Electrocardiographic abnormalities in patients with diphtheria: a prospective study.

Purpose: To determine the incidence of and risk factors for electrocardiographic (ECG) abnormalities in adults with diphtheria.

Methods: A prospective study was conducted involving 122 adult patients with respiratory tract diphtheria. Diphtheria was confirmed by isolation of a toxin-producing strain of Corynebacterium diphtheriae. Patients had serial clinical evaluations and ECGs for a minimum of 21 days.

Results: Cardiac involvement was detected in 25 (28%) of 88 evaluable patients, with a median time from symptom onset to an abnormal ECG of 9 days (range, 4 to 24 days). In a logistic regression analysis, age (odds ratio [OR] = 4.1; 95% confidence interval [CI]: 1.6 to 11.0), shared accommodation (OR = 2.9; 95% CI: 1.0 to 8.6), fever (OR = 4.2; 95% CI: 1.1 to 16.6), and extensive respiratory tract infection with subcutaneous edema (OR = 7.0; 95% CI: 1.2 to 42.2) were independent risk factors for cardiac involvement.

Conclusion: Cardiac involvement is a common complication of respiratory tract infection with C. diphtheriae, and occurs more often among older patients, those with lower socioeconomic status, and those with severe respiratory tract involvement.