Coronary_Circulation_and_conduction.pdf

Coronary circulation &Conduction system Fraser Chisholm [email protected] Learning Outcomes After this lecture, time spent in the dissecting room, and further private study you should be able to: 1. Describe the origin, course and distribution of the coronary arteries 2. Explain the importanc...

Coronary circulation &Conduction system Fraser Chisholm [email protected] Learning Outcomes After this lecture, time spent in the dissecting room, and further private study you should be able to: 1. Describe the origin, course and distribution of the coronary arteries 2. Explain the importance of the anastomoses between the coronary arteries 3. Describe the venous drainage of the heart 4. Describe the anatomical position of the conducting system of the heart and how it controls heart rate 5. List the arteries that supply the conduction system of the heart 6. Describe the autonomic innervation of the heart 7. Discuss the effects of ischaemia of the myocardium and how it may affect the conducting system 8. Explain where pain originating from the heart is referred to and why 9. Identify major branches of coronary arteries on angiograms 2 Heart • It never sleeps (hopefully!) – How is it innervated? • It changes gear. – Who/what controls this? How? • It cannot use the oxygenated blood in its chambers – Why? – Is it “the truth, the whole truth and nothing but the truth”? • Has its own very reliable blood supply 3 Heart Muscle Cardiac muscle • Striated but involuntary • Fibres branch and join with each other with intercalated discs • work as a single functional organ or syncytium • synchronized contraction • does not tetanize 4 Blood supply to the Heart • Supplied by coronary arteries and their branches • Emerge in aortic sinuses • Right coronary artery (RCA) • Left coronary artery (LCA) • Anastomoses between them • The endocardium receives oxygen and nutrients directly from the chambers of the heart • Coronary arteries fill during diastole 5 Coronary arteries • Are the only branches of the ascending aorta • Emerge in aortic sinuses 6 • Fill during diastole 7 Right Coronary artery: Branches • Starts at Right Aortic Sinus • SA nodal branch • Right Marginal (Acute) Branch • Posterior Interventricular • AV nodal branch 8 RCA posterior view Right coronary artery Posterior interventricular artery ? 9 Angiogram: RCA 1. SA nodal Left Anterior Oblique view 2. RCA 1. SA nodal 3. R. Marginal 2. RCA 5. AV nodal 5. AV nodal 3. R. Marginal 4. Post. Interventricular 4. Post. Interventricular 10 Left Coronary Artery • Arises from the left aortic sinus between left auricle and the pulmonary trunk • Shorter but thicker than right coronary artery • Enters the coronary sulcus • Divides into circumflex and anterior interventricular branches 11 Left Coronary artery: Branches • Starts at Left Aortic Sinus: “Left Main Stem” • Anterior Interventricular (LAD, Widowmaker) • Circumflex artery • Left Marginal (Obtuse) Branch • Wraps around apex onto posterior: Anastomosis? 12 Angiogram: LCA Right Anterior Oblique view 1. LCA 3. Ant. Interventricular 4. L. Marginal 1. LCA 3. Ant. Interventricular 4. L. Marginal 2. Circumflex 2. Circumflex 13 14 15 Summary of Coronary Blood Supply 16 Coronary dominance • The artery that gives off the posterior interventricular/posterior descending artery determines the coronary dominance • In ~80% of the people RCA is dominant 17 Dominance • Right Dominant • Left Dominant • Co-Dominant 40 18 Coronary obstruction Obstruction of the Right Coronary artery can lead to an __________ infarct; and mild cases are likely to cause_____________ 19 Coronary obstruction Obstruction of left anterior descending causes an ___________ infarct; that of circumflex artery causes a _____ infarct _______infarcts → loss of LV function → ventricular fibrillation 20 Coronary occlusion Myocardial infarction (MI) • LAD 40-50% • RCA 30-40% • Circumflex 15-20% May damage conducting system • LAD (septal branches) supplies AV bundles • RCA supplies both SA and AV nodes • Heart block (bradycardia) 21 Coronary Angioplasy https://www.youtube.com/watch?v=e13TGGccvT4 • Percutaneous Transluminal Coronary Angioplasty • With or without stent (drug-eluting v bare-metal stents) • Anticoagulation medication 22 Coronary Artery Bypass Graft - CABG • Vessels grafted to bypass blockages • Autograft from: Internal thoracic, great saphenous vein 23 Cardiac Veins • Great cardiac (anterior interventricular) vein joins the coronary sinus • Small cardiac vein accompanies right marginal branch • Middle cardiac (posterior interventricular) vein drains into coronary sinus • Anterior cardiac veins drain independently into the RA 24 Coronary Sinus • Lies between the LA and LV • Surrounded by muscle fibers from LA • Drains 60% of the venous blood of the heart into the RA • 40% is drained by smallest cardiac veins (Thebesian veins) and anterior cardiac veins 25 Cardiac veins • • • • Great cardiac (anterior interventricular) vein joins the coronary sinus Small cardiac vein accompanies right marginal branch Middle cardiac (posterior interventricular) vein drains into coronary sinus Anterior cardiac veins drain independently into the RA 26 Conduction system • Take a breath 27 Cardiac Conduction system • There is a group of specialized, modified cardiac muscle cells that – lie immediately beneath the endocardium – can generate electrical impulses without external stimuli • Cardiac muscle cells distribute electrical impulses through the myocardium – causing the heart to contract in the proper sequence • Autonomic nervous system shortens or prolongs the duration of a cardiac cycle 28 Cardiac Conduction system • The components of the conduction system are: • Sinu-atrial node (SA node) • Atrioventricular node (AV node) • Atrioventricular bundle (bundle of His) • Left bundle branch • Right bundle branch • − Purkinje fibers. Madhero88 (original files); Angelito7 (this SVG version); (https://commons.wikimedia.org/wiki/File:ConductionsystemoftheheartwithouttheHear t-en.svg), „ConductionsystemoftheheartwithouttheHeart-en“, https://creativecommons.org/licenses/by-sa/3.0/legalcode • None of them are macroscopic 29 SA and AV nodes 30 AV Bundle of His & Bundle branches Bundle of His • Runs along the membranous part of the IV septum. • Only conductive route through the fibrous skeleton • Right Bundle branch • Descends on the right side of the membranous part of the IV septum. • Enters the septomarginal trabecula to reach the base of the anterior papillary muscle • Splits into Purkinje fibres which spread out into the ventricular walls • Left Bundle branch • Descends on the left side of the membranous part of the IV septum. • Splits into Purkinje fibres 31 Cardiac Conduction system 32 Nerve Supply to the heart • Cardioacceleratory and Cardioinhibitory centers in the Brainstem (Medullary reticular formation) • Superficial and deep cardiac plexus – Supply conduction system, coronary blood vessels, and myocardium • 1. Presynaptic sympathetic fibres travel in T1-5(6) spinal nerves – Increase the heart rate and force of contraction – Dilate coronary arteries • 2. Parasympathetic fibers travel in the Vagus nerve – Decrease the heart rate – Constrict coronary arteries • 3. General visceral afferents 33 Nerve supply to the heart 34 Cardiac Referred pain 35 Sources of figures and Images • • • • • • • • DAFFNER: Daffner & Hartman. Clinical Radiology. The Essentials ,4th Ed, 2014 © Lippincott Williams & Wilkins. DRAKE: Drake et al. Gray’s Atlas of Anatomy 2nd Ed, 2018 © Elsevier. GILROY: Gilroy et al. Atlas of Anatomy 2nd Ed, 2012 © Thieme KELLEY: Kelly&Petersen. Sectional Anatomy for Imaging Professionals, 3rd Edition, 2013 © Mosby, Elsevier Inc MOORE: Moore et al. Clinically Oriented Anatomy 8th Ed, 2018 © Wolters Kluver. NETTER: Hansen. Netter's Clinical Anatomy, 3rd Edition, 2014 © Saunders, Elsevier Inc SOBOTTA: Putz&Pabst. Sobotta Atlas of Human Anatomy, 14th Edition, 2006 © Urban and Fischer Verlag, Elsevier Inc ONI: Soni et al. Point-of-care Ultrasound, 2015 © Saunders. 36