ИСТИНА

Objectives. Thoracic veins in most mammals possess by myocardial tissue. Bioelectrical properties of pulmonary veins myocardium is well described since considered to be responsible for the onset of supraventricular arrhythmias. Nevertheless, excitation pattern of cardiac tissue in caval veins remains poor investigated. The present study is aimed to characterization of the excitation pattern in rat caval veins myocardium under basal condition and adrenergic stimulation. Methods. Multicellular preparations of left atrium (LA), right (RAV) and left anterior (LAV), posterior caval (PAV) and azygos veins (AzV) were dissected from male rats (200-250 g) and perfused at 37C with Tirode solution. Excitation was mapped in electrically paced preparations treated with potential sensitive dye di-4-ANEPPS (5 µM) and blebbistatin (1 µM) with use of CCD camera (WuTech Instruments). Conduction velocity (CV) was assessed with aid of RedShirtImaging software in control or after administration of isoproterenol (1 μM, ISO) or phenylephrine (10 μM, Phe). Results. At basal conditions all preparations of caval veins, excepting PAV, demonstrated excitability, atrial-like action potentials (AP), uniform conduction and similar CV. In LA, RAV, LAV and AzV averaged CV was 84±15, 80±12, 76±14, 66±16 cm/c, respectively. ISO weakly affected conduction in caval veins. Phe administration resulted in significant reduction of CV, conduction blocks and initiation of temporal AP alternans in caval veins; similar effects were observed at rapid pacing.