Download - Coronary circulation
![Page 1: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/1.jpg)
Coronary Circulation
Physiology Seminar18/04/2013
PowerPoint® Seminar Slide Presentation prepared by Dr. Anwar Hasan Siddiqui, Senior Resident, Dep't of Physiology, JNMC
©Dr. Anwar Siddiqui
![Page 2: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/2.jpg)
CORONARY CIRCULATION
• CONSIST OF 1) Arterial supply
2) Venous drainage
3) Lymphatic drainage
![Page 3: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/3.jpg)
ARTERIAL SUPPLY
• The cardiac muscle is supplied by two coronary arteries the right and left coronary arteries.
• Both arteries arises from the sinuses behind the cusps of the aortic valves at the root of the aorta.
![Page 4: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/4.jpg)
![Page 5: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/5.jpg)
RT. CORONARY ARTERY
• Smaller than left coronary artery.
• Arises from anterior coronary sinus.
![Page 6: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/6.jpg)
COURSE:• Emerges from the surface of heart
between pulmonary trunk and right auricle.
• Winds round the inferior border to reach the diaphragmatic surface to reach the posterior inter-ventricular groove.
• Terminates by anastomising with left
coronary artery
![Page 7: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/7.jpg)
BRANCHES• Large Branches
– marginal– Post-interventricular
• Small branches:– Right atrial – Infundibular– Nodal – in 60% cases– Terminal
![Page 8: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/8.jpg)
Anterior schematic diagram of heart shows course of dominant right coronary artery and its tributaries. AV = atrioventricular, PDA = posterior descending artery, RCA = right coronary artery, RV = right ventricular, SA = sinoatrial
![Page 9: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/9.jpg)
AREAS OF DISTRIBUTION• Right atrium• Ventricles– Greater part of right ventricle, except the
area adjoining the anterior inter-ventricular groove.
– A small part of the left ventricle adjoining the posterior interventricular groove.
• Posterior part or the inter-ventricular septum
• Whole of the conducting system of the heart except a part of the left branch of AV bundle. The SA node is supplied by left coronary artery in 40% cases
![Page 10: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/10.jpg)
LEFT CORONARY ARTERY
• Larger than the right coronary artery.
• Arises from left posterior aortic sinus.
![Page 11: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/11.jpg)
COURSE• Runs forward and to the left and emerges
between the pulmonary trunk and the left auricle.
• Here the anterior inter-ventricular branch is given .
• The further continuation of the left coronary artery is sometimes called the circumflex artery.
• After giving off the anterior interventricular branch it runs into the left anterior coronary sulcus.
• It winds around the left border and near posterior interventriular groove it terminates by anastomosing with the right coronary artery.
![Page 12: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/12.jpg)
BRANCHES:• Large Branches:
– Anterior interventricular– Branch to the diaphragmatic surface of the
left ventricle• Small Branches:
― Left atrial― Pulmonary― Terminal
![Page 13: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/13.jpg)
Dominant left coronary artery anatomy. Left anterior oblique schematic diagram of dominant left coronary artery anatomy, including left anterior descending artery and left circumflex artery tributaries, is shown. AVGA = atrioventricular groove artery, PDA = posterior descending artery.
![Page 14: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/14.jpg)
Areas of distribution• Left atrium• Ventricles:
−Greater part of left ventricle, except the area adjoing the posterior interventricular groove.
−A small part of right ventricle adjoining the anterior interventricular groove.
• Anterior part of interventricular septum.• Part of left branch of AV bundle
![Page 15: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/15.jpg)
COLLATERAL CIRCULATION• Cardiac anatomosis: The two coronary arteries
anastomose in the myocardium.
• Extra cardiac anastomosis: The coronary arteries anastomose with the
• Vasa vasorum of the aorta,• Vasa vasorum of pulmonary arteries,• Internal thoracic arteries• The bronchial arteries• Phrenic arteries.
• These channels open up in the emergencies when the coronary arteries are blocked.
![Page 16: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/16.jpg)
CORONARY ARTERY DOMINANCE
• The artery that gives the posterior interventricular artery determines the coronary dominance.
• If the posterior interventricular artery is supplied by the right coronary artery (RCA), then the coronary circulation can be classified as "right-dominant".
• If the posterior interventricular artery is supplied by the circumflex artery (CX), a branch of the left artery, then the coronary circulation can be classified as "left-dominant".
• If the posterior interventricular artery is supplied by both the right coronary artery (RCA) and the circumflex artery, then the coronary circulation can be classified as "co-dominant".
![Page 17: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/17.jpg)
FUNCTIONAL DIVISION• Large coronary arteries(epicardial
cortonary arteries) - lies on epicardial surface,– conduct blood with little resistance.
• Small coronary arteries – descends into myocardium, are of two types: – subepicardial vessels and – subendocardial vessels.
• Small coronary arteries are the principle resistance vessels of the heart, change in their diameter regulate the coronary blood flow
![Page 18: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/18.jpg)
VENOUS DRAINAGE OF THE HEART
• The venous drainage of the heart is by three means: – Coronary sinus.
– Anterior cardiac veins
– Venae Cordis minimae.
![Page 19: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/19.jpg)
CORONARY SINUS• This is the largest of vein of heart situated in
the left posterior coronary sulcus. It is about 3 cm long and ends by opening into the posterior wall of the right atrium.
• Its tributaries are:−Great cardiac vein: It enters the left end of
the coronary sinus.−Middle cardiac vein: It accompanies the
posterior interventricular artery and joins the right end of the coronary sinus.
−Small cardiac vein: It accompanies the right coronary artery and joins the right end of the coronary sinus.
![Page 20: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/20.jpg)
−Posterior vein of left ventricle: It runs on the diaphragmatic surface of the left ventricle and ends in the middle of the coronary sinus.
−Oblique vein of left atrium ( of Marshall): It runs on the posterior surface of the left atrium, joins the left end of coronary sinus and develops from the left common cardinal vein.
−The right marginal vein: It accompanies the marginal branch of the right coronary artery.
![Page 21: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/21.jpg)
ANTERIOR CARDIAC VEIN3 to 4 small veins run on the anterior wall of the right ventricle, open directly into the right atrium.
VENAE CORDIS MINIMAE(also called smallest cardiac veins, venae cardiacae minimae, or Thebesian veins)
• Numerous small veins present in all 4 chambers of heart which open directly into the cavities.
• The Thebesian venous network is considered an alternative (secondary) pathway of venous drainage of the myocardium. It is named after German anatomist Adam Christian Thebesius, who described them in a 1708 treatise called Disputatio medica inauguralis de circulo sanguinis in corde.
![Page 22: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/22.jpg)
Lymphatics of heart
• Lymphatics of the heart accompany the coronary arteries and form 2 trunks.
• Right trunk ends in brachiocephalic nodes and the left trunk into the tracheobronchial lymph nodes at the bifurcation of the trachea.
![Page 23: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/23.jpg)
PECULIARITIES OF COR.CIRCULATION
• BF during diastole• End arteries • High capillary density• High 02 extraction• Regulation is mainly by metabolites • Anatomical anastomosis• The coronary vessels are susceptible to degeneration
and atherosclerosis.• There is evident regional distribution: The
subendocardial myocardial layer in the left ventricle receives less blood, due to more myocardial compression (but this is normally compensated during diastoles by V.D). However, this renders this area more liable to ischemia and infarction
![Page 24: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/24.jpg)
CORONARY BLOOD FLOW (CBF):
• The resting coronary blood flow is about 225 ml/min., which is about 0.7 – 0.8 ml/gm of heart muscle, or 4- 5 % of the total cardiac output.
• In severe muscular exercise, the work of the heart increased and the CBF may be increased up to 2 liters/ minute
![Page 25: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/25.jpg)
FACTORS REGULATING CORONARY BL.FLOW
• Physical • Chemical • Neural • Hormonal • Reflex
![Page 26: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/26.jpg)
PHYSICAL FACTORAortic blood pressure: • CBF is directly proportional to aortic blood
pressure, especially the diastolic aortic pressure , most of CBF occur during diastole.
• When diastolic pressure decreases e.g. aortic incompetence or when MAP is decreased e.g. shock or aortic stenosis, the CBF decreases.
• Blood flow to the endocardial regions is more severely impaired than is that to the epicardial regions of the ventricle
![Page 27: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/27.jpg)
Heart Rate:• Excessive in the heart rate e.g.
paroxysmal tachycardia diastolic period coronary filling (as it occurs mainly during ventricular diastole) CBF.
Cardiac Output: • CBF is directly proportional to COP i.e.COP CBF
COP CBF• Increased cardiac output BP in aorta + reflex
inhibition of the vagal vasoconstrictor tone (a nrepis reflex) coronary vasodilatation CBF.
![Page 28: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/28.jpg)
• C.B.F. occurs mainly during diastole due to compression of coronary blood vessels during systole by the contracted muscle fibers.
During systolic phases C.B.F. is less than that during diastole. With minimal blood flow during iso volumetric contraction phase. (due to compression of coronary blood vessels with low aortic pressure).
During diastolic phases C.B.F. is more than that during systole.With maximal blood flow during iso volumetric relaxation phase. (due to dilated coronary blood
vessels with high aortic pressure).
![Page 29: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/29.jpg)
CHEMICAL FACTORS:Metabolic factors:
cardiac metabolism O2tension (local hypoxia), CO2, K+, lactic acid & adenosine in the cardiac muscle coronary vasodilatation CBF.
O2 lack (hypoxia) is the most effective coronary vasodilator. It produces coronary vasodilatation through:
• Direct action on coronary blood vessels and
• Release of chemical substances such as adenosine (from ATP) which is a potent coronary vasodilator.
Drugs:
• Nitrites, angised, aminophylline, caffeine & Khellin are coronary vasodilator coronary vasodilatation CBF.
![Page 30: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/30.jpg)
NERVOUS FACTORS:
Direct effect:• Parasympathetic: vagus has very slight distribution to
coronary, so its stimulation has slight dilator effect.• Sympathetic: Both alpha and Beta receptors exist in the
coronary vessels. Sympathetic stimulation causes slight direct coronary constriction.
Indirect effect:• Plays a far more important role in normal control of
coronary blood flow than the direct. Sympathetic stimulation increase both heart rate and myocardial contractility, as well as its rate of metabolism leading to dilatation of coronary blood vessels. The blood flow increase proportional to the metabolic need of heart muscle
![Page 31: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/31.jpg)
HORMONAL FACTOR
• Thyroxin cardiac metabolism coronary vasodilator CBF.
• Vasopressin (antidiuretic hormone) coronary vasoconst CBF.
![Page 32: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/32.jpg)
REFLEX CONTROL
• Anrep’s reflex: Increased venous return causes increased pressure in right atrium, leading to reflex increase in CBF e.g. during muscular exercise.
• Gastro-coronary reflex: Distention of the stomach with heavy meal causes reflex vasoconstriction of coronary blood vessels decreasing CBF.
![Page 33: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/33.jpg)
Coronary Autoregulation• If there is sudden change in aortic
pressure, coronary vascular resistance will adjust itself proportionally within few seconds; so that a constant blood flow is maintained.
• Range of autoregulation: 60 – 140 mmHg.Mechanism:• Myogenic response: an increase in
passive stretch, caused by increased perfusion pressure, causes active smooth muscle contraction.
![Page 34: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/34.jpg)
• Chemical theory: • Decrease perfusion pressure leads to
Increase adenosine & Decreased oxygen which causes Vasodilatation and increase CBF
• Endothelium derived relaxation factor (EDRF): • Hypoxia, ADP, VIP, muscular exercise (increase
distention force), stimulate vascular endothelium to secrete EDRF, which is a potent vasodilator, that causes coronary dilatation and increase CBF.
![Page 35: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/35.jpg)
Applied aspects
![Page 36: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/36.jpg)
CORONARY ARTERY DISEASE ANGINA PECTORIS• Angina Pectoris means severe chest pain (usually
retrosternal i.e. behind the sternum) due to ischemia of the cardiac muscle.
• Angina pectoris is usually due to narrowing of the coronary arteries ischemia.
• When the coronary artery is only partly obstructed (by spasm or atherosclerosis) and the coronary blood flow is only moderately reduced, symptoms of ischemia appears only when cardiac work is increased by effort, exercise, excitement, food or severe cold, or anemia and relived by treatment.
• Pain is due to accumulation of pain producing substances in the myocardium such as, P factor, lactic acid, histamine, K, and Kinins.
![Page 37: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/37.jpg)
• MYOCARDIAL INFARCTION• Myocardial Infarction means necrosis of a part of
the myocardium due to
− Severe & prolonged ischemia due to narrowing of the coronary arteries.
− Occlusion of one of the coronary arteries or its branches by coronary thrombosis severe ischemia.
• Myocardial Infarction produces also chest pain which is more severe than that of angina and it cannot be relieved by rest or coronary VD drugs.
• It is usually complicated by fatal ventricular fibrillation.
![Page 38: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/38.jpg)
![Page 39: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/39.jpg)
Coronary bypass operation
![Page 40: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/40.jpg)
Angioplasty
![Page 41: Coronary circulation](https://reader036.vdocuments.us/reader036/viewer/2022062404/554b6590b4c905030a8b47a8/html5/thumbnails/41.jpg)
A Presentation By DR ANWAR H SIDDIQUI, JR, Physiology