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Non-Invasive Transcutaneous Pacing Application Note This Application Note provides an overview of non-invasive transcutaneous pacing. It includes a brief history of pacing, describes the electrical activity of the heart, and explains how pacing works. Non-Invasive Transcutaneous Pacing
What is Non-Invasive Transcutaneous Pacing? Non-invasive transcutaneous pacing is a technique of cardiac depolarization and myocardial contraction. electrically stimulating the heart externally through a set Pacing is one method of treating patients when their of electrode pads. The stimulus is intended to cause heart's own conduction system slows dangerously.
Electrical Activity of the Heart The unique physiologic characteristics of cardiac muscle In order for the heart to beat with a smooth and efficient cells produce intrinsic pacing and efficient conduction, pumping action, the various parts of the myocardium leading to optimal synchrony and contractility (see must contract in a well-defined sequence. The atria must contract before the ventricles, the ventricles must begin contracting near the apex, etc. An orderly sequence of The Cardiac Cycle 1
contraction during systole is provided for by specialized conductive pathways in the myocardium. These pathways consist of highly specialized myocardial cells which have the ability to conduct a depolarization wave at a much greater velocity than ordinary myocardial The normal sequence of myocardial depolarization and contraction, is described below: Ventricular systole  A cluster of highly conductive cells called the
sino-atrial (SA) node is located near the back wall of the right atrium at the SA node that the depolarization wave is normally initiated.
Approximate time (sec) Normal Myocardial Sequence
The myocardial cell membrane, like the membranes of other muscle cells in the body, has the ability to conduct a propagated action potential or depolarization wave. Likewise, depolarization of the myocardial cell membrane by a propagated action potential results in myocardial contraction. The propagation of an action potential can be initiated by intrinsic automaticity, direct electrical stimulation (i.e. transvenous or transthoracic pacing), or by a transmitted external stimulus.
The cardiac cell membrane does not require an external stimulus to reach threshold. It possesses a special ability that allows it to spontaneously depolarize at periodic From the SA node, the depolarization wave passes intervals without the need for an external stimulus. This from right to left over both atria, resulting in atrial property is called automaticity.
systole. Within 70 ms, all portions of both atria have started to contract. Electrical Activity of the Heart  The atrio-ventricular (AV) node consists of a cluster
Because our bodies require more oxygen during periods of cells leading from the lower portion of the right of physical and emotional stress, the SA node is liberally atrium to the ventricular septumhe supplied with nerve endings which can stimulate its cells AV node is highly specialized and conducts the more rapidly when necessary. Hence, during periods of depolarization wave very slowly. It delays its progress excitement, the SA node responds with a faster rate of for approximately 70 ms, which allows atrial systole depolarization and the heart rate increases to ensure the to reach completion before ventricular systole begins.
muscles have enough oxygen to cope with the sudden demand.
The properly functioning Bundle of His and Purkinje network ensure that the heart always contracts rhythmically, and therefore pumps efficiently. The fact that all conductive cells in the heart possess the capability of spontaneous depolarization provides a natural back-up pacemaking capability, in case the SA node should fail.
The progress of the depolarization wave causing the muscle contraction can be followed and recorded. The recorded ECG waveforms and their correlation to the activity of the heart are illustrated in Figureh The depolarization of the atria is represented by the P-wave). During this time, the atria contract and force blood into the ventricles. At the point labeled "Q", the ventricles begin depolarizing and contracting.  From the AV node, the depolarization wave moves to
the Bundle of His and its bundle branches. These lie Atrial Depolarization
in the ventricular septum and conduct the depolarization wave to the apex of the heart.
 From the bundle branches, the depolarization wave
rapidly travels through the Purkinje network, a fine mesh of highly conductive fibers that cover the endocardial (inner) surfaces of both ventricles.
 At this point, depolarization and contraction of the
ventricular myocardium begin. From the Purkinje network, the depolarization wave moves through the ventricular myocardium from the endocardial (inner) to the epicardial (outer) surfaces. Because of its course of travel through the bundle branches and Purkinje network, myocardial contraction begins in the ventricular septum, then moves rapidly to the apex of the heart and finally proceeds towards the base.
 As soon as the cells in the myocardium have
depolarized, they begin entering the refractory state and repolarizing. They rest until the next stimulus, which under normal conditions, is supplied by the cells in the SA node.
Non-Invasive Transcutaneous Pacing
Notice the time delay between the P-wave and Q. This is The "T" wave represents the refractory period of the the 70 ms delay introduced by the AV Node).
heart when the ventricles are repolarizing ).
AV Node Delay
Ventricular Repolarization
The time between "Q" and "S" (called the QRS complex) immediately precedes full contraction of the ventricles when blood is forced into the arterial system . Ventricular Depolarization
Application of Pacing Disease in the conduction system or failure in the symptomatic bradycardia or other arrhythmias which automaticity of the myocardial cells can lead to may necessitate pacing intervention.
Application of Pacing The following table explains the indications and Fixed Rate or Demand symptoms of emergency pacing. Pacing—Which One To Use? Indications of Emergency Pacing and
Many non-invasive transcutaneous pacemakers operate Pacing Readiness 6
in two modes: fixed rate (also referred to as asynchronous Immediate Emergent Pacing
or non-demand) and demand mode (also referred to as synchronous).
Fixed Rate Mode Pacing Hemodynamically symptomatic, compromising bradycardias that are too slow and unresponsive to In the fixed rate mode, the pace rate is set by the clinician atropine.a Symptoms can include blood pressure less regardless of the patient's intrinsic heart rate. This option than 80 mmHg systolic, change in mental status, is preferable when the ECG signal becomes extremely angina, pulmonary edema. noisy due to motion artifact or when the pacemaker is sometimes unable to sense the intrinsic beat. Bradycardia with escape rhythms unresponsive to Another reason for using the fixed rate mode is to pharmacologic therapy terminate tachyarrhythmias by overdriving the patient's Pacing for patients in cardiac arrest with profound intrinsic beat. This method has been successful in a bradycardia or PEAb due to drug overdose, acidosis, limited number of patients7,8,9. The above methods are or electrolyte abnormalities not widely used in a clinical setting. The danger with Standby pacing: prepare for pacing for specific fixed rate mode pacing is the possibility of further AMI-associatedb rhythms: exacerbating the tachyarrhythmia and triggering ventricular fibrillation9. Fixed rate mode does not sense • Symptomatic sinus node dysfunction• Mobitz type II second-degree heart block the QRS complex for the R-wave and may pace on the • Third degree heart block c T-wave, which could trigger ventricular fibrillation.
• Newly acquired left, right, or alternating BBBb or bifascicular block Demand Mode Pacing In demand mode pacing, the pacer senses the patient's intrinsic heart rate and will pace if the intrinsic signal is Override pacing of either supraventricular or ventricular tachycardia that is refractory to slower than the rate programmed by the clinician.
pharmacologic therapy or electrical cardioversion For example, if the patient's heart rate becomes slower Bradyasystolic cardiac arrest than the prescribed setting, the pacer will send an electrical stimulus. If the pacer senses that the heart rate a. Including complete heart block, symptomatic second-degree is faster than the pacing rate, it inhibits an electrical heart block, symptomatic sick sinus syndrome, drug-induced bradycardias (i.e., amiodarone, digoxin, -blockers, calcium signal. The advantages of demand mode pacing are: channel blockers, procainamide), permanent pacemaker competition between the pacemaker stimuli and the failure, idioventricular bradycardias, symptomatic atrial intrinsic heart rate is minimized, decreasing the risk of R fibrillation with slow ventricular response, refractory on T, and the number of pace pulses introduced are bradycardia during resuscitation of hypovolemic shock, and bradyarrhythmias with malignant ventricular escape minimized reducing patient discomfort. For this reason, demand mode pacing is primarily used as the default setting.
b. PEA indicates pulseless electrical activity; AMI, acute myocardail infarction; and During demand mode pacing, Philips' defibrillators BBB, bundle branch block.
detect R waves, or beats. Intrinsic beats are defined as c. Relatively asymptomatic second- or third-degree heart block those that are generated naturally by the patient. Paced can occur in patients with an inferior myocardial infarction. In (or captured) beats are defined as those that are a result of such patients pacing should be based on symptoms of delivered pacing energy.
Philips' ALS defibrillators also define the paced refractory period, which is simply a period of time after the delivery of a pace pulse. The refractory period is approximately Non-Invasive Transcutaneous Pacing
340 ms for pacing rates less than or equal to 80 pulses per algorithm to interpret R-waves, such as tall P-waves, tall minute (PPM), and approximately 240 ms for pacing T-waves, aberrantly conducted beats, and P-waves rates greater than or equal to 90 PPM.
without a conducted R-wave that follows. In most With the pacer on, the defibrillator marks intrinsic beats instances, tall T-waves and P-waves can be addressed by on the R-wave with an arrow on the Efficia DFM100. selecting different leads to minimize the P-wave or The intrinsic beats are also marked in the print strip. T-wave amplitudes relative to the R-wave amplitude. When an intrinsic beat is detected, the time interval for You may choose to display an annotated ECG with the next pace pulse starts at the intrinsic beat. If no ST/AR arrhythmia beat labels in Wave Sector 2. The intrinsic beat is detected, the time interval for the next same ECG source appearing in Wave Sector 1 may be pace pulse starts at the last pace pulse.
displayed with a six-second delay along with white Philips' defibrillators use the ST/AR Basic Arrhythmia arrhythmia beat labels. The R-waves marked in Wave Algorithm for arrhythmia analysis. This analysis provides Sector 1 are annotating the intrinsic beats that control information on your patient's condition, including heart the demand pacing function. The R-waves marked with rate and arrhythmia alarms. The lead appearing in Wave beat labels in Wave Sector 2 control the analysis and Sector 1 is used for arrhythmia analysis. Because the arrhythmia alarms. ST/AR Basic Arrhythmia Algorithm is the source needed Clinicians must not rely solely on the defibrillator's to generate heart rate and heart rate alarms, the algorithm classification of beats as intrinsic or paced to determine cannot be disabled. However, if desired, arrhythmia and electrical capture. Consider the situation where the heart rate alarms can be turned off. During arrhythmia patient's intrinsic HR is 62, and the pacer is set at a rate analysis, the ECG monitoring parameter continuously: of 60. Since the two rates are very close, pacer spikes and Optimize ECG signal quality to facilitate arrhythmia intrinsic beats may occur very close to each other for analysis. The ECG signal is continuously filtered to several seconds. In this circumstance, the defibrillator remove baseline wander, muscle artifact, and signal may think the beats are paced based on its simple timing algorithm, but in fact the beats are intrinsic and the timing coincidental. There may also be cardiac Measure signal features such as R-wave height, width, conditions which can cause a truly paced beat to fall outside of the refractory period.
Create beat templates and classify beats to aid in Capture must be determined by a clinician who is trained rhythm analysis and alarm detection.
to interpret the ECG being displayed by the defibrillator. Examine the ECG signal for ventricular arrhythmias The defibrillator's marking of beats can be used as a and asystole.
guide, but not as an absolute indication, of whether or It is impossible to design a computerized arrhythmia not capture has been achieved.
algorithm that accurately identifies R-waves 100% of the time. Several conditions can cause difficulty for the How to Implement Non-Invasive Pacing Pads Application and Placement the pads since reversing electrode pad placement increases the pacing threshold. Thus, more current will Before applying the pads, clean and dry skin sites with a be needed to capture the heart resulting in greater patient towel. It may be necessary to shave or clip excessive hair discomfort10. The most common electrode placement is in the area of the pads. Follow the manufacturer's the anterior-anterior position ). suggested placement of electrode pads. Do not reverse How to Implement Non-Invasive Pacing be viewed and exported to a data card, and the date and Anterior-Anterior Position
time may be changed. However, a password is required to change the configuration of the device. When modifying configuration settings, the device should be connected to external power and have a battery with at least 20% capacity installed. Changing Rate and Output (mA) During an Event The pacer rate can be adjusted during pacing from the
default configuration by pressing the [Pacer Rate] soft
The anterior-posterior position is also an effective key on the device and then the navigational keys to select the desired number of pace pulses per minute. The pacer output can also be adjusted during pacing from the Anterior-Posterior Position
default configuration by pressing the [Pacer Output] soft
key and then the navigational keys to:
a. Increase the output until electrical capture occurs. Electrical capture is indicated by the appearance of a QRS complex after each pacing marker.
b. Decrease the output to the lowest level that still maintains capture.
Presence of a peripheral pulse must be verified to assess mechanical capture.
During pacing, verify that arrows appear above the R-wave on the ECG waveform. A single arrow should be Monitoring Electrodes associated with each R-wave. If the arrows do not appear or do not coincide with the R-wave, select another lead. When performing demand mode pacing, the patient Press the Lead Select button to select the best lead with must be monitored through either 3- or 5-lead an easily detectable R-wave. If you are using monitoring electrodes. Philips' ALS defibrillator/ anterior-anterior pads placement while pacing and are monitors use the heart rate from this monitoring source experiencing difficulty with Lead II, select another lead. to determine if a paced pulse should be delivered. If a lead cannot be found with correct markers or arrows Monitoring electrodes are not required for fixed mode above the R-waves, then switch to fixed mode pacing.
Changing to Fixed Mode Pacing During an Setting Pacing Rate and Pacing With the Efficia DFM100, you can switch to fixed mode pacing during an event, as follows: Setting the Default Configuration  Press the [Pause Pacing] soft key and acknowledge the
The Efficia DFM100 allows you to customize the defibrillator to best meet your needs with configurable  Press the Smart Select knob and select Pacer Mode.
default pacer rate and output settings. Configuration is  Use the Smart Select knob to highlight Fixed and press
performed through Configuration mode of the device the Menu Select button. and may be saved to a data card for replication on multiple devices. At any time, configuration settings may  Press the [Resume Pacing] soft key to resume pacing in
Non-Invasive Transcutaneous Pacing
What to Look for When Pacing Therefore, a patient's response to pacing must be verified by signs of improved cardiac output, such as: a palpable pulse rate the same as the rate which pace pulses are being delivered, a rise in blood pressure, and/or improved skin Capture is defined as gaining control of the patient's dysfunctional heart by an electrical stimulus (that is, depolarization). Electrical capture can be determined by An integral or standalone pulse oximeter can be useful for observing the monitor, which should show a clear confirming capture (by comparing the pulse rate indication of the ECG and the pulse marker. Skeletal measured by the pulse oximeter to the set pacing rate) muscle contraction is not an indication that capture has and perfusion (by measuring blood oxygen saturation, been established, nor is electrical capture alone an SpO2)11. Philips' defibrillator/monitors integrate the indication of effective cardiac perfusion. The patient may optional SpO2 package into the defibrillator for speed, be suffering from pulseless electrical activity (PEA), simplicity, and convenience. The SpO2 percentage (%) previously referred to as electromechanical dissociation and SpO2 alarm violations will be recorded in the Event (EMD). When the patient is successfully paced:  electrical and mechanical capture are achieved Another important factor in effective pacing is the amount of current applied. Sufficient current must be  cardiac output may improve applied to stimulate the heart into contractions. Unlike  the patient's pulse rate is at least equal to the pacer invasive pacemakers, non-invasive pacemakers must pass electrical current through the skin and thorax. This requires significantly higher current. The higher current blood pressure may improve loads can cause the chest muscles to contract and relax  skin color may improve strenuously, which may be painful and distressing for the A pulse oximeter is a powerful tool when used in conjunction with the pacer/ECG monitor for confirming Using the lowest output setting necessary to achieve capture because both mechanical and electrical activities capture will minimize the discomfort. If the discomfort is can be measured. ECRI provided a theoretical and an intolerable, sedation and/or analgesia may be necessary.
operational overview of non-invasive pacemakers and concluded that monitoring ECG alone is not enough to Patient Discomfort verify that the patient's heart is providing cardiac output.
Pacing will likely cause some discomfort in conscious The article states that: patients. Two types of discomfort often experienced are a  Clear recognition of capture continues to be a burning sensation at the electrode site, and muscle challenge with today's non-invasive pacemakers.
contraction. Thus, setting the expectations with the patient and family is very important. This should  Artifact from skeletal muscle contractions induced by alleviate any anxiety or tension and allow the patient to pacing stimuli can mimic a captured waveform, become more relaxed. Patients should always be making verification of capture with the ECG alone comforted throughout the procedure, and sedation may be necessary. Make sure the pads are positioned according  Electrical capture does not always produce an effective to the manufacturer's recommendation. Avoid placing mechanical (cardiac) contraction.
the pads directly over lesions, injuries or large bone structures (sternum, spine, scapula). Otherwise, more pacer output will be needed to achieve capture.
Special Pacing Situations Special Pacing Situations Pediatric Pacing  Atrial flutter is faster in children than in adults. Newborns may have rates of 600 BPM with distinct If transcutaneous pacing is elected, the physiological P-waves. The usual ventricular rate in a newborn with differences between adults and pediatric patients must be atrial flutter is 200 to 300 BPM12.
 Ventricular tachycardia in infants under the age of Electrode Size per AAMI Specification two years averages 260 BPM, which is similar to the rates for supraventricular tachycardia13.
adult — total active area of both pads combined should be at least 150 cm2. Adult pads are recommended for use on children weighing 10 kg or The discomfort associated with pacing may necessitate sedation in younger conscious children.
pediatric — total active area of both pads combined should be at least 45 cm2. Recommended for use on children weighing less than 10kg. The use of Lead II is not recommended when using See ANSI/AAMI DF2-1996.
anterior-anterior lead placement.
NOTE: Unlike adult pacing, the use of pediatric
transcutaneous pacing will likely be limited for
Electrodes should be checked frequently (every thirty cardiopulmonary arrest since most complications are minutes) to avoid burns and should not be left on for precipitated by respiratory failure rather than by a more than two hours. primary cardiac problem14.
Higher Heart Rate Defibrillation During Pacing  100 BPM is considered tachycardia in adults. A heart In defibrillator/pacer combinations, Philips defibrillators rate less than 100 BPM is considered bradycardia in a will automatically terminate pacing once the defibrillator charge switch is enabled.  Supraventricular tachycardia is faster in children than in adults (the heart rate is typically 300 BPM in infants younger than three months of age). Supraventricular tachycardia is more common than ventricular tachycardia in children. Non-Invasive Transcutaneous Pacing
Troubleshooting Transcutaneous Pacing  Is there discomfort or pain during pacing?
 Check electrode/patient contact.
 Explain and set expectations with the patient on  Check electrode connections.
the procedure. Comfort and provide  ECG signal may be too noisy (see below).
encouragement to the patient.
 Is there a noisy ECG signal?
 Make sure electrodes have been applied following manufacturer's guidelines. Electrodes should not  Was the patient's skin clean and dry and excessive be placed over bone (i.e. on the sternum or hair removed prior to electrode attachment?  Was the expiration date checked before applying  Consider analgesia or sedation.
the electrodes? Dry gel will have an adverse effect on the ECG signal.
 Is there electrical capture?
 Check the electrode connections.  Pacer output may be too low. Increase pacer  Were the electrodes positioned according to the  Observe the ECG monitor and not just the patient. Electrical capture occurs when there is a  Is there redness or burns after electrode removal?
consistent ST segment and T-wave after each  Ring-shaped erythema can be expected after pacing. The appearance is similar to the erythema  Check electrode placement.
seen after receiving shocks from standard external paddle sets. The reaction may vary from patient to  Check contact between the electrode and the patient due to a number of variables: skin composition, medication at the time of pacing,  Check to see if the pacer is turned on.
age (very young and older patients may be more  Check viability of the patient.
prone to erythema), dehydration, length of time the patient was paced, and improper pads  Is there mechanical capture?
application. Case reports of burns on neonates and  Check pulse (palpate).
children have been documented. In most cases, the children had numerous other complications Check pulse oximeter (SpO2).
which may have contributed to the burns.  Check blood pressure.
Neonates in particular may be more susceptible to  Check skin color.
thermal injury than adults due to thinner skin, less hair, weaker intercellular attachments, fewer  Evaluate mental status of patient.
eccrine and sebaceous gland secretions, and an  Is the pacer not sensing heart rate in demand mode?
increased susceptibility to external irritants. To minimize thermal injury, pacing duration should Check size of R-wave. If it is too small, increase be kept to a minimum with frequent skin the ECG size.
inspection (every 30 minutes)15.
 Check to see if the pacer is turned on.
Rudd M. Basic concepts of cardiovascular physiology. Hewlett ECRI. Reprinted with permission from Health Devices, Packard Company, 1973, Mar; 7:1-8:4.
American Heart Association, ACLS Provider Manual, 2002 Garson A. "Pediatric arrhythmias. How different from Zoll P.M., "Non-invasive temporary cardiac pacing." adults?" Med. Surg. Ped., 1987; 9: 543-52.
Journal of Electrophysiology, 1987; 1:156-161.
Garson A., Smith R.T., Cooley D.A., et al. "Incessant Luck J.C., Davis D. "Termination of sustained tachycardia ventricular tachycardia in infants: Purkinje hamartomas by external non-invasive pacing." PACE, 1987; and surgical cure". J Am Col Card, publication pending. 10 Beland M.J., Hesslein P.S., Finlay C.D., et al.
Barold S.S., Falkoff M.D., Ong L.S., et al. "Termination of "Non-invasive transcutaneous cardiac pacing in children". ventricular tachycardia by transcutaneous cardiac pacing." PACE, 1987 Nov-Dec; 10:1262-70.
American Heart Journal, 1987; 114:180-182.
11 Pride H.B., McKinley D.F. "Third degree burns from the
Bartecchi C.E. "Temporary cardiac pacing — Diagnostic use of an external cardiac pacing device." Critical Care and therapeutic indications." Postgraduate Medicine, 1987 Medicine, 1990; 18(5):572-73. June; 81(8):269-77.

Non-Invasive Transcutaneous Pacing
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