Cardiac dysrhythmias
are abnormal rhythms of the heart's electrical system that can affect its ability to effectively pump oxygenated blood throughout the body.
The electrophysiologic properties of those cells regulate heart rate and rhythm and possess unique properties:
automaticity, excitability, conductivity, and contractility.
automaticity
The ability of a cell to initiate an impulse spontaneously and repetitively; in cardiac electrophysiology, the ability of primary pacemaker cells (SA node, AV junction) to generate an electrical impulse.
excitability
The ability of a cell to respond to a stimulus by initiating an impulse; also called "depolarization." In cardiac electrophysiology, it is the ability of non-pacemaker myocardial cells to respond to an electrical impulse generated from pacemaker cells and
conductivity
The ability of a cell to transmit an electrical stimulus from cell membrane to cell membrane.
contractility
The ability of a cell to contract in response to an impulse. In cardiac electrophysiology, the ability of atrial and ventricular muscle cells to shorten their fiber length in response to electrical stimulation, generating sufficient pressure to propel blo
The SA node is the heart's primary
pacemaker. It can spontaneously and rhythmically generate electrical impulses at a rate of 60 to 100 beats per minute and therefore has the greatest degree of automaticity.
electrocardiogram (ECG)
A graphic recording of the electrical current generated by the heart. The ECG provides information about cardiac dysrhythmias, myocardial ischemia, site and extent of myocardial infarction, cardiac hypertrophy, electrolyte imbalances, and effectiveness of
The relationship between the cardiac axis and the lead axis is responsible for the deflections seen on the ECG pattern:
� The baseline is the isoelectric line. It occurs when there is no current flow in the heart after complete depolarization and also after complete repolarization. Positive deflections occur above this line, and negative deflections occur below it. Deflect
For continuous ECG monitoring, the electrodes are not placed on
the limbs because movement of the extremities causes "noise," or motion artifact, on the ECG signal.
The clarity of continuous ECG monitor recordings is affected by
skin preparation and electrode quality.
Electrodes cannot be placed on
irritated skin or over scar tissue.
The P wave
is a deflection representing atrial depolarization. The shape of the P wave may be a positive, negative, or biphasic (both positive and negative) deflection, depending on the lead selected. When the electrical impulse is consistently generated from the si
The PR segment
is the isoelectric line from the end of the P wave to the beginning of the QRS complex, when the electrical impulse is traveling through the atrioventricular (AV) node, where it is delayed. It then travels through the ventricular conduction system to the
The PR interval
is measured from the beginning of the P wave to the end of the PR segment. It represents the time required for atrial depolarization as well as the impulse delay in the AV node and the travel time to the Purkinje fibers. It normally measures from 0.12 to
The QRS complex
represents ventricular depolarization. The shape of the QRS complex depends on the lead selected. The Q wave is the first negative deflection and is not present in all leads. When present, it is small and represents initial ventricular septal depolarizati
The QRS duration
represents the time required for depolarization of both ventricles. It is measured from the beginning of the QRS complex to the J point (the junction where the QRS complex ends and the ST segment begins). It normally measures from 0.04 to 0.10 second (up
The ST segment
is normally an isoelectric line and represents early ventricular repolarization. It occurs from the J point to the beginning of the T wave. Its length varies with changes in the heart rate, the administration of medications, and electrolyte disturbances.
The T wave
follows the ST segment and represents ventricular repolarization. It is usually positive, rounded, and slightly asymmetric. If an ectopic stimulus excites the ventricles during this time, it may cause ventricular irritability, lethal dysrhythmias, and pos
The U wave,
when present, follows the T wave and may result from slow repolarization of ventricular Purkinje fibers. It is of the same polarity as the T wave, although generally it is smaller. It is not normally seen in all leads and is more common in lead V3. An abn
The QT interval
represents the total time required for ventricular depolarization and repolarization. The QT interval is measured from the beginning of the QRS complex to the end of the T wave. This interval varies with the patient's age and gender and changes with the h
Artifact
is interference seen on the monitor or rhythm strip, which may look like a wandering or fuzzy baseline. It can be caused by patient movement, loose or defective electrodes, improper grounding, or faulty ECG equipment, such as broken wires or cables. Some
Analysis of an ECG rhythm strip requires a systematic approach using a six-step method facilitated by use of a measurement tool called an ECG caliper:
1 Determine the heart rate.
2 Determine the heart rhythm.
3 Analyze the P waves.
4 Measure the PR interval
5 Measure the QRS duration.
6 Interpret the rhythm.
Normal sinus rhythm (NSR) is the rhythm originating from the sinoatrial (SA) node (dominant pacemaker) that meets these ECG criteria:
� Rate: Atrial and ventricular rates of 60 to 100 beats/min
� Rhythm: Atrial and ventricular rhythms regular
� P waves: Present, consistent configuration, one P wave before each QRS complex
� PR interval: 0.12 to 0.20 second and constant
� QRS duration: 0
Sinus arrhythmia is a variant of NSR. It results from
changes in intrathoracic pressure during breathing. In this context, the term arrhythmia does not mean an absence of rhythm, as the term suggests. Instead, the heart rate increases slightly during inspiration and decreases slightly during exhalation. This
Sinus arrhythmia has all the characteristics of NSR except for its irregularity.
� Rate: Atrial and ventricular rates between 60 and 100 beats/min
� Rhythm: Atrial and ventricular rhythms irregular, with the shortest PP or RR interval varying at least 0.12 second from the longest PP or RR interval
� P waves: One P wave before each QRS
Dysrhythmias result from:
� A disturbance in the relationship between electrical conductivity and the mechanical response of the myocardium
� A disturbance in impulse formation (either from an abnormal rate or from an ectopic focus)
� A disturbance in impulse conduction (delays an
Tachydysrhythmias are
heart rates greater than 100 beats per minute.
Tachydysrhythmias are serious because they:
� Shorten the diastolic time and therefore the coronary perfusion time (the amount of time available for blood to flow through the coronary arteries to the myocardium).
� Initially increase cardiac output and blood pressure. However, a continued rise in h
The patient with a tachydysrhythmia may have:
� Palpitations
� Chest discomfort (pressure or pain from myocardial ischemia or infarction)
� Restlessness and anxiety
� Pale, cool skin
� Syncope ("blackout") from hypotension
Bradydysrhythmias occur when
the heart rate is less than 60 beats per minute.
Bradydysrhythmias can also be significant because:
� Myocardial oxygen demand is reduced from the slow heart rate, which can be beneficial.
� Coronary perfusion time may be adequate because of a prolonged diastole, which is desirable.
� Coronary perfusion pressure may decrease if the heart rate is too slo
premature complex
In the electrocardiogram, an early complex that occurs when a cardiac cell or cell group other than the sinoatrial node becomes irritable and fires an impulse before the next sinus impulse is generated. After the premature complex, there is a pause before
bigeminy
A type of premature complex that exists when normal complexes and premature complexes occur alternately in a repetitive two-beat pattern, with a pause occurring after each premature complex so that complexes occur in pairs.
trigeminy
A type of premature complex consisting of a repetitive three-beat pattern; usually occurs as two sequential normal complexes followed by a premature complex and a pause, with the same pattern repeating itself in triplets.
quadrigeminy
A type of premature complex consisting of a repetitive four-beat pattern; usually occurs as three sequential normal complexes followed by a premature complex and a pause, with the same pattern repeating itself in a four-beat pattern.
When the rate of SA node discharge is more than 100 beats per minute, the rhythm is called
sinus tachycardia
For patients with sinus tachycardia, assess for
fatigue, weakness, shortness of breath, orthopnea, decreased oxygen saturation, and decreased blood pressure. Also assess for restlessness and anxiety from decreased cerebral perfusion and for decreased urine output from impaired renal perfusion. The pati
When the sinus node discharge rate is less than 60 beats/min, the rhythm is called
sinus bradycardia
The patient with sinus bradycardia may be asymptomatic except for the decreased pulse rate. At times, however, the rhythm may not be well tolerated. Assess the patient for:
� Syncope ("blackouts" or fainting)
� Dizziness and weakness
� Confusion
� Hypotension
� Diaphoresis (excessive sweating)
� Shortness of breath
� Chest pain
The most common atrial dysrhythmias are:
� Premature atrial complexes
� Supraventricular tachycardia
� Atrial fibrillation
A premature atrial complex (PAC) occurs when
atrial tissue becomes irritable. This ectopic focus fires an impulse before the next sinus impulse is due. The premature P wave may not always be clearly visible because it can be hidden in the preceding T wave. Examine the T wave closely for any change i
The causes of atrial irritability include:
� Stress
� Fatigue
� Anxiety
� Inflammation
� Infection
� Caffeine, nicotine, or alcohol
� Drugs such as epinephrine, sympathomimetics, amphetamines, digitalis, or anesthetic agents
Supraventricular tachycardia (SVT)
involves the rapid stimulation of atrial tissue at a rate of 100 to 280 beats/min in adults. During SVT, P waves may not be visible, especially if there is a 1:1 conduction with rapid rates, because the P waves are embedded in the preceding T wave. SVT ma
paroxysmal supraventricular tachycardia (PSVT) is used when
the rhythm is intermittent. It is initiated suddenly by a premature complex such as a PAC and terminated suddenly with or without intervention.
atrial fibrillation (AF)
A cardiac dysrhythmia in which multiple rapid impulses from many atrial foci, at a rate of 350 to 600 times per minute, depolarize the atria in a totally disorganized manner, with no P waves, no atrial contractions, a loss of the atrial kick, and an irreg
For patients with AF Assess the patient for
fatigue, weakness, shortness of breath, dizziness, anxiety, syncope, palpitations, chest discomfort or pain, and hypotension. Some patients may be asymptomatic.
cardioversion
A synchronized countershock that may be performed in emergencies for hemodynamically unstable ventricular or supraventricular tachydysrhythmias or electively for stable tachydysrhythmias that are resistant to medical therapies. The shock depolarizes a cri
maze procedure
An open chest surgical technique often performed with coronary artery bypass grafting for patients in atrial fibrillation with decompensation.
The most common or life-threatening ventricular dysrhythmias include:
� Premature ventricular complexes
� Ventricular tachycardia
� Ventricular fibrillation
� Ventricular asystole
Premature ventricular complexes (PVCs), also called premature ventricular contractions,
result from increased irritability of ventricular cells and are seen as early ventricular complexes followed by a pause. When multiple PVCs are present, the QRS complexes may be unifocal or uniform, meaning that they are of the same shape or multifocal or
Three or more successive PVCs are usually called
nonsustained ventricular tachycardia (NSVT).
Ventricular tachycardia (VT), sometimes referred to as "V tach,
occurs with repetitive firing of an irritable ventricular ectopic focus, usually at a rate of 140 to 180 beats/min or more (Fig. 36-11). VT may result from increased automaticity or a re-entry mechanism. It may be intermittent (nonsustained VT) or sustain
People with more than 5000 PVCs in a 24-hour period are usually placed on
beta blockers.
Ventricular fibrillation (VF), sometimes called "V fib,
is the result of electrical chaos in the ventricles and is life threatening! Impulses from many irritable foci fire in a totally disorganized manner so that ventricular contraction cannot occur. There are no recognizable ECG deflections. The ventricles me
Ventricular asystole, sometimes called ventricular standstill,
is the complete absence of any ventricular rhythm. There are no electrical impulses in the ventricles and therefore no ventricular depolarization, no QRS complex, no contraction, no cardiac output, and no pulse, respirations, or blood pressure. The patien
If asystole occurs,
call for assistance and begin high-quality CPR immediately (unless there is a do-not-resuscitate [DNR] order). Check another ECG lead to ensure the rhythm is asystole and not fine VF, which requires immediate defibrillation. Do NOT shock asystole!
. Atrioventricular (AV) blocks exist when
supraventricular impulses are excessively delayed or totally blocked in the AV node or ventricular conduction system. Conduction may be temporarily or permanently abnormal for a number of reasons. The SA node continues to function normally, and atrial dep
The degrees of heart blocks include:
� In first-degree AV block, all sinus impulses eventually reach the ventricles.
� In second-degree heart block, some sinus impulses reach the ventricles but others do not because they are blocked.
� In third-degree heart block (complete heart block), none
Nonsurgical management of dysrhythmias includes
oxygen therapy, drug therapy, temporary pacing, cardioversion, CPR, defibrillation, and catheter ablation.
Class I antidysrhythmics
are membrane-stabilizing agents used to decrease automaticity.
type IA drugs,
which moderately slow conduction and prolong repolarization, prolonging the QT interval. These drugs are used to treat or to prevent supraventricular and ventricular premature beats and tachydysrhythmias, but they are not as commonly used as other drugs.
Type IB drugs
shorten repolarization. These drugs are used to treat or prevent ventricular premature beats, ventricular tachycardia (VT), and ventricular fibrillation (VF). Examples include lidocaine and mexiletine hydrochloride (Mexitil).
Type IC drugs
markedly slow conduction and widen the QRS complex. These agents are used primarily to treat or to prevent recurrent, life-threatening ventricular premature beats, VT, and VF. Examples include flecainide acetate (Tambocor) and propafenone hydrochloride (R
Class II antidysrhythmics
control dysrhythmias associated with excessive beta-adrenergic stimulation by competing for receptor sites and thereby decreasing heart rate and conduction velocity. Beta-adrenergic blocking agents, such as propranolol (Inderal) and esmolol hydrochloride
Class III antidysrhythmics
lengthen the absolute refractory period and prolong repolarization and the action potential duration of ischemic cells. Class III drugs include amiodarone (Cordarone) and ibutilide (Corvert) and are used to treat or prevent ventricular premature beats, VT
Class IV antidysrhythmics
slow the flow of calcium into the cell during depolarization, thereby depressing the automaticity of the sinoatrial (SA) and atrioventricular (AV) nodes, decreasing the heart rate, and prolonging the AV nodal refractory period and conduction. Calcium chan
What is usually a first-line agent in all cardiac arrests?
Epinephrine (Adrenalin)
In carotid sinus massage,
the physician massages over one carotid artery for a few seconds, observing for a change in cardiac rhythm.
temporary pacing
A nonsurgical intervention for cardiac dysrhythmia that provides a timed electrical stimulus to the heart when either the impulse initiation or the intrinsic conduction system of the heart is defective.
noninvasive temporary pacing (NTP)
Cardiac pacing that is accomplished through the application of two large external electrodes attached to an external pulse generator; used as an emergency measure to provide demand ventricular pacing in a profoundly bradycardic or asystolic patient until
invasive temporary pacemaker
A cardiac pacing system consisting of an external battery-operated pulse generator and pacing electrodes, or lead wires, that attach to the generator on one end and are in contact with the heart on the other end. Electrical pulses are emitted from the neg
Monitor for these complications of invasive temporary pacing, which may be serious and include:
� Infection or hematoma at the pacemaker wire insertion site
� Ectopic complexes (usually premature ventricular complexes [PVCs]) caused by irritability from the pacing wire in the ventricle, use of high current, or undersensing with pacemaker competition
Complications of CPR include:
� Rib fractures
� Fracture of the sternum
� Costochondral separation
� Lacerations of the liver and spleen
� Pneumothorax
� Hemothorax
� Cardiac tamponade
� Lung contusions
� Fat emboli
cardioversion
A synchronized countershock that may be performed in emergencies for hemodynamically unstable ventricular or supraventricular tachydysrhythmias or electively for stable tachydysrhythmias that are resistant to medical therapies. The shock depolarizes a cri
Nursing care after cardioversion includes:
� Maintaining a patent airway
� Administering oxygen
� Assessing vital signs and the level of consciousness
� Administering antidysrhythmic drug therapy, as prescribed
� Monitoring for dysrhythmias
� Assessing for chest burns from electrodes
� Providing e
defibrillation
An asynchronous countershock that depolarizes a critical mass of myocardium simultaneously to stop the re-entry circuit, allowing the sinus node to regain control of the heart.
radiofrequency catheter ablation
An invasive procedure that uses radiofrequency waves to abolish an irritable focus that is causing a supraventricular or ventricular tachydysrhythmia.
The nurse administers amiodarone (Cordarone) to a client with ventricular tachycardia. Which monitoring by the nurse is necessary with this drug? Select all that apply.
A. Respiratory rate
B. QT interval
C. Heart rate and rhythm
D. Magnesium level
E. Urin
QT interval
Heart rate and rhythm
Magnesium level
The nurse is caring for a client with acute coronary syndrome (ACS) and atrial fibrillation who has a new prescription for metoprolol (Lopressor). Which monitoring is essential when administering the medication?
A. ST segment
B. Heart rate
C. Troponin
D.
Heart rate
The nurse is caring for a client with atrial fibrillation. In addition to an antidysrhythmic, what medication does the nurse plan to administer?
A. Heparin
B. Atropine
C. Dobutamine
D. Magnesium sulfate
Heparin
The nurse is caring for a client on a telemetry unit with a regular heart rhythm and rate of 60; a P wave precedes each QRS complex, and the PR interval is 0.24 second. Additional vital signs are as follows: blood pressure 118/68, respiratory rate 16, and
Continue to monitor.
You are the charge nurse on the telemetry unit and are responsible for making client assignments. Which client would be appropriate to assign to the float RN from the medical-surgical unit?
A. The 64-year-old admitted for weakness who has a first-degree h
The 64-year-old admitted for weakness who has a first-degree heart block with a heart rate of 58 beats/min
A client with atrial fibrillation with rapid ventricular response has received medication to slow the ventricular rate. The pulse is now 88. For which additional therapy does the nurse plan?
A. Synchronized cardioversion
B. Electrophysiology studies (EPS)
Anticoagulation
The nurse is caring for a client with unstable angina whose cardiac monitor shows ventricular tachycardia. Which action is appropriate to implement first?
A. Defibrillate the client at 200 J.
B. Check the client for a pulse.
C. Cardiovert the client at 50
Check the client for a pulse.
A client admitted after using crack cocaine develops ventricular fibrillation. After determining unresponsiveness, which action should the nurse take next?
A. Defibrillate at 200 J.
B. Establish IV access.
C. Place an oral airway and ventilate.
D. Start c
Defibrillate at 200 J.
Which information would cause the nurse to withhold digoxin in the client with atrial fibrillation and heart failure?
A. The client has sinus tachycardia with a rate of 102.
B. The cardiac monitor shows atrial fibrillation with a heart rate of 98.
C. The
The digoxin level is 2.8 mg/dL.
In teaching clients at risk for bradydysrhythmias, what information does the nurse include?
A. "Avoid potassium-containing foods."
B. "Stop smoking and avoid caffeine."
C. "Take nitroglycerin for a slow heartbeat."
D. "Use a stool softener.
Use a stool softener.
The nurse is determining whether the client's rhythm strip demonstrates proper firing of the sinoatrial (SA) node. Which waveform indicates proper function of the SA node?
A. The QRS complex is present.
B. The PR interval is 0.24 second.
C. A P wave prece
A P wave precedes every QRS complex.
The professional nurse is supervising a nursing student performing a 12-lead electrocardiogram (ECG). Under which circumstance does the nurse correct the student?
A. The client is semirecumbent in bed.
B. Chest leads are placed as for the previous ECG.
C.
The client is instructed to breathe deeply through the mouth.
The nurse is caring for a client with heart rate of 143. For which manifestations should the nurse observe? Select all that apply.
A. Palpitations
B. Increased energy
C. Chest discomfort
D. Flushing of the skin
E. Hypotension
Palpitations
Chest discomfort
Hypotension
The nurse is caring for a client who has developed a bradycardia. Which possible causes should the nurse investigate?
A. Bearing down for a bowel movement
B. Possible inferior wall myocardial infarction (MI)
C. Client stating that he just had a cup of cof
Bearing down for a bowel movement
Possible inferior wall myocardial infarction (MI)
Diltiazem (Cardizem) administered an hour ago
How does the nurse recognize that atropine has produced a positive outcome for the client with bradycardia?
A. Client states he is dizzy and weak.
B. The nurse notes dyspnea.
C. The client has a heart rate of 42.
D. The monitor shows sinus rhythm.
The monitor shows sinus rhythm.
The nurse teaches a client with new-onset atrial fibrillation that risk factors for this dysrhythmia may include which? Select all that apply.
A. Use of beta-adrenergic blockers
B. Excessive alcohol use
C. Advancing age
D. High blood pressure
E. Palpitati
Excessive alcohol use
Advancing age
High blood pressure
What teaching does the nurse include for a client with atrial fibrillation who has a new prescription for warfarin?
A. It is important to consume a diet high in green leafy vegetables.
B. You should take aspirin or ibuprofen for headache.
C. Report nosebl
Report nosebleeds to your provider immediately.
The nurse is caring for a client with advanced heart failure who develops asystole. The nurse corrects the new graduate when the graduate offers to perform which intervention?
A. Defibrillation
B. Cardiopulmonary resuscitation (CPR)
C. Administration of a
Defibrillation
The nurse receives in report that the client with a pacemaker has experienced loss of capture. Which situation is consistent with this?
A. The pacemaker spike falls on the T wave.
B. Pacemaker spikes are noted, but no P wave or QRS complex follows.
C. The
Pacemaker spikes are noted, but no P wave or QRS complex follows.
The nurse recognizes that which intervention provides safety during cardioversion?
A. Using the defibrillator at 200 joules
B. Obtaining informed consent
C. Setting the defibrillator to the synchronized mode
D. Removing oxygen
Setting the defibrillator to the synchronized mode
Which teaching is essential for a client who has had a permanent pacemaker inserted?
A. Avoid talking on a cell phone.
B. Avoid contact sports and blows to the chest.
C. Avoid sexual activity.
D. Do not take tub baths.
Avoid contact sports and blows to the chest.
The client's rhythm strip shows a heart rate of 76 beats/min, one P wave occurring before each QRS complex, a PR interval measuring 0.24 second, and a QRS complex measuring 0.08 second. How does the nurse interpret this rhythm strip?
A. Normal sinus rhyth
Sinus rhythm with first-degree atrioventricular (AV) block
The nurse is teaching the client with a new permanent pacemaker. Which statement by the client indicates the need for further discharge education?
A. "I will be able to shower again soon."
B. "I need to take my pulse every day."
C. "I might trigger airpor
I no longer need my heart pills."'
The nurse is caring for a client with unstable angina whose cardiac monitor shows ventricular tachycardia. Which action is appropriate to implement first?
A. Defibrillate using 200 J.
B. Check the client for a pulse.
C. Cardiovert the client at 50 J.
D. A
Check the client for a pulse.