EKG Flashcards
Review lead placement
What is an ECG
12 lead ECG provides information about rate, rhythm, conduction, areas of ischemia and infarct, hypertrophy, electrolyte imbalance, and systemic pathologies
P wave
arterial depolarization
Always the same
P-R interval time
required for impulse to travel from atria through conduction system to Purkinje fibers
0.12 - 0.2 sec
QRS Wave
Ventricle depolarization
0.04 - 0.1 sec
ST segment
beginning of ventricular depolarization
T wave
ventricular repolarization
QT interval
time for electric systole
Counting heart rate by ECG
-count intervals between QRS complexes in 6 second strip and multiply by 10
Possible etiology of arrthymias
- ischemic conditions of myocardium, electrolyte imbalance, acidosis or alkalosis, hypoxia, hypotension, emotional stress, drugs, alcohol, caffeine
ventricular arrhythmia
- originate from an ectopic focus in the ventricles (outside the normal conduction system)
- significant in adversely affecting cardiac output
what is a premature ventricular contraction
- a premature beat arising from the ventricle
- occurs occasionally in the majority of normal population
How does PVC look on ECG
- no P wave
- A bizarre and wide QRS that is pre-mature followed by a compensatory pause
Serious PVCs
- > 6 per minute
- paired or in sequential runs
- multifocal
- very early PVC (R on T phenomena)
Ventricular tachycardia
- A run of four or more PVC’s occurring sequentially
- very rapid rate (150-200 bpm)
-may occur paroxysmally (abrupt onset) - usually the result of an ischemic ventricle
What does ventricular tachycardia look like on ECG
- wide, bizarre QRS waves, no P wave
- very compromised cardiac output
Non-sustained ventricular tachycardia (NSVT)
a run of four or more consecutive beats in duration, terminating spontaneously in less than 30 seconds
Sustained ventricular tachycardia (VT)
VT > 30 seconds in duration and/or requiring termination due to hemodynamic compromise in less than 30 seconds
Ventricular fibrillation
- a pulseless, emergency situation requiring emergency medial treatment (CPR, defibrillation), and medication
- characterized by chaotic activity of ventricle originating from multiple foci
- unable to determine rate
how does V-Fib look on ECG
Bizarre, erratic cardiac output without QRS complexes
- no effective cardiac output
- clinical death within 4-6 mins
Atrial Arrhythmia (supraventricular)
- rapid and repetitive firing of one or more ectopic foci in the atria (outside the sinus note)
- cardiac output usually maintained if rate is controlled; may precipitate ventricular failure in an abnormal heart
how does atrial arrhythmia look on ECG
- P waves are abnormal (variable in shape) or not identifiable (a-fib)
- rhythm may be irregular: chronic or occurring paroxysmally
- Rate: rapid w/ arterial tachycardia (140-250 bpm), atrial flutter (250-350 bpm), fibrillation (>300 bpm)
AV Blocks
abnormal delays or failure to conduct through normal conducting system
- First, second, or third (complete) degree blocks; bundle branch blocks
- if ventricular rate is slowed, CO is decreased
Third degree heart block
- complete heart block
- life threatening
- requires medication (atropine), surgical implantation of pacemaker
Hyperkalemia on ECG
widens QRS, flattens P wave, T wave becomes peaked
Hypokalemia on ECG
flattens T wave (or inverts), produces a U wave
Hypercalcemia on ECG
widens QRS, shortens QT interval
Hypocalcemia on ECG
prolongs QT interval
Hypothermia on ECG
- elevates ST segment
- slows rhythm
Digitalis
Depresses ST segment
- flattens T wave (or inverts)
- QT shortens
Quinidine
- QT lengthens
- T wave flattens (or inverts)
- QRS lengthens
Beta blockers
- decreases heart rate
- blunt heart rate response to exercise
Nitrates
increases heart rate
anti arrhythmic agents
may prolong QRS and QT intervals
Holter monitoring
- continuous ambulatory ECG monitoring via recording of cardiac rhythm for up to 24 hours
- used to evaluate cardiac rhythm, transient symptoms, pacemaker function, effect of meds
- allows correlation of symptoms with activity
