Management of Patients With Dysrhythmias and Conduction Problems Flashcards
What are dysrhythmias?
- Disorders of formation or conduction (or both) of electrical impulses within heart
- Can cause disturbances of
— Rate
— Rhythm
— Both rate and rhythm - Potentially can alter blood flow and cause hemodynamic changes
- Diagnosed by analysis of electrographic waveform
- Electrolyes: potassium sodium, calcium (muscle): Is what’s picked up on the leads
CO: SV x HR - Beta blockers, calcium channel blockers, digoxin, keep HR low
Types of Dysrhythmias: Sinus
- Sinus bradycardia: <60
- Sinus tachycardia : >100
— Comes from the Sinus node
Types of Dysrhythmias: Atrial
- Premature atrial complex (PAC)
- Atrial flutter
- Atrial fibrillation; has pulse
- SVT
— Comes from atrial tissue, above AV node
— Kinda look like a p wave but its not. (P waves come from sinus node)
Types of Dysrhythmias: Ventricular
- Premature ventricular complex (PVC)
— Interruption in the rhythm - Ventricular tachycardia
— Electricity is fired from the ventricle
— Can be lethal, verify they have a pulse
— Check one side at a time on coraded - Ventricular fibrillation
— Will not have a pulse - Ventricular asystole
— No pulse
Normal Electrical Conduction
- SA node (sinus node: beats the heart at 60-100 bpm
- Conduction – electrical impulse quickly travels from the SA node through to the Atria to the AV node
- AV node: beats the heart at 40- 60 bpm (if SA node fails)
- Bundle of His: located on the interventricular septum
- Right and left bundle branches
- Purkinje fibers: beats the heart at 20-40 bpm (if the AV node fails)
- Depolarization = stimulation = systole
- Repolarization = relaxation = diastole
Conduction Abnormalities
- First-degree AV Block
— a delay in conduction through the AV node
— defined as a prolongation of the PR interval > 0.20 secs (>5 small boxes); PR interval is consistent/ doesn’t gradually lengthen with each beat - Second-degree AV Block, Type I (Wenckebach)
— In Mobitz type I (Wenckebach) is a progressively lengthening/ prolongation of the PR interval (gradually lengthens with each beat), until it is followed by a non-conducted/ dropped/ missed ventricular beat/ QRS complex. - Second-degree AV Block, Type II
— no progressively increasing PR interval, only a P wave with out a QRS that follows - Third-degree AV Block (complete heart block)
— no association between atrial and ventricular contractions
— P waves that do not lead to QRS waves and more P waves than QRS waves; higher atrial rate than ventricular rate
Relationship of ECG Complex, Lead System, and Electrical Impulse
Deflections on the EKG
Isoelectric line
- imaginary line that goes straight across
Positive deflection
- above
Negative deflection
- Below
ECG 12 Lead Electrode Placement
RA: right arm
RL: right leg
LL: left leg
LA: left arm
V1: on right side of heart, posterior wall
V2: center, inferior wall/ septum
V3: anterior wall, front of heart
V4: lateral wall
V5: lateral wall
Components of the Electrocardiogram
- P wave – represents the electrical impulse starting in the SA node and spreading through the Atria. Atrial depolarization
- QRS – represents ventricular depolarization
— Not all QRS complexes have all three waveforms
— Q wave is the first negative deflection after P wave
— R wave is the first positive deflection after P wave
— S wave is the first negative deflection after R wave - T wave represents ventricular repolarization
P-wave
- Begins with the firing of the Sinoatrial Node (SA node)
- Represents atrial depolarization/ contraction of the atria
PR segment:
- Signal travels to AV node, which fires after blood leaves atria
- represents the time required for the impulse to travel through the AV node, where it is delayed. And then through the bundle of His, bundle, branches, and Purkinje, fiber, network just before ventricular depolarization.
- Demonstrates the delay the AV node created
— AV node is the “gatekeeper”, giving the atria time to dump blood into the ventricles - PR segment is after P-wave
- Represents the completion of atrial depolarization
PR interval:
- Measures AV conduction time
- Normal: 0.12-0.20 secs (3-5 small boxes)
- It starts at the beginning of the P-wave, and extends to the beginning of the QRS complex
- PR interval is before P-wave
- Demonstrates the time it takes for electrical signal to go from atria to AV node
- This can be used to help determine if a patient has a heart block if too long
QRS complex:
- Represents ventricular depolarization/ contraction
- Signal travels down the Bundle of His to the bundle branches; Then travels to the purkinje fibers, and causes the ventricular depolarization/ ventricular contraction
- Atrial repolarization also occurs here, but is not visible due to size of ventricles
- Represents a ventricle depolarization and is measured from the beginning of the Q wave / end of the PR interval to the end of their S wave
- Normal: 0.06-0.12 secs (1.5 - 3 small boxes)
- Always < 0.12 secs
- Longer is a wide QRS; issue with ventricle
J Point:
represents the junction where the QRS complex ends, and the ST segment begins
ST segment:
- represents early ventricular repolarization
- Represents completion of ventricular depolarization, and the beginning of ventricular repolarization
- This segment should be flat (isoelectric) with no depression or elevation
— Isoelectric describes straight lines of the PQRST Complex, representing resting of the heart cells - Important for diagnosing MI’s (ST elevation)
T-wave:
- Represent beginning of ventricular repolarization, relaxation
- Caused by large size of ventricles as they relax
- The isoelectric line following the T- wave represents the completion of ventricular repolarization
QT interval:
- represents the total time required for ventricular, depolarization and repolarization,
- is measured from the beginning of the QRS complex to the end of the T-wave
U- wave:
- Theorized to represent late repolarization resting of Purkinje fibers
- Does not appear in all patients
- May be caused by low potassium (Hypokalemia) or dig toxicity
3 R’s:
Regularity:
- Are the ___ occurring at the same regularity as consecutive ___ on the EKG strip?
Rate:
- Count the ___ in the six second strip, then multiply by 10 to get rate
— P- wave: atrial rate
— QRS complex: ventricular rate
Resemblance:
- Do they resemble a ___?
- Are all ___, identical in how they’re appear?
- Measurement within range?
7 steps for analyzing EKG strips
- Are there any p waves present?
- How many P waves in 6 secs?
- Are the P waves regular? (Equally spaced)
- How many R waves in 6 secs?
- Are your R waves regular? (Equally spaced)
- What is the length of the PR interval? (*important for heart block)
- What is the width of the QRS complex?
5 Lead System Placement
RA: White
RL: green
LA: black
LL: red
V: brown
Lead Placement
- Clean the skin
- Abrade the surface lightly
- Attach “wires” to the “patches”
- Pull disposable electrode pads from backing
Six (6) second strip
1 small box = __ secs
0.04
3 small boxes = ___ secs
0.12
1 large box =
__ small boxes?
__ secs
- 5 small boxes
- 0.20 secs
1 sec=
__ small boxes
__ large boxes
25 small boxes
5 large boxes
1 mV= the height of how many large boxes
2
The height of 1 large box = __ mV
0.5
The Five Steps to Rhythm Interpretation
- Ask the following questions for each rhythm strip:
- Are there QRS complexes?
- Is the rhythm regular, regular but interrupted, or irregular?
- What is the heart rate?
- Are there P waves?
- What are the PR and QRS intervals?
Methods for Calculating Heart Rate
The Memory Method
- Widely used in hospitals
- Fastest method
- 300 big blocks every minute
- Count the number of big blocks between consecutive QRS complexes and divide that number into 300.
- Memorize this sequence of numbers:
— 300-150-100-75-60-50-43-37-33-30
*Normal Sinus Rhythm
*Sinus Bradycardia
Occurs when the SA node creates an impulse at a slower than normal rate.
Causes include lower metabolic needs; sleep, athlete at rest, hypothyroidism, vagal stimulation or medications
All characteristics the same as NSR except rate
*Sinus Tachycardia
Causes:
- Occurs when the sinus node creates an impulse faster than normal.
Causes: - blood loss
- hypovolemia
- exercise
- shock
- anxiety
- heart failure pain
- fever
- atropine
- caffeine
- nicotine
- illicit drugs (amphetamines, cocaine)
Premature Atrial Complex
occurs when an electrical impulse starts in the atrium before the next normal impulse of the sinus node.
*Atrial Flutter
- saw tooth appearance; regular R waves; no p waves
occurs because of a conduction defect in the atrium that causes a rapid, regular atrial impulse at a rate 250-400 bpm. - Atrial rate is regular and the ventricle rate regular but slower 70-150 as the AV node cannot conduct that fast and causes a therapeutic block
7 steps:
— Are there any p waves present? No; F waves
— How many P waves in 6 secs? Unable to determine
— Are the P waves regular? (Equally spaced): Unable to determine;
— How many R waves in 6 secs? 7; 70 bpm
— Are your R waves regular? (Equally space): yes
— What is the length of the PR interval? (*important for heart block): Unable to determine
— What is the width of the QRS complex? <0.12; narrow
*Supraventricular Tachycardia (SVT)
Cause:
Treatment:
- Catchall term for tachycardias that originate above the ventricles in either the sinus node, the atrium, or the AV Junction
- Cannot discern exact origin because P waves are not discernible
- Rate 130 or higher (usually >150)
- Regular
- P waves not discernible – cannot measure the PR
- QRS < 0.12 seconds
- Cause – Atria become “hyper” and fire early, before next sinus beat is due. Medications (stimulants, caffeine, bronchodilators), tobacco, hypoxia or heart disease.
- Treatment – Adenosine, digitalis, calcium channel blockers, beta-blockers. Elective cardioversion can also be done if unstable
*Atrial Fibrillation
irregular R waves; no p waves
- Most common sustained dysrhythmia
- Results from abnormal impulse formation that occurs when structural or electrophysiological abnormalities alter the atrial tissue causing rapid, disorganized and uncoordinated twitching of the atrial musculature (atrial dysrhythmia)
- The foci in the heart are sending multiple signals to the atrium causing them to quiver, this quivering causes blood to pool in the atria and not shoot through the valves
- This pooling creates a huge risk for a thrombi to form; huge risk for stroke/ Pulmonary Embolism
- Atrial rate is 300-600 bpm; ventricular rate is usually 120- 200 bpm in untreated (uncontrolled)
- R waves are Irregularly irregular
- You mostly see the QRS and T waves. the P waves just look like a bunch of squiggles: these squiggles are not called p waves they are called F waves or fibrillatory waves
7 steps:
- Are there any p waves present? No; only F waves
- How many P waves in 6 secs? None; unable to determine
- Are the P waves regular? (Equally spaced) unable to determine
- How many R waves in 6 secs? 14; 140 bpm
- Are your R waves regular? (Equally spaced) No; irregular
- What is the length of the PR interval? (*important for heart block) unable to determine
- What is the width of the QRS complex? Seems to be 0.04 secs (1 box);<0.12 narrow
Ectopy
- Irritable tissues discharges before the SA node
- Can be in different parts of heart, can make P and QRS look different.
- After the premature complex, there is pause before next normal complex, creating irregularity in the rhythm.
Premature Ventricular Contractions (PVC’s)
- Irritable ventricular foci
- Conducts through the ventricle before the next sinus beat
- QRS is wide (>.12) PVC
- Bigeminy, trigeminy, couplets
- > 3 In a row is called baby V-Tach
*Ventricular Tachycardia (VT)(V-tach)
Causes:
Treatment:
- Multiple PVC’s (in a row)
- Ventricular rate between 140-250 beats/min
Causes - Heart disease, electrolyte imbalance, hypoxia, side effect of drugs
- Treatment
— Amiodarone
— Cardioversion if unstable with pulse, defibrillation if pulseless
— Treat the cause.
— Supplemental potassium, oxygen.
— Automated implantable cardioverter-defibrillator (AICD) or catheter ablation
— If pulse-less CPR and Advanced Cardiac Life Support (ACLS)
Torsades de pointes
Cause:
Treatment:
- A polymorphic VT preceded by a prolonged QT interval
- Causes – Medications, low levels of potassium, calcium or magnesium
- Congenital QT prolongation
- Immediate treatment is necessary – IV Magnesium
*Ventricular Fibrillation (VF) (Vfib)
- Rapid rate of electrical discharges from many irritable ventricular foci
- Produces erratic, unrecognizable waves (fibrillation) (electrical chaos)
- Ventricular rate 350-450/min
- Ventricles provide no mechanical pumping
- A life threatening emergency
*Asystole (Ventricular)
Treatment:
- Flat line EKG
- All pacemakers have failed
- Confirm in two or more leads
Treatment - High quality CPR with minimal interruptions
- Identify underlying causes and contributing factors
- Key to successful treatment is a rapid assessment to identify possible cause known as Hs and Ts:
- hypoxia
- hypovolemia
- hydrogen ion (acid –base imbalance)
- hypo or hyperglycemia
- hyperkalemia
- hyperthermia
- trauma
- toxins
- tamponade
- tension pneumothorax
- thrombus.
Conduction Abnormalities
- What is the underlying rhythm?
- Atrioventricular blocks (AV) occur when conduction of the impulse through the AV node or bundle of his is decreased or Stopped
- Can be caused by medications, MI, cardiomyopathy
- AV block may be temporary or resolve on its own
- Permanent pacemaker may be needed
First Degree Atrioventricular Block
All atrial impulses are conducted through AV node into the ventricles at a rate slower than normal. PR > 0.20 seconds
Second Degree Atrioventricular Block, Type 1 (Wenckebach)
- Repeating pattern in which all but one of a series of atrial impulses are conducted through the AV node into ventricles. Each atrial impulse takes a longer time for conduction than the one before, until one is completely blocked.
Second Degree Atrioventricular Block, type II (Mobitz II)
- Occurs when only some of the atrial impulses are conducted through the AV node into the ventricles.
- P-P and PR remain constant (where there is a QRS)
- R-R intervals are irregular as a QRS is not conducted with every P
- Ventricular rate is lower than atrial rate
*Third-Degree AV Block (Complete Heart Block)
- Occurs when no atrial impulse is conducted through the AV node into the ventricles
- Two impulses are stimulating the heart:
— one stimulates the ventricle (QRS)
— one stimulates the atria (P wave) - AV dissociation
Pacemakers
- Electronic device that provides electrical stimuli to heart muscle
- Pacemaker leads inserted into subclavian vein, threaded into right atrium (xray done to check placement)
- Pulse generator is the machine placed in a small pouch sewn under your collar bone
- Capture: depolarization of intended chamber (QRS complex)
- Before placement:
— Blood and urine labs
— Chest xray
— EKG
— Local anesthetic - After placement
— Monitor HR and BP
— Tylenol Ibuprophen
— Dont drive for 2 weeks
Pacemaker Rhythms
Collaborative Problems and Potential Complications
- Cardiac arrest
- Heart failure
- Thromboembolic event, especially with atrial fibrillation
