title: Histological substrate of atrial biopsies in patients with lone atrial fibrillation.
abstract: BACKGROUND
  Lone atrial fibrillation (LAF) is a common clinical syndrome, but its origin remains unknown.
  
  
  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 specimens (average, 2.8 per patient) showed abnormalities (P<.0001). The type of abnormalities varied: Two patients had a severe hypertrophy with vacuolar degeneration of the atrial myocytes and ultrastructural evidence of fibrillolysis occupying >50% of the areas assessed morphometrically (P=.50), 8 had lymphomononuclear infiltrates with necrosis of the adjacent myocytes (5 with fibrosis and 3 without; P<.003), and 2 had only nonspecific patchy fibrosis (P=.50). Biventricular biopsies were abnormal in only 3 patients and showed inflammatory infiltrates similar to those found in atrial biopsies.
  
  
  CONCLUSIONS
  Abnormal atrial histology was uniformly found in multiple biopsy specimens in all patients with LAF. It was compatible with a diagnosis of myocarditis in 66% of patients (active in 25%) and of noninflammatory localized cardiomyopathy in 17% and was represented by patchy fibrosis in 17%. The cause of the pathological changes, which were found only in atrial septal biopsies but not in biventricular biopsies, in 75% of patients remains unknown.
authors.affiliation: Istituto di Cardiologia, Università Cattolica del S. Cuore, and the Dipartimento di Medicina Sperimentale e Patologia, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Frustaci
authors.forename: C
authors.initials: C
authors.lastname: Chimenti
authors.forename: F
authors.initials: F
authors.lastname: Bellocci
authors.forename: E
authors.initials: E
authors.lastname: Morgante
authors.forename: M A
authors.initials: MA
authors.lastname: Russo
authors.forename: A
authors.initials: A
authors.lastname: Maseri
mesh_terms: D000328:Adult; D001281:Atrial Fibrillation / Q000188:drug therapy / Q000209:etiology / Q000473:pathology*; D001706:Biopsy; D009202:Cardiomyopathies / Q000150:complications / Q000473:pathology; D016022:Case-Control Studies; D004699:Endocardium / Q000473:pathology; D005260:Female; D006325:Heart Atria / Q000000981:diagnostic imaging / Q000473:pathology*; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009205:Myocarditis / Q000150:complications / Q000473:pathology; D014463:Ultrasonography; D014927:Wolff-Parkinson-White Syndrome / Q000473:pathology