from these countries are scarce.

Objective: To present the natural history of diphtheritic myocarditis from a hospital in northeastern Thailand.

Methods: The clinical features of 38 patients with diphtheria admitted to the Khon Kaen University Hospital in northeastern Thailand between 1983 and 1996 were reviewed.

Results: Of the 38 cases of diphtheria, 10 progressed to diphtheritic myocarditis (26%). Electrocardiographic findings of the 10 patients with myocarditis were myocardial and conduction abnormalities. The presence of a clinically severe (toxic) type (P < 0.001) or a swollen neck (bull neck) (P = 0.001) was a predictor of the occurrence of myocarditis. Five (50%) of the 10 patients with myocarditis had conduction abnormalities (third-degree atrioventricular block 3, left bundle branch block 1, and right bundle branch block 1). Four patients with severe symptomatic bradyarrhythmia (third-degree atrioventricular block 3, and left bundle branch block 1) received ventricular pacing, and 3 patients died after this pacing. Echocardiographic abnormalities of left ventricular dilatation and myocardial hypertrophy were found in all 5 patients with conduction abnormalities. All 6 of 7 survivors of diphtheritic myocarditis had normal 12-lead electrocardiographic results at 1-month follow-up. A patient who was the survivor of third-degree AV block had an electrocardiographic finding of flat T waves, and with a complete echocardiographic normalization of left ventricular dilatation and myocardial hypertrophy.

Conclusion: The present study confirms that increasing diphtheria immunization coverage in the population remains the most important strategy for the control of diphtheria. In resource limited countries, clinical findings, electrocardiography, and sometimes where available, echocardiography are helpful in assessing the severity of diphtheritic myocarditis, decision making of acute management, and predicting fatal outcome.