Background-Rapid activations due to either focal discharge or reentry are often present during atrial fibrillation (AF) in the pulmonary veins (PVs). The mechanisms of these rapid activations are unclear. Methods and Results-We studied 7 isolated, Langendorff-perfused canine left atrial (LA) and PV preparations and used 2 cameras to map membrane potential alone (Vm, nϭ3) or Vm and intracellular calcium simultaneously (Ca i , nϭ4). Rapid atrial pacing induced 26 episodes of focal discharge from the proximal PVs in 5 dogs. The cycle lengths were 223Ϯ52 ms during ryanodine infusion (nϭ13) and 133Ϯ59 ms during ryanodine plus isoproterenol infusion (nϭ13). The rise of Ca i preceded Vm activation at the sites of focal discharge in 6 episodes of 2 preparations, compatible with voltage-independent spontaneous Ca i release. Phase singularities during pacing-induced reentry clustered specifically at the PV-LA junction. Periodic acid-Schiff (PAS) stain identified large cells with pale cytoplasm along the endocardium of PV muscle sleeves. There were abrupt changes in myocardial fiber orientation and increased interstitial fibrosis in the PV and at the PV-LA junction. Conclusions-PV

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Idiopathic granulomatous lobular mastitis (IGLM) is a rare breast condition with prominent skin findings. It is typically seen in young parous women. Painful breast masses, draining sinuses, scarring, and breast atrophy are the main clinical manifestations. IGLM can resemble a variety of other inflammatory and neoplastic processes of the breast. It is thought to result from obstruction and rupture of breast lobules. Extravasated breast secretions then induce an inflammatory reaction. Corynebacteria have also been implicated in the pathogenesis. Treatment is surgical, but systemic corticosteroids, methotrexate, and antibiotics also play a role.

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