CORONARY CIRCULATION

CORONARY CIRCULATION

1. DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
DEPT. OF PHYSIOLOGY
CORONARY
CIRCULATION

2. OBJECTIVES.
Coronary blood vessels
Coronary blood flow: characteristic
features.
Measurement of coronary blood flow.
Regulation of coronary blood flow
Factors affecting coronary blood flow.
Coronary artery disease.
Friday, November 25, 2016

3. CORONARY BLOOD VESSELS
Coronary arteries –
arise from Root of the
Aorta
Right coronary artery
– Supplies Rt ventricle,
Rt atrium, the Posterior
part of left ventricle,
posterior part of
Interventricular
septum & SA node
Friday, November 25, 2016

4. CORONARY BLOOD VESSELS
Left coronary artery –
supplies left ventricle, left
atrium, Ant part of
Interventricular septum &
left branch of bundle of
His.
Predominant supply. –
50% by Right coronary
artery, 20% Left coronary
artery, 30% Both.
Friday, November 25, 2016

5. CORONARY BLOOD VESSELS
Major coronary arteries. –
Rt coronary artery travel in
the Epicardium of heart
( superficial vessels) &
subdivides into
Penetrating branches.
End arteries- appears to be
End arteries but shows
some Anastomosis.
Friday, November 25, 2016

6. ANASTOMOSIS
Types.
Cardiac – Between branches of
two coronary artery & between
branches of 2 coronary arteries
& Deep Venous System.
Extra cardiac –Between
coronary arteries & Vasa vasora
of aorta, Vasa vasora of
pulmonary arteries, intra
thoracic arteries , bronchial
arteries & Phrenic arteries.
Friday, November 25, 2016

7. CORONARY VEINS
Coronary sinus -- Wide
vein which drain blood
from Myocardium to
Right atrium.
Tributaries are – Great
cardiac veins, Small
cardiac vein, Posterior
vein of left ventricle &
Oblique vein of left
ventricle.
Friday, November 25, 2016

8. CORONARY VEINS
Anterior cardiac vein
– Drains from right
ventricle to right
atrium.
Thebesian vein –
coronary luminal
vessels forms Deep
Venous System.
Friday, November 25, 2016

9. CORONARY BLOOD FLOW:
CHARACTERISTIC FEATURES
Normal coronary
blood flow & oxygen
demand.
A continuous flow of
blood for supply of
oxygen & nutrients
Friday, November 25, 2016

10. CORONARY BLOOD FLOW:
CHARACTERISTIC FEATURES
Normal coronary
blood flow – at rest
250 ml (70ml/100
gm/min)
5% of cardiac output.
During exercise
increases to 3-6 fold.
Blood flow to left is
twice Rt ventricle.
Friday, November 25, 2016

11. CORONARY BLOOD FLOW:
CHARACTERISTIC FEATURES
Oxygen consumption
by the myocardium.
Very high –
8ml/min/100 gm
tissue
70-80% of oxygen
extracted from each
unit as compared to
25% in other tissue.
Friday, November 25, 2016

12. PHASIC CHANGES IN
CORONARY BLOOD FLOW
Blood flow is
determined by
Balance between
Pressure head Aortic
pressure &
Resistance by
myocardium.
Friday, November 25, 2016

13. PHASIC CHANGES IN
CORONARY BLOOD FLOW
Blood flow to left
ventricles
During systole – During
contraction myocardium
produces Throttling
effect on coronary arteries
, during Isometric
contraction phase blood
flow to heart practically
Ceases.
Friday, November 25, 2016

14. PHASIC CHANGES IN
CORONARY BLOOD FLOW
During Diastole –
Myocardium relax &
blood flow increases.
Flow Increases
maximally in
Isovolumic relaxation
phase
Friday, November 25, 2016

15. EFFECT OF HEART RATE ON
CORONARY BLOOD SUPPLY.
During Tachycardia
Duration of diastole
decreases so coronary
blood flow reduces but
due to Local
Metabolite
Regulation of blood
flow is not seriously
affected.
Friday, November 25, 2016

16. BLOOD FLOW TO RIGHT
VENTRICLE & ATRIA.
Through coronary
capillaries of right
ventricle shows
similar changes but
to Less extent.
Blood flow occurs
during Both systole &
diastole.
Friday, November 25, 2016

17. BLOOD FLOW THROUGH
CORONARY SINUS.
Inflow Rises from Iso
volumic contraction
phase reaches peak
during Protodiastole
phase & then
gradually Falls.
Friday, November 25, 2016

18. CLINICAL IMPORTANCE OF
PHASIC CORONARY BLOOD FLOW.
Sub endocardial
region of left
ventricle
In Aortic stenosis
In Congestive Heart
failure.
Friday, November 25, 2016

19. SUBENDOCARDIAL REGION OF
LEFT VENTRICLE
Most Vulnerable to
Ischemia so most
common site of
Myocardial Infarction.
As this part receives
almost No blood
supply during systole.
Friday, November 25, 2016

20. COMPENSATORY MECHANISM
Capillary Density – Much Higher (1100
capillaries /mm
2
) than Epicardial region (750
capillaries/mm
2
)
Minimum diffusion distance – 20% Shorter (16.5
µm) as compared to Epicardial (20.5 µm)
Myoglobin content – Higher than Epicardial
region.
Friday, November 25, 2016

21. IN AORTIC STENOSIS
Pressure in Left
ventricle increases --so
severe compression of
coronary vessels during
systole & Increase
Chance Of MI.
Friday, November 25, 2016

22. IN CONGESTIVE HEART
FAILURE.
Increase in Venous
Pressure --
Decreases aortic
diastolic pressure -- so
effective coronary
perfusion falls &
Coronary Blood Flow
Decreases.
Friday, November 25, 2016

23. .
MEASUREMENT OF CORONARY
BLOOD FLOW.
Nitrous oxide method (Kety Method)
Radionuclides utilization techniques.
Coronary angiographic technique.
Electromagnetic flow meter technique.
Friday, November 25, 2016

24. NITROUS OXIDE METHOD
(KETY METHOD)
Principle – based on
Fick’s Principle.
Procedure – Inhale
mixture of NO & air for 10
min.
During inhalation serial
sample of arterial &
coronary sinus venous
blood taken at fixed
intervals
Coronary blood flow
= N
2
O taken up/min
-------------------------------
(A-V)
Friday, November 25, 2016

25. RADIONUCLIDES UTILIZATION
TECHNIQUES.
Radioactive Tracers
pumped into cardiac
muscle cells by Na-K
ATPase enz & equilibrate
with intracellular K pool.
Distribution of
radioactive tracers is
Directly proportional to
Myocardial blood flow.
Friday, November 25, 2016

26. PROCEDURE
Radionuclide Thallium
-201 injected IV.
After 10 min amount of
Thallium taken by
myocardial cells
measured by Gamma-
Scintillation camera
Areas of ischemia
detected by low uptake.
Friday, November 25, 2016

27. CORONARY ANGIOGRAPHIC
TECHNIQUE.
Combined with
133
Xe
washout using
crystal syntillation
camera tells about
coronary blood flow.
Friday, November 25, 2016

28. ELECTROMAGNETIC FLOW
METER TECHNIQUE.
It tells about Phasic
flow & flow per min.
Blood flow through left
ventricle determined
with the help of
Electromagnetic Flow
Meter implanted
around main left
coronary artery.
Friday, November 25, 2016

29. REGULATION OF CORONARY
BLOOD FLOW
LOCAL CONTROL MECHANISM
Auto regulation
Role of local metabolite
Role of endothelial cells.
NERVOUS CONTROL MECHANISM
Direct nervous control
Indirect nervous control
Neurohumoral control factors.
Friday, November 25, 2016

30. LOCAL CONTROL MECHANISM
AUTO REGULATION
Ability of organ or tissue to
adjust its vascular resistance
& maintain relatively constant
blood flow over a wide range
of blood pressure.
But Fails below 70 mm
Hg blood pressure.
Friday, November 25, 2016

31. ROLE OF LOCAL METABOLITE
At rest 50-70% oxygen
released to
myocardium from
Haemoglobin.
Almost direct & linear
relationship observed
between coronary
blood flow & O2
consumption.
Friday, November 25, 2016

32. ROLE OF LOCAL METABOLITE
Role of Adenosine
(Berne Hypothesis) –
increased myocardial
metabolism leads to
degradation of
Adenine nucleotide
to adenosine.
Friday, November 25, 2016

33. ROLE OF LOCAL METABOLITE
This crosses Myocardial cell
membrane , ECF, reaches
Precapillary Sphincters of
coronary system producing
strong Vasodilator
response.
Role of other metabolite –
hydrogen ions,
Bradykinins, CO2, PG are
other vasodilator
substances.
Friday, November 25, 2016

34. ROLE OF ENDOTHELIAL CELLS.
Endothelium releases
vasodilator Autacoids – EDRF,
Prostacyclin, Endothelium
Derived Hyperpolarizing Factors
(EDHF)
Also releases Vasoconstrictors
Autacoids – Endothelin-1 ,
Angiotensin II, Endothelium
Derived Contracting Factors
(EDCF)
Friday, November 25, 2016

35. NERVOUS CONTROL
MECHANISM
Direct nervous
control
Indirect nervous
control
Neurohumoral
control factors.
Friday, November 25, 2016

36. DIRECT NERVOUS CONTROL
Through Sympathetic & Parasympathetic nerve
supply.
Sympathetic – Innervate Coronary vessels
Transmitters – E & NE
NE – act on α receptors - Vasoconstriction
E – act on β receptors – Vasodilation.
Net result is – Vasoconstriction.
Parasympathetic – Through Vagus very little
effect – Vasodilation.
Friday, November 25, 2016

37. INDIRECT NERVOUS CONTROL
THROUGH ACTION ON HEART.
Sympathetic stimulation – Increases heart rate &
increase force of contraction of heart – increases
conversion of ATP to ADP – Coronary Vasodilation
– Overrides direct effect of sympathetic
Friday, November 25, 2016

38. INDIRECT NERVOUS CONTROL
THROUGH ACTION ON HEART.
Parasympathetic stimulation. Decreases
coronary blood flow.
Friday, November 25, 2016

39. NEUROHUMORAL CONTROL
FACTORS.
ATP (Purine) – Released with NE causes
Vasoconstriction through P1 & Vasodilatation
through P2 receptors.
NEUROPEPTIDE Y (NPY) – Released with NE
during sympathetic stimulation causes severe
Vasoconstriction.
Friday, November 25, 2016

40. NEUROHUMORAL CONTROL
FACTORS.
CALCITONIN GENE RELATED PEPTIDE (CGRP) –
with substance P releases EDRF & Produces
maximal Dilation of Epicardial coronary arteries.
Friday, November 25, 2016

41. FACTORS AFFECTING
CORONARY BLOOD FLOW.
Mean aortic pressure.
Muscular exercise.
Emotional excitement.
Hypotension.
Hormones.
Heart rate
Effect of ions
Metabolic factors.
Temperature.
Friday, November 25, 2016

42. MEAN AORTIC PRESSURE.
Force for driving
blood into coronary
arteries.
Directly
proportional.
Friday, November 25, 2016

43. MUSCULAR EXERCISE.
At rest – 70ml/100
gm/min
During exercise –
increases 4 times due
to sympathetic
stimulation by
Increased heart
activity
Increase cardiac output
Increase MAP
Friday, November 25, 2016

44. EMOTIONAL EXCITEMENT.
Increase coronary
blood flow due to
increase Sympathetic
discharge
Friday, November 25, 2016

45. HYPOTENSION.
Hypotension – reflex increase in NE discharge –
coronary vasodilation – Increase CBF
Friday, November 25, 2016

46. HORMONES.
Thyroid Hormone – by increasing metabolism
Adrenaline & Non adrenaline – by acting on B receptors
Acetylcholine – Increases same as parasympathetic
stimulation
Pitressin – Decrease by decreasing coronary resistance
Nicotine – Increases by liberating NE.
Friday, November 25, 2016

47. HEART RATE
As heart rate increases
– stroke volume
decreases- phasic CBF
& O2 consumption
decreases
Inverse relationship.
Friday, November 25, 2016

48. EFFECT OF IONS
K ion in low conc – dilate coronary vessels –
Increases CBF
In Higher conc- constrict coronary vessels-
Decreases -CBF
Friday, November 25, 2016

49. METABOLIC FACTORS.
Friday, November 25, 2016

50. TEMPERATURE.
Hyperthermia – increase metabolism – increase
adenosine – Increase CBF
Direct relationship
Friday, November 25, 2016

51. CORONARY ARTERY DISEASE.
Also called Ischemic Heart
disease –
Causes –
Atherosclerosis of coronary
arteries.
Thrombus formation.
Embolus
Spasm of coronary vessels
Atheromatous coronary vessels
stenosis.
Friday, November 25, 2016

52. Thank
You