Chapter 36: Dysrhythmias or Arrhythmias

Question 1

Electrical conduction

Answer 1

SA node-> AV node-> Bundle of His-> Bundle branches-> Purkinje fibers

Question 2

12 Lead Placement

Answer 2

10 leads. Trying to see where the problem is.
V1- 4th RICS at the sternal border
V2- 4th LICS at the sternal border
V3- 1/2 between V2 and V4
V4- 5th LICS at midclavicular line
V5- Anterior axillary line at same horizontal plane as V4
V6- Placed in mid-axillary line at same horizontal plane as V4

Question 3

Obtaining best ECG reading:

Answer 3

Properly prepare the skin: clip excessive chest hair. wipe with alcohol if skin is oily. rub the skin with dry gauze until slightly pink. if skin is diaphoretic apply a skin protectant.
Be sure the gel on the pad is still moist.
12 lead must be placed identically each time to get accurate readings.
Electrodes must be secure or will be artifact on the monitor.
Also affected by muscle activity.

Question 4

ECG Paper

Answer 4

Small square= 0.04 seconds
Large square= 0.2 seconds (5 small squares)
1 second=5 large squares
1 minute= 300 large squares
Used to calculate HR and measure time intervals
Every 3 seconds there is a marker on the ECG

Question 5

Calculating HR

Answer 5

Count # of QRS complexes in 1 minute (very time consuming, but most accurate)
6 second strip test**- count # of QRS complexes in 6 seconds and multiply that number by 10
Small block method- count # of small squares between one R-R interval, divide by 1500
Big block method- count # of large squares between one R-R interval, divide by 300

Question 6

Represents atrial contraction (depolarization)
Smooth and rounded (no peaks or notches)
0.12 seconds
Suggests problem with conduction in the atria

Answer 6

P wave

Question 7

No P wave, but consistent QRS because the AV node gives consistent beats. Atrial contraction is gone, ventricle still fills passively. Lose at least 30% of CO.
P wave can become inverted or come after the QRS complex (SA too slow, still fires but after the AV).

Answer 7

Junctional rhythm. When AV node has become the main pacemaker of the heart @ 40-60 BPM. 
Junctional regular (40-60 bpm) 
Junctional brady (60. body sends adrenergic response to get heart to speed up. still no SA node) 
Junctional tachy (>100. also adrenergic response)

Question 8

From the beginning of the P wave to the end of the PR segment.
0.20 seconds.
Represents the time it takes the electrical impulse to travel from the SA node to the ventricle.
At the end, the ventricles are starting to contract while the atria relax.
Suggests problems like heart block (>.2 sec)

Answer 8

PR interval

Question 9

Represents ventricular contraction (depolarization).
0.12 seconds (if its wide, it’s concerning)
__ wave is the first downward stroke (wide or deep suggests previous MI)
__ wave is the first positive stroke
__ wave is a negative stroke that follows a positive upward stroke
Problems are usually from bundle braces or in the ventricles.

Answer 9

QRS complex

Question 10

Measures at the end of the QRS through the beginning of the T wave.
Indicates the period of time between the end of ventricular contraction (depolarization) and the start of ventricular relaxation (depolarization)
Usually on baseline (should be no electrical activity), deviation may be indicative of myocardial ischemia, injury or infarction
If elevated, full occlusion of artery
If depressed, some blood flow through artery

Answer 10

ST segment

Question 11

Ventricular relaxation (depolarization) 
Usually follows the QRS complex and deflects in the same direction, should be smooth and rounded (no peaks or notches) 
Problems are usu from electrolyte imbalances, ischemia, or infarction 
Peaked=hyperkalemia 
Flattened with U wave=hypokalemia 
Inverted=ischemia

Answer 11

T wave

Question 12

Measured from beginning of QRS complex to end of T wave
Represents the total time for ventricular contraction and relaxation
Problems are usu from something affecting repolarization (i.e. drugs, electrolyte imbalances, changes in HR)
Want at .44 or less

Answer 12

QT interval

Question 13

Not very common and easy to overlook
Often associated with electrolyte imbalance, heart disease, or HTN
Most prominent with hypokalemia

Answer 13

U wave

Question 14

Causes of dysrhythmias

Answer 14

Problem with impulse formation:
SA node- main pacemaker of the heart, 60-100 bp
AV node- secondary pacemaker, 40-60 bpm
Purkinje fibers- tertiary pacemaker, 20-40 bp (not sustainable to life)
Ectopic foci from atria, AV node, or ventricles
Problem with conduction of beats: delays, blocks
Combination of the above

Question 15

Always cause a risk of decrease perfusion, decreased cardiac output.
Always assess the pt (not just the ECG): how is the pt tolerating the rhythm? (i.e. pulse deficit, chest pain, consciousness, HR changes, hypotension)
Causes include CAD, electrolyte imbalances, changes in heart muscle, injury from an MI, healing process after cardiac surgery, dig toxicity

Answer 15

Cardiac dysrhythmias

Question 16

Asymptomatic or mild symptoms (ie palpitations)

Answer 16

Stable

Question 17

Decreased perfusion/CO.

Pulseless, dizziness, syncope, hypotension, chest pain, SOB

Answer 17

Unstable

Question 18

Fainting. Not always c/b cardiovascular problems but can be vasovagal response or dysrhythmias.
Must consider hypoglycemia, hysteria, seizure, stroke, TIA
If we think it is cardiac:
Dx tests- echocardiogram (test ejection fraction- how much blood the heart is pumping out), stress testing (exercise or drug), may need EPS, head-up tilt-test, Holter monitor, event monitor/cardiac loop

Answer 18

Syncope

Question 19

Diagnostic tests

Answer 19

Continuous ECG monitoring 
Transesophageal echocardiogram (TEE) 
Electrophysiologic study (EPS) 
Holter monitoring 
Event monitoring (loop recorder) 
Exercise treadmill testing

Question 20

Mending a broken heart

Answer 20

Top priority in ACLS: High quality CPR and defibrillation (if indicated)
Oxygen to keep sats >94% (100% O2 if cardiac arrest)
Medications
Vagal stimulation for tachycardia (get pt to bear down)
Pacemakers for bradycardia
Defibrillation/cardioversion
Implanted cardioverter-defibrillator (ICD)
Radio frequency Catheter Ablation Therapy

Question 21

Anticholinergic drug=blocks PSNS=only SNS stimulation
For bradycardia
0.5 mg every 3-5 minutes, up to 3 mg total

Answer 21

Atropine

Question 22

For tachycardia (SVT, some VT)
Nodal-blocking agent (Causes heart to stop and hope to get out of the jolt it was in)
6 mg RAPID IVP, 2nd dose of 12 mg
Causes a brief period of systole

Answer 22

Adenosine

Question 23

For cardiac arrest to stimulate the heart
1 mg every 3-5 min or 2-10 mcg/min
Alpha1-adrenergic drug in high doses= contraction of heart

Answer 23

Epinephrine

Question 24

For recurrent VF and unstable VT
300 mg IV, 2nd dose 150 mg
Very toxic, very long half-life
Not used routinely for oral management of dysrhythmias

Answer 24

Amiodarone

Question 25

Slows conduction of electrical impulses, decreasing heart rate in SVT
Techniques: valsalva, coughing, immersing the face in ice water (diving reflex), carotid massage

Answer 25

Vagal stimulation

Question 26

Includes a power source and one or more pacing leads.
Permanent- through SC vein, leads into tissue, shocks myocardium.
Temporary- power source is outside the body:
transcutaneous (non-invasive. crash cart); transvenous (until permanent one put in. wire through SC), epicardial wires (after heart surgery)
Synchronous or asynchronous

Answer 26

Pacemakers
Failure to sense- goes off at inappropriate time.
Failure to capture- goes off but not strong enough to cause a reaction.

Question 27

Pacemaker lead wire

Answer 27

Atrial pacing: the pacing lead is inserted into the atrium to cause atrial depolarization
Ventricular pacing: the pacing lead is inserted into the ventricle to cause ventricular depolarization
A-V sequential pacing: the pacing leads are inserted into both the atrium and ventricle stimulating at set intervals

Question 28

Provides small amount of blood flow to the heart and brain, but can’t restore an organized rhythm (won’t save someone who is in VT or VF). Circulates blood and meds.
Push hard and fast. 100 compressions/minute, 2 inches deep. Switch providers every 2 min (5 cycles).
Keep interruption to a minimum.
Board under the pt for a firm surface (crash cart).
Cx: sternum and rib fractures, liver and spleen lacerations, pneumothorax, cardiac tamponade (rupture of pericardial sac)

Answer 28

CPR

Question 29

For each minute defibrillation is delayed, the change of survival is reduced by 10% (takes 8-12 minutes for first responders to arrive).

Answer 29

AEDs

Question 30

Defibrillation vs. Cardioversion

Answer 30

Both cause the heart cells to contract simultaneously interrupting abnormal electrical activity without damaging the heart and allowing the SA node to resume normal activity
Defibrillation is used ONLY for pulseless VT and VF, non synchronized delivery of energy during any phase of the cardiac cycle
Cardioversion is delivery of energy synchronized to the QRS complex, used for SVT, afib, aflutter, VT

Question 31

The sooner the better! works best when cells are not anoxic or acidotic
CPR until it is available
Turn on and select proper energy level (200 for biphasic, 360 for monophonic)
TURN OFF SYNCHRONIZER SWITCH
Apply conductive material
Charge the device, position the paddles firmly (if using paddles).
Call and look to see that everyone is “clear”
Delivery the charge
ONLY FOR PULSELESS VTACH AND VFIB

Answer 31

Defibrillation

Question 32

Synchronized circuit delivers a countershock to occur on the R wave of the QRS complex.
Procedure same as other except for:
Be sure the SYNCHRONIZER SWITCH IS ON (want the machine to pick up when you are on the QRS). Start at lower energy levels (i.e. 500-100 joules and increase as needed). If non-emergent (i.e. pt awake), sedate with Versed before. If the pt become pulseless or develops Vfib, turn off synchronization and begin defibrillation

Answer 32

Synchronized Cardioversion

Question 33

Used for pts who survive SCD, have spontaneous sustained VT, have syncope with VT/VF, are at high risk for life-threatening dysrhythmias.
Pulse generator is implanted sQ on non-dominant side with leads through the SC vein into the endocardium.
If the system senses VT or VF, it will send a 25 joule shock.
Can have combo device.
It hurts

Answer 33

Implanted Cardioverter-Defibrillator (ICD)
Pt teaching:
Discharge will feel like blow to the chest. Sit or lie down immediately if feeling faint. If it fires more than once, call EMS. Caregivers should learn CPR. If device is beeping, call Dr.

Question 34

Electrical energy is used to “burn” (ablate) ectopic areas
EPS is done first to identify the source of the dysrhythmia
Nonpharmacologic tx of choice for atrial dysrhythmias that cause rapid ventricular rates
Low complication rate
Post procedure care is similar to cardiac cath

Answer 34

Radio frequency Catheter Ablation Therapy

Question 35

After Resturn of spontaneous circulation post cardiac arrest:

Answer 35

Transport pt to higher level of care
Identify and treat the cause to prevent recurrence
Use therapeutic hypothermia if pt remains comatose (decreased temp=decreased cellular metabolism=decrease O2 workload [shift from demand to supply]).