EKG/ECG Interpretation Flashcards
What is an electrocardiogram (ECG)?
A graphic representation of the heart’s electrical rhythm recorded from electrodes on the surface of the body.
Describe the normal cardiac cycle on a ECG. (pg 191 has a great picture in therapy ed)
P wave = atrial depolarization
PR interval = time required for impulse to travel from the SA node to the AV node
QRS wave = ventricular depolarization and atrial repolarization
ST segment = beginning of ventricular repolarization
T wave = ventricular repolarization
QT interval = time for electrical systole (time for both ventricular depolarization and repolarization)
How is heart rate calculated using an ECG strip?
Count the number of intervals between QRS complexes in a 6 second strip and multiply by 10.
Atrial depolarization begins in the _____.
SA node
What is sinus arrest?
A sinus rhythm with intermittent failure of either SA node impulse formation or AV node conduction that results in the occasional complete absence of P or QRS waves
What is a premature ventricular contraction (PVC)?
Premature depolarization arising in the ventricle due to an ectopic focus
What is the difference between unifocal and multifocal PVCs?
Unifocal = arise from the same ectopic focus and have the same configuration
Multifocal = arise from different ectopic foci and have different configurations
What do PVCs typically look like on a ECG strip?
No P wave, a bizarre and wide QRS that is premature, followed by a long compensatory pause
What is the difference between PVCs that occur in bigeminy versus trigeminy?
Bigeminy = normal sinus impulse is followed by a PVC Trigeminy = PVC occurs after every two normal sinus impulses
When are PVCs considered to be serious?
> 6 per minute OR 3 consecutive PVCs
What is ventricular tachycardia? How does it appear on an ECG?
3 or more PVCs at a ventricular rate >150 beats/minute
ECG: P waves are absent and QRS complexes are wide and aberrant in appearance
When does ventricular tachycardia become a medical emergency? What happens to a patient who is sustained v-tach?
V-tach that lasts greater than 30 seconds is a life threatening arrhythmia that requires immediate medical attention
Sustained v-tach = patients are unable to maintain adequate BP and become very hypotensive
What is ventricular fibrillation? How does it appear on an ECG?
Ventricles do not beat in a coordinated fashion, but fibrillate or quiver asynchronously and ineffectively
ECG: Bizarre, erratic activity without QRS complexes
What happens to a patient who is in ventricular fibrillation?
No cardiac output
Patient becomes unconscious
Clinical death within 4-6 minutes
What is ventricular asystole? How does it appear on an ECG?
Ventricular standstill with no rhythm
ECG: straight line pattern
What is atrial flutter? What does it look like on an ECG?
An ectopic, very rapid atrial tachycardia
Atrial rate of 250-350 beats per minute; ventricular rate dependent upon AV node conduction
ECG: Saw-tooth shaped P waves are characteristic
What is atrial fibrillation? What does it look like on an ECG?
A common arrhythmia where the atria are depolarized between 350-600 times/min
ECG: irregular RR interval with irregular non-discrete P waves
What are atrioventricular blocks?
Abnormal delays or failure to conduct through normal conducting system
What is a 1st degree atrioventricular block?
PR interval is longer than 0.2 seconds, but relatively constant from beat to beat
No symptoms or significant change in cardiac function
What is a 2nd degree heart block? List the types of 2nd degree AV blocks.
AV conduction disturbance in which impulses between the atria and ventricles fail intermittently
Mobitz type I block (Wenckebach block)
Mobitz type II block
What is a Mobitz type I (Wenckebach) AV block?
Progressive prolongation of the PR interval until one impulse is not conducted (dropped)
Longer, longer, longer, drop, now you have a Wenckebach
Describe a Mobitz type II AV block.
Consecutive PR intervals are the same and normal followed by nonconduction of one or more impulses (a more serious condition)
Describe a 3rd degree heart block.
All impulses are blocked at the AV node and none are transmitted to the ventricles (complete heart block)
What interventions are used to treat a 3rd degree heart block?
Atropine
Pacemaker implantation
ST segment depression or elevation greater than ____ measured at the J point in ___ consecutive leads is considered abnormal.
Greater than 1mm in 2 consecutive leads is considered abnormal.
What does ST segement elevation typically indicate?
Myocardial infarction (STEMI)
What influence does hyperkalemia have on ECG waves?(3)
Widens QRS wave
Flattens P wave
T wave becomes peaked
What influence does hypokalemia have on ECG waves?(2)
Flattens or inverts T wave
Produces a U wave
What influence does hypercalcemia have on ECG waves? (2)
Widens QRS
Shortens QT interval
What influence does hypocalcemia have on ECG waves? (1)
Prolongs QT interval
