Ischemic Heart Disease Overview

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Questions and Answers

Which of the following is NOT a cause of coronary artery occlusion leading to myocardial infarction?

  • Severe fixed coronary atherosclerosis
  • Embolization from mural thrombi
  • Severe vasculitis affecting small intramyocardial arterioles (correct)
  • Disruption of preexisting atherosclerotic plaque

In what percentage of myocardial infarctions does transmural infarction occur in the absence of occlusive atherosclerotic vascular disease?

  • 20%
  • 10% (correct)
  • 5%
  • 1%

What is the most common cause of death in older adult women?

  • Pneumonia
  • Stroke
  • Ischemic Heart Disease (correct)
  • Cancer

Which of the following factors is NOT involved in platelet aggregation and vasospasm during an MI?

<p>Nitric Oxide (A)</p> Signup and view all the answers

Which of the following is LEAST likely to be a contributing factor to plaque disruption leading to MI?

<p>Increased levels of High-Density Lipoprotein (HDL) (B)</p> Signup and view all the answers

Why is ischemic heart disease (IHD) considered a leading cause of mortality worldwide?

<p>It frequently results in myocardial infarction, a potentially fatal event. (B)</p> Signup and view all the answers

In most cases, IHD is a direct consequence of which underlying factor?

<p>Obstructive atherosclerotic vascular disease. (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of the pathogenesis of a typical MI?

<p>The initial plaque disruption is caused by the accumulation of calcium deposits (A)</p> Signup and view all the answers

What does the term "stable angina" signify in the context of IHD?

<p>Chest pain that occurs predictably at certain levels of exertion. (A)</p> Signup and view all the answers

Which statement BEST describes the risk of MI in men and women?

<p>Men are at a higher risk of MI throughout their lives, except during their reproductive years. (A)</p> Signup and view all the answers

Which of the following conditions can also cause cardiac ischemia, apart from obstructive atherosclerosis?

<p>Diminished blood oxygenation due to pneumonia or CHF. (E)</p> Signup and view all the answers

Which of the following is a potential cause of an MI in the absence of detectable atherosclerosis?

<p>Small intramyocardial arteriole disorders (A)</p> Signup and view all the answers

What is the primary energy source for cardiac myocytes?

<p>Mitochondrial oxidative phosphorylation. (B)</p> Signup and view all the answers

What specific type of cardiac arrhythmia is commonly associated with sudden cardiac death (SCD) in the context of IHD?

<p>Ventricular fibrillation. (C)</p> Signup and view all the answers

What is the difference between angina pectoris and myocardial infarction?

<p>Angina pectoris is a milder form of chest pain, while myocardial infarction is a more severe form. (D)</p> Signup and view all the answers

Which of these choices correctly describes the relationship between coronary artery disease (CAD) and ischemic heart disease (IHD)?

<p>CAD is a specific type of IHD, while IHD encompasses a broader range of conditions. (D)</p> Signup and view all the answers

Which of the following statements about fixed obstructions in coronary arteries is TRUE?

<p>Fixed obstructions that occlude more than 70% of a vessel lumen generally cause symptoms in the setting of increased demand. (B)</p> Signup and view all the answers

Which of the following factors has NOT significantly contributed to the decline in IHD mortality since 1963?

<p>Advances in treatment for acute coronary syndrome (ACS) like bypass surgery and angioplasty have had no impact on mortality. (D)</p> Signup and view all the answers

Which of the following is NOT a factor contributing to the pathogenesis of IHD?

<p>Increased blood pressure leading to hypertension. (B)</p> Signup and view all the answers

What is the most common location for transmural myocardial infarcts (MIs)?

<p>Left ventricle and/or interventricular septum (C)</p> Signup and view all the answers

The term 'critical stenosis' refers to:

<p>A fixed obstruction that occludes more than 70% of a coronary vessel lumen. (D)</p> Signup and view all the answers

What is the approximate percentage of MIs that involve the right ventricle?

<p>15% to 30% (C)</p> Signup and view all the answers

Which of the following is NOT a characteristic sequence of morphologic changes observed in myocardial infarcts?

<p>Regeneration of damaged myocytes (C)</p> Signup and view all the answers

Which of the following is a TRUE statement about the epidemiology of IHD?

<p>Approximately 800,000 Americans experience an MI each year, with nearly half of those affected dying from the condition. (B)</p> Signup and view all the answers

What is the timeframe for visible gross changes in myocardial infarcts?

<p>More than 3 hours (A)</p> Signup and view all the answers

What is the primary factor contributing to the inadequate coronary perfusion relative to myocardial demand in the majority of cases of IHD?

<p>A combination of both preexisting atherosclerotic occlusion and acute plaque change. (D)</p> Signup and view all the answers

What is the typical color change seen in myocardial infarcts stained with triphenyl tetrazolium chloride?

<p>Yellow-tan (D)</p> Signup and view all the answers

Which of the following statements accurately describes the relationship between coronary artery stenosis and symptoms?

<p>Stenosis greater than 70% often causes symptoms, particularly with increased demand. (D)</p> Signup and view all the answers

What is the microscopic feature that may be present at the edges of an infarct, reflecting stretching and buckling of noncontractile dead fibers?

<p>Wavy fibers (B)</p> Signup and view all the answers

Which of the following is NOT a type of coronary artery that can be affected by atherosclerotic narrowing?

<p>Internal carotid artery (D)</p> Signup and view all the answers

What happens to necrotic myocardium in the acute inflammatory phase of an MI?

<p>It is removed by macrophages (B)</p> Signup and view all the answers

Which of the following conditions can contribute to myocardial infarcts?

<p>Cocaine use (A)</p> Signup and view all the answers

What is the primary mechanism by which leukocyte aggregation contributes to the 'no-reflow' phenomenon during reperfusion after myocardial ischemia?

<p>Leukocyte aggregation obstructs the microvasculature, impairing blood flow. (D)</p> Signup and view all the answers

Which of the following contributes to the electrical instability and arrhythmias observed in ischemic regions of the heart?

<p>Abnormal ion channel activity, creating electrical disturbances. (C)</p> Signup and view all the answers

What is the primary reason why the subendocardial zone is particularly vulnerable to ischemic injury?

<p>The subendocardial zone is the final area to receive blood from the epicardial vessels and is under relatively high pressures. (A)</p> Signup and view all the answers

Which of the following factors does NOT influence the location, size, and morphologic features of an acute myocardial infarct?

<p>Genetic predisposition to coronary artery disease. (C)</p> Signup and view all the answers

What is the typical consequence of acute occlusion of the proximal left anterior descending (LAD) artery?

<p>Infarction of the anterior wall of the left ventricle, the anterior two-thirds of the ventricular septum, and most of the heart apex. (C)</p> Signup and view all the answers

What is the approximate time frame in which an infarct typically reaches its full extent?

<p>3-6 hours. (C)</p> Signup and view all the answers

Acute occlusion of the proximal left circumflex (LCX) artery most commonly causes infarction of which heart region?

<p>Lateral wall of the left ventricle. (C)</p> Signup and view all the answers

Which statement is TRUE regarding the effect of collateral supply on myocardial infarction?

<p>Collateral supply can reduce the size of the infarct by providing alternative blood flow. (B)</p> Signup and view all the answers

What is the primary outcome of early thrombolysis or angioplasty in a patient experiencing acute MI?

<p>Prevention of further necrosis and preservation of the myocardium (D)</p> Signup and view all the answers

A patient presents with acute MI symptoms, and angiography reveals coronary thrombosis. Which of the following is NOT a likely consequence of this condition if left untreated?

<p>Increased production of ATP in the affected region (B)</p> Signup and view all the answers

Based on the provided information, which of these timescales MOST accurately reflects the critical period for intervention in acute MI to potentially prevent irreversible damage?

<p>Within the first 20-40 minutes (C)</p> Signup and view all the answers

A patient presents with acute MI, and angiography performed 24 hours after symptom onset shows no evidence of thrombosis. Which of the following is the MOST likely explanation for this finding?

<p>The thrombus was successfully dissolved by spontaneously occurring lysis (B)</p> Signup and view all the answers

Which of these is MOST likely to contribute to the development of arrhythmias in a patient experiencing myocardial ischemia?

<p>Reduced electrical conductivity through the ischemic zone (C)</p> Signup and view all the answers

What is the primary mechanism by which myocardial ischemia leads to a drop in ATP levels within cardiac myocytes?

<p>Decreased oxygen supply due to reduced blood flow to the affected area (A)</p> Signup and view all the answers

Even with successful reperfusion of ischemic myocardium, a patient might experience a period of "stunned myocardium." What is the main reason for this temporary dysfunction?

<p>Persistent abnormalities in cellular biochemistry despite the return of blood flow (C)</p> Signup and view all the answers

What is the most likely explanation for the finding that coronary thrombosis is observed in only 60% of patients with acute MI when angiography is performed 12-24 hours after symptom onset?

<p>The initial thrombus has partially or completely resolved spontaneously through lysis or relaxation of spasm (A)</p> Signup and view all the answers

Flashcards

Ischemic Heart Disease (IHD)

A syndrome caused by an imbalance between cardiac blood supply and myocardial oxygen demands, leading to various clinical manifestations.

Coronary Artery Disease (CAD)

A condition where atherosclerosis reduces blood flow in coronary arteries, commonly associated with IHD.

Angina Pectoris

Chest pain caused by ischemia that doesn't cause myocyte death, can be stable or unstable.

Stable Angina

Chest pain that occurs predictably at certain levels of exertion, alleviated by rest.

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Unstable Angina

Chest pain that occurs with progressively less exertion or at rest, indicating worsening IHD.

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Myocardial Infarction (MI)

Death of heart muscle cells due to prolonged ischemia, commonly known as a heart attack.

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Chronic IHD with CHF

Progressive heart failure resulting from repeated ischemic insults or a prior MI.

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Sudden Cardiac Death (SCD)

Abrupt death due to lethal ventricular fibrillation from myocardial ischemia, often with CAD present.

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Acute Myocardial Infarction (MI)

A condition where blood supply to the heart is suddenly blocked, causing tissue damage.

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Thrombotic occlusion

Blockage of a blood vessel due to a blood clot (thrombus).

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Angiography timing

A imaging study showing high thrombus presence if done within 4 hours of MI onset.

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Reperfusion therapy

Restoration of blood flow post-ischemia to preserve heart tissue.

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Ischemic consequences

Effects of reduced blood flow, like loss of ATP and contractility in heart muscle.

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Coagulative necrosis

Irreversible cell death in heart tissue due to prolonged ischemia.

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Stunned myocardium

Heart muscle dysfunction that can persist even after blood flow is restored.

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Electrical instability

Increased irritability in heart muscle regions during ischemia, leading to arrhythmias.

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Risk Factors for MI

Men are at greater risk of MI; the gap with women narrows with age.

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Atherosclerosis

A condition where plaque builds up in the arteries, leading to potential MIs.

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Acute Thrombosis

A sudden formation of a blood clot in a coronary artery leading to MI.

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Coronary Artery Vasospasm

Temporary constriction of a coronary artery, which can cause MI.

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Ischemic Necrosis

Tissue death due to lack of blood flow to the heart muscle.

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Sequence of Events in MI

Steps including plaque disruption, platelet activation, and thrombus formation leading to MI.

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Role of Platelets in MI

Platelets aggregate and release chemicals, causing further blockage during an MI.

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Vasculitis

Inflammation of blood vessels that can lead to complications like MI.

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Myocardial necrosis

Cell death in heart muscle due to lack of blood flow, usually leads to scar formation.

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Acute inflammation after MI

Occurs 1 to 3 days post-MI, characterized by immune response to necrotic tissue.

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Granulation tissue in MI

High blood flow tissue that forms around dead myocardium, seen by 10 to 14 days.

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Infarct visual detection

Infarcts older than 3 hours can be visualized with stains indicating cell damage.

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Right ventricle infarcts

Occur in only 1% to 3% of IHD cases, usually associated with other infarcts.

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Wavy fibers

Stretched and buckled heart muscle fibers at the edge of an infarct visible after damage.

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Acute Coronary Syndrome

A critical condition encompassing unstable angina, myocardial infarction (MI), and sudden cardiac death (SCD).

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Critical Stenosis

Narrowing of a coronary artery by 70% or more, leading to significant cardiac symptoms.

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Coronary Care Units

Specialized hospital departments for managing acute cardiac conditions and emergencies.

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No-Reflow Phenomenon

Leukocyte aggregation that occludes microvasculature after reperfusion, impairing blood flow.

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Phospholipase A2 Activation

Enzyme activation contributing to reversible cardiac failure during myocardial ischemia.

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Myocardial Ischemia Effects

Causes ventricular irritability and arrhythmias due to damaged heart regions.

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Fatal Mechanical Failure

Massive myocardial damage causing heart failure or death, often from arrhythmias.

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Subendocardial Injury

Initial irreversible injury in the heart's inner layer during ischemia.

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Transmural Infarct

Infarct involving the whole wall thickness, typically from epicardial vessel occlusion.

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Proximal LAD Occlusion

Most common cause of MI, affecting anterior left ventricle and septum.

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Collateral Circulation

Alternative blood supply that can lessen myocardial damage during occlusion.

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Study Notes

Ischemic Heart Disease (IHD)

  • IHD is a broad term encompassing closely related syndromes caused by an imbalance between cardiac blood supply and myocardial oxygen/nutritional demands.
  • IHD is the leading cause of mortality in high-income countries, accounting for 7.5 million deaths annually.
  • In over 90% of cases, IHD is a consequence of reduced coronary blood flow due to obstructive atherosclerotic vascular disease.
  • IHD is often synonymous with coronary artery disease (CAD).
  • IHD syndromes result from coronary atherosclerosis progressing over decades.
  • IHD may also result from increased demand (e.g., heart rate or hypertension), decreased blood volume (e.g., hypotension or shock), diminished blood oxygenation (e.g., pneumonia or CHF), or decreased blood oxygen-carrying capacity (e.g., anemia or carbon monoxide poisoning).

Cardiac Myocytes & Energy

  • Cardiac myocytes primarily generate energy via mitochondrial oxidative phosphorylation.
  • Their survival relies heavily on a continuous flow of oxygenated blood through coronary arteries.
  • IHD manifestations stem from inadequate oxygen delivery to the heart.

Cardiac Syndromes

  • Angina pectoris (chest pain): Ischemic pain that does not cause myocyte death; can be stable (predictable with exertion), vasospastic (vessel spasm), or unstable (occurring with less exertion or at rest).
  • Myocardial infarction (MI): Myocyte death due to severe or prolonged ischemia, often caused by acute thrombosis. A common cause of death.
  • Sudden cardiac death (SCD): A catastrophic consequence of myocardial ischemia resulting in lethal ventricular fibrillation.

Epidemiology

  • Approximately 800,000 Americans experience an MI annually, with about half of those affected succumbing to the illness.
  • IHD mortality in the United States has decreased by 50% since its 1963 peak, primarily due to interventions that diminished risk factors (e.g., smoking cessation, management of hypertension).
  • Advances in diagnostics and treatment contribute to this trend.

Pathogenesis

  • IHD stems from inadequate coronary perfusion relative to myocardial demand.
  • This is most often caused by preexisting atherosclerotic occlusion, acute plaque change, or vasospasm.

Chronic Vascular Occlusion

  • Critical stenosis (70%+ vessel blockage) may be asymptomatic but can cause symptoms like angina in response to increased demands.
  • A fixed stenosis of 90% or more can cause symptoms even at rest.

Acute Plaque Change

  • Acute plaque change, often resulting in rupture, fissuring, ulceration, or erosion of a plaque, is a major trigger for IHD (i.e., acute coronary syndrome).
  • This exposes thrombogenic constituents leading to rapid thrombosis and potentially acute coronary events like MI, unstable angina, and SCD.
  • Hemorrhage into plaque cores leads to expansion and worsening of luminal occlusion.

Microsopic Infarcts

  • Small-vessel occlusions might cause microscopic infarcts without significant ECG changes.
  • Causes may include vasculitis, emboli, or vasospasm.

Morphology

  • Recent myocardial infarcts (less than 12 hours old) may not be easy to distinguish macroscopically.
  • Transmural infarcts (affecting more than 50% of ventricular wall) commonly involve the left ventricle and the interventricular septum.
  • Infarcts progress through distinct morphologic changes (coagulative necrosis to inflammation to fibrosis) over time, eventually forming a scar.

Myocardial Response to Ischemia

  • Loss of blood supply leads to immediate loss of contractility as ATP levels decrease, leading to lactic acid buildup.
  • Irreversible damage occurs within 20-40 mins of ischemia.
  • Reperfusion may offer benefits but also has potential harm.

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