ECG Flashcards
Who developed the ECG?
1) Augustus Waller
2) William Einthoven
Where does Lead I go?
Right arm (-) –> Left arm (+)
Where does Lead 2 go?
Right arm (-) –> Left leg (+)
Where does Lead 3 go?
Left arm (-) –> Left leg (+)
Where does aVR go?
Lead 3 –> Right arm (+)
Where does aVL go?
Lead 2 –> Left arm (+)
Where does aVF go?
Lead 1 –> Left leg (+)
How many precordial leads may be used?
6
What does the ECG measure?
extracellular electrical potential (affinity for electron to move away from - node toward + node)
What is the plot output of the ECG?
voltage vs. time
What is the scale for each axis of the ECG plot?
X: 1in = 1sec
Y: 1cm = 1mV
Why is the T wave positive?
repolarization occurs from epicardium to endocardium
How does depolarization occur in terms of heart layers?
endocardium to epicardium
What represented by inconsistently-shown U wave?
papillary muscle repolarization
With what part of the ECG does ventricular contraction correlate with?
ST segment (plateau phase of myocyte ap)
How is activation of AV node & bundle of His shown on the ECG?
PR/PQ interval
Define tachycardia?
HR > 100 bpm
Define bradycardia.
HR < 60 bpm
Define sinus arrhythmia.
HR variance during inhaling & exhaling (inhaling > exhaling)
Define 1st degree heart block.
PR > 0.2 seconds
Define 2nd degree heart block.
PR > 0.25 seconds
Define 3rd degree heart block.
complete blockage, aka Stokes-Adams syndrome
What are causes of heart block?
1) AV bundle ischemia
2) AV bundle compression (scar tissue)
3) AV bundle inflammation
4) extreme vagal stimulation (basovagal block)
What are causes of ectopic pacemakers?
1) local ischemia
2) coronary calcification
3) AV Node- & Purkinje-altering drugs (Nicotine/caffeine)
4) Catheterization
How does premature atrial contraction present on an ECG?
1) premature P wave
2) compensatory pause
- - depolarized SA node must repolarize
What are the two pathophysiologies of pvc?
1) AV node becomes ectopic
2) irritable focus in the ventricle
How does pvc via irritable ventricular focus manifest in an ECG?
1) prolonged QRS
2) amplified QRS
3) negative T-wave
Why would a QRS be amplified?
signal propagates in 1 direction
Why would the t-wave be negative?
when myocytes (instead of purkinje) are used to depolarize…slower depol & therefore first to depol are first to repol
What are causes of irritable ventricular foci causing pvc?
1) nicotine/caffeine
2) sns
3) sleep deprivation
4) ischemia
5) ion channel disorders
what is paroxysmal tachycardia?
spontaneous tachycardia in the atria or ventricles
how does an atrial paroxysmal tachycardia manifest?
QRS with obscured P
What causes V-fib?
abnormal lack of full refractory period in a depolarizing event caused by sudden electric shock, or ischemia
What is treatment for V-fib?
defib-& hope SA node re-fires
1) 110 V for 0.1 seconds
2) 1000 V for 0.003 seconds
What generally causes a-fib?
many ectopic foci
what is atrial flutter?
coordinated contractions @ 200-350 bpm
What generally causes atrial flutter?
1 ectopic focus
