Cardiac biopsy findings in patients with 'primary' atrial fibrillation: Histologic evidence of occult myocardial diseases

Eighteen patients (13 men, 5 women, mean age 37 years) with lone atrial fibrillation (AF) (1 to 18 months duration), were evaluated by thyroid function tests, two-dimensional echocardiography, hemodynamics, coronary angiography and left ventricular endomyocardial biopsy, because they were unresponsive to usual antiarrhythmic therapy. T3, T4, TSH, TRH test were normal in all patients; cardiac valves and ventricular and atrial sizes (left atrium <40 mm) were in the normal limits; also normal were left ventricular end-diastolic pressure (LVEDP <= 10 mmHg) and EF (>0.50). Histology was abnormal in all cases showing in 4 patients cardiomyopathic changes, in other 4 patients active myocarditis (lymphocytic in 3 and eosinophilic in 1), in 10 patients non-specific necrosis or fibrosis (or both). Steroids (prednisone 50 mg daily/m² of body surface area daily), used in addiction to antiarrhythmics in patients with eosinophilic and lymphocytic active myocarditis, were able to revert sinus rhythm, while the other patients continued to have AF. The study documents that occult myocardial diseases (myocarditis, cardiomyopathy, non-specific necrosis or fibrosis) can underlie 'primary' AF. Addition of steroids to antiarrhythmics, in patients with refractory AF and histologic evidence of active myocarditis, seems to be useful to control the arrhythmia.