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We studied a biomaterial for a new domestic product, a biological envelope for implantation of cardiac electronic devices. The product is designed to prevent complications after pacemaker implantation and to facilitate the reimplantation procedure. By chemical and biological processing of raw materials (submucosa of porcine small intestine), an acellular extracellular collagen matrix was obtained. The biocompatibility of the material was tested in vitro using stem cell cultures. The biomaterial for fabrication of the envelope is not cytotoxic, biocompatible, and represents a suitable substrate for attachment, growth, and reproduction of stem cells. The biological effect of the material was studied in vivo on the model of heterotopic implantation in small laboratory animals. The biomaterial did not induce inflammation and tissue reaction and was completely transformed into healthy vascularized tissue without scars in 90 days after implantation.

The myocardium of the right and left atrial appendages (auricles) in patients with paroxysmal, persistent, and permanent forms of atrial fibrillation was examined by histological methods and electron microscopy. Isolated atrial amyloidosis was detected in the left (50.0-56.3% patients) and in the right (45.0-55.6% patients) atrial appendages. In all cases, immunohistochemistry revealed atrial natriuretic peptide in fibrillary amyloid deposits. Ultrastructurally, amyloid masses formed clusters of myofibrils 8-10 nm in diameter. They were chaotically located in the extracellular space along the sarcolemma as well as in membrane invaginations, dilated tubules of cardiomyocyte T-tubular system, and vascular walls. Amyloidosis was predominantly observed in women; its degree positively correlated with age of patients and duration of atrial fibrillation but negatively correlated with atrial fibrosis. The study revealed positive (in permanent atrial fibrillation) and negative (in paroxysmal atrial fibrillation) correlation of amyloidosis with myofibril content in atrial cardiomyocytes.