Rapid Interpretation of EKGs - Chapter 9 highlights Flashcards
Infarction
Will a necrotic, infarcted area of the left ventricle conduct electricity?
nope. it is electrically dead
What is the myocardial infarction triad?
Must ischemia, injury, and necrosis all be present at once to diagnose myocardial infarction?
nope
What does the word “ischemia” mean?
reduced blood supply
(represented by an inverted T wave)
Where are ischemic areas located?
at the periphery of the infarct
Marked T wave inversion in leads V2 and V3 is the hallmark sign of what syndrome?
Wellens syndrome (this alerts us to stenosis of the anterior descending coronary)
What does injury indicate?
the “acuteness” of an infarct
Can ST elevation, alone, indicate an infarction?
yes. yes it can.
If the ST segment is elevated without associated Q waves, this represents what?
non-Q wave infarction
What hereditary condition can cause sudden cardiac death in individuals WITHOUT heart disease.
Brugada Syndrome - characterized by RBBB with ST elevation in leads V1, V2, and V3
(this syndrome is responsible for nearly 1/2 of the sudden deaths in healthy young individuals without structural heart disease)
What 3 things may cause ST segment depression?
(subendocardial infarcts do not extend through the full thickness of the left ventricular wall)
Classic myocardial infarction is said to be _________; that is, the full thickness of the left ventricular wall is damaged in the infarcted area.
transmural
The diagnosis of myocardial infarction is usually based on the presence of significant types of which waves?
Q waves
Are tiny Q waves significant?
nah.
(septal depolarization (initiated at mid-septum by the left bundle branch) is left-to-right, and this initial rightward ventricular activation may produce tiny, insignificant Q waves)
What is the definition of an insignificant Q wave?
less than 1mm (0.04 seconds) in duration
What is the definition of a significant Q wave?
at least one small square wide (0.04 seconds) or 1/3 of the entire QRS amplitude
If the infarcted area of the heart cannot depolarize and has no vectors, which part of the heart will the electrode see?
the opposite wall
Which leads indicate an anterior infarct?
Which leads indicate a lateral infarct?
Which leads indicate an inferior infarct?
What would you see in a posterior infarct?
a large Q wave that is represented as a large R wave since it is on the opposite side of the heart. see the pic.
If you see ST elevation with an anterior infarct, what would happen to the ST segment with a posterior infarct?
ST depression (because it’s the opposite)
What do you always check for in leads V1 and V2?
A lateral infarction is caused by an occlusion of what coronary artery?
Circumflex
An anterior infarction is due to an occlusion of what coronary artery?
Anterior Descending branch of the Left Coronary Artery
True posterior infarctions are generally caused by an occlusion of what coronary artery?
Right Coronary Artery
An inferior infarction is caused by an occlusion of what coronary artery?
either the Right or Left Coronary Artery, depending on which is “dominant”
What is a hemiblock?
they are blocks of either the Anterior or the Posterior Division of the Left Bundle Branch
What is meant by a “bifascicular” block?
when two fascicles are blocked
