EKG Flashcards
SA Node ↓—AV Node↓—Bundle of His ↓ —Purkinje Fibers
The Electrical Conduction System of the Heart
ability of pacemaker cells to spontaneously initiate an electrical impulse
Automaticity
ability of myocardial cells to respond to stimuli generated by pacemaker cells
Excitability
ability to transmit an impulse from cell to cell
Conductivity
inability of cardiac cells to respond to additional stimuli immediately following depolarization.- keeps you from going into Vfib
Refractory
ability of myocardial fibers to shorten in response to a stimulus
Contractility
Fastest rate of automaticity.
Primary pacemaker of the heart
Rate: 60 to 100 bmp
SA node
Has a delay which allows for atrial contraction and more filling of the ventricles
Rate: 40 to 60 bmp
AV node
Has the ability to self-initiate electrical activity
Rate: 40 to 60 bmp
Bundle of His
Network of fibers that carry electrical impulses directly to ventricular muscle cells
Rate: 20 to 40 bmp
Purkinje Fibers
Shows: Heart rate, rhythm/regularity, impulse conduction time intervals, abnormal conduction pathways
Information Obtainable From EKG Rhythm Strip Analysis
Does not show: pumping action, cardiac output, blood pressure, cardiac muscle hypertrophy
Information NOT Obtainable From EKG Rhythm Strip Analysis
Defines the graphic representation of the electrical activity of the heart
Electrocardiogram
SA node fires, sends the electrical impulse outward to stimulate both atria and manifests as a P-wave.
Approximately 0.10 seconds in length
P wave
Time which impulse travels from the SA node to the atria and downward to the ventricles
PR Interval (PRI)
Impulse from the Bundle of HIS throughout the ventricular muscles
Measures less than 0.12 seconds or less than 3 small squares on the EKG paper
QRS complex
Ventricular repolarization, meaning no associated activity of the ventricular muscle
Resting phase of the cardiac cycle
T wave
Ventricular repolarization
Preparing for the next heartbeat
ST segment
Step 1: Heart Rate Step 2: Regular/Irregular Step 3: P waves Step 4: PR interval Step 5: QRS complex
Interpretation of an EKG Strip
6-second method: have a six second strip, count the number of QRS complexes and multiply by 10
Heart Rate
Heart rhythms are classified as regular or irregular
Determining the heart rhythm involves establishing a pattern of QRS complex occurrences.
Measure ventricular rhythm by measuring the interval between R-to-R waves and atrial rhythm by measuring the P-to-P waves.
Intervals > than 0.06 seconds, irregular
Heart Rhythm
Are P-waves present? Are P-waves occurring regularly? Is there a P-wave for each QRS complex? Are the P-waves smooth, rounded, and upright in appearance, or are they inverted? Do all P-waves look similar?
5 questions to ask about P waves
Normal length of the PRI is 0.12 to 0.20 second (3-5 small squares)
Are PRI greater than 0.20 second?
Are PRI less than 0.12 second?
Are the PRI constant across the EKG strip?
PRI and 3 questions to ask
Are QRS intervals greater than 0.12 second (wide)? If so, the complex may be ventricular in origin.
Are QRS intervals less than 0.12 second (narrow)? If so, the complex is most likely supraventricular in origin.
Are QRS complexes similar in appearance across the EKG strip?
3 questions to ask about QRS
Patient movement
Loose or defective electrodes
Improper grounding
Faulty EKG apparatus
4 common causes of artifact
rate of < 60 bmp
bradycardia
rate of 60 to 100 bpm
normal rate
rate of > 100 – 150 bpm
tachycardia
SA node
sinus
SA node fails, impulse comes from the atria (internodal or the AV node)
atrial
SA node or AV junction fails; ventricles will shoulder responsibility of pacing the heart
ventricular
Normal Sinus Rhythm (NSR)
Sinus Arrythmia- speeds up during inspiration- due to lungs expanding and pushing on heart- heart gets a little sensitive- this is normal
Sinus Bradycardia (SB)
Sinus Tachycardia (ST)
sinus rhythms
SA node fails to generate an impulse, the atrial tissue or areas in the internodal pathways may initiate impulse.
These are called atrial dysrhythmias
Generally not considered life-threatening or lethal. Careful and deliberate patient assessment must be continuous.
atrial rhythms
o What is the rate: atrial 250-300 BPM ventricular- variable
o What is the rhythm: atrial regular, ventricular- regular or irregular
o Is there a p wave before each QRS? Are the P waves upright and uniform? Normal P waves are absent replaced by F waves- sawtooth
o What is the length of the PR interval? Not measurable
o Do all the QRS complexes look alike? Yes
o The length of the QRS complexes? Usually less than 0.12 se- 3 small squares
Atrial Flutter
o What is the rate: atrial 350-400 BPM ventricular- variable
o What is the rhythm? Irregularly irregular
o Is there a P wave before each QRS? Are there P waves upright and uniform? Normal P waves are absent, replaced by f waves
o What is the length of the PR interval? Not discernable
o Do all the QRS complexes look alike? Yes
o The length of the QRS complexes is? Usually less than 0.12 sec
Atrial Fibrillation
o What is the rate: atrial- 150-250 BPM Ventricular 150-250 BPM
o What is the rhythm: regular
o Is there a p wave before each QRS? Are the P waves upright and uniform? Usually not discernable especially at the high rate range
o What is the length of the PR interval? Usually not discernable
o Do all the QRS complexes look alike? Yes
o The length of the QRS complexes is? Usually less than 0.12 sec
Supraventricular tachycardia
once given rapidly, then 20ml of NS, will see 6 sec of asystole – resets pacemaker of heart- if 6 mg doesn’t work go up to 12 mg- have everything ready first
adenosine
most common, can be due to electrolyte issues, hypokalemia, nicotine, tea, coffee, anything that interferes with blood supply to the heart- less cardiac filling so less cardiac output- no P wave
Premature Ventricular Complexes
100-250; no atrial rhythm, very regular rhythm , can still have a pulse; Amiodarone, antiarythmic- class 3, bolus then start a drip , there are pills after drip is weaned off- tx- medication, if unstable cardiovert with pulse, if pulseless- defibrillate
Ventricular Tachycardia
French term that signifies the “twisting of the points.”
May wax and wane in amplitude and may “flip” or “twist” on its electrical axes.
Similar to ventricular tachycardia.
Caused by hypomagnesemia or by antiarrhythmic drugs.
common in Alcoholics – bc low mag, cocaine, certain meds that deplete mag
Torsades de Pointes
The absence of a palpable pulse and myocardial muscle activity with the presence of an organized electrical activity (excluding VT and VF) on cardiac monitor.
It is not an actual rhythm. It represents a clinical condition wherein the patient is clinically dead, despite the fact that some type of organized rhythm appears on the monitor.
Pulseless Electrical Activity (PEA)
hypovolemia, hypoxia, hydrogen ion, hyper/hypokalemia, hypothermia, hypoglycemia
6 Hs
tamponade, tension pnuemophorax, thrombosis, trauma, toxins
5 Ts
PR interval is greater that 0.20- everything is regular rhythm, rate etc just longer PR interval – caused by cardiac medications
First Degree AV Block
– lengthening PR interval until QRS is dropped- then resets to short and then lengthens all over again- ventricular rhythm irregular –tolerated unless heart rate is really slow
Second Degree AV Block (Mobitz Type I) or Wenckebach
intermittent failure of the AV node to conduct an impulse to the ventricles without delay-no QRS- a pt may get dizzy depending on how fast rate is – anterior wall MI, if symptomatic- will pace them- on or in them – poor prognosis if remain symptomatic
Second Degree AV Block (Mobitz Type II)
atria and ventricles don’t associate- fire whenever, no correlation – totally variable- dig toxic can cause- if tolerated they are watched
Third Degree AV Block (Complete)
sensing or pacing
artificial pacemaker
