atherosclerosis and MI

1. ATHEROSCLEROSIS AND MYOCARDIAL
INFARCTION
Dr Ravi Shrivastava

2. DEFINITION
Atherosclerosis
 It is characterised by fibrofatty plaques or atheromas.
 It is an thickening and hardening of large and medium-sized
muscular arteries, primarily due to involvement of tunica intima
and
 The term atherosclerosis is derived from
 athero-(meaning porridge)
 referring to the soft lipid-rich material in the centre of
atheroma, and
 sclerosis (scarring)
 referring to connective tissue in the plaques.

3. ATHEROSCLEROSIS (ATH)
 Intimal lesions called atheromas (fibrofatty plaques)
that weaken the muscular media, protrude into
vessel lumen
 Atheromatous plaques-
 a raised lesion with a soft, Yelllow, grumous core of lipid
(cholesterol and cholesterol esters ) covered by a fibrous
cap.

4. MAJOR COMPONENTS OF PLAQUE
 Cells (SMC, macrophages and other WBC)
 ECM (collagen, elastin, and PGs)
 Lipid = Cholesterol (Intra/extracellular)
 (Often calcification)

6. RESPONSE TO INJURY

7. ENDOTHELIAL DYSFUNCTION

8. INITIATION OF FATTY STREAK

9. FATTY STREAK

10. FIBRO-FATTY ATHEROMA

12. CONSEQUENCES OF PLAQUE FORMATION
Generalized
 Narrowing/Occlusion
 Rupture
 Emboli
 Leading to specific problems:
 Myocardial and cerebral infarcts
 Aortic aneurysms
 Peripheral vascular disease

13. GROSS APPEARANCE
 Affected vessels will show raised
yellowish white lesions.
 Cut section shows firm fibrous
cap(sclerosis) and a central core
composed of yellow white soft material

14. MICROSCOPIC FEATURES
 Lesion is composed of afibrous cap and a
necrotic core.
 The superficial part of the fibrous cap is
composed of smooth muscle cells,dense
connective tissue and components of
extracellular matrix.
 The cellular area under the fibrous cap is
composed of macrophages,lymphocytes and
lipid laiden foam cells

16. IHD and MI

17. Ischaemic heart disease (IHD)
 Defined as acute or chronic form of cardiac
disability arising from imbalance between the
myocardial supply and demand for oxygenated
blood.
 Since narrowing or obstruction of the coronary
arterial system is the most common cause of
myocardial anoxia.
 The alternate term ‘coronary artery disease
(CAD)’ is used synonymously with IHD.

18. ETIOPATHOGENESIS
 IHD is invariably caused by disease affecting
the coronary arteries,
 the most prevalent being atherosclerosis
accounting for more than 90% cases,
 while other causes are responsible for less than
10% cases of IHD.
 Therefore, it is convenient to consider the
etiology of IHD under three broad headings:
i. Coronary atherosclerosis
ii. Superadded changes in coronary atherosclerosis
iii. Non-atherosclerotic causes

19. III. NON-ATHEROSCLEROTIC
CAUSES
 Several other coronary lesions may cause
IHD in less than 10% of cases.
1. Vasospasm
2. Stenosis of coronary ostia
3. Arteritis Various types
4. Embolism
5. Thrombotic diseases
6. Trauma
7. Aneurysms
8. Compression

20. ACUTE MYOCARDIAL INFARCTION
 Acute myocardial infarction (MI) is the most important and
feared consequence of coronary artery disease.
 Many patients may die within the first few hours of the
onset, while remainder suffer from effects of impaired
cardiac function.
 A significant factor that may prevent or diminish the
myocardial damage is the development of collateral
circulation through anastomotic channels over a period of
time.
 A regular and well-planned exercise programme
encourages good collateral circulation and improved

21. 5. Transmural versus subendocardial infarcts
 There are some differences in the pathogenesis of
the transmural infarcts involving the full thickness of
ventricular wall
 and the subendocardial (laminar) infarcts affecting
the inner subendocardial one-third to half. (1/3
to1/2)

24. MORPHOLOGIC FEATURES
 The gross and microscopic changes in the
myocardial infarction vary according to the
age of the infarct and are therefore
described sequentially in the Table.
 From 0-6 hours to 4th week changes

27. CHRONIC ISCHAEMIC HEART DISEASE
 Chronic ischaemic heart disease, ischaemic
cardiomyopathy or myocardial fibrosis, are the
terms used for focal or diffuse fibrosis in the
myocardium
 characteristically found in elderly patients of
progressive IHD.
 Such small areas of fibrous scarring are
commonly found in the heart of patients who
have history of episodes of angina and
attacks of MI some years back.

28. ETIOPATHOGENESIS
 In majority of cases, coronary
atherosclerosis causes progressive
ischaemic myocardial damage and
replacement by myocardial fibrosis.
 A small percentage of cases may result
from other causes such as emboli, coronary
arteritis and myocarditis.

30. THANK YOU