Flashcards in Diagnostic Features of ECG Deck (18):
Associate each of the waves on ECG with what's going on in the heart:
P wave = atrial depolarization
QRS complex = ventricular depolarization
T wave = ventricular repolarization
If your QRS takes up 3 heavy lines, what is your HR?
HR = 300 / # heavy lines between 2 QRS's
HR = 1500 / # mm between 2 QRS's
EKG leads measure:
1. Two different points on body (bipolar)
2. One point on the body and a virtual reference point with 0 potential in the center of heart (unipolar)
Depolarization moving ___ a positive electrode produces a ___ deflection
Toward a positive electrode produces a positive deflection
V1 & V2 are what type of leads?
R-sided chest leads, measuring R ventricle
V5 & V6 are what type of leads?
L-sided chest leads, measuring L ventricle
If have LV hypertrophy, expect to see large R waves on which leads?
L-sided leads: V5 & V6, sometimes I, aVL
More muscle = more volts = greater amplitude can be seen in which cardiomyopathy?
If have RV hypertrophy, expect to see large R waves on which leads?
R-sided leads: V1 & V2
How does demand ischemia change the EKG?
Depression of ST segment
How does acute coronary artery obstruction change EKG?
T wave inversion
How do demand ischemia and acute coronary obstruction differ?
Demand - normal ECG @ rest
Obstruction - abnormal even at rest
Transmural infarcts produce which kinds of waves?
Q - waves;
Absence of normal transmural vector produces a negative deflection in leads over infarcted myocardium
What rules can you use to determine if you can associate infarct with a Q wave?
1. Is > 1/4 of the amplitude of the R wave
2. Is one small box (0.04) seconds wide
3. Is usually in at least 2 leads reflecting the same region of the LV
Transmural vs subendocardial infarct as seen by ECG
Transmural: ST elevation with Q waves
Subendocardial: ST depression without Q wave
Why are we worried about prolonged QT interval? What is normal?
Increases susceptibility to arrhythmias
Normally: < 1/2 of total difference of 1 QRS to the next
Bad if > 1/2
What acquired things prolong QT interval?
Hypokalemia, Hypomagnesemia, Class 1A or 3 anti-arrhythmic drugs, Hypothermia