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Cardio Pulm Quiz 4

Terms in this set (71)

Cardiac cells
in the AV junctional area have automaticity and are capable of initiating impulses and controlling the heart rhythm
Junctional arrhythmias
• premature junctional contraction (PJC)
• junctional rhythm
• accelerated junctional rhythm
• paroxysmal junctional tachycardia (PJT)
atria, ventricles
When a junctional focus fires, the wave of depolarization spreads backward (retrograde)into the _______ as well as forward (antegrade) into the ________
speed
The location of the P wave
in relation to the QRS complex depends
on the __________of antegrade and retrograde
conduction
inverted
If the impulse arrives in the atria before it arrives in the ventricles, the P wave will be before the QRS complex. The P waves will be ___________ (due to retrograde depolarization of the atria) and the PR interval will be short (0.10 second or less). The QRS is normal duration
inverted, short
If the impulse arrives in the ventricles before it arrives in the atria, the P wave will be after the QRS complex. The P wave will be _________ and the PR interval will be __________ (0.10 second or less). The QRS complex is normal duration
hidden
If the impulse reaches both the atria and the ventricles at the same time, the P wave is __________ within the QRS complex and only a QRS is seen. The QRS complex is normal duration
AV
if no SA node firing ______ node acting as pacemaker
Premature junctional contraction
early beat originating in an ectopic pacemaker site in the AV junction
• that may occur before the QRS, after the QRS, or be hidden within the QRS complex
• a short PR interval of 0.10 second or less
• a normal QRS complex
and a pause following the QRS complex
PJC
the early beat is characterized by an inverted p wave
• a single beat
• every other beat (bigeminal pattern)
• every third beat (trigeminal pattern)
• every fourth beat (quadrigeminal pattern)
• in pairs
in runs of three or more
PJCs are not common and may appear as
enhanced automaticity of the AV junction
the most likely cause of PJCs is
ingestion of caffeine, alcohol, or tobacco; electrolyte imbalances; inferior wall MI, which can disrupt blood flow to the AV node; and digitalis toxicity
Conditions associated with PJCs include
Infrequent require no treatment.
Frequent are treated by correcting the underlying cause
treatment of PJCs
Junctional rhythm
originates in an ectopic pacemaker site in the AV junction
40 to 60 bpm
Junctional rhythm at a rate of
• an inverted P wave that may occur before the QRS, after the QRS, or be hidden within the QRS complex
• a short PR interval of 0.10 second or less
and a normal QRS complex
junctional rhythm is characterized by
• not a common arrhythmia.
• the normal rhythm of the AV junction.
• usually occurs when the rate of the sinus rhythm drops below the normal inherent rate of the AV junctional pacemaker.
• Conditions associated with include inferior wall MI and digitalis toxicity.
has the same identifying features as accelerated junctional rhythm and junctional tachycardia. The rhythms are differentiated by the heart rate
Facts about junctional rhythm
• The rhythm rarely requires treatment unless the rate is too slow to maintain cardiac output.
• If the rate is slow and the patient is symptomatic, atropine can be given to increase the sinus rate and override the junctional focus. Pacing may become necessary.
• Treatment should also be directed toward identifying and correcting the underlying cause
treatment of junctional rhythm
accelerated junctional rhythm
originates in an ectopic pacemaker site in the AV junction
60 to 100 bpm
accelerated junctional rhythm at a rate of
• an inverted P wave that may occur before the QRS, after the QRS, or be hidden within the QRS complex
• a short PR interval of 0.10 second or less
and a normal QRS complex
Accelerated junctional rhythm is a regular, continuous rhythm characterized by
• not a common arrhythmia.
• The mechanism responsible for this rhythm is most likely enhanced automaticity of the AV junction.
• has the same identifying features as junctional rhythm and junctional tachycardia.
The rhythms are differentiated by the heart rate
facts about accelerated junctional rhythm
• A reduction in cardiac output may be present due to the retrograde depolarization of the atria with subsequent loss of the atrial kick.
• Treatment is directed toward reversing the consequences of reduced cardiac output.
Identify and correct the underlying cause of the arrhythmia
treatment of accelerated junctional rhythm
paroxysmal junctional tachycardia
originates in an ectopic pacemaker site in the AV junction
exceeding 100 bpm
paroxysmal junctional tachycardia at a heart rate
paroxysmal junctional tachycardia
often precipitated by a PJC and commonly starts and stops abruptly
paroxysmal junctional tachycardia
may appear as a sustained, continuous rhythm or occur intermittently in runs of three or more beats
junctional tachycardia
Three or more consecutive PJCs at a rate exceeding 100 beats/minute is considered to be
• An inverted P wave that may occur before the QRS, after the QRS, or be hidden within the QRS complex
• A short PR interval of 0.10 second or less
and a normal QRS complex
paroxysmal junctional tachycardia is characterized by
• not a common arrhythmia.
• may occur due to enhanced automaticity of the AV junction or to a reentry circuit.
• Conditions associated with include damage to the AV junction from myocardial infarction (usually inferior wall MI), congestive heart failure, or digitalis toxicity.
• has the same identifying features as junctional rhythm and accelerated junctional rhythm.
The rhythms are differentiated by the heart rate
facts about paroxysmal junctional tachycardia
• A reduction in cardiac output may be present due to the ventricular rate and to the retrograde depolarization of the atria with subsequent loss of the atrial kick.
• Treatment is directed toward slowing the ventricular rate and reversing the consequences of decreased cardiac output.
Identify and correct the underlying cause of the arrhythmia
treatment of paroxysmal junctional tachycardia
av blocks
describes an arrhythmia in which there is delayed or failed conduction of impulses into the ventricles
AV node, bundle of His, or the bundle branches
The delay or interruption in impulse conduction may occur within the
normal duration
AV Blocks
The QRS complexes will be _____________ if the block is located at the level of the AV node or bundle of His
wide
AV Blocks
The QRS complexes will be ___________ if the block is located in the bundle branches
first degree AV block
Impulses are delayed in the AV node, but all are conducted to the ventricles
second degree AV block (Mobitz I and Mobitz II)
Some impulses are conducted to the ventricles and some are blocked
third degree AV block
All impulses are blocked and none are conducted to the ventricles
the wider the QRS complex and the slower the rate
the lower the block is located in the conduction system
first degree AV block
• the mildest form of AV block.
• The electrical impulse originates in the sinus node and travels normally to the AV node, where it's delayed longer than usual.
• The delay in the AV node results in a prolonged PR interval (greater than 0.20 second).
• Even though the impulse is delayed in the AV node, each impulse is conducted to the ventricles.
• The location of the conduction disorder is within the AV node and, therefore, the QRS will be of normal duration.
The underlying rhythm is usually identified along with the AV block when interpreting the rhythm (for example, normal sinus rhythm with first-degree AV block)
first degree AV block
may occur due to ischemia or injury to the AV node secondary to acute myocardial infarction (usually inferior wall MI), increased vagal tone, drug effects (calcium channel blockers, beta blockers, and digitalis), hyperkalemia, or degeneration of the conduction pathways associated with aging
first degree AV block
does not require any specific treatment, but it should be observed for progression to more serious block
• also known as Wenckebach for the 20th century physician who discovered it.
• the sinus impulse is normally conducted to the AV node, but each successive impulse has increasing difficulty passing through the AV node until, finally, an impulse does not pass through (isn't conducted).
• reflected on the ECG by PR intervals that get progressively longer and longer until a P wave appears without a QRS complex.
• A pause follows the dropped QRS complex. After each dropped beat, the cycle repeats itself.
• Because QRS complexes are periodically dropped, the ventricular rhythm is irregular.
The conduction disorder is located within the AV node and, therefore, the QRS duration is normal
second degree AV block (mobitz I)
• common following acute inferior wall MI due to ischemia of the AV node. Other causes include increased vagal tone, effects of medications (calcium channel blockers, beta blockers, digitalis), and hyperkalemia.
• Mobitz I may progress to a higher degree of AV block under certain conditions, but this is generally not the case.
Mobitz I is usually temporary and resolves spontaneously
Mobitz I
nonconducted PAC
will have an abnormal P wave and will occur prematurely
mobitz I
P wave is normal and occurs on schedule, not prematurely
• usually asymptomatic and requires no treatment.
If the ventricular rate is slow and the patient develops symptoms, symptomatic bradycardia protocols should be followed
treatment of mobitz I
mobitz II
characterized by a failure of some of the sinus impulses to be conducted to the ventricles
mobitz II
there are more than one P wave to each QRS complex (usually two or three, but sometimes more) with only one of the impulses being conducted to the ventricles
mobitz II
• This results in conduction ratios of 2:1, 3:1, or more (for every two, three, or more P waves, there is only one QRS complex)
mobitz II
rhythm is interpreted as _______________, with 2:1 AV conduction, 3:1 AV conduction, etc
mobitz II
PR intervals are consistent, with no progressive increase
the QRS complex will be of normal duration
second degree AV block
If the block is located in the bundle of His
the QRS will be wide
second degree AV block
If the block occurs in the bundle branches
• less common than Mobitz I, but more serious.
• has the potential to progress suddenly to third-degree AV block or ventricular standstill with little or no warning.
• commonly occurs with anterior wall MI. Other causes include acute myocarditis and degeneration of the electrical conduction system as seen in the elderly.
Syncopal episodes, called Stokes-Adams attacks, are associated
facts about mobitz II
mobitz II
commonly occurs with anterior wall MI. Other causes include acute myocarditis and degeneration of the electrical conduction system as seen in the elderly
• Treatment usually involves pacemaker therapy because this type of block is often permanent and progresses to third-degree AV block.
• External pacing can be used for treatment of symptomatic until transvenous pacing can be initiated.
• Unresolved will require a permanent pacemaker.
Atropine is not recommended (especially if the QRS complexes are wide) because it may result in further slowing of the ventricular rate
treatment of mobitz II
third degree AV block
also called complete heart block, there is no conduction of impulses from the atria into the ventricles
third degree AV block
The atria and ventricles beat independently of each other with no relationship between the P waves and QRS complexes
third degree AV block
The atria are usually paced by the sinus node, and the ventricles are paced by a junctional or ventricular pacemaker site
• P waves that appear across the rhythm strip, hiding inside the QRS or in the ST segment or T wave
• a highly inconsistent PR interval
• an atrial rate that's higher than the ventricular rate
and usually a regular atrial and ventricular rhythm
complete heart block is reflected on the ECG by
the AV node, the bundle of His, or the bundle branches
third degree AV block may be located in
the AV node or bundle of His
third degree AV block
The QRS will be of normal duration if the block is located in
the QRS will be wide
third degree AV block
If the block is located in the bundle branches
complete heart block
has the potential to progress suddenly to ventricular standstill with little or no warning
usually stable and resolves on its own
Third-degree AV block with inferior wall MI is
usually unstable and may require permanent pacing
Third-degree AV block with anterior wall MI is
third degree AV block, other causes
include Lyme disease, digitalis toxicity, and degeneration of the electrical conduction system
complete heart block
stokes-adams attacks are associated with
• External pacing can be used until transvenous pacing can be initiated.
• Unresolved will require a permanent pacemaker.
Atropine is not recommended with wide QRS complexes because it may result in further slowing of the ventricular rate
treatment of third degree AV block
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