L-48 Ischemic Heart Disease And Myocardial Infarction

Question 1

What is ischemic heart disease

Answer 1

Broad term encompassing several closely related syndromes caused by Myocardial ischemia

Question 2

Most frequent cause of IHD

Answer 2

Obstruction in a main coronary artery

Atherosclerosis

Question 3

Zone most vulnerable to ischemia

Answer 3

Subendocardium

Question 4

Causes of ischemic heart disease

Answer 4

Impaired O2 supply due to:
▪️Coronary narrowing
Atherosclerotic lesion
Spasm
▪️impaired coronary filling(in diastole) affected by:
 Dec Diastolic time as in tachycardia 
 Dec filling pressure as in hypotension
▪️impaired O2 carrying capacity(in anaemia) 

Increased myocardial demand:
inc pumping which inv cardiac work
Cardiac work inc heart rate
Work load
Bp

Question 5

What is angina pectoris

Answer 5

Chest pain due to ischemia of heart muscle caused by obstruction or spasm of coronary arteries

Question 6

Character and site of angina pectoris

Answer 6

Character: constricting and tight oppressive crushing
Site:starts in center behind sternum or on left side on front chest and spread out to shoulder arm and left side of jaw

Question 7

Describe stable angina

Answer 7

Develops on exertion 
Resolves at rest
Lasts about 5 mins
Insidious onset 
Stimulation of sympathetic and vagal afferent nerves

Question 8

Describe unstable angina

Answer 8

Occurs at rest or during minimal exertion
Severe lasts longer than 10 mins
Either of:
New onset
Crescendo pattern
Thrombosis in a vulnerable plaque without complete obstruction

Question 9

Describe spastic angina

Answer 9

Prinzmetal angina
Occurs at rest
Cyclic 
vasospasm due to contraction of vascular SM
Symptoms are unrelated to exertion
More in young women

Question 10

What is MI

Answer 10

Follows complete interruption of blood flow to an area of myocardium

Question 11

Causes of MI

Answer 11

▪️Rupture of an atherosclerotic plaque+ thrombosis and vasospam
▪️Completely occluding lumen of critical major epicardial blood vessel
▪️Infarction occurs downstream from occluded blood vessel

Question 12

Outcome of complete coronary occulsion

Answer 12

Depends on the severity and duration of Flow deprivation
Within 60 seconds:
Severe ischemia leading to ATP depletion and loss of contractile function
Complete deprivation of blood flow for 20 to 30 minutes leading to irreversible myocardial injury

Question 13

What does Distribution of necrosis depend on

Answer 13

Collateral perfusion
Location of occlusion within vessel
Vessel involved
Duration of ischemia

Question 14

Pattern of infarct in LAD

Answer 14

50% of cases
Infarcts in anterior wall of left ventricle
ECG changes in anterior chest leads (V1-V3)
Occlusion of this artery may cause sudden death

Question 15

Pattern of infarct: right coronary artery

Answer 15

30% of cases
In inferior wall and posterior septum
ECG changes in leads II, III and aVF

Question 16

Pattern of infarcts:circumflex artery

Answer 16

20% of cases
In lateral wall
ECG changes in leads I, aVL and lateral chest leads (V4-V6)

Question 17

What chamber do nearly all transmural MIs affect

Answer 17

Left ventricle

If in right ventricle then posterior inferior left ventricle is affected

Question 18

Describe subendocardial MIs

Answer 18

Limited to inner 30% to 50% of ventrivle
Due to lysis of a thrombotic occlusion before full thickness infarction
Result in NSTEMI

Question 19

Describe transmural MIs

Answer 19

Involves full thickness of ventricular wall
Due to atherosclerosis and acute plaque change with thrombosis
STEMI

Question 20

Morphology of heart in less than 12 hours

Answer 20

Usually inapparent

Question 21

Morphology in 12-24 hrs

Answer 21

Dead myocytes become hyperesinophyllic with loss of nuclei
(Coagulative necrosis)
Grossly:pale

Question 22

Morphology in 24-72 hrs

Answer 22

Neutrophils infiltrate necrotic tissue

Grossly: lesions become more defined,yellow and softened

Question 23

Morphology in 3 to 7 days

Answer 23

Dead myocytes are digested by macrophages

Question 24

7-10 days morphology

Answer 24

Granulation tissue replaced necrotic tissue

Question 25

More than 2 weeks morphology

Answer 25

Granulation tissue is replaced by fibrotic tissue

Question 26

Morphology 1 to 2 months

Answer 26

Grossly: gray white fibrous scar progressively fills in defect

Question 27

Morphology more than 2 months

Answer 27

Scarring is complete but can remodel with time

Question 28

Clinical picture of MI

Answer 28

▪️Severe crushing chest pain which may have sudden onset or may build up slowly
▪️Nausea ,vomiting, sweating ,pallor restlessness, collapse
▪️On examination: hypotension and bradycardia

Question 29

Test used for early confirmation of MI

Answer 29

CK-MB

Question 30

Gold standard for MI

Answer 30

Tropnonin T and I

Question 31

Complications of MI

Answer 31

▪️Contractile dysfunction:
Systemic hypotension
Pulmonary edema
▪️Cariogenic shock:
Severe pump failure with loss of left ventricular mass
▪️Arrhythmias
▪️Fibrinous pericarditis(dressler syndrome):2 to 3 days after an MI

Question 32

What does rupture of free wall cause

Answer 32

Pericardial tamponade

Question 33

What does septal rupture cause

Answer 33

A left to right shunt with right sided volume overload

Question 34

What does papillary muscle infarction cause

Answer 34

Mitral regurgitation

Question 35

What does poor contractility lead to

Answer 35

Stasis
Turbulence
Endocardial damage
Creation of a thrombotic surface
Mural thrombosis adj to a non contractile area
Can cause peripheral embolization

Question 36

Why does ventricular aneurysm occur

Answer 36

Due to healing of a large transmural infarct

Prone to mural thrombosis

Question 37

What does long term prognosis depend on

Answer 37

Size in location of injury
Residual left ventricular function
Reperfusion