Exam Review Flashcards
Inherent rate of SA node
60 to 100
Inherent rate of AV node
40 to 60
“Junctional tissue”
AV node + bundle of his can combine to become the pacemaker of the heart, if necessary.
Inherent rate of Purkinje fibers
20 to 40
Sympathetic Nervous System
- Innervation affects both atria and ventricles
- Causes coronary artery vasodilation, increases HR, increases speed of conduction through the AV node, increases force of contraction
- “Speeds up”
Parasympathetic
- Innervation effect atria
- Causes decrease in HR, decrease speed of conduction through the AV node, decreases force of contraction
- “Slows down”
Polarization
Resting state
Polarized state, no current flow
+ and - are relatively equal
Depolarization
Cardiac muscle cell is stimulated
Cell membrane changes and becomes more permeable
Na+ moves into the cell
Depolarization - contraction
Repolarization
Takes place after depolarization.
Cells begin to recover and restore electrical charges to normal
Inside of the cell is restored to negatively charged state
Absolute refractory period
Portion of ventricular cardiac cycle where no stimulus, no matter how strong, can excite the cardiac tissue. Stimulus will be rejected.
“Absolutely nothing will happen.”
Relative Refractory Period
Portion of the ventricular cardiac cycle when all cardiac cells are not fully repolarized. A strong enough stimulus can excite cardiac tissue. This is referred to as the vulnerable period and if hit right can initiate arrhythmias.
“When relatives are there, something bad can happen.”
Relative refractory period is visualized in the last 1/2 of the ‘T’ wave.
ECG Deflections
Definition: any wave or complex recorded in the ECG is inscribed as positive or negative deflection.
- A current flowing toward a (+) electrode gives a (+) deflection.
- A current flowing away from a (+) electrode gives a (-) deflection.
P wave
Usually the 1st wave
Usually originates in the SA node
Reflects atrial depolarization
PR interval
Measured from the beginning of the P wave to beginning of QRS complex
Represents interval from time the impulse leaves the SA node, the delay at the AV node, until it arrives at the Purkinje fibers.
Normal PR interval is 0.12 to 0.20
QRS complex
Ventricular activity
Represents ventricular depolarization
Represents time required for impulse to travel through the R and L ventricles
Normal range is 0.12 or less.
Bundle branch block has QRS of 0.12 or greater
T wave
Represents ventricular Repolarization, last half of T wave is relative refractory period
ST segment
Represents time between completion of ventricular depolarization and beginning of Repolarization.
This is the segment between QRS and T wave
QT interval
Represents total ventricular activity, depolarization and Repolarization.
QT interval varies with heart rate.
Normal sinus rhythm characteristics
HR 60 to 100 Rhythm is regular PR interval is 0.12 to 0.20 QRS is less than 0.12 One P wave for each QRS, uniform in appearance
Sinus bradycardia characteristics
HR less than 60 Rhythm is regular PR interval 0.12 to 0.20 QRS less than 0.12 One P wave for every QRS, uniform appearance
Sinus tachycardia characteristics
HR 100-160 Rhythm regular PR interval 0.12 to 0.20 QRS less than 0.12 Uniform appearance
Sinus arrhythmia characteristics
Rate: slightly increases with inspiration, decreases with expiration
Rhythm: irregular, varies with respiration
PR interval: 0.12 to 0.20
QRS: less than 0.12
Sinus bradycardia Cause/Treatment
Cause: athlete, vegal stimulation, decreased metabolism, medications, elevated ICP, sinus node disease
Treatment: assess PT, IV/O2, atropine to increase HR, pacemaker
Sinus tachycardia causes/treatment
Cause: sympathetic stimulation (fever, stress, pain, anxiety, exercise), hyperthyroid, medications, caffeine, atropine, hypotension, shock, hypo olefin
Treatment: Treat the underlying cause!! Do not give cardiac med.
Sinus Arrhythmia causes/treatment
Cause: usually seen with deep breathing, commonly seen in the young and the elderly
Treatment: usually doesn’t require intervention - if symptomatic, IV/O2, atropine, pacemaker
Premature atrial contractions (PACs) characteristics
Rhythm is regular except for the premature beat
P wave early with premature beat, may have different configuration
PR interval with PAC may vary
QRS with PAC should be similar to regular QRS
T wave shape may change when early P wave is buried in proceeding T wave
Premature atrial contractions (PACs) causes/treatment
Cause: sympathetic stimulation, altered electrolytes, hypoxia, digoxin toxicity, HF, stress, caffeine, alcohol, may be normal for some people
Treatment: Assess patient, treat underlying cause, BB/CCB may help when idiopathic.
Atrial tachycardia characteristic
Rate usually 160 to 250, classic rate is 180, may be precipitated by PAC
P waves “should be seen”, but may be lost in preceding T wave
PR interval may be different than normal PR interval, may not be measurable
QRS less than 0.12
- *Sinus tachycardia 100-160 (slow onset)
- *Atrial tachycardia 160-250 (sudden onset)
Atrial tachycardia causes/treatment
Cause: dig toxicity, hypoxia, ischemia, electrolyte imbalance, CAD
Treatment: if stable - vagle maneuver, adenosine, CCB, BB, amiodarone
If unstable - synchronized cardio version
Paroxysmal Atrial Tachycardia (PAT) characteristics
Same as atrial tachycardia, but has a sudden onset/cessation
**Causes/treatment same as atrial tachycardia
Atrial flutter characteristics
Saw tooth pattern - flutter waves
Atrial rate (use exact method) is 250 to 400
PR interval is not measurable
Ventricular rate depends on amount of blocking occurring at AV node; may be regular or irregular
QRS less than 0.12
QT is usually immeasurable in flutter
Atrial flutter causes/treatment
Causes: rheumatic heart disease, valve disease, ischemia, hypoxia, pericarditis, sick sinus syndrome
Treatment: Control rate (BB, CCB, dig, amiodarone), convert the rhythm (rate > 48 hrs then anticoagulate first) use amiodarone, synchronized electrical cardioversion, ablation
Atrial fibrillation characteristics
Absence of P waves *zero coordinated electrical activity, atrial just quiver.
Atrial rate is 400+ (known from research, this cannot actually be measured
Rhythm is irregular
Ventricular rate depends on amount of blocking by the AV node
If ventricular rate is greater than 100 then it is called a fib with RVR
QRS is less than 0.12
Atrial fibrillation causes/treatment
Cause: rheumatic heart disease, hypertension, MI/ischemia, COPD, frequent PAC’s, post cardiac surgery
Treatment: control rate, convert rhythm, concerns for clot formation (this is the same as atrial flutter)
Supra ventricular tachycardia (SVT) characteristics
Broad term
Any tachycardia originating from somewhere above the ventricles
Cannot see P waves
Skinny QRS
Junctional rhythm characteristics
Rate is 40 to 60 P wave may be inverted, absent, or after the QRS PR interval less than 0.12 QRS less than 0.12 R-R interval is regular
Junctional rhythm causes/treatment
Cause: digoxin, hypokalemia, ischemia, SA node disease, electrolyte imbalances, cardiomyopathy
Treatment: determine underlying cause, withold medications, potassium replacement, is s/s give atropine to stimulate SA node, may need to pace temporarily.
Accelerated junctional rhythm characteristics
Rate is 61 to 100
P wave is inverted, absent, or after QRS
QRS less than 0.12
Accelerated junctional rhythm causes/treatment
Causes: dig toxicity, MI, HF, valvular disease
Treatment: treat the underlying cause
Junctional tachycardia characteristics
Rate 101 to 200
P wave absent, inverted, or after QRS
QRS 0.12 or less
Junctional tachycardia causes/treatment
Causes: #1 cause is dig toxicity
Treatment: Treat underlying cause, O2/IV, BB, CCB, amiodarone, cardioversion
Premature ventricular contractions (PVCs) characteristics
Rhythm is irregular due to premature beat
QRS is wide and ugly; greater than 0.12
ST & T wave slope in opposite direction of the ectopic QRS
PVC causes/treament
Causes: sympathetic stimulation, dig toxicity, ischemia, MI, HF, electrolyte imbalance, hypoxia, stimulants
Treatment: assess PT, O2/IV, replace electrolytes, amiodarone, lidocaine
Ventricular tachycardia characteristics
Rate 100 to 250 - use exact method
Rhythm R-R is regular
Usually no visible P waves
QRS is wide, >0.12
V tach causes/treatment
Causes: same as PVCs
Treatment: Assess Pt, check pulse, O2/IV, amiodarone, cardioversion, if no pulse, call code, CPR, defibrillation, epi/amiodarone.
Torsades de Pointes
Torsades V Tach
Characteristics
Variation of v tach in which the QRS appears to twist around baseline
QRS complex changes shape, size, amplitude, width
Torsades V tach cause/treatment
Cause: any drug that may prolong QT interval, inherited prolonged QT interval, low K, low mag, low Ca, acute MI
Treatment: Call code, CPR, defibrillation, magnesium, Epi
Ventricular Fibrillation Characteristics
No measurable rate No identifiable ECG waveform No contraction, no cardiac output Wavy baseline Rhythm is fine or coarse
V fib cause/treatment
Cause: CAD/CHF, ACS, MI, drug toxicities, electrical shock, post cardioversion, antiarrhythmics
Treatment: Call code, CPR, defibrillation, epi, amiodarone
Idioventricular rhythm characteristics
Rate 20 to 40
P wave absent, sometimes retrograde
QRS wide, greater than 0.12, look alike
Idioventricular causes/treatment
Cause: ischemia, MI, dying heart, hypoxia, dig toxicity, SA node/AV junction have failed
Treatment: avoid antiarrhythmics, correct underlying cause, atropine, temporary pacing
Accelerated idioventricular rhythm (AIVR) characteristics
Rate 41 to 100
QRS > 0.12
AIVR cause/treament
Cause: ischemia, reperfusion, dig toxicity, cocaine, cardiomyopathy
Treatment: do not give antiarrhythmics, give atropine if rate is slow
Asystole
Complete absence of electrical activity in the heart
May resemble fine v fib
Confirm in 2 leads
Check PT Call code CPR Epi Fix the cause
Cause: hypovolemia, hypoxia, acidosis, hypokalemia, hypothermia, toxins, tamponade, tension pneumothorax, thrombosis
Agonal rhythm
Dying heart
Rate is less than 20
Tx: transcutaneous pacing, call code, CPR, epinephrine, atropine
Beta Blockers
Decreases HR, BP, strength of contractions
Used with MI and unstable angina
Examples: metoprolol, labetalol, atenolol, carvedilol
Calcium channel blockers
Decreases myocardial contractility, decreases conduction of SA and AV nodes.
Used to control atrial tach
Ex: diltiazem, amylodipine
Digoxin
Cardiac glycoside
Used to control a fib with RVR and a flutter
Very narrow therapeutic window
Amiodarone
Antiarrhythmics used to control atrial and v tach dysrhythmias.
Adenosine
Push fast
Depresses AV and SA node activity
Amiodarone
Treat v-tach
Lidocaine
Grate ventricular arrhythmias.
Epinephrine
Only IVP when doing CPR
Vasopressor
Increases HR, BP, perfusion pressure to the brain and heart
Magnesium
Shortens QT interval
Used to treat or prevent recurrence of torsades de Pointes v tach.
1st degree heart block
Rhythm regular, originates in the SA node
P wave is present, appears normal
PR is greater than 0.20 consistently
QRS less than 0.12
Cause: seen in aging, may be normal, may be a forerunner to further AV block
Tx: usually no tx, hold medication, continue to monitor
2nd degree heart block type I
Atrial rate is greater than ventricular rate
P-P is constant, originates in SA node (P-P always regular)
Some P waves not conducted, more P waves than QRSs
PR interval progressively lengthens until QRS is dropped
Ventricular rhythm is irregular (R-R irregular)
QRS less than 0.12
Has a consistent pattern
Cause: increased parasympathetic tone, medications, MI
Tx: usually none required, hold medications, monitor for further block, atropine if bardycardic, may need to externally pace if atropine doesn’t work.
2nd degree heart block type II
Atrial rate is regular, P to P is constant (exact method)
More P waves than QRS’s (P waves all on time)
Ventricular rate varies, R-R is usually irregular
PR interval constant where present, may be greater than 0.12
QRS less than 0.12
Cause: MI, drugs, degeneration of the conduction system
Tx: hold meds, atropine if symptomatic, temporary pacemaker
3rd degree heart block
Complete heart block
A/V rates unrelated, complete a sense of conduction between atria and ventricle
Atrial rate regular, P to P constant, P waves normal (exact method)
Ventricular rate regular (R to R constant)
PR interval varies and has no pattern
QRS may be wise or narrow - depends on where impulse originates
Cause: ischemia or injury, CCP, BB, trauma
Tx: hold meds, pacing, epi drip, atropine (maybe)
Conduction system electrical pathway
Name the components
Sinus node –> Bachmann’s bundle
Internodal pathways –>AV node –> Bundle of His –>
Left bundle branch –> Purkinje fibers
Right bundle branch –> Purkinje fibers
