Myocardial Ischemia Flashcards
What is the significance of a ruptured plaque in a coronary artery?
It can lead to ischemia of myocardial tissue or myocardial infarction.
Myocardial infarction refers to the death of heart muscle tissue due to lack of blood supply.
What does ‘myocardial ischemia’ mean?
It is a condition where perfusion of the myocardium is compromised due to an imbalance between oxygen supply and demand.
What regulates oxygen supply to the myocardium?
Oxygen supply is regulated by:
* Patency or size of the coronary vessel
* Ability of the ventricular wall to compress
* Duration of diastole
What factors determine myocardial oxygen demand?
Demand is dependent on:
* Myocardial contractility
* Heart rate
* Amount of ventricular wall stress
Fill in the blank: An abrupt reduction in blood flow to the myocardium can be caused by __________.
[thrombus, coronary vasospasm, platelet aggregation]
What is the difference between preload and afterload?
Preload is the volume in the ventricle before contraction, while afterload is the resistance the ventricle must overcome to contract.
What is ‘supply ischemia’?
It refers to a situation where there is not enough oxygenated blood supply to meet myocardial demands.
What can cause ischemia even at rest?
Ischemia at rest can be caused by:
* Blockage within the coronary artery
* Coronary artery spasm (Prinzmetal Angina)
What are the three possible outcomes of ischemia?
The outcomes are:
* Injury
* Apoptosis (cell removal)
* Necrosis (cell death)
How quickly do myocardial cells start to become ischemic after blood flow interruption?
Myocardial cells become ischemic within 10 seconds of blood flow interruption.
What type of metabolism occurs when oxygen is insufficient?
Anaerobic metabolism occurs, producing only 2 molecules of ATP and creating lactic and pyruvic acid.
What is the consequence of inadequate ATP in cells?
Inadequate ATP leads to:
* Inefficient sodium-potassium pump
* Uncoordinated electrical impulses
* Possible dysrhythmias
True or False: Anaerobic metabolism is more efficient than aerobic metabolism.
False
What are the hemodynamic effects of ischemia?
The effects include:
* Reduced contractility
* Abnormal wall motion
* Changes in wall compliance
* Decreased cardiac output and stroke volume
What happens to the heart’s compliance when myocardial cells die?
The ventricular walls become less compliant and lose elasticity.
What triggers the sympathetic nervous system response during ischemia?
A drop in cardiac output (CO) triggers the sympathetic response.
Fill in the blank: Cardiac output (CO) is calculated as __________.
[Heart Rate (HR) x Stroke Volume (SV)]
What are common symptoms of a myocardial infarction?
Symptoms may include:
* Shortness of breath
* Tightness in the chest
* Intense prolonged chest pain
* Nausea
* Fainting
* Intense pain in the left shoulder, arm, jaw, and back
