Clinical EKGs Flashcards
If you have a PR interval greater than 0.2 s (> 5 boxes), what do you have?
First degree AV heart block.
If you have a QRS interval greater than 0.12 s (> 3 boxes), what do you have?
A bundle branch block of some sort.
What again are the abnormal QTc intervals for men and women?
Men= > 0.45 s Women= > 0.47 s
What is the definition of a sinus rhythm?
upright deflection of the P wave in Lead II
What is an easy way to think about what lead sees what?
The area of the heart that is closest to the + (ex. Lead I will look at the left lateral side of the heart because it’s + is the left shoulder).
How can upward or downward deflection of lead I help you to determine axis?
If lead I is positive (upward deflection) then the axis will be pointing toward the left. If lead I is negative (downward deflection) then the axis will be pointing in the right direction.
How does ischemia affect polarization?
it leads to constant depolarization because the ions cannot be pumped back out for repolarization.
What do cardiologists call an ST elevation?
A current of injury, because it is not an infarction until you have Q waves. This is an injury current flowing between an injured (DEpolarized) tissue and a normally polarized tissue. So tissue that is ischemic can’t repolarize itself :(
How are ST segment changes measured?
relative to the T-P segment, during which the heart is repolarized completely. So if the ST segment is above the T-P segment, you have ST elevation.
What is the J point?
the junction between the S point and T point. This is the point after depolarization has completed and the resting potential is 0.
What does ischemia cause?
low blood flow leads to an increase in CO2 and a lack of nutrients (fatty acids and glucose). Repolarization requires energy, therefore the process is impaired.
How is acute myocardial infarction (AMI) diagnosed?
only when Q waves are present.
What are the common areas for AMI?
LAD, LCX, or their Subepicardial, subendocardial, or collateral arteries.
What area infarcts first when a coronary artery becomes blocked by a thrombus?
the endocardium because it is farthest from the blood supply. After 24hrs the tissue becomes necrotic.
Will a subendocardial injury cause an ST elevation or ST depression?
ST depression of V5 because the positive electrode of V5 on the anterior chest wall detects the movement of positive charge away from the electrode (due to the current flowing from the more positive subepicardium to the less positive subendocardium) and record it as a downward deflection on the ECG paper.
Can you localize the coronary artery involved with ST depression?
NO
Will a transmural (entire wall) injury cause an ST elevation or ST depression?
ST elevation. If you see this in V1-5, you know it is LAD coronary artery current of injury (ischemia), and not infarct yet because there is no Q wave.
What are the criteria for ST elevation in ischemia?
new ST elevation at the J point in 2 contiguous leads with >0.1 mV or mm in all leads excpet V2-3 (>0.2 mV or mm).
What are the criteria for ST depression in ischemia?
new horizontal downsloping ST depression >0.05 mV or mm in 2 contiguous leads or T wave inversion in two contiguous leads