Explain how the cardiac impulse travels through the heart
bundle of His
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.
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.
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.
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 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
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 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
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
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
What is the treatment for first-degree AV block.
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
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 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.
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.
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.
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.
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.
__________ is the therapy of choice for the patient with hemodynamically unstable ventricular or supraventricular tachydysrhythmias.
Synchronized cardioversion is used to deliver a countershock that is programmed to occur on the_______ of the QRS complex of the ECG.
The ___________ must be turned on when cardioversion is planned.
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
An ST-segment elevation and a pathologic Q wave may be seen on the ECG with ____________.
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
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
head-upright tilt table testing may be performed