Coronary circulation and fetal circulation

circulation of adult and fetus

1. CORONARY CIRCULATION AND FETAL CIRCULATION Princy Francis M II nd Yr MSc (N) JMCON

2. DEFINTIONS Coronary circulation: Coronary circulation is the circulation of blood in the blood vessels that supply the heart muscle (myocardium). Fetal circulation : The fetal circulation is the circulatory system of a human fetus, often encompassing the entire fetoplacental circulation which includes the umbilical cord and the blood vessels within the placenta that carry fetal blood.

3. Coronary circulation The heart receives its own supply of blood from the coronary arteries. Two major coronary arteries branch off from the aorta near the point where the aorta and the left ventricle meet. These arteries and their branches supply all parts of the heart muscle with blood.

4. Coronary Circulation Arterial Supply Venous supply Lymphatic drainage

5. ARTERIAL SUPPLY The right coronary artery The left coronary artery / Left main coronary artery. These arteries branch from the aorta in the region of the sinus of Valsalva . They extend over the pericardium surface of the heart and branch several times.

6. Right Coronary Artery Smaller than left coronary artery COURSE It emerges from the surface of heart between pulmonary trunk and right auricle, then winds round the inferior border to reach the diaphragmatic surface to reach the posterior inter-ventricular groove and terminates by anastomosing with left coronary artery.

7. BRANCHES Conus branch Sinus node artery Right ventricular branch Right atrial branch Acute marginal branch AV Nodal branch Posterior descending branch Left ventricular branch Left atrial branch

8. Conus branch The conus branch is small and exit within the first 2 cm of the RCA. The branch proceeds centrally to the left of the pulmonic valve. When the conus branch anastomosis with a right ventricular branch of the left anterior descending artery, the resulting structure is called the circle of vieussens . It supplies the upper part of the right ventricle, near the outflow tract at the level of the pulmonic valve.

9. Sinus node artery It arises from right coronary artery and proceeds in the opposite direction from the conus branch, coursing cranially and to the right, encircling the venacava . It usually have 2 branches one supplies to the sinus node and \ parts of right atrium other branches to the left atrium.

10. Right ventricular branches The right coronary artery course along the AV groove, giving rise next to one or more right ventricular branches that vary in length and distribute to the right ventricular wall. Right Atrial Branch: It proceeds cranially toward the right heart border and perfuses the right atrium.

11. Acute marginal branch It is a large branch of the right coronary artery. It originates at the margin of the heart near the right atrial artery and courses in the opposite direction towards the apex. It perfuses the inferior and diaphragmatic surface of the right ventricle and occasionally the posterior apical portion of the interventricular septum.

12. AV Nodal Branch It originates at the crux and is directed inward toward the center of the heart. It perfuses the AV node and the lower portion of the interatrial septum. Posterior Descending branch It supplies the posterosuperior portion of the interventricular septum. It exits at the crux and courses in the posterior interventricular sulcus

13. Left Ventricular Branch It originates just beyond the crux. It runs centrally in the angle formed by the left posterior AV groove and the posterior interventricular sulcus. It perfuses the diaphragmatic aspect of the left ventricle.

14. Left atrial branch May course along the posterior left AV groove and perfuses the left atrium.

15. 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.

16. CLINICAL SIGNIFICANCE Right and left ventricular ischemic involvement , including prevalent right ventricular dysfunction and severe cardiac failure. Sometimes its go unnoticed due to a lack of symptoms . Young athletes , specifically those who have heart attacks while participating in strenuous sports, sometimes have an undetected coronary artery anomaly. According to the Children's Hospital of Pittsburg, this condition has been traced to four to fifteen percent of sudden cardiac deaths in children. Right-sided coronary artery occlusion can result in bradycardia, heart block, and inferior or right ventricular myocardial infarction (MI)

17. LEFT CORONARY ARTERY It is larger than the right coronary artery It arises from left posterior aortic sinus.

18. COURSE It runs forward and to the left and emerges between the pulmonary trunk and the left auricle. 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 inter-ventricular groove it terminates by anastomosing with the right coronary artery.

19. BRANCHES Left anterior descending artery First diagonal branch First septal branch Right ventricular branch Apical branches Circumflex artery Atrial circumflex branch Sinus node artery Obtuse marginal branch Posterolateral branches

20. Left Anterior Descending Artery It supplies the portions of the left and right ventricular myocardium and much of the interventricular septum. LAD appears to be a continuation of the left main coronary artery.

21. First Diagonal branch It originates close to the bifurcation of the left main coronary artery and passes diagonally over the free wall of the left ventricle. It perfuses the high lateral position of the left ventricular free wall. Several smaller diagonal branches may exit from the left side of the left anterior descending artery and run parallel to the first diagonal branch. The second diagonal branch takes its origin approximately two thirds of the way from the origin to the termination of the left anterior descending artery. This second diagonal branch perfuses the lower lateral portion of the free wall to the apex.

22. First Septal Branch The first septal branch is first is to exit the left anterior descending artery. A variable number of septal branches occur. The others are refferred to as minor septal branches. The septal branches exits at a 90 degree angle and course in the septum from the front to the back and caudally. Together, the septal branches perfuse two third of the upper portion of the septum and most of the inferior of the septum.

23. Right ventricular branches one or more right ventricular branches may exist. One runs toward the conus branch of the right coronary artery and may anastamose into the circle of Vieussens . Apical branches These are final branches. These perfuse the anterior and diaphragmatic aspects of the left ventricular free wall and apex.

24. Circumflex artery The circumflex artery supplies blood to parts of the left atrium and left ventricle. The circumflex artery exit from the left main coronary artery at a near right angle and courses posteriorly in the AV groove toward, but usually not reaching, the crux.

25. Atrial Circumflex branch It is usually small in caliber but may be as wide as the remaining portion of the circumflex. It runs along the left AV groove and perfuses the left atrial wall. Sinus node artery It originates from the initial portion from the circumflex; it runs cranially and dorsally, to the base of superior venacava in the region of the sinus node. This artery perfuses portions of the left and right atria as well as the sinus node.

26. Obtuse marginal Branches From 1 -4 obtuse marginal may be seen. They run along the ventricular wall laterally and posteriorly, toward the apex, along the obtuse margin of the heart. The marginal branch supplies the obtuse margin of the heart and the adjacent posterior wall of the left ventricle above the diaphragmatic surface.

27. Posterolateral branches The branches originates in the terminal portion of the circumflex artery course caudally and to the left on the posterior left ventricular wall, supplying the posterior and diaphragmatic wall of the left ventricle.

28. AREA OF DISTRIBUTION Left atrium Ventricles Greater part of left ventricle, except the area adjoining the posterior inter ventricular groove Small part of right ventricle adjoining the anterior interventricular groove. Anterior part of interventricular septum. Part of left branch of AV bundle

29. CLINICAL SIGNIFICANCE The left main artery and even the LAD artery are so important that critical blockages in these arteries are known as the Widow maker .

30. COLLATERAL CIRCULATION Cardiac anastomosis : 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.

31. 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.

32. 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 ".

33. VENOUS DRAINAGE Most of the venous drainage is through epicardial veins. The venous drainage of the heart is by three means: Coronary sinus Anterior cardiac vein Venae cordis minimae

34. 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

35. Small cardiac vein: It accompanies the right coronary artery and joins the right end of the coronary sinus. 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. An incompetent Semilunar valve, called the valve of Vieussens , mark the junction between the great cardiac veins and the coronary sinus.

36. ANTERIOR CARDIAC VEIN 3 to 4 small veins run on the anterior wall of the right ventricle, open directly into the right atrium.   VENAE CORDIS MINIMAE 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.

37. 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. Lymph from this vessel empties to the pretracheal lymph node and then proceeds by way of two channels to the cardiac lymph node, the right lymphatic duct, and then into the superior venacava .

38. PECULIARITIES OF CORONARY CIRCULATION Blood flow during diastole End arteries High capillary density High oxygen extraction Regulation is mainly by metabolites Anatomical anastomosis The coronary vessels are susceptible to degeneration and atherosclerosis.  

39. CORONARY BLOOD FLOW 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 coronary blood flow may be increased up to 2 liters/minute

40. FACTORS AFFECTING CORONARY BLOOD FLOW 1. PHYSICAL FACTORS Aortic blood pressure Heart Rate Cardiac Output

41. CHEMICAL FACTORS Metabolic factors: Increase cardiac metabolism reduces oxygen tension increase carbon dioxide, increase potassium, lactic acid & adenosine in the cardiac muscle leads to coronary vasodilatation causing increasing coronary blood flow. b. Drugs: Nitrites, angised , aminophylline, caffeine & Khellin are coronary vasodilator causing increased coronary blood flow.

42. 3 . NERVOUS FACTORS a. Direct effect : In Parasympathetic system, vagus stimulation has slight dilator effect. In Sympathetic, both alpha and Beta receptors stimulation causes slight direct coronary constriction. b. Indirect effect : Sympathetic stimulation increases both heart rate and myocardial contractility, as well as its rate of metabolism leading to dilatation of coronary blood vessels.

43. 4. HORMONAL FACTOR Thyroxin increases cardiac metabolism leads causing increased coronary blood flow. Vasopressin (antidiuretic hormone)causes coronary vasoconstriction and decreases coronary blood flow. 5. REFLEX CONTROL Anrep’s reflex : Increased venous return causes increased pressure in right atrium leading to reflex increase in coronary blood flow. e.g. during muscular exercise. Gastro-coronary reflex : Distention of the stomach with heavy meal causes reflex vasoconstriction of coronary blood vessels decreasing coronary blood flow.

44. CORONARY AUTOREGULATION The normal coronary vasculature bed usually autoregulates over a range of systemic arterial pressure ranging from 60 – 140 mm Hg.

45. Mechanism Myogenic response : An increase in passive stretch, caused by increased perfusion pressure, causes active smooth muscle contraction. Chemical theory : A decrease perfusion pressure leads to increase adenosine & decreased oxygen which causes vasodilatation and increase coronary blood flow. Endothelium derived relaxation factor(EDRF): Hypoxia, muscular exercise stimulate vascular endothelium to secrete EDRF, which is a potent vasodilator, that causes coronary dilatation and increase coronary blood flow. Nitrous Oxide is the principal EDRF.

46. Mechanical control: The pattern of blood flow to the left ventricle, which receives the greatest portion of coronary flow, is unique in that arterial flow is markedly decreased during systole owing to the intramyocardial pressure generated by contracting myocardial fibers. Most of the coronary flow to the LV occurs during diastole and coronary perfusion pressure is largely determined by aortic diastolc pressure. Blood flow to the right ventricle myocardium is much lower. Autonomic control: The larger epicardial coronary arteries have both α adrenergic receptors, which mediate vasoconstriction and β adrenergic receptors, which mediate vasodilation.

47. FETAL CIRCULATION

48. COMPONENTS PLACENTA The placenta functions as the respiratory center for the fetus as well as a site of filtration for plasma nutrients and wastes. UMBILICAL CORD The blood vessels responsible for foetal circulation are umbilical vein and umbilical artery. Umbilical vein carries the oxygenated blood from the placenta to the growing fetus. The blood pressure inside the umbilical vein is approximately 20 mmHg. Umbilical artery is a paired artery that supplies de-oxygenated blood from the fetus to the placenta

49. Foetal Lungs: Pulmonary vascular resistance is the resistance offered to blood through lungs. The resistance is very high in fetus because of the non-functioning of fetal lungs. The blood is diverted from pulmonary artery into aorta.

50. Shunts Involved In Foetal Circulation: Ductus Venosus : Connects the umbilical vein to the inferior vena cava. Ductus Arteriosus : Connects the pulmonary artery to the proximal descending aorta Foramen Ovale : It is an opening in the intra-atrial septum. It allows the blood to enter the left atrium from the right atrium

51. PATHWAY

52. FETAL PULMONARY CIRCULATION In fetal life, the alveoli are fluid filled and the pulmonary arteries and arterioles have relatively thick walls and a small lumen, similar to arteries in the systemic circulation. The low pulmonary blood flow in the fetus (7 – 10 percent of the total cardiac output) is the result of high pulmonary vascular resistance. Fetal pulmonary vessels are highly reactive to changes in oxygen tension or in the pH of blood perfusing them, as well as to a number of physiological and pharmacological influences.

53. CIRCULATORY CHANGES AT BIRTH The Placenta is replaced by the Lungs as the organ of respiratory exchange. The lungs and pulmonary vessels expand thereby significantly lowering the resistance to blood flow. Subsequently the pressure in the pulmonary artery and the right side of the heart is decreased. The pressure of the left side of the heart increases and the increasing pressure of blood in the left side of the heart decreases the vascular resistance of the lungs .

54. CLINICAL SIGNIFICANCE The amniotic fluid embolism is a disorder occurs during the last stages of labor when amniotic fluid enters the circulatory system of the mother via tears in the placental membrane or uterine vein rupture. Any breach of the barrier between maternal blood and amniotic fluid forces the entry of amniotic fluid into the systemic circulation and results in a physical obstruction of the pulmonary circulation.

55. JOURNAL ABSTRACT Improved Visualization of Coronary Arteries Using a New Three-Dimensional Submillimeter MR Coronary Angiography Sequence with Balanced Gradients. Fifteen healthy volunteers underwent MR coronary angiography with a new balanced turbo field-echo sequence in comparison with the standard turbo field-echo sequence. Signal-to-noise, blood-to-myocardium, blood-to-fat, and blood-to-pericardial fluid contrast ratios of the left and right coronary artery systems were measured.

56. Image quality was graded, the length and diameter of the coronary arteries were measured, and the number of visible side branches was assessed. Compared with standard turbo field-echo MR coronary angiography, optimized balanced turbo field-echo MR coronary angiography improves the visualization of the coronary arteries and their side branches within a significantly shorter imaging time.

57. 2. The fetal circulation and essential organs – a new twist to an old tale. Local autoregulatory vascular adjustments that control organ perfusion are of three principal types . The first type acts synergistically with venous and arterial redistribution to augment organ blood flow. The second type counteracts an ‘organ-steal effect’ that may occur as a result of redistribution.

58. The third type is relatively independent of redistribution, because the vascular beds supplying the organs arise distal to the ductus arteriosus and therefore are little affected by redistribution. Of the local organ sparing effects, brain sparing is the longest recognized in the human fetus, while heart, liver and adrenal sparing were described more recently.

59. ASSIGNMENT Write an assignment on “Comparison between fetal circulation an adult circulation.”

60. REFERENCES Woods LS, Froelicher SSE, Motzer US, Bridges EJ. Cardiac Nursing. 6 th edition. Baltimore: Wolters Kluwer Publication; 2010 Libby P, Bonow OR, Mann LD, Zipes PD. Heart Disease. 8 th edition. Philadelphia: Saunders publications; 2008. Garg K. BD Chaurasia’s Human Anatomy. Volume 1. Fourth edition. India: CBS Publishers; 2006. Hall EJ, Guyton CA. Medical Physiology. 10 th edition. India: Saunder’s company; 2001.