4 - ECG at the Bedside 1 Flashcards
1 mm / small box = how much time on an ECG?
40 ms
5 mm / large box = how much time on an ECG?
200 ms
normal PR interval
3-5 small boxes (120-200 ms)
normal QRS interval
2-3 small boxes (80-120 ms)
normal QTc interval
9-11 small boxes (360-440 ms)
normal sinus rhythm rate
60-100 bpm
atrial fibrillation on ECG
absent p waves and irregular rate
HR assessment from ECG
divide 300 by RR interval expressed as number of large boxes
what two leads normally have negative p waves?
aVR and V1
ECG sign of LA enlargement
bifid p wave “p-mitrale” due to delayed LA depolarization
ECG sign of RA enlargement
tall P wave > 2.5 mm
which leads are best for assessing p wave morphology?
2, 3, aVF
ECG sign of AV block
PR interval > 200 ms (5 small boxes)
causes of PR prolongation
drugs: beta blockers, Ca channel blockers, digoxin, amiodarone, clonidine
acute ischemia / infarction
degenerative or calcific dz of conduction system (irreversible) - Lev’s or Lenegre’s dz
tx for irreversible AV block
pacemaker
Wolf Parkinson White syndrome ECG findings
short PR interval (120 ms
Wolf Parkinson White syndrome mechanism
accessory branch back to AV node causing tachycardia and irregular rhythm
ECG signs of bundle branch block
RSR’ pattern in qrs complex in precordial leads
wide qrs complex (>120 ms)
how do you distinguish between left and right bundle branch block on ECG?
if signs are in V1/2 > right
if signs are in V5/6 > left
what causes bundle branch block (2)?
ischemia/infarction of bundle branch
eccentric hypertrophy of ventricles
how do you calculate QTc?
QT / sqrt (RR interval)
acquired causes of prolonged QT interval
drugs: anti-arrhythmics, anti-psychotic phenothiazines, TCAs, antifungals
electrolyte abnormalities - low K, Mg, Ca
complication of long QT syndrome
Torsades de pointes - varying ventricular tachycardia. Can cause sudden death
