A Morphological And Electrophysiological Study Of Sinus Coronary Musculature

Coronary sinus was a main component of heart venous system, which provided identification marker and passageway for cardiac disease diagnosis and therapy, such as endocardial mapping, radiofrequency catheter ablation and pericardial pacing. Coronary sinus was surrounded by striated muscle, which was named coronary sinus musculature. Recent studies have found that coronary sinus musculature participated several kinds of arrhythmia, such as atrial fibrillation, atrial flutter, atrioventricular nodal reentrant tachycardia and atrioventricular reentrant tachycardia. Therefore, the recognition of the morphological and electrophysiological features of coronary sinus musculature will deepen apprehension of those arrhythmias and facilitate active treatment. This study aimed at investigating the morphological features as well as tissue and cell electrophysiological characteristics of the coronary sinus musculature obtained from healthy male canine, and try to find the relationship between coronary sinus musculature and cardiac arrhythmia.Sixteen excised canine hearts were perfused in a Langendorff preparation. A 20-electrode catheter (2-8-2-mm spacing center to center) was placed along the coronary sinus. Then pulmonary veins were excised to provide access to left atrium, and a second 20-electrode catheter was placed along left atrial endocardium opposite the coronary sinus catheter. Programmed stimulation was delivered at coronary sinus ostium, distal coronary sinus and lateral wall of left atrium.Sixteen hearts undergone electrophysiological study in the former experiment were examined by performing serial longitudinal sections parallel to the long axis of the coronary sinus, which was followed by hematoxylin and eosin stain or Masson's trichrome stain. The expression and distribution of connexin 43(Cx43) was determined through immunohistology method.The gross structures of coronary sinus musculature in additional five canine hearts were observed.The response to isoproterenol and electrical stimulation of myocytes both in the coronary sinus and outside the ostium were studied through standard glass microelectrode technology to investigate the mechanism of ectopia arrhythmia nearby coronary sinus musculature.During coronary sinus ostium pacing, coronary sinus electrodes recorded double potentials, a sharp and high-frequency potential followed by a rounded, low-frequency potential. The sharp potential represented coronary sinus activation from coronary sinus ostium to distal coronary sinus, while the rounded initial potential propagated in theposterior to septal and lateral direction and represented "far-field" left atrial activation. When a short interval coupling premature stimuli was delivered, 4 hearts developed conduction block in the coronary sinus-left atrium pathway, which changed the left atrial activation mode to septal-lateral. Pacing at distal coronary sinus was successful only in 3 hearts and in coronary sinus catheter the sharp signals propagate from lateral to septal and the rounded signals propagate from posterior to both lateral and septal direction. Only 1 heart out of the three hearts showed coronary sinus-left atrium block when extra stimuli were delivered. During lateral wall of left atrium pacing, coronary sinus electrodes recorded double potentials, a rounded, low-frequency potential followed by a sharp potential. The rounded initial potential propagated in the lateral-to-septal direction and represented left atrial activation. No left atrium-coronary sinus conduction block was recorded during lateral left atrium pacing.All venous wall of coronary sinus was surrounded by a sleeve of striated muscle whose morphological characteristics were similar to that of the atrial myocardium. The musculature extended 36.8 + 6.2 mm from the coronary sinus ostium. The thickness of the musculature were 1.14 + 0.43 mm and 0.56 + 0.23mm mm at the ostium and distal extremity of coronary sinus, respectively. Striated myocardial connections of varying width left this coronary muscle sleeve and connected to t...