Ischemic Heart Disease

Question 1

Define Ischemic Heart Disease

Answer 1

Imbalance between supply and demand for oxygen and nutrients and removal of metabolites

Question 2

What is the leading cause of death and disability in the USA?

Answer 2

Ischemic Heart Disease (IHD)

Question 3

What most commonly causes IHD?

Answer 3

≥ 90%: reduced coronary blood flow due to atherosclerotic narrowing

Question 4

Causes of decreased blood flow?

Answer 4

• Fixed atherosclerotic narrowing
• Acute plaque change
• Thrombosis overlying ruptured plaque
• Vasospasm

Question 5

What coronary arteries are most commonly affected by fixed obstruction?

Answer 5

First several centimeters of the LAD, left circumflex, and entire length or right coronary artery

Question 6

How does the degree or anatomic narrowing/occlusion lead to different types of ischemia?

Answer 6

Narrowing of >70% causes symptomatic ischemia with exercise

>90% stenosis causes ischemia at rest

Question 7

What are risks associated with acute plaque change?

Answer 7

Ruptures/fissures/ulcers that can expose underlying thrombogenic substances

Hemorrhage into atheroma

Question 8

What are some intrinsic factors that influence acute plaque change?

Answer 8

Large areas of foam cells

Thin fibrous cap

Most dangerous leasions are the moderately stenoic, lipid rich atheromas (soft core)

Abundant inflammation

Few smooth muscle cells

Question 9

What are some extrinsic factors that contribute to acute plaque change?

Answer 9

Adrenergic stimulation

Upon awakening

Emotional

Question 10

What is coronary thrombosis?

What are the problems associated with total occlusion vs. incomplete occlusion?

Answer 10

Coronary thrombosis - partial or total occlusion superimposed on a partially stenotic plaque

Total occlusion can cause acute transmural MI or sudden death

Incomplete occlusion (mural thrombus) can lead to unstable angina, acute subendocardial infarction, or sudden death

Question 11

What can stimulate vasoconstriction?

Answer 11

• Adrenergic agonists in circulation
• Locally released platelet contents
• Endothelial dysfunction leading to impaired secretion of endothelial relaxing factors
• Mediators released from mast cells

Question 12

Four basic syndromes of IHD?

Answer 12

• Angina pectoris
• Myocardial infarction
• Chronic ischemic heart disease
• Sudden cardiac death

Question 13

What is Angina Pectoris?

Answer 13

Paroxysmal and recurrent attacks of chest pain caused by transient myocardial ischemia (15 seconds to 15 minutes) - no necrosis

Question 14

What are the three patterns or Angina Pectoris presentation?

Answer 14

Stable - produced by physical activity or emotional excitement - attributed to chronic stenosis coronary aortic sinus

Prinzmetal - due to coronary artery spasm, at rest

Unstable - occurs with progressively increasing frequency and progressively less effort - often at rest and of prolonged duration

Question 15

What is often the event that induces Unstable angina pectoris

Answer 15

Induced by disruption of plaque with superimposed partial thrombosis (often a prodrome of acute MI)

Question 16

What is a Myocardial Infarction?

Answer 16

Death of cardiac muscle due to ischemia

Question 17

What are risk factors associated with MI?

What are the most common causes of MI?

Answer 17

M>F

• Risk factors: increasing age and predisposition to atherosclerosis
• Pathogenisis
  
  • 90% - acute plaque change - thrombosis and occlusion of coronary artery
  • 10% - vasospasm, emboli or unexplained

Question 18

What are the characteristics of a Transmural MI?

Answer 18

• Full thickness of ventricular wall
• Confined to distribution of one vessel
• Fixed coronary obstruction with superimposed acute plaque change and complete obstructive thrombosis

Question 19

What are the characteristics of a Subendocardial MI?

Answer 19

• Necrosis limited to inner 1/3
• May extend laterally beyond perfusion of one vessel
• Fixed coronary obstruction with acute plaque change but with non-occlusive thrombus or lysis of thrombus or hypotension

Question 20

What is the myocardial response to…

60 seconds of ischemia?

20-40 minutes of ischemia?

Early thrombolytic therapy (3-4 hours) after ischemia?

Loss of blood supply?

Answer 20

60 seconds of ischemia: loss of contractility

20-40 minutes of ischemia: irreversible damage

Early thrombolytic therapy (3-4 hours) after ischemia: Reperfusion and limited size of infarct

Loss of blood supply? reversible damage in early stages

* Arrhythmias can lead to sudden death

Question 21

Which area of the blood vessel (in relation to the obstruction) is first to necrose?

Answer 21

The area farthest away from the obstruction

Question 22

Frequency of involvement of coronary arteries in MI?

Answer 22

LAD: most often (40-50%)

RCA: next most often (30-40%)

LCA (left circumflex): Least common (15-20%)

Question 23

Myocardial infarction: Gross morphology

<12 hours:

12-24 hours:

1-14 days:

>2 weeks:

Answer 23

<12 hours: pale areas 2-3 hours post occurance

12-24 hours: Dark red-blue mottling (stagnant blood)

1-14 days: early: sharply defined yellow-tan area; late: hyperemic peripheral zone (increased blood flow)

>2 weeks: Gray-white scar begins to form

Question 24

Histology of MI

4-12 hours:

12 hours - 7 days:

7 -14 days:

>2 weeks:

Answer 24

4-12 hours: wavy fibers

12 hours - 7 days: coagulative necrosis (neutrophils, lack of nuclei, macrophages at border)

7 -14 days: Granulation tissue well established

>2 weeks: Progressively more collagen deposition - eventually dense fibrous scar

Question 25

Reperfusion injury associated with acute MI usually occurs after what treatments? Prevention of necrosis occurs with reperfusion within __ minutes

Answer 25

Thrombolysis, balloon angioplasty, or bypass grafts

20 minutes

Question 26

Possible causes of reperfusion injury

Answer 26

• Oxygen free radicals released from leukocytes
• Microvascular injury causes hemorrhage and endothelial swelling that occludes capillaries
• Platelet and complement activation

*Microscopically: Necrosis with contraction bands due to influx of calcium

Question 27

How do you diagnose MI?

Answer 27

Chest pain

Rapid weak pulse, dyspnea due to pulmonary edema

ECG patterns

Lab evaluation of cardiac enzymes, C-reactive protein

Approximately 10-15% without symptoms

Question 28

What are some potential complications of MI?

Answer 28

Contractile dysfunction

Cardiogenic shock (pump failure) with damage to 40% or more

Arrhythmia

Myocardial rupture (shunts)

Pericarditis

Question 29

What types of mycocardial rupture are associated with MI?

Answer 29

Free wall - hemopericardium, tamponade, aneurysm

Ventricular septum - Lt to Rt shunt

Papillary muscle due to mitral regurgitation

Question 30

What are some later complications of MI?

Answer 30

Ventricular aneurysm

Progressive heart failure

Papillary muscle dysfunction secondary to scarring

Question 31

Long term prognosis of acute MI depends on…

Answer 31

Quality of left ventricular function and the extent of vascular obstruction

Question 32

What makes chronic IHD different than acute IHD?

Answer 32

Usually in elderly patients with progressive heart failure due to ischemic myocardial damage - myocardial dysfunction

Question 33

What is the morphology associated with Chronic IHD?

Answer 33

Heart is enlarged and heavy with left ventricular hypertrophy and dilation, coronary atherosclerosis, scars, subendocardial myocyte vacuolization

Question 34

Sudden Cardiac Death is most often due to…

Answer 34

IHD and its first manifestation (80-90%)