ECG basics Flashcards
heart rate calculations
- standard paper speed
- time and length of dark/light lines
- formula
SPS: 25 mm/sec
dark: every 0.2 sec, so 5 “big boxes” per second
light: every 0.04 sec, so 1500 “small boxes” per minute
HR = # beats in 6 seconds x 10 = 1500/# light lines between beats
AV and IV conduction
AV = PR interval, less than or equal to 0.2 seconds IV = QRS interval, less than or equal to 0.1 seconds
QTc interval
less than or equal to 0.45 seconds
- from onset of QRS to end of T (depol and repol)
- QT interval varies with HR
- QTc = QT/square root of R-R interval
right bundle branch block appearance
prolonged QRS
- late upward deflections in right sided leads (V1, aVR)
- late downward deflections in left sided leads (1, V6)
left bundle branch block appearance
prolonged QRS
- late upward deflection in left sided leads (1, aVL, V6)
- late downward deflections in right sided leads (V1)
AV conduction levels of heart block
1st degree: prolongation of PR interval only
2nd degree: some but not all beats are conducted
-Mobitz type 1: gradually increasing PR interval until a P wave is not conducted
–following P wave is conducted with shorter PR interval
–not serious, more common
-Mobitz type 2: sudden non-conducted P waves with no change in PR intervals
–more serious, but uncommon; may go to 3rd degree
3rd degree: no P waves are conducted, need pacemaker
complications of 3rd degree heart block
- escape rhythm
- junctional bradycardia with BBB or ventricular bradycardia (idioventricular rhythm)
ventricular tachycardia
HR > 100/min originates from one of the ventricles, resulting in a wide QRS complex
-potentially life threatening b/c can degenerate into ventricular fibrillation resulting in sudden death
narrow VS wide QRS complexes in tachycardias
narrow: QRS < 100 ms are supraventricular origin, with intact IV conduction
wide: QRS > 120 ms are supraventricular rhythm with aberrant IV conduction (RBBB, LBBB), or ventricular tachycardia
