• 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.
• 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.
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
Sinus Node Dysfunction:
• may be manifested as sinus arrest,sick sinus syndrome or
• is a common indication for elective permanent pacing, it is
seldom cause for emergency pacemaker insertion.
• 17% percent of patients with acute myocardial infarction
(AMI) will experience sinus bradycardia. (occurs more
frequently with inferior > anterior infarction)
• Sinus node dysfunction frequently responds to medical
therapy but requires prompt pacing if such therapy fails.
• Transvenous pacing in an asystolic or bradyasystolic
patient has little value and is not recommended
• Failure of effective pacing is primarily related to the state
of the myocardial tissue.
• 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
• 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
• Because these patients tend to progress to high-degree block
without warning, a pacemaker is often placed prophylactically
• A hemodynamically unstable patient who is unresponsive to
medical therapy should be paced promptly.
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:
RBBB with left axis deviation or other bifascicular block
Alternating bundle-branch block
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
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, β-adrenergic blockers,
Cardiac pacing is not generally effective for serious toxin-
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 patient’s condition does not
An amperage control allows the operator to vary the amount of electrical
current delivered to the myocardium, usually 0.1 to 20 mA
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
The typical pacing generator has a sensitivity setting that ranges from
about 0.5 to 20 mV
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
In the full-demand mode, however, the pacemaker senses the underlying
ventricular depolarizations, and the unit does not fire as long as the
patient’s ventricular rate is equal to or faster than the set rate of the pacing
Pacing Catheters and Electrodes
Pacing catheters, most range from 3 to 5 Fr in size and are
approximately 100 cm in length.
For emergency pacing, the semifloating bipolar electrode
catheter with a balloon tip is used most frequently
Before insertion, the balloon is checked for leakage of air
by inflating and immersing it in sterile water.
An inflated balloon helps the catheter “float” into the
heart, even in low-flow states, but is obviously not
advantageous in the cardiac arrest situation
All pacemaker systems must have both a positive (anode)
and a negative (cathode) electrode
Pacing Catheters and Electrodes
In the typical bipolar catheter used for temporary transvenous
pacing, the cathode (stimulating electrode) is at the tip of the pacing
The anode is located 1 to 2 cm proximal to the tip, and a balloon or
an insulated wire separates the two electrodes.
With a bipolar catheter, the cathode does not need to be in direct
contact with the endocardium for pacing to occur, although it is
preferable to have direct contact.
In a unipolar system, the cathode is at the tip of the pacing catheter
and the anode is located in one of three places: in the pacing
generator itself, more proximally on the catheter (outside the
ventricle), or on the patient’s chest.
The introducer set is used to enhance passage of the
pacing catheter through the skin, subcutaneous tissue, and
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.
• 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
• This route is preferred because of its easy accessibility,
close proximity to the heart, and ease in catheter
maintenance and stability
Skin Preparation and Venous Access
• Clean the skin over the venipuncture site twice with an antiseptic
solution such as chlorhexidine or povidone-iodine
• An existing central venous pressure (CVP) line can be used to place
the pacing catheter if the lumen of the catheter is large enough to
accept a guidewire.
• Withdraw the CVP line 3 to 5 cm to expose an area of sterile
• Transect the tubing through a sterile area while holding it firmly at
• Pass a guidewire through the tubing, and then withdraw the tubing
so that only the wire is left in the vein
• Connect the patient to the limb leads of an ECG machine,
and turn the indicator to record the chest (V) lead
• The distal terminal of the pacing catheter (the cathode or
lead marked “negative”,“−.” or “distal”) must be
connected to the V lead of the ECG machine
• The ECG tracing recorded from the electrode tip localizes
the position of the tip of the pacing electrode.
• If a balloon-tipped catheter is used, inflate the balloon
with air after the catheter enters the superior vena cava
(≈10 to 12 cm for a subclavian or internal jugular
• The sum of the electrical forces will be negative if the
depolarization is moving away from the catheter tip and positive if
the depolarization is moving toward the catheter tip.
• if the tip of the catheter is above the atrium, both the P wave and
QRS complex will be negative (i.e., the electrical forces of a
normally beating heart will be moving away from the catheter tip).
• As the tip progresses inferiorly in the atrium, the P wave will
become isoelectric (biphasic) and will eventually become positive
as the wave of atrial depolarization advances toward the tip of the
• Once the pacing catheter is in the desired position, deflate the
balloon by unlocking the port, observing that the syringe refills with
air spontaneously, and then removing the syringe
• At the high right atrial level, both the P wave and QRS complex are
negative. The P wave is larger than the QRS complex and is deeply
inverted (see Fig. 15-6C and D). As the center of the atrium is
approached, the P wave becomes larger and biphasic (see Fig. 15–
6E). As the catheter approaches the lower atrium (see Fig. 15-6F),
the P wave becomes smaller and upright. The QRS complex is
fairly normal. When striking the right atrial wall, an injury pattern
with a P-Ta segment is seen (Fig. 15-6G). As the electrode passes
through the tricuspid valve, the P wave becomes smaller and the
QRS complex becomes larger (see Fig. 15-6H). Placement in the
inferior vena cava may be recognized by a change in the
morphology of the P wave and a decrease in the amplitude of both
the P wave and the QRS complex
• One should avoid drawing back on the syringe because this may
rupture the balloon
• If the syringe does not refill spontaneously, the operator should
suspect that the balloon might be ruptured.
• After successful passage of the catheter into the right
ventricle,advance the tip until contact is made with the endocardial
wall. When this occurs, the QRS segment will show ST-segment
• If the pacer enters the pulmonary artery outflow tract,the P wave
again becomes negative, and the QRS amplitude diminishes
• Once ventricular endocardial contact is made, disconnect the
catheter from the ECG machine and connect the distal lead to the
negative terminal on the pacing generator
• Set the pacing generator at a rate of 80 beats/min or 10
beats/min faster than the underlying ventricular rhythm
• Select the full-demand mode with an output of about 5
• Assess the patient for electrical and mechanical capture:
Electrical capture will be manifested on the ECG monitor
as a pacer spike followed by a QRS complex
Mechanical capture means that a pacer spike with its
corresponding QRS triggers a myocardial contraction
• If complete capture does not occur or if it is intermittent,
the pacer will need to be repositioned
Catheter Placement in Low-Flow States
• If cardiac output is too low to “float” a pacing catheter or
if the patient is in extremis, there may not be enough time
to advance a pacing catheter via the previously described
• In such emergency situations, connect the pacing catheter
to the energy source, turn the output to the maximum
amperage, and select the asynchronous mode.
• Advance the catheter blindly in the hope that it will enter
the right ventricle and pacing will be accomplished
• The threshold is the minimum current necessary to obtain capture.
Ideally, it is less than 1.0 mA, and usually it is between 0.3 and 0.7
• To determine the threshold, set the pacing generator to maximum
sensitivity (full-demand mode) at 5-mA output and a rate of
approximately 80 beats/min (or at least 10 beats/min greater than
the patient’s intrinsic rate
• Reduce the current (output) slowly until capture is lost. This
current is the threshold
• Increase the amperage to 2.5 times the threshold to ensure
consistency of capture (usually between 2 and 3 mA).
• Set the rate at about 10 beats/min greater than the endogenous rhythm,
place the pacemaker in asynchronous mode (minimum sensitivity,
which is the maximum setting on the sensitivity voltage control), and
ensure that there is complete capture
• Then adjust the sensitivity control to its midposition or approximately
3 mV, and gradually decrease the rate until pacing is suppressed by
the patient’s intrinsic rhythm.
• The sensing indicator on the pacing generator should signal each time
that a native beat is sensed and should be in synchrony with each QRS
complex on the ECG monitor.
• If the pacer fails to sense the intrinsic rhythm,increase the sensitivity
(decrease the millivolts) until the pacer is suppressed
• Conversely, if the sensing indicator is triggered by P or T waves or by
artifact, decrease the sensitivity until only the QRS complex is sensed
• 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
• If an RBBB pattern is noted, coronary sinus placement or left
ventricular pacing secondary to septal penetration should be
• When the pacemaker achieves ventricular capture, there may be times
when the atria contract against a closed tricuspid valve and a cannon
• 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.
• Perforation of the ventricle is a well-described complication
that can result in loss of capture
• two-dimensional echocardiogram usually demonstrates the
catheter’s extracardiac position.
• Simply pulling the catheter back and repositioning it in the
right ventricle can usually treat uncomplicated perforation.
• During insertion of a temporary pacing catheter when a
nonfunctioning permanent catheter is in place, there is a
small risk of entanglement or knotting.
• This potential also exists with other central lines and PACs.
Even without the presence of other lines, the pacing catheter
can become knotted.
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
• TCP is indicated for the treatment of hemodynamically
significant bradydysrhythmias that have not responded to
• Hemodynamically significant implies hypotension,
anginal chest pain, pulmonary edema, or evidence of
decreased cerebral perfusion
TRANSCUTANEOUS CARDIAC PACING
• This technique is temporary and is indicated for short
intervals as a bridge until transvenous pacing can be
initiated or the underlying cause of the bradydysrhythmia
(e.g., hyperkalemia,drug overdose) can be reversed.
• 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).
• All transcutaneous pacemakers have similar basic
features.Most allow operation in either a fixed rate
(asynchronous) or a demand mode (VVI).
• Take care to avoid placing the electrodes over an implanted
pacemaker or defibrillator.
• Remove any transdermal drug delivery patches if they are in
• 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
• On females, place the electrode beneath the breast and against
the chest wall.
• Although the polarity of the electrodes does not appear to
be important for defibrillation, at least one study has
indicated that it may important be for pacing.
• 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
• Inadvertent contact with the active pacing surface results
in only a mild shock.
Pacing Bradycardiac Rhythms
• Slowly increase the output from minimal settings until capture is
• Generally, a heart rate of 60 to 70 beats/min will maintain adequate
• 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
• 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
Pacing Bradycardiac Rhythms
• Patients who are conscious or who regain consciousness
during TCP will experience discomfort because of muscle
• 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
• Overdrive pacing of ventricular tachycardia or PSVT is
performed in patients who are stable enough to tolerate
the brief delay associated with the preparation needed for
• Set the pacer rate at approximately 20 to 60 pulses/min
greater than the dysrhythmia rate
• Generally, an impulse rate of 200 pulses/min is used for
ventricular tachycardias and a rate of 240 to 280 pulses/
min is used for PSVT .
• 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