Dysrhythmias

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Heart Dysrhythmias, Nursing management, chapter 36

Explain how the cardiac impulse travels through the heart

SA node
atrial contraction
AV node
bundle of His
Purkinje fibers
ventricular contraction.

Components of the autonomic nervous system that affect the heart are the

right and left vagus nerve fibers of the parasympathetic nervous system and fibers of the sympathetic nervous system.

Six of the 12 ECG leads measure

electrical forces in the frontal plane (leads I, II, III, aVr, aVl, and aVf).

Leads (V1 through V6) measure the electrical forces in the

horizontal plane (precordial leads).

Continuous ECG monitoring is done using leads

II, V1, and MCL1.

MCL1 is a modified chest lead that is similar to V1 and is used when only

three leads are available for monitoring.

________ _______ involves the observation of a patient's HR and rhythm to rapidly diagnose dysrhythmias, ischemia, or infarction.

Telemetry monitoring

on the ECG- represents the depolarization of the atria , causing atrial contraction.

The P wave

On the ECG-represents the time period for the impulse to spread through the atria, AV node, bundle of His, and Purkinje fibers.

The PR interval

on the ECG - represents depolarization of the ventricles

The QRS complex

on the ECG - represents the time it takes for depolarization.

QRS interval

on the ECG - represents the time between ventricular depolarization and repolarization.

The ST segment

This segment should be flat or isoelectric and represents the absence of any electrical activity between these two events.

the ST segment

on the ECG - represents repolarization of the ventricles.

The T wave

on the ECG - represents the total time for depolarization and repolarization of the ventricles.

The QT interval

the SA node spontaneously discharges _______times per minute

60 to 100

area outside the normal conduction pathway in the atria, AV node, or ventricles.

ectopic focus

a high-resolution ECG used to identify the patient at risk for developing complex ventricular dysrhythmias.

Signal-averaged ECG (SAECG)

This type of study identifies different mechanisms of tachydysrhythmias, heart blocks, bradydysrhythmias, and causes of syncope.

An electrophysiologic study (EPS)

parasympathetic drugs do what to the heart rate

slow it down

Disease states associated with sinus bradycardia are

hypothyroidism, increased intracranial pressure, obstructive jaundice, and inferior wall myocardial infarction (MI).

Treatment for bradycardia are

atropine (an anticholinergic drug) for the patient with symptoms.
Pacemaker therapy may be required.

Treatment for tachycardia are

to treat the underlying problem

Define: Premature atrial contraction (PAC)

a contraction originating from an ectopic focus in the atrium in a location other than the sinus node.

Clinical associations. PACs can result from:

emotional stress or physical fatigue; from the use of caffeine, tobacco, or alcohol; from hypoxia or electrolyte imbalances; and from disease states such as hyperthyroidism, chronic obstructive pulmonary disease (COPD), and heart disease including coronary artery disease (CAD) and valvular disease.

In healthy persons, isolated PACs are not significant. In persons with heart disease, frequent PACs may indicate

enhanced automaticity of the atria or a reentry mechanism and may warn of or initiate more serious dysrhythmias.

Paroxysmal supraventricular tachycardia (PSVT)

a dysrhythmia originating in an ectopic focus anywhere above the bifurcation of the bundle of His.

PSVT occurs because of

a reentrant phenomenon and is usually triggered by a PAC.

What is a a reentrant phenomenon

reexcitation of the atria when there is a one-way block

In the normal heart, PSVT is associated with

overexertion, emotional stress, deep inspiration, and stimulants such as caffeine and tobacco. It is also associated with rheumatic heart disease, digitalis toxicity, CAD, and cor pulmonale.

Prolonged PSVT with HR greater than 180 beats/minute may precipitate

a decreased Cardiac Output, resulting in hypotension, dyspnea, and angina.

Treatment for PSVT includes

vagal stimulation and drug therapy (i.e., IV adenosine).

_________ is an atrial tachydysrhythmia identified by recurring, regular, sawtooth-shaped flutter waves that originate from a single ectopic focus in the right atrium.

Atrial flutter

Atrial flutter is associated with what diseases and drugs

CAD, hypertension, mitral valve disorders, pulmonary embolus, chronic lung disease, cor pulmonale, cardiomyopathy, hyperthyroidism, and the use of drugs such as digoxin, quinidine, and epinephrine.

High ventricular rates (over 100/minute) and the loss of the atrial "kick" can decrease what and cause what

CO and cause serious consequences such as chest pain and HF.

atrial contraction reflected by a sinus P wave

atrial "kick"

Why are patients with atrial flutter at increased risk of stroke

because of the risk of thrombus formation in the atria from the stasis of blood.

The primary goal in treatment of atrial flutter is to

slow the ventricular response by increasing AV block.

total disorganization of atrial electrical activity due to multiple ectopic foci resulting in loss of effective atrial contraction.

Atrial fibrillation

Atrial fibrillation usually occurs in the patient with underlying heart disease, such as

CAD, rheumatic heart disease, cardiomyopathy, hypertensive heart disease, HF, and pericarditis

Besides underlying heart disease, atrial fibrilation can be caused by

thyrotoxicosis, alcohol intoxication, caffeine use, electrolyte disturbances, stress, and cardiac surgery.

Atrial fibrillation can often result in

a decrease in CO, and thrombi may form in the atria as a result of blood stasis.
An embolized clot may develop and pass to the brain, causing a stroke.

The goals of treatment for A Fib include

a decrease in ventricular response and prevention of cerebral embolic events.

dysrhythmias that originate in the area of the AV node

Junctional dysrhythmias

Why do junctional dysrhythmias originate in area of the AV node.
When this happens, what becomes the hearts pacemaker

primarily because the SA node has failed to fire or the signal has been blocked.
In this situation, the AV node becomes the pacemaker of the heart.

Junctional premature beats are treated in a manner similar to that for

PACs.

Other junctional dysrhythmias include

junctional escape rhythm, accelerated junctional rhythm, and junctional tachycardia

junctional escape rhythm, accelerated junctional rhythm, and junctional tachycardia are treated according to

the patient's tolerance of the rhythm and the patient's clinical condition.

Junctional dysrhythmias are often associated with

CAD, HF, cardiomyopathy, electrolyte imbalances, inferior MI, and rheumatic heart disease, and drugs such as digoxin, amphetamines, caffeine, nicotine

a type of AV block in which every impulse is conducted to the ventricles but the duration of AV conduction is prolonged.

First-degree AV block

First-degree AV block is associated with

MI, CAD, rheumatic fever, hyperthyroidism, vagal stimulation, and drugs such as digoxin, b-adrenergic blockers, calcium channel blockers, and flecainide.

First-degree AV block is usually not serious but can be a precursor of ____________. Patients with first-degree AV block are ____________.

higher degrees of AV block
asymptomatic

What is the treatment for first-degree AV block.

NONE
Patients should continue to be monitored for any new changes in heart rhythm.

a gradual lengthening of the PR interval. It occurs because of a prolonged AV conduction time until an atrial impulse is nonconducted and a QRS complex is blocked or missing

Second-degree AV block, Type I (Mobitz I or Wenckebach heart block)

Type I AV block may result from

myocardial ischemia or infarction
use of drugs such as digoxin or b-adrenergic blockers.
CAD and other diseases that can slow AV conduction.

______ is almost always transient and is usually well tolerated. However, it may be a warning signal of a more serious AV conduction disturbance.

First-degree AV block
Second-degree AV block, Type I (Mobitz I or Wenckebach heart block)

If the patient is symptomatic Second degree Type I, what is used to treat

atropine is used to increase HR, or a temporary pacemaker may be needed.

_______________ involves a P wave that is nonconducted without progressive antecedent PR lengthening.

Second-degree AV block, Type II (Mobitz II heart block)

This almost always occurs when a block in one of the bundle branches is present.

Second-degree AV block, Type II

The type of block in which a certain number of impulses from the SA node are not conducted to the ventricles.

Type II second-degree

Type II AV block is associated with

rheumatic heart disease, CAD, anterior MI, and digitalis toxicity.

Type II AV block often progresses to

third-degree AV block and is associated with a poor prognosis.

What may be done before the insertion of a permanent pacemaker if the patient becomes symptomatic (e.g., hypotension, angina)

temporary transvenous or transcutaneous pacemaker.

This constitutes one form of AV dissociation in which no impulses from the atria are conducted to the ventricles.

Third-degree AV block, or complete heart block

Third-degree AV block is associated with

severe heart disease, including CAD, MI, myocarditis, cardiomyopathy, amyloidosis and scleroderma.

Third-degree AV block almost always results in

reduced CO with sycope, subsequent ischemia, HF, and shock

Syncope from third-degree AV block may result from

severe bradycardia or even periods of asystole.

Treatment for Third-degree AV block

pacemaker

Premature ventricular contraction (PVC)

a contraction originating in an ectopic focus in the ventricles.

PVCs are associated with what drugs? what disease? what else?

stimulants such as aminophylline, epinephrine, isoproterenol, and digoxin, caffiene, alcohol, nicotine
Associated with electrolyte imbalances, hypoxia, fever, exercise, and emotional stress.
Disease states include MI, mitral valve prolapse, HF, and CAD.

Drugs that treat PVS's include

b-adrenergic blockers, procainamide, amiodarone, or lidocaine (Xylocaine).

________ is a run of three or more PVCs. It occurs when an ectopic focus or foci fire repetitively and the ventricle takes control as the pacemaker.

Ventricular tachycardia (VT)

____ is a life-threatening dysrhythmia because of decreased CO and the possibility of deterioration to ventricular fibrillation, which is a lethal dysrhythmia.

VT

VT is associated with

MI, CAD, significant electrolyte imbalances, cardiomyopathy, mitral valve prolapse, long QT syndrome, digitalis toxicity, and CNS disorders.

VT can be stable eg.(_________) or unstable eg.(__________).

patient has a pulse
patient is pulseless

What is the treatment for VT

Precipitating causes must be identified and treated (e.g., electrolyte imbalances, ischemia).

irregular undulations of varying shapes and amplitude. Mechanically the ventricle is simply "quivering," and no effective contraction, and consequently no CO, occurs.

ventricular fibrilation

What can cause a V fib

acute MI and myocardial ischemia and in chronic diseases such as CAD and cardiomyopathy.

What is the treatment for V Fib

CPR and advanced cardiac life support (ACLS) measures with the use of defibrillation and definitive drug therapy.

Asystole

The total absence of ventricular electrical activity. No ventricular contraction occurs because depolarization does not occur.

Asystole is a lethal dysrhythmia that requires immediate treatment consisting of

CPR with initiation of ACLS measures (e.g., intubation, transcutaneous pacing, and IV therapy with epinephrine and atropine).

describes a situation in which electrical activity can be observed on the ECG, but there is no mechanical activity of the ventricles and the patient has no pulse.

pulseless electrical activity (PEA)

Prognosis and treatment of PEA

Prognosis is poor unless the underlying cause can be identified and quickly corrected.
Treatment begins with CPR followed by intubation and IV therapy with epinephrine.

The majority of SCDs (sudden cardiac deaths) result from

ventricular dysrhythmias, specifically ventricular tachycardia or fibrillation.

PRODYSRHYTHMIA

Antidysrhythmia drugs may cause life-threatening dysrhythmias similar to those for which they are administered.

The patient who has severe ________ is the most susceptible to prodysrhythmias.

left ventricular dysfunction

______ the most effective method of terminating VF and pulseless VT.

Defibrillation

Explain defibrilation

shock through the heart to depolarize the cells of the myocardium. The intent is that subsequent repolarization of myocardial cells will allow the SA node to resume the role of pacemaker.

defibrillators that have rhythm detection capability and the ability to advise the operator to deliver a shock using hands-free defibrillator pads.

AED's

__________ is the therapy of choice for the patient with hemodynamically unstable ventricular or supraventricular tachydysrhythmias.

Synchronized cardioversion

Synchronized cardioversion is used to deliver a countershock that is programmed to occur on the_______ of the QRS complex of the ECG.

R wave

The ___________ must be turned on when cardioversion is planned.

synchronizer switch

IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR (ICD) is used for patients who fill these 4 quota

(1) have survived SCD
(2) have spontaneous sustained VT
(3) have syncope with inducible ventricular tachycardia/fibrillation during EPS
(4) are at high risk for future life-threatening dysrhythmias (e.g., have cardiomyopathy).

Where is the ICD lead system placed?

via a subclavian vein to the endocardium, usually over the pectoral muscle on the patient's nondominant side.

How long after the ICD detects a lethal dysrhythmia does the defibrillating mechanism deliver a shock to the patient's heart. What happens if unsucsessful?

Approximately 25 seconds
it keeps on hittin'

a pacing technique that resynchronizes the cardiac cycle by pacing both ventricles, thus promoting improvement in ventricular function.

Cardiac resynchronization therapy (CRT)

There are three types of temporary pacemakers with the power source outside the body:

transvenous, epicardial, and transcutaneous

is considered the nonpharmacologic treatment of choice for AV nodal reentrant tachycardia, reentrant tachycardia, and for control the ventricular response of certain tachydysrhythmias.

RADIOFREQUENCY CATHETER ABLATION THERAPY

Typical ECG changes seen in myocardial ischemia include

ST-segment depression and/or T wave inversion.

The typical ECG change seen during myocardial injury is

ST-segment elevation.

An ST-segment elevation and a pathologic Q wave may be seen on the ECG with ____________.

myocardial infarction

Patient monitoring guidelines for patients with suspected ACS include

continuous, multilead ECG and ST-segment monitoring.

a brief lapse in consciousness accompanied by a loss in postural tone

Syncope

The causes of syncope can be categorized as what 2 main catagories?

cardiovascular or noncardiovascular.

Common cardiovascular causes of syncope include

(1) neurocardiogenic syncope or "vasovagal" syncope (e.g., carotid sinus sensitivity)
(2) primary cardiac dysrhythmias (e.g., tachycardias, bradycardias).

Noncardiovascular causes can include

hypoglycemia, hysteria, unwitnessed seizure, and vertebrobasilar transient ischemic attack.

The diagnostic workup for a patient with syncope from a suspected cardiac cause begins with ruling out structural and/or ischemic heart disease by using

Echocardiography and stress testing
EPS
head-upright tilt table testing may be performed
Holter monitors

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