Szilvia Kugler1, Nándor Nagy2, Gergely Rácz3, Anna-Mária Tőkés4, Bence Dorogi2, Ágnes Nemeskéri5. 1. Department of Anatomy, Histology and Embryology, Faculty of Medicine, Semmelweis University, Budapest, Hungary; Heart and Vascular Center, Semmelweis University, Budapest, Hungary. 2. Department of Anatomy, Histology and Embryology, Faculty of Medicine, Semmelweis University, Budapest, Hungary. 3. 1st Department of Pathology and Experimental Cancer Research, Faculty of Medicine, Semmelweis University, Budapest, Hungary. 4. 2nd Department of Pathology, Faculty of Medicine, Semmelweis University, Budapest, Hungary. 5. Department of Anatomy, Histology and Embryology, Faculty of Medicine, Semmelweis University, Budapest, Hungary. Electronic address: nemeskeri.agnes@med.semmelweis-univ.hu.
Abstract
BACKGROUND: Pulmonary vein (PV) myocardium is a known source of atrial fibrillation. A debated question is whether myocardial extensions into caval veins and coronary sinus (CS) have similar properties. No studies have documented specific pacemaker and/or conducting properties of human extracardiac myocardium. OBJECTIVE: The purpose of this study was to characterize the histology and immunohistochemical features of myocardial sleeves in the wall of cardiac veins. METHODS: Sections of 32 human hearts were investigated. Specimens of PVs, superior caval vein (SVC), CS, sinoatrial and atrioventricular nodes, and left ventricle were stained with Best's Carmine for selective staining of intracellular glycogen. Anti-connexin45 (Cx45)- and Cx43-specific antibodies were used to determine the conduction properties of extracardiac myocardium. RESULTS: Myocardial sleeve was found in the wall of PVs of 15 of 16 hearts, 21 of 22 SVCs, and 8 of 8 CSs. Bundles of glycogen-positive cardiomyocytes exhibiting pale cytoplasm and peripheral myofibrils were observed in the venous sleeves. Strong Cx45 and weak Cx43 labeling was detected in the extracardiac myocardium. Similar staining pattern was observed for the pacemaker and conduction system, whereas ventricular myocardium exhibited prominent Cx43 and no Cx45 immunoreactivity. CONCLUSION: Myocardial fibers of PVs, SVC, and CS exhibit morphology similar to that of Purkinje fibers and are enriched in glycogen. We provide data for the first time on prominent positive staining for Cx45 in the extracardiac myocardium, indicating its potential pacemaker and/or conducting nature.
BACKGROUND: Pulmonary vein (PV) myocardium is a known source of atrial fibrillation. A debated question is whether myocardial extensions into caval veins and coronary sinus (CS) have similar properties. No studies have documented specific pacemaker and/or conducting properties of human extracardiac myocardium. OBJECTIVE: The purpose of this study was to characterize the histology and immunohistochemical features of myocardial sleeves in the wall of cardiac veins. METHODS: Sections of 32 human hearts were investigated. Specimens of PVs, superior caval vein (SVC), CS, sinoatrial and atrioventricular nodes, and left ventricle were stained with Best's Carmine for selective staining of intracellular glycogen. Anti-connexin45 (Cx45)- and Cx43-specific antibodies were used to determine the conduction properties of extracardiac myocardium. RESULTS: Myocardial sleeve was found in the wall of PVs of 15 of 16 hearts, 21 of 22 SVCs, and 8 of 8 CSs. Bundles of glycogen-positive cardiomyocytes exhibiting pale cytoplasm and peripheral myofibrils were observed in the venous sleeves. Strong Cx45 and weak Cx43 labeling was detected in the extracardiac myocardium. Similar staining pattern was observed for the pacemaker and conduction system, whereas ventricular myocardium exhibited prominent Cx43 and no Cx45 immunoreactivity. CONCLUSION: Myocardial fibers of PVs, SVC, and CS exhibit morphology similar to that of Purkinje fibers and are enriched in glycogen. We provide data for the first time on prominent positive staining for Cx45 in the extracardiac myocardium, indicating its potential pacemaker and/or conducting nature.
Authors: Lisa A Gottlieb; Charly Belterman; Shirley van Amersfoorth; Virginie Loyer; Marion Constantin; Mélèze Hocini; Lukas R C Dekker; Ruben Coronel Journal: Front Physiol Date: 2021-11-24 Impact factor: 4.566
Authors: Maen D Abou Ziki; Neha Bhat; Arpita Neogi; Tristan P Driscoll; Nelson Ugwu; Ya Liu; Emily Smith; Johny M Abboud; Salah Chouairi; Martin A Schwartz; Joseph G Akar; Arya Mani Journal: Hum Mutat Date: 2021-07-29 Impact factor: 4.700