Test 4 continued Flashcards
Electrodes
-detect and conduct voltage potentials from the skin and send message through leadwires to a monitor
Leads logic: 12 possible leads
- 3 limb leads: bipolar to measure both positive and negative impulses from the heart (1 positive and 1 negative) (I,II,III)
- 3 augmented limb leads: Use limb lead electrodes but uses central negative lead to measure positive charges through single electrode with a reference point having zero activity (aVR, aVL, aVF)
- 6 unipolar leads (V1 on right side of sternum, V2-6 on left side)
Lead placement
Right shoulder: White
Left shoulder: black
Right side: green
Left lower: red
Einthoven’s triangle
- Center corresponds to the vector summation of all electrical activity from the heart
- as the current (electrons) travels to the positive pole, negative deflection
- as the current travels to the negative pole, positive deflection
- perpendicular current= biphasic deflection
Common frontal ECG Limb leads created by which leads (Einthoven’s triangle)
-Bipolar leads I, II, and III
Augmented leads
- aVR, aVL, and aVF measure electrical activity between a limb and a single electrode
- fill in the ninety degrees between leads I, II, and III
Precordial leads
- V1-V6 placed across the chest
- provide frontal view of the heart’s electrical activity
The presence of different ECG leads does not effect the interpretation of cardiac rhythms
know it
Rhythm originated in SA node: Normal sinus rhythm (NSR)
SA nodal Rhythm
- Rhythm: regular
- Rate: 60-100 bpm
- P wave: one visible before every QRS complex
- P-R interval: Normal (less than 5 small squares; more than 5 would indicate heart block)
- QRS duration: Normal
- indicates the electrical impulse generated in the SA node is travelling along the normal conduction paths at a normal speed
Sinus bradycardia
SA nodal Rhythm
-HR=
Sinus Techycardia
SA nodal Rhythm
-HR= >100 bpm
Wandering Atrial Pacemaker
SA nodal Rhythm
- Pacemaker site bounces from the SA node to other atrial sites, the AV junction, and then back to the SA node
- HR= normal
- Rhythm= irregular
- P waves: at least three different morphologies, determined by the focus of the atrial stimulus
- P-R interval: variable
- QRS: Normal to irregular
- Reach threshold quicker than SA node
Premature Atrial Contraction(s) (PAC)
SA nodal Rhythm
-Results when an ectopic atrial electrical signal initiates a heart beat rather than the SA node
Sinus Arrhythmia
SA nodal Rhythm
- Generally normal in young, healthy people
- irregular in conjuction with the respirations
- rate increases with inspiration and decreases with expiration
- The difference between the shortest and longest P-P interval exceeds .12
Atrial Fibrillation (a-Fib) SA nodal Rhythm
- Rhythm: irregularly irregular
- rate: 100-160 bpm but may be slower if on meds
- P wave and P-R interval: good luck!
- QRS duration: usually normal
Atrial flutter
SA nodal Rhythm
- Rhythm: regular
- Rate: 110 bpm
- P wave replaced with multiple F (flutter) waves (2:1 to 3:1 ratio)
- P wave/ F wave rate: 300 bpm
- QRS duration: usually normal
- caused by abnormal tissue in the atria generating rapid, repeating electrical stimulus
- similar to atrial fibrillation but flutter is much more rhythmic
Wolff-Parkinson-White (WPW Syndrome)
SA nodal Rhythm
- An accessory conduction path exists between the atria and ventricles
- bypass the AV node and the “delaying” effect of the AV node
- This rapid impulse conduction causes a “slurring” of the first part of the QRS complex; creating a Delta wave
- PR interval: short (
Supraventricular Tachycardia (SVT) Non-SA nodal Rhythms
- Tachycardia with impulses generated in the atria but NOT in the SA node
- impulses usually from tissue adjacent to the AV node
- Rhythm: regular
- Rate: 140-220 bpm
- P wave: usually buried in the preceding T wave because of the speed of the impulses
- PR interval: depends on the site of the supraventricular pacemaker source
- QRS duration: normal
Junctional Rhythm
Non-SA nodal Rhythms
- Rhythm starts at the AV junction
- Rhythm: regular
- rate: 40-60 bpm
- P wave: inverted in lead II
- P wave rate: same as QRS rate
- PR interval: variable
- QRS duration: normal
Premature Junctional Contraction (PJC)
Non-SA nodal Rhythms
- An electrical impulse starts in the ventricles
- Rhythm: regular
- Rate: normal
- QRS: normalish
- diagnosed by a big, odd QRS waveform which represents the ventricles depolarizing prematurely in response to a signal within the ventricles
- QRS vector is odd
Idioventricular Rhythm
Non-SA nodal Rhythms
- Rate: 20-40 bpm
- Rhythm: regular
- P waves: none
- PR interval: non-existent
- QRS: wide (>.10 seconds)
Accelerated Idioventricular Rhythm
Non-SA nodal Rhythms
-an idioventricular rhythm with a rate of 41-100 bpm
Unifocal Premature Ventricular Contraction (PVC)
Non-SA nodal Rhythms
-arises from single premature beat so each PVC is identicle
Multifocal premature Ventricular Contractions (PVC’s)
Non-SA nodal Rhythms
-arises from two or more premature beats so each QRS complex is different
Bigeminy
Non-SA nodal Rhythms
- One good, one bad PVC
- they repeat like that
Trigeminy
Non-SA nodal Rhythms
- Two good, one bad PVC
- they repeat like that
Quadrigeminy
Non-SA nodal Rhythms
- Three good, one bad PVC
- they repeat like that
Couplets
Non-SA nodal Rhythms
-Coupled PVC (occur in pairs
Bundle Branch Blocks (BBBs)
Non-SA nodal Rhythms
- dopolarization delay through the bundle branches causing a widening of the QRS complex
- RBBB and LBBB depending on the side the delay occurs
- ideally requires evaluation of the V1 and V6 leads
Right Bundle Branch Block (RBBB) causes
- MI, coronary artery disease CAD, cardiomyopathy, Pulmonary embolism
- V1: T wave inversion
- V6: wide S and upright T
Left Bundle Branch Block (LBBB) causes
- NEVER occurs “normally”
- Hypertension, aortic stenosis, and coronary artery disease
- V1: wide S and positive T
- V6: No initial Q
1st degree AV Block (AVB)
Non-SA nodal Rhythms
- conduction delay through the AV node (the signal eventually reaches the ventricles normally)
- prolonged PR interval (>5 small squares)
2nd degree heart block and two types
Non-SA nodal Rhythms
- some of the arterial beats get through to stimulate the ventricles
1. Mobitz type I or Wenkebach
2. Mobitz type II
Mobitz type I/ Wenkebach
like a relationship
-the PR interval keeps lengthening until a QRS complex is eventually dropped then it starts back to regular and does it again
Mobitz type II
-the PR interval remains relatively constant but intermittently atrial contractions are not always followed by ventricular contractions (a P wave not followed by QRS then back to normal)
3rd degree Heart Block (CHB)
- atrial contractions are normal but this electrical activity does not reach the ventricles
- so the ventricles must generate their own electrical activity
- ventricular escape beats have a slower rate
3rd degree Heart Block (CHB) symptoms
-Rythm: regular
-Rate: SLOW
-P wave: unrelated
-P wave rate: normal but faster than QRS rate
PR interval: VARIABLE
-QRS duration: PROLONGED
-no atrial impulses pass through the av node and the ventricles generate their own inherent rhythm
Really deadly rhythms
- ventricular tachycardia
- ventricular fibrillation
- asystole
Ventricular tachycardia (V-Tach)
- Rhythm: regular
- Rate: 180-190 bpm
- P wave: not seen
- QRS duration: prolonged
- result from abnormal tissues in the ventricles generating a rapid and irregular heart rhythm. Poor cardiac ooutput is usually associated with v-tach and causes the patient to go into cardiovascular arrest. Shock this rhythm if patient is unconscious and pulseless
V-Tach: Monophoric
-there is only one form of ventricular tachycardia
V-tach: Polymorphic
-more than one form of ventricular tachycardia
Tarsades de Points (“Twisting of the Points”)
- Looks like a twisted streamer
- QRS complex keeps cyclically reversing polarity
- represents polymorphic v-tach with long QT intervals
Ventricular Fibrillation (V-Fib)
A disorganized series of electrical signals cause the ventricles to quiver
- zero cardiac output
- brain is not perfused
- if not on bypass, the patient requires defibrillation ASAP or they die
- if on bypass, this is an unpleasant but not necessarily life-threatening cosmetic problem that must be addressed before being taken off CPB
Ventricular Fibrillation symptoms
- Rhythm: irregular
- Rate: 300+ and disorganized
- P wave: not seen
- QRS duration: not recognizable
Course ventricular fibrillation
- very bad
- larger peaks
Fine ventricular fibrillation
- worse than course ventricular fibrillation
- pre-death
- very small peaks
Asystole
- Rhythm: flat
- Rate: 0 bpm
- P wave: none
- QRS duration: none
- induced on CPB with cardioplegia
- if not on bypass, immediate CPR or death
Ischemia
- insufficient blood supply
- decreased ST segment
Injury
- heart cell damage
- increased ST segment
Infarction (necrosis)
- cellular death (apoptosis)
- Deep Q wave
Evolving MI
Ischemia to Injury leading to infarction
