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Thorax
Published in Bobby Krishnachetty, Abdul Syed, Harriet Scott, Applied Anatomy for the FRCA, 2020
Bobby Krishnachetty, Abdul Syed, Harriet Scott
The conducting system is the unique tissue specific to the heart and has specialised cardiac muscle. It generates and transmits impulses that regulate cardiac contraction. The sinoatrial node (SA node) is situated in the upper part of the crista terminalis, within the myocardium, to the right of the SVC opening. It is also called the pacemaker of the heart as it initiates and modulates the heart rate and transmits impulses to the atria and the ventricles.The atrioventricular node (AV node) is situated in the endocardium, near the atrial septum, immediately above the opening of the coronary sinus. It receives electrical impulses that originate in the SA node and transmits them to the bundle of His.The atrioventricular bundle of His transmits impulses to the walls of the ventricles. It first transits along the membranous part of the interventricular septum and then divides at the junction of the muscular and membranous parts of the interventricular septum. The subendocardial branches are the Purkinje fibres, specialised cardiac fibres, which then ascend within the muscular walls of the ventricles.
Electrical Properties of the Heart
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
After passing down the right side of the interventricular septum for 1 cm, the bundle of His splits into right and left bundle branches to the right and left ventricles (the left bundle branch divides into anterior and posterior divisions). The bundle branches supply the dense network of Purkinje fibres, which innervate the ventricles. Purkinje cells are the largest-diameter cells in the heart, and their conduction velocity is fast (1–4 m/s) so that ventricular activation is rapid.
Conduction problems
Published in Andrew R Houghton, Making Sense of the ECG, 2019
Moving down the conducting system beyond the bundle of His, bundle branch block can affect either the left or right bundle branch (Figure 9.1). If both the left and right bundle branches are blocked, this is equivalent to third-degree AV block, as no impulses will reach the ventricular myocardium from the atria.
Conventional aortic root vs valve-sparing root replacement surgery in aortic dilatation syndromes: a comparison of mortality and postoperative complications
Published in Expert Review of Cardiovascular Therapy, 2023
Hashrul N Rashid, Omar Chehab, Harriet Hurrell, Vitaliy Androshchuk, Agata Sularz, Tiffany Patterson, Gianluca Lucchese, Simon Redwood
The Dacron graft is sutured to the annulus with a single horizontal plane, but the number of stitches may vary from 3 (below the Nadir of each aortic cusp) up to 12 (in circumferential fashion) according to different approaches (Figure 2). The Bundle of His is ideally left without a suture to reduce the risk of conduction disturbance. The commissures are resuspended, and the cusps are sutured onto the Dacron graft. The coronary ostia are finally reimplanted at their respective sinuses. The cusps and leaflet coaptation are visually reviewed before the superior portion of the Dacron graft is sutured to the ascending aorta. The latest modification of the David procedure implies adopting a second Dacron graft to recreate the sinotubular junction (Stanford modification). The David procedure has evolved into various similar techniques since its conception, detailed in this expert review article.
Anatomical Considerations and Emerging Strategies for Reducing New Onset Conduction Disturbances in Percutaneous Structural Heart Disease Interventions
Published in Structural Heart, 2021
Mazen S. Albaghdadi, Andrew O. Kadlec, Horst Sievert, Srijoy Mahapatra, Alexander Romanov, Usman Siddiqui, Itzhak Kronzon, Michael Nguyen Young, Apostolos Tzikas, Martin B. Leon, Siew Yen Ho, Karl-Heinz Kuck
Similar to the aortic valve, the tricuspid valve is in close proximity to the conduction system, particularly the AV node, bundle of His, and right bundle branch.51 The bundle of His traverses the right trigone of the central fibrous body to reach the ventricular septum which is near the commissure of the septal and anterior tricuspid leaflets.52 Percutaneous interventions may increase the risk of injury to the conduction system; however, the incidence and prognostic significance of new onset conduction disturbances following percutaneous repair of the tricuspid valve remain unknown.51 Considering that this approach is gaining recognition as a favorable alternative to surgery,49 future studies will help to delineate the incidence and impact of arrhythmias on short-term and long-term outcomes following this intervention.
Right and left-sided infective endocarditis in an IV drug abuser
Published in Journal of Community Hospital Internal Medicine Perspectives, 2020
Maryam Nemati, Kristine Galang, Syung Min Jung
Patients with IE can also develop heart blocks. Usually, heart blocks occur when the cardiac valves on the left side of the heart are affected. The occurrence of first-degree AV blocks is clinically significant not only because these heart blocks can progress, as it did in our patient, but its presence strongly suggests a perivalvular extension of an aortic abscess [9]. Furthermore, the conduction system of the heart is easily affected due to the proximity of the aortic valve with the bundle of His in turn leading to problems with AV blocks or bundle branch blocks. It is particularly prudent to monitor these patients on telemetry as disruptions in the conduction system carry increased mortality and overall a poorer prognosis. The presence of an AV block alone carries a 97% specificity in the detection of perivalvular aortic involvement [9,10].