circulation of adult and fetus

2. CORONARY CIRCULATION
AND
FETAL CIRCULATION
Princy Francis M
IInd Yr MSc (N)
JMCON

3. 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.

4. 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.

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.

7. Right CoronaryArtery
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.

8. BRANCHES
1. Conus branch
2. Sinus node artery
3. Right ventricular branch
4. Right atrial branch
5. Acute marginal branch
6. AV Nodal branch
7. Posterior descending branch
8. Left ventricular branch
9. Left atrial branch

9. 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.

10. 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.

11. 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.

12. 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.

13. 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

14. 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.

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

16. 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.

17. 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)

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

19. 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.

20. BRANCHES
1. Left anterior descending artery
a) First diagonal branch
b) First septal branch
c) Right ventricular branch
d) Apical branches
2. Circumflex artery
a) Atrial circumflex branch
b) Sinus node artery
c) Obtuse marginal branch
d) Posterolateral branches

21. 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.

22. 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.

23. 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.

24.  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.

25. 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.

26.  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.

27. 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.

28. 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.

29. 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

30. 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.

31. 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.

32. 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.

33. 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".

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

35. 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

36. • 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.

37. 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.

38. 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.

39. 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.

40. 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

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

42. CHEMICAL FACTORS
a. 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.

43. 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.

44. 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.

45. CORONARY
AUTOREGULATI
ON
The normal coronary vasculature
bed usually autoregulates over a
range of systemic arterial pressure
ranging from 60 – 140 mm Hg.

46. 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.

47. 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.

48. FETAL CIRCULATION

49. 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

50. 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.

51. 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

53. PATHWAY

55. 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.

56. 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.

58. 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.

59. 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.

60.  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.

61. 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.

62.  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.

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

64. REFERENCES
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Philadelphia: Saunders publications; 2008.
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Saunder’s company; 2001.