Histological Substrate of Atrial Biopsies in Patients With Lone Atrial Fibrillation

TLDR: Abnormal atrial histology was uniformly found in multiple biopsy specimens in all patients with LAF and was compatible with a diagnosis of myocarditis in 66% of patients and of noninflammatory localized cardiomyopathy in 17% and was represented by patchy fibrosis in 17%.

Abstract: Background Lone atrial fibrillation (LAF) is a common clinical syndrome, but its origin remains unknown. Methods and Results We performed endomyocardial biopsies of the right atrial septum (2 to 3 per patient; mean, 2.8) and of the two ventricles (6 per patient) in 12 patients (10 men, 2 women; mean age, 32 years) with paroxysmal LAF refractory to conventional antiarrhythmic treatment. As controls, we used endomyocardial biopsies (3 to 5 per patient; mean, 4.4) from the right atrial septum of 11 patients with Wolff-Parkinson-White syndrome (WPW) undergoing resection of the abnormal AV pathway. The weight of the biopsies ranged from 2.8 to 4.5 mg. Biopsy samples were processed for histology and electron microscopy and were read by a pathologist blinded to clinical data. All patients underwent two-dimensional Doppler echocardiography; cardiac catheterization; coronary angiography; and hormonal, virologic, and electrophysiological studies. All tests and WPW biopsies were normal, but all LAF atrial biopsy spe...