6 infarction

for Undergraduate medical students (MBBS)

1. INFARCTIONINFARCTION
Dr.CSBR.Prasad, M.D.

2. Common clinical examples of Common clinical examples of
infarction:infarction:
•Myocardial infarction
•Cerebral infarction
•Pulmonary infarction
•Gangrene of limbs

7. Atrial fibrillation Atrial fibrillation
with mural thrombiwith mural thrombi

10. INFARCTIONINFARCTION
Def: An infarct is an area of
ischemic necrosis caused by
occlusion of either the arterial supply
or the venous drainage in a
particular tissue

11. Basis of infarction:Basis of infarction:
Vascular compromise
•Obstruction to arterial supply
•Impeded venous drainage

12. Common causes:Common causes:
Arterial occlusion:Arterial occlusion:
•99% result from arterial occlusion (thrombotic or embolic events)
•Other causes:
local vasospasm
expansion of an atheroma (hemorrhage within a plaque)
extrinsic compression of a vessel (e.g., by tumor)
twisting of the vessels (e.g., in testicular torsion or bowel
volvulus)
compression of the blood supply by edema or by entrapment in a
hernia sac
traumatic rupture of the blood supply
Venous occlusion:Venous occlusion: (organs with single veinous out flow)
•Thrombosis

13. Classification Classification
Based on the colour & presence or absence of
infection

14. MorphologyMorphology
Red (hemorrhagic) infarctsRed (hemorrhagic) infarcts occur

(1)with venous occlusions (such as in ovarian torsion);
(2)in loose tissues (such as lung), which allow blood to
collect in the infarcted zone;
(3)in tissues with dual circulations (e.g., lung and small
intestine), permitting flow of blood from the
unobstructed vessel into the necrotic zone (obviously
such perfusion is not sufficient to rescue the ischemic
tissues);
(4)in tissues that were previously congested because of
sluggish venous outflow; and
(5)when flow is re-established to a site of previous arterial
occlusion and necrosis (e.g., following fragmentation of
an occlusive embolus or angioplasty of a thrombotic
lesion)

15. MorphologyMorphology
White (anemic) infarctsWhite (anemic) infarcts occur
with arterial occlusions in solid organs with
end-arterial circulation (such as heart,
spleen, and kidney), where the solidity of
the tissue limits the amount of
hemorrhage that can seep into the area of
ischemic necrosis from adjoining capillary
beds

16. Most of the infarcts are wedge Most of the infarcts are wedge
shapedshaped
•with the occluded vessel at the apex and
the periphery of the organ forming the
base
•when the base is a serosal surface, there
is often an overlying fibrinous exudate.
•The lateral margins may be irregular,
reflecting the pattern of vascular supply
from adjacent vessels.

17. Margins become hyperemicMargins become hyperemic
•Initially:Initially: all infarcts are poorly defined and
slightly hemorrhagic
•Later:Later: margins tend to become better
defined by a narrow rim of hyperemia
attributable to inflammation at the edge of
the lesion.

18. Examples of infarcts:
A, Hemorrhagic, roughly wedge-shaped pulmonary infarct.
B, Sharply demarcated white infarct in the spleen.

19. Pulmonary infarctionPulmonary infarction

22. Splenic infarctionSplenic infarction

23. Histology of infarctionHistology of infarction
Changes depends on time
Ischemic coagulative necrosis
Inflammation
Liquifactive necrosis
Abscess formation
Scar tissue

24. Remote kidney infarct,
now replaced by a large
fibrotic cortical scar.

25. Factors That Influence Factors That Influence
Development of an InfarctDevelopment of an Infarct
The major determinants include:
(1)the nature of the vascular supply;
(2)the rate of development of the occlusion;
(3)the vulnerability of a given tissue to
hypoxia; and
(4)the blood oxygen content.

26. Factors That Influence Factors That Influence
Development of an InfarctDevelopment of an Infarct
The major determinants:
(1)Nature of the vascular supply (double or single blood
supply)
The availability of an alternative blood supply is the most important
factor in determining whether occlusion of a vessel will cause
damage.
Lungs, for example, have a dual pulmonary and bronchial artery blood
supply; thus, obstruction of a small pulmonary arteriole does not
cause infarction in an otherwise healthy individual with an intact
bronchial circulation.
Similarly, the liver, with its dual hepatic artery and portal vein
circulation, and
the hand and forearm, with their dual radial and ulnar arterial supply,
are all relatively insensitive to infarction.
In contrast, renal and splenic circulations are end-arterial, and
obstruction of such vessels generally causes infarction.

27. Factors That Influence Factors That Influence
Development of an InfarctDevelopment of an Infarct
The major determinants:
(2)Rate of development of occlusion.
Slowly developing occlusions are less likely to cause
infarction because they provide time for the
development of alternative perfusion pathways. For
example, small interarteriolar anastomoses —normally
with minimal functional flow—interconnect the three
major coronary arteries in the heart. If one of the
coronaries is only slowly occluded (i.e., by an
encroaching atherosclerotic plaque), flow within this
collateral circulation may increase sufficiently to
prevent infarction, even though the major coronary
artery is eventually occluded.

28. Factors That Influence Factors That Influence
Development of an InfarctDevelopment of an Infarct
The major determinants:
(3) Vulnerability to hypoxia.
The susceptibility of a tissue to hypoxia influences
the likelihood of infarction.
Neurons undergo irreversible damage when
deprived of their blood supply for only 3 to 4
minutes.
Myocardial cells, although hardier than neurons,
are also quite sensitive and die after only 20 to
30 minutes of ischemia.
In contrast, fibroblasts within myocardium remain
viable even after many hours of ischemia

29. Factors That Influence Factors That Influence
Development of an InfarctDevelopment of an Infarct
The major determinants:
(4) Oxygen content of blood.
The partial pressure of oxygen in blood also
determines the outcome of vascular occlusion.
Partial flow obstruction of a small vessel in an
anemic or cyanotic patient might lead to tissue
infarction, whereas it would be without effect
under conditions of normal oxygen tension.
In this way, congestive heart failure, with
compromised flow and ventilation, could cause
infarction in the setting of an otherwise
inconsequential blockage.

30. Factors That Influence Factors That Influence
Development of an InfarctDevelopment of an Infarct
The major determinants:
(4) Oxygen content of blood.
What is the critical value for HGB ?

31. Compartment syndrome

32. Compartment syndrome

33. Inguinal hernia

34. Inguinal hernia

35. Strangulated hernia

36. Umbilical hernia

37. Umbilical Hernia

38. Umbilical hernia

39. Volvulus

40. Volvulus

41. Volvulus involving
caecum

42. Torsion - ovary

43. Torsion - ovary

44. Torsion - ovary

45. Torsion – Fallopian tube

46. Torsion testis – torsion of hydatid

47. Torsion - testis

50. Gangrene of Gangrene of
the fingersthe fingers

54. E N DE N D