Emergency Cardiac Pacing Emergency cardiac pacing may be instituted either prophylactically or...
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Emergency Cardiac Pacing Emergency cardiac pacing may be instituted either prophylactically or therapeutically. Prophylactic indications include patients
Emergency cardiac pacing may be instituted either
prophylactically or therapeutically. Prophylactic indications
include patients with a high risk for AV block. Therapeutic
indications include symptomatic bradyarrhythmias and overdrive
pacing. Transcutaneous and transvenous are the two techniques most
commonly used in the ED.
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Because it can be instituted quickly and noninvasively,
transcutaneous pacing is the technique of choice in the ED when
time is of the essence. Transvenous pacing should be reserved for
patients who require prolonged pacing or have a very high (>30%)
risk for heart block.
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EMERGENCY TRANSVENOUS CARDIAC PACING The technique can be
performed in less than 20 minutes in 72% of patients and in less
than 5 minutes in 30%. Transcutaneous cardiac pacing (TCP) has
become the mainstay of emergency cardiac pacing and is often used
pending placement of a transvenous catheter or to determine whether
potentially terminal bradyasystolic rhythms will respond to
pacing.
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Bradycardias Sinus Node Dysfunction: may be manifested as sinus
arrest,sick sinus syndrome or sinus bradycardia is a common
indication for elective permanent pacing, it is seldom cause for
emergency pacemaker insertion. 17% percent of patients with AMI
will experience sinus bradycardia (occurs more frequently with
inferior > anterior infarction)
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Bradycardias Asystolic Arrest: Transvenous pacing in an
asystolic or bradyasystolic patient has little value and is not
recommended Cardiac pacing may be used as a last-ditch effort in
bradyasystolic patients but is rarely successful and is not
considered standard practice. Given the continued emphasis on the
importance of maximizing chest compressions during CPR,
interrupting CPR to institute emergency pacing is not
recommended
Slide 10
Bradycardias AV Block: In symptomatic patients without
myocardial infarction (MI) and in asymptomatic patients with a
ventricular rate lower than 40 beats/min, pacemaker therapy is
indicated. AV block occurring during anterior infarction is
believed to result from diffuse ischemia in the septum and
infranodal conduction tissue. Because these patients tend to
progress to high-degree block without warning, a pacemaker is often
placed prophylactically
Slide 11
Bundle Branch Block and Ischemia Bundle branch block occurring
in AMI is associated with a higher mortality rate and a greater
incidence of third degree heart block than is uncomplicated
infarction. Because of the increased risk, consider pacing for the
following conduction blocks: New-onset LBBB RBBB with left axis
deviation or other bifascicular block Alternating bundle-branch
block
Slide 12
Tachycardias Hemodynamically compromising tachycardias are
usually treated by medical means or electrical cardioversion
Supraventricular dysrhythmias,with the exception of AF, respond
well to atrial pacing. By overdrive pacing the atria at rates 10 to
20 beats/min faster than the underlying rhythm, the atria become
entrained, and when the rate is slowed, the rhythm frequently
returns to normal sinus. Overdrive pacing is especially useful for
arrhythmias with recurrent prolonged QT intervals such as those
seen with quinidine toxicity or torsades de pointes Transvenous
pacing is also useful in patients with digitalis-induced
dysrhythmias, in whom direct current cardioversion may be
dangerous
Slide 13
Cardiac Pacing for Drug-Induced Dysrhythmias Tachycardic
rhythms from amphetamines, cocaine, anticholinergics, cyclic
antidepressants,theophylline, and other drugs do not benefit from
cardiac pacing Severe bradycardia and heart block often accompany
overdose of digitalis preparations, -adrenergic blockers, and CCB
Cardiac pacing is not generally effective for serious toxin-
induced bradycardias
Slide 14
Contraindications The presence of a prosthetic tricuspid valve
is generally considered to be an absolute contraindication to
transvenous cardiac pacing Severe hypothermia will occasionally
result in ventricular fibrillation when pacing is attempted Rapid
and careful rewarming is often recommended first, followed by
pacing if the patients condition does not improve.
Slide 15
Pacing Generator An amperage control allows the operator to
vary the amount of electrical current delivered to the myocardium
increase the output improves the likelihood of capture By
increasing the sensitivity, one can convert the unit from a
fixed-rate (asynchronous mode) to a demand (synchronous mode)
pacemaker Decreasing the setting increases the sensitivity and
improves the likelihood of sensing myocardial depolarization In the
fixed-rate mode,the unit does not sense any intrinsic electrical
activity In the full-demand mode, however, the pacemaker senses the
underlying ventricular depolarizations, and the unit does not fire
as long as the patients ventricular rate is equal to or faster than
the set rate of the pacing generator
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Pacing Generator
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Pacing Catheters and Electrodes
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ECG Machine
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Introducer Sheath The introducer set is used to enhance passage
of the pacing catheter through the skin, subcutaneous tissue, and
vessel wall. The size of the pacing catheter refers to its outside
diameter, whereas the size of the introducer refers to its inside
diameter. Thus, a 5-Fr pacing catheter will fit through a 5-Fr
introducer.
Slide 20
Site Selection The four venous channels that provide easy
access to the right ventricle are the brachial, subclavian,
femoral, and internal jugular veins The right internal jugular and
left subclavian veins have the straightest anatomic pathway to the
RV and are generally preferred for temporary transvenous pacing For
subclavian,the infraclavicular approach is most commonly reported
for all temporary transvenous pacemaker insertions This route is
preferred because of its easy accessibility, close proximity to the
heart, and ease in catheter maintenance and stability
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Site Selection
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Final Assessment Assess pacemaker function again, and take a
chest film to ensure proper positioning. Ideal positioning of the
pacing catheter is at the apex of the right ventricle A 12-lead ECG
tracing should be obtained after placement of the transvenous
pacemaker. If the catheter is within the right ventricle, a left
bundle branch pattern with left axis deviation should be evident in
paced beats If an RBBB pattern is noted, coronary sinus placement
or left ventricular pacing secondary to septal penetration should
be suspected.
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Final Assessment
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Complications Therapy for catheter-induced ectopy during
insertion involves repositioning the catheter in the ventricle.
This usually stops the ectopy if after repeated attempts it is
found that the catheter cannot be passed without ectopy,myocardial
suppressant therapy may be used to desensitize the myocardium.
Simply pulling the catheter back and repositioning it in the right
ventricle can usually treat uncomplicated perforation
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Complications
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TRANSCUTANEOUS CARDIAC PACING May be preferable to transvenous
pacing in patients who have received thrombolytic agents or other
anticoagulants Although small pediatric electrodes for TCP have
been developed, experience with pediatric TCP has been limited
Though generally unsuccessful, TCP may be attempted for the
treatment of asystolic cardiac arrest. In this setting the
technique is efficacious only if used early after the onset of
arrest (usually within 10 minutes).
Slide 44
Pad Placement Take care to avoid placing the electrodes over an
implanted pacemaker or defibrillator. Remove any transdermal drug
delivery patches if they are in the way. Remove excessive hair if
time permits Place the anterior electrode (cathode or negative
electrode) as close as possible to the point of maximal impulse on
the left anterior chest wall Place the second electrode directly
posterior to the anterior electrode
Slide 45
Pad Placement There is little risk for electrical injury to
health care providers during TCP. The power delivered during each
impulse is less than 1/1000 of that delivered during defibrillation
Inadvertent contact with the active pacing surface results in only
a mild shock.
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Pacing Bradycardiac Rhythms Slowly increase the output from
minimal settings until capture is achieved Generally, a heart rate
of 60 to 70 beats/min will maintain adequate blood pressure Assess
electrical capture by monitoring the ECG tracing Assess mechanical
capture by palpating the pulse Because of muscular contractions
triggered by the pacer, carotid pulses may be difficult to assess,
so palpating the femoral pulse may be easier
Slide 48
Pacing Bradycardiac Rhythms Failure to capture with TCP may be
related to electrode placement or patient size. Patients with
barrel-shaped chests and large amounts of intrathoracic air conduct
electricity poorly and may prove refractory to capture Patients who
are conscious or who regain consciousness during TCP will
experience discomfort because of muscle contraction. Analgesia with
incremental doses of an opioid agent, sedation with a
benzodiazepine compound, or both, will make this discomfort
tolerable until transvenous pacing can be instituted
Slide 49
Complications The major potential complication of TCP is
failure to recognize the presence of underlying treatable
ventricular fibrillation. This complication is primarily due to the
size of the pacing artifact on the ECG screen A rare complication
of TCP is induction of ventricular Fibrillation. longer impulse
durations used in modern devices seem to decrease the chance of
inducing ventricular fibrillation