Myocardial Ischemia and Its Causes
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Questions and Answers

What characterizes STEMI on an ECG?

  • Normal ST segment
  • Inverted T waves
  • ST segment elevation (correct)
  • Presence of Q waves

    • Which type of myocardial infarction is related to athero-thrombosis?

  • Type 1 (correct)
  • Type 3
  • Type 4b
  • Type 5

    • What typically occurs within the first 10 seconds after myocardial infarction?

  • Stabilization of cardiac function
  • Increased ATP production
  • Hypoxic injury to myocardial cells (correct)
  • Formation of necrotic tissue

    • Which condition is classified under Type 4 myocardial infarction?

    <p>Myocardial infarction with percutaneous coronary intervention</p> Signup and view all the answers

    What is a common cause of myocardial infarction in atherosclerotic coronary arteries?

    <p>Thrombus formation on plaque</p> Signup and view all the answers

    What is the primary metabolic consequence of anaerobic metabolism during myocardial infarction?

    <p>Decreased ATP production</p> Signup and view all the answers

    Which characteristic is common to both transmural and non-transmural necrosis?

    <p>Necrosis involves injury to myocardial tissue</p> Signup and view all the answers

    What is the primary indicator of myocardial injury according to the Fourth Universal Definition?

    <p>Elevated troponin levels</p> Signup and view all the answers

    What does a CK-MB/total CK index ratio greater than 5 indicate?

    <p>Cardiac source of CK-MB</p> Signup and view all the answers

    When does myoglobin typically rise following myocardial injury?

    <p>4-6 hours</p> Signup and view all the answers

    What is the likelihood of a future cardiac event in a patient with elevated troponin levels but no ECG changes?

    <p>High risk of future cardiac events</p> Signup and view all the answers

    What is a significant limitation of C-Reactive Protein (CRP) as a marker?

    <p>General marker for inflammation</p> Signup and view all the answers

    How long does it take for Lactate Dehydrogenase (LDH) to return to normal levels after a myocardial infarction?

    <p>8-14 days</p> Signup and view all the answers

    What is the significance of elevated C-Reactive Protein levels greater than 3 mg/L?

    <p>High risk for heart disease</p> Signup and view all the answers

    Which LDH isoenzyme indicates myocardial injury when elevated?

    <p>LDH-1</p> Signup and view all the answers

    Which laboratory finding is not typically associated with myocardial injury?

    <p>Increased hemoglobin</p> Signup and view all the answers

    What role do neutrophils play in myocardial cell injury?

    <p>They release inflammatory mediators and reactive oxygen species.</p> Signup and view all the answers

    What causes further cardiac injury during reperfusion of hypoxic myocardial tissue?

    <p>Formation of reactive oxygen species.</p> Signup and view all the answers

    What type of necrosis is associated with myocardial infarction?

    <p>Coagulative necrosis.</p> Signup and view all the answers

    Which cardiac biomarker is considered the best indicator of acute myocardial infarction?

    <p>Troponin I and T.</p> Signup and view all the answers

    How long do elevated levels of troponin typically remain in circulation after myocardial injury?

    <p>4-10 days.</p> Signup and view all the answers

    What clinical consequence follows a myocardial infarction regarding heart function?

    <p>Reduced ventricular contractility.</p> Signup and view all the answers

    What is NOT a factor that can reduce the effectiveness of reperfusion therapy?

    <p>Increased blood flow.</p> Signup and view all the answers

    Which of the following represents a common misconception about inflammatory mediators released by neutrophils?

    <p>They are always beneficial to myocardial repair.</p> Signup and view all the answers

    What is a primary cause of myocardial ischemia?

    <p>Coronary atherosclerosis</p> Signup and view all the answers

    Which term describes the chest pain characterized by a consistent pattern of onset, duration, and intensity?

    <p>Stable angina pectoris</p> Signup and view all the answers

    Which of the following is NOT a contributing factor to myocardial ischemia?

    <p>Overhydration</p> Signup and view all the answers

    What symptom is typical of unstable angina pectoris?

    <p>Chest pain lasting 15 to 20 minutes</p> Signup and view all the answers

    What might precipitate myocardial infarction by increasing metabolic demand?

    <p>Extreme physical stress</p> Signup and view all the answers

    Which type of pain is often associated with stable angina?

    <p>Tightness or pressure</p> Signup and view all the answers

    Which factor is commonly associated with decreased oxygen supply to the myocardium?

    <p>Anemia</p> Signup and view all the answers

    What is a common clinical consequence of myocardial ischemia?

    <p>Decreased ventricular contractility</p> Signup and view all the answers

    What serious condition can accompany unstable angina?

    <p>Myocardial infarction</p> Signup and view all the answers

    Which of the following medications can potentially precipitate myocardial ischemia?

    <p>Cocaine and other illicit drugs</p> Signup and view all the answers

    What happens to myocardial cells after 20 minutes without oxygen?

    <p>They become irreversibly injured and die.</p> Signup and view all the answers

    Which of the following is a consequence of failed Na+-K+ pump function in myocardial cells?

    <p>Increased intracellular sodium leading to swelling.</p> Signup and view all the answers

    What role do reactive oxygen species (ROS) play in myocardial injury?

    <p>They cause direct damage to myocardial cells.</p> Signup and view all the answers

    Which process is initiated by the lack of adequate oxygen supply to myocardial cells?

    <p>Anaerobic metabolism resulting in lactic acid formation.</p> Signup and view all the answers

    What is one of the inflammatory mediators released by neutrophils that may cause myocardial cell injury?

    <p>Tumor Necrosis Factor (TNF).</p> Signup and view all the answers

    What primarily signifies stable angina pectoris?

    <p>Intermittent chest pain with a consistent pattern</p> Signup and view all the answers

    Which symptom is most commonly associated with unstable angina?

    <p>Crushing or burning chest pain not relieved by rest</p> Signup and view all the answers

    What is the primary clinical consequence of hypoxia in myocardial cells?

    <p>Decreased ATP production</p> Signup and view all the answers

    What is a morphologic characteristic of transmural myocardial infarction?

    <p>Necrosis extending through the entire wall of the myocardium</p> Signup and view all the answers

    Which factor can lead to a decrease in oxygen supply to the myocardium?

    <p>Coronary artery blockage</p> Signup and view all the answers

    Which of the following is the most common cause of myocardial ischemia?

    <p>Coronary atherosclerosis</p> Signup and view all the answers

    What effect does atherosclerotic plaque have on coronary arteries?

    <p>It decreases the lumen size and inhibits relaxation.</p> Signup and view all the answers

    Which of the following can cause transient ischemia associated with specific symptoms?

    <p>Vasospasm of coronary arteries</p> Signup and view all the answers

    Which factor is NOT a risk factor for coronary artery disease?

    <p>Hypoxemia</p> Signup and view all the answers

    Which condition can lead to an increase in myocardial oxygen demand?

    <p>Tachycardia</p> Signup and view all the answers

    How does anemia contribute to myocardial ischemia?

    <p>By decreasing hemoglobin levels, reducing oxygen delivery</p> Signup and view all the answers

    What is a common consequence of myocardial ischemia?

    <p>Myocardial infarction</p> Signup and view all the answers

    Which of the following statements about increased myocardial workload is true?

    <p>It can be caused by conditions like tachycardia.</p> Signup and view all the answers

    What is a consequence of oxidative stress that occurs within minutes of reperfusion injury?

    <p>Mitochondrial damage</p> Signup and view all the answers

    Which of the following best describes calcium overload during reperfusion?

    <p>It contributes to additional cell injury.</p> Signup and view all the answers

    What is the role of neutrophils during reperfusion injury?

    <p>Adhesion to damaged tissues</p> Signup and view all the answers

    Which cardiac biomarker is unique to cardiac muscle and useful for diagnosing an acute myocardial infarction?

    <p>Troponin I</p> Signup and view all the answers

    In terms of timing, when do troponin levels typically begin to rise after a myocardial infarction?

    <p>2-3 hours post-infarct</p> Signup and view all the answers

    What is a potential clinical consequence related to the size of the infarct due to reperfusion injury?

    <p>Decreased ventricular contractility</p> Signup and view all the answers

    What occurs in the inflammatory cascade as a result of reperfusion injury?

    <p>Release of proteolytic enzymes</p> Signup and view all the answers

    What factor is NOT typically associated with the consequences of reperfusion injury?

    <p>Enhanced oxygenation</p> Signup and view all the answers

    Which type of myocardial infarction is characterized by supply-demand mismatch not related to acute athero-thrombosis?

    <p>Type 2</p> Signup and view all the answers

    What is a significant factor that can contribute to the development of myocardial infarction due to reduced oxygen content in the blood?

    <p>Hypoxemia</p> Signup and view all the answers

    Which circumstance does NOT contribute to the pathophysiology of myocardial infarction?

    <p>Coronary artery dilation</p> Signup and view all the answers

    What is a characteristic of Type 4 myocardial infarction?

    <p>MI associated with percutaneous coronary intervention</p> Signup and view all the answers

    Which of the following is NOT considered a precipitating condition for myocardial infarction?

    <p>Chronic heart failure</p> Signup and view all the answers

    What does the presence of elevated troponins indicate in the context of myocardial injury?

    <p>Myocardial injury</p> Signup and view all the answers

    What mechanism primarily leads to thrombus formation during a myocardial infarction?

    <p>Rough surface of atherosclerotic plaque</p> Signup and view all the answers

    Which option is a common cause of myocardial infarction aside from coronary artery disease?

    <p>Coronary artery trauma</p> Signup and view all the answers

    What does an increase in the ratio of CK-MB to CK greater than 5 suggest?

    <p>Acute myocardial infarction is suspected.</p> Signup and view all the answers

    How long after an acute myocardial infarction do CK-MB levels typically peak?

    <p>24 hours after onset.</p> Signup and view all the answers

    Which cardiac marker is most sensitive for detecting muscle injury but lacks specificity?

    <p>Myoglobin</p> Signup and view all the answers

    What does a C-reactive protein (CRP) level greater than 3.0 mg/L indicate?

    <p>High risk of cardiovascular disease.</p> Signup and view all the answers

    Which LDH isoenzyme elevation is primarily associated with cardiac muscle injury?

    <p>LDH-1</p> Signup and view all the answers

    What is the approximate sensitivity of Lactate Dehydrogenase (LDH) in diagnosing acute myocardial infarction?

    <p>Close to 98%.</p> Signup and view all the answers

    Why is myoglobin considered a less reliable marker for myocardial injury compared to other biomarkers?

    <p>Other tissues also contain myoglobin.</p> Signup and view all the answers

    What characteristic of a patient with CRP levels between 1.0 to 2.9 mg/L is indicated?

    <p>Intermediate cardiovascular risk.</p> Signup and view all the answers

    Study Notes

    Myocardial Ischemia

    • Partial blockage of one or more branches of the left or right coronary artery causes myocardial ischemia.
    • Causes of Myocardial Ischemia:
      • Coronary atherosclerosis (coronary artery disease): Repetitious endothelial injury leads to inflammatory response, plaque buildup, and reduced blood flow to coronary arteries.
      • Vasospasms (Prinzmetal or variant angina): Spasms in the coronary arteries.
      • Decreased oxygen supply: Conditions like hypoxemia (low oxygen in the blood) or anemia (low red blood cells).
      • Increased myocardial demand: Increased heart rate or cardiac output (CO).

    Pathophysiology

    • Coronary atherosclerosis is a key contributor to myocardial ischemia.
    • Oxygen demand exceeds oxygen supply in the coronary arteries.

    Clinical Consequences

    • Decreased ventricular contractility: Reduced heart pumping ability.

    • Conduction disturbances: Irregular heart rhythms.

    • Ischemic pain: Characteristic pain type.

      • Stable angina pectoris: Intermittent chest pain relieved by rest.
      • Unstable angina pectoris: Chest pain lasting 15-20 minutes, not relieved by rest, position change, or nitroglycerin. This is often described as crushing, pressure, tightness or burning and radiates to arms, shoulders, and jaw. Sign of an impending myocardial infarction.

    Myocardial Infarction (MI)

    • Causes:
      • Coronary atherosclerosis: Primary, severe narrowing of the coronary arteries.
      • Coronary artery emboli: Blood clots.
      • Aortic dissection: Tear in the aorta, impacting coronary arteries.
      • Coronary vasospasm: Spasm of coronary arteries.
      • Coronary artery trauma: Injury to a coronary artery.
      • Illicit drug use (e.g., cocaine): Impacts the heart.
      • Medications: Some prescriptions and over-the-counter medications.
      • Precipitating conditions: Factors increasing oxygen demand (e.g., extreme physical exertion, hypertension, aortic stenosis) or reducing oxygen supply (e.g., hypoxemia, anemia).
    • Severe reduction of coronary artery blood flow: Leading to cell death.

    Types of MI

    • Morphological Classification:
      • Transmural: Necrosis throughout the entire myocardium wall.
      • Non-transmural: Necrosis limited to the endocardium or subendocardium or a segment of the myocardium.
    • STEMI vs. NSTEMI: Based on ECG findings (ST segment elevation).
    • Fourth Universal Definition of Myocardial Infarction (2018): Categorizes MI by cause and clinical presentation.

    Pathophysiology of MI

    • Infarction of atherosclerotic coronary artery: Thrombus formation, plaque rupture, plaque obstruction, and plaque embolus.

    Hypoxic Injury

    • Within 10 seconds of infarction, hypoxic injury occurs in myocardial cells.
    • Consequences of anaerobic metabolism include decreased ATP production and lactic acid formation.
    • Irreversible injury and cell death begin after 20 minutes of complete occlusion..
    • Inflammation: Neutrophils release inflammatory mediators and reactive oxygen species (ROS) and lysosomal enzymes, contributing to myocardial injury.

    Reperfusion Injury

    • If the hypoxic myocardial tissue gets re-oxygenated, reperfusion injury can occur, causing further cardiac injury.
    • Oxidation stress, and formation of reactive oxygen species due to reintroduction of oxygen to hypoxic tissue.

    Repair and resolution

    • Inflammation leads to scar tissue deposition at the site of infarct.
    • This scarring process replaces and repairs damaged tissue..

    Clinical Consequences:

    • Functional impairment is determined by location and severity of infarction.
    • Clinical Consequences : Reduced ventricular (and atrial) contractility, disturbances in cardiac conduction, and ischemic pain.

    Laboratory Evaluation - Cardiac Biomarkers

    • Troponin I & T: Cardiac proteins released into circulation after myocardial cell injury. Elevated levels are diagnostic for MI.
    • CK-MB (Creatine Kinase - muscle and brain type): Enzyme primarily in myocardial muscle cells, elevated after cell injury and a sign of cardiac damage.
    • Myoglobin: Intracellular protein similar to hemoglobin released after myocardial cell injury. High sensitivity but not very specific for MI.
    • C-Reactive Protein (CRP): Plasma protein released by the liver during inflammation. Elevated levels are associated with a higher risk of cardiovascular disease, including MI.
    • Lactate Dehydrogenase (LDH): Intracellular enzyme; elevated LDH-1 levels indicate myocardial cell damage.

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    Description

    This quiz covers the essential aspects of myocardial ischemia, including its causes, pathophysiology, and clinical consequences. Explore how factors like coronary atherosclerosis and oxygen demand play a crucial role in this condition. Test your knowledge on this vital cardiovascular topic.

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