EKG Review Flashcards
What is the significance of the AV node?
- Sole pathway for electrical conduction from the atria to the ventricles
- AV node slows conduction, providing time for atrial blood to enter the ventricles prior to ventricular contraction
When is the QT interval normal?
When it is less than 1/2 the R-R interval
What does the ST segment represent?
- “Plateau” or “slow” initial phase of ventricular re-polarization [rapid phase of ventricular depolarization occurs at T wave]
- ST horizontal segment following QRS - horizontal and flat and normally following the other levels of the baseline
Ventricular Systole (contraction):
Begins with the QRS and ends with the T wave - systole stands de and re polarization of the ventricles (the QT interval is normal when less than 1/2 R-R interval)
What does Na+ cause in conduction?
Na+ causes cell to cell conduction (depolarization) in the heart (Na+ flows into myocytes)
What does Ca2+ cause in conduction?
Ca2+ causes slow conduction at the AV node and myocyte contraction upon release into the myocytes
What does K+ cause in conduction?
K+ outflow causes re-polarization of myocytes
What is the normal PR interval?
0.12-0.20 seconds (3-4 horizontal boxes)
What is the PR interval?
It’s measured from the onset of the P wave to the onset of the QRS complex regardless if the initial wave is a Q or R wave.
What does the PR interval represent?
Atria to ventricular conduction time (through His bundle)
What is the normal duration of the QRS complex?
0.08-0.12 sec
2-3 horizontal boxes
What does a bundle branch block look like at R wave?
Looks like bunny ears - Rwave, Swave, R’wave
When is the QT interval?
Duration of action and recovery of the ventricular muscle. This various inversely with heart rate.
-Should be
What does the ST segment represent?
- Important in identifying pathology such as myocardial infarctions (transmural - elevations) and ischemia (subendocardial - depressions).
- In normal situations, it serves as the isoelectric line from which to measures the amplitudes of the other waveforms
What is the amplitude?
- Vertical deflection of the wave
- 10 mm = 1 mV
- 1 mm = 0.1 mV
What is the size of each small and large square?
Small = 1 mm Large = 5 mm
What is measured as positive on EKG?
When wave of stimulation is advancing toward a positive electrode
What time does each small and large square represent?
Small = 0.04 seconds Large = 0.2 seconds
What are the pacing rates?
Atrial 60-80
Junctional 40-60
Ventricular 20-40
What are regular rhythms?
- Sinus arrhythmias (breathing in and out)
- Tachy-arrhythmias (e.g. supraventricular tachycardia)
- Junctional Rhythms
- Ventricular Rhythms
- Heart Blocks
- Atrial Rhythms
What are irregular rhythms (chaotic)?
- Sinus arrhythmia
- Atrial fibrillation
- Ventricular fibrillation
- Multifocal Atrial Arrhythmias
- Escape - not SA but another atrial foci
- Atrial flutter - variable ventricular response
- Record general average ventricular rate
What pattern is associated with second degree heart block type 1?
-PR interval is getting longer and longer and then drops off
What is a bigeminal pattern?
Continuous alteration of long and short heart beats
ex: PVC following every normal beat
What is a trigeminal pattern?
Two consecutive sinus beats followed by a ventricular premature beat.
