Ischemic Heart Disease Flashcards Preview

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Flashcards in Ischemic Heart Disease Deck (34):

Define Ischemic Heart Disease

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


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

Ischemic Heart Disease (IHD)


What most commonly causes IHD?

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


Causes of decreased blood flow?

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


What coronary arteries are most commonly affected by fixed obstruction?

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


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

Narrowing of >70% causes symptomatic ischemia with exercise

>90% stenosis causes ischemia at rest


What are risks associated with acute plaque change?

Ruptures/fissures/ulcers that can expose underlying thrombogenic substances

Hemorrhage into atheroma

A image thumb

What are some intrinsic factors that influence acute plaque change?

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


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

Adrenergic stimulation

Upon awakening



What is coronary thrombosis?

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

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

A image thumb

What can stimulate vasoconstriction?

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


Four basic syndromes of IHD?

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


What is Angina Pectoris?

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


What are the three patterns or Angina Pectoris presentation?

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


What is often the event that induces Unstable angina pectoris

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


What is a Myocardial Infarction?

Death of cardiac muscle due to ischemia


What are risk factors associated with MI?

What are the most common causes of MI?


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


What are the characteristics of a Transmural MI?

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


What are the characteristics of a Subendocardial MI?

  • 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


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?

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


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

The area farthest away from the obstruction

A image thumb

Frequency of involvement of coronary arteries in MI?

LAD: most often (40-50%)

RCA: next most often (30-40%)

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


Myocardial infarction: Gross morphology

<12 hours:

12-24 hours:

1-14 days:

>2 weeks:

<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


Histology of MI

4-12 hours:

12 hours - 7 days:

7 -14 days:

>2 weeks:

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


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

Thrombolysis, balloon angioplasty, or bypass grafts

20 minutes


Possible causes of reperfusion injury

  • 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


How do you diagnose MI?

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


What are some potential complications of MI?

Contractile dysfunction

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


Myocardial rupture (shunts)



What types of mycocardial rupture are associated with MI?

Free wall - hemopericardium, tamponade, aneurysm

Ventricular septum - Lt to Rt shunt

Papillary muscle due to mitral regurgitation


What are some later complications of MI?

Ventricular aneurysm

Progressive heart failure

Papillary muscle dysfunction secondary to scarring


Long term prognosis of acute MI depends on...

Quality of left ventricular function and the extent of vascular obstruction


What makes chronic IHD different than acute IHD?

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


What is the morphology associated with Chronic IHD?

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


Sudden Cardiac Death is most often due to...

IHD and its first manifestation (80-90%)