update on implantable pacemakersdownloads.lww.com/wolterskluwer_vitalstream_com/... · pacemakers...

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Journal of Cardiovascular NursingVol. 20, No. 4, pp 261–268 ❘ © 2005 Lippincott Williams & Wilkins, Inc.

The goal of pacemaker therapy at its most basiclevel is to support the cardiac electrical system in

the initiation or conduction of impulses, but pace-makers are also employed in the treatment of certainforms of syncope and cardiomyopathy. Pacemakersmay be single- or dual-chamber, to provide atrioven-tricular (AV) synchrony, or biventricular, to improveventricular synchronization. Advanced nurse clini-cians should have a basic understanding of pace-maker function, indications for implantation, and anawareness of potential complications as well as facil-ity with basic troubleshooting.

The first pacemaker was implanted in 1958.1 In theinterim, the pacemaker has evolved from a large, cum-bersome device that only paced asynchronously into asmall, very sophisticated device that can be synchro-nized with intrinsic electrical activity. The first dual-chamber pacemakers were introduced in 1969. Theseearly models paced both the right atrial and ventricu-lar chambers of the heart but only sensed ventricular

Update on ImplantablePacemakersJennifer Woodruff, BSN, RNLiza A. Prudente, MSN, RN, ACNP-C

There are currently more than 3 million patients worldwide with implanted pacemakers, andindications for implants are expanding. Pacemakers today are smaller (23–30 g) and fashionedin a more physiologic shape so as to be less obtrusive. They are replete with sophisticateddiagnostic and programming features that make troubleshooting of complicated arrhythmiaseasier. Advanced nurse clinicians need to have a basic understanding of pacemaker function,indications for implantation, an awareness of potential complications, and facility with basictroubleshooting. The purpose of this article is to describe the features of the pacemakersavailable today and approaches to troubleshooting these devices.

KEY WORDS: conduction disorders, implant indications, pacemakers, programming

events. In 1978, a pacemaker was introduced thatallowed both pacing and sensing in the atrium andventricle to provide AV synchrony and mimic thebody’s response to physiologic needs.2 The pacemak-ers of today, whether single- or dual-chamber, havemultiple programming features. These features includeprogrammable lead configuration, event-electrogramstorage, rate responsiveness to adapt heart rate tophysiologic needs, and automatic mode switchingwhen an atrial tachycardia is detected. Indications forpacemaker implantation have expanded to includebiventricular pacing in heart failure patients toimprove ventricular synchronization and heart failuresymptoms. Currently, there are 500,000 patients withpacemakers in the United States, and that number willlikely increase with the broadened indications, makingit imperative that all clinicians have a basic knowledgeof pacemaker function and follow-up.3,4

Pacemaker SystemThe pulse generator (pacemaker), about the size of aman’s wristwatch, is constructed of titanium and con-tains a lithium battery along with the electronic cir-cuitry that controls the pacing system. Battery lifevaries from 5 to 10 years and is dependent on outputvoltage, resistance to current, pacing rate, and theamount of time the patient is pacing.1,4 Implantationof the pacemaker system involves obtaining venous

Jennifer Woodruff, BSN, RNDevice Nurse, Electrophysiology, University of Virginia HealthSystem, Charlottesville, Va.

Liza A. Prudente, MSN, RN, ACNP-CNurse Practitioner, Electrophysiology, University of Virginia HealthSystem, Charlottesville, Va

Corresponding authorJennifer Woodruff, BSN, RN, University Of Virginia Health System,Charlottesville, VA.

262 Journal of Cardiovascular Nursing ❘ July/August 2005

access through the subclavian or cephalic veins andcreating a subcutaneous device pocket in the subclav-icular area via a small cutaneous incision. The leadsare passed transvenously into the intended cardiacchambers and anchored to the myocardium either bysoft tines or a tiny screw. These leads, which connectthe pulse generator to the myocardium, consist of a tipelectrode and an insulated wire conductor. Most leadstoday are bipolar, such that a single lead has both apositive (anode) and a negative pole (cathode) to com-plete the circuit. The tip electrode, serving as the cath-ode, is located at the distal end of the lead, while theanode (ring electrode) is typically located about 10mm above the tip of the lead. Maintaining a reliableconnection between the tip and the myocardium isimportant for preventing many pacemaker problems.Today, most leads are steroid eluting, which decreasesthe inflammation at the tip-myocardium interface,thereby improving chronic pacing thresholds.5

Basic FunctionThe basic function of the pacemaker is to pace theheart in the absence of intrinsic impulses and to senseintrinsic cardiac electrical activity if present andinhibit pacing. The way in which a pacemaker func-tions within each chamber, by either pacing or sens-ing, or both, is dependent on the mode of pro-grammed operation. Pacemakers are coded by a spe-cific abbreviation according to the type of pacemakerand mode of pacing, as defined by the NorthAmerican Society of Pacing and Electrophysiologyand the British Pacing and Electrophysiology group.The mode is usually noted by a 3- or 4-letter desig-nation such as VVI. The first letter refers to thechamber(s) being paced (Atrium, Ventricle, or both,labeled Dual) and the second letter refers to thechamber(s) being sensed or monitored for intrinsicelectrical activity. The third letter refers to theresponse to a sensed event (Inhibit pacing output,Triggered pacing after a sensed event, or Dualresponse), the fourth letter represents the presence ofrate responsiveness (R). Thus, a pacemaker pro-grammed to a DDDR mode would have the capabil-ity to pace in both the atrium and ventricle, sense inboth the atrium and ventricle, be both inhibited andtriggered by sensed events, and have rate responsive-ness capabilities. A single-chamber pacemaker stimu-lates or paces the atria or ventricles on the basis of aprogrammed timing interval rather than in responseto a sensed impulse, but will inhibit pacing if anintrinsic impulse is sensed. Dual-chamber devicestime the delivery of ventricular stimuli relative tosensed atrial depolarizations to maintain AV syn-chrony. Single-chamber pacing is often a reasonableintervention for treatment of some disorders.

However, a variety of hemodynamic studies havedocumented a 10% to 53% improvement in cardiacoutput with AV sequential pacing compared tosingle-chamber ventricular pacing.6,7

Indications for ImplantationThe most common reason for pacemaker implanta-tion is sinus node dysfunction (SND), an abnormalityof the collection of cells in the upper right atrium(sinus node) that initiate the electrical impulsesresponsible for a regular heartbeat.8 In this condition,these cells fail to generate impulses appropriately,leading to bradycardia or paroxysms of tachycardiathat alternate with periods of bradycardia (tachy-brady syndrome). Sinus node dysfunction can mani-fest as sinus bradycardia, sinoatrial nodal block, sinusarrest, chronotropic incompetence, tachy-brady, orasystole3,4,6,9 (Fig 1), and it can occur in individuals ofany age, but is more commonly seen in elders becausethe number of cells in the sinus node diminish overtime as the body ages.8 When symptoms such asfatigue, shortness of breath, dizziness, or syncope arepresent, the term sick sinus syndrome is used.Symptoms, regardless of the type of sinus node dys-function, justify implantation of a pacemaker.

Another common reason for pacemaker implanta-tion is atrioventricular heart block (AV block).Possible causes for AV block include certain drugs,myocardial infarction (MI), coronary artery disease(CAD), cardiomyopathy, primary disease of the con-duction system, and congenital anomaly. A conditionin which the conduction of electrical signals from theatria to the ventricles is impaired, AV block is classi-fied on the basis of the extent and location of thisbreak in the electrical conduction: first-, second-, orthird-degree AV block, or AV block above or belowthe His bundle. Generally, first-degree AV block isnot considered an indication for pacemaker implant.However, in some cases such as when a patient devel-ops symptoms (pseudo–pacemaker syndrome) as theprolonged PR interval creates an alteration in atrialand ventricular timing and synchronization, a pace-maker will be implanted for first-degree AV block.10

FIGURE 1. SND-sinus Arrest.

Pacemaker Update 263

Second-degree heart block involving delayed conduc-tion may be treated with cardiac pacing if the patientis symptomatic. Even in the absence of symptoms,the higher-degree AV blocks (Mobitz II and Type III)or those located below the His bundle are typicallytreated with pacemaker implantation because of thepotential for complete loss of conduction to the ven-tricles (Fig 2). The risk for the development of third-degree heart block increases with the existence of dif-ferent types of fascicular block. Right bundle branchblock by itself is usually a benign condition.However, a combination of right bundle branchblock and conduction block of one of the left ven-tricular bundle branches (anterior or posterior) hasmore clinical significance.3,6,11

There are some additional, albeit less common,indications for pacemaker implantation, includingneurocardiogenic syncope, hypertrophic obstructivecardiomyopathy and, most recently, congestive heartfailure and wide QRS. Syncope is a common disorderthat accounts for approximately 6% of all hospitaladmissions.6 Thought to be neurally mediated inmany patients, neurocardiogenic or vasovagal syn-cope can include vasodepression (blood pressuredrop) and cardioinhibition (heart rate drop).Exaggerated response of the sympathetic nervoussystem to a variety of different stimuli, such as pres-sure on the carotid sinus (carotid sinus hypersensitiv-ity), pain, swallowing, or defecation can lead topresyncope or frank syncopal spells. Pacemakerimplantation is a treatment option, and it appearsthat dual-chamber pacemakers are better than single-chamber for treatment.12–14 Particularly appropriatefor treating this condition are pacemakers that havea “rate-drop response” feature. This feature allowsan interval of relatively rapid pacing to be initiated,when the heart rate drops suddenly below a set rate.The algorithm may also combine this element with atrigger to intervene on the basis of the rate of fall ofthe heart rate as well.12,15

Patients with severely symptomatic hypertrophicobstructive cardiomyopathy may benefit from theimplantation of a dual-chamber pacemaker. In thisdisorder, there is excessive myocardial hypertrophy,

especially in the area of the interventricular septumthat impedes diastolic relaxation and, consequently,ventricular filling owing to the noncompliant andthickened nature of the ventricle. Pacing induces abeneficial effect by causing paradoxical septal motion,ventricular dyssynchrony, and dilatation, whichimproves ventricular filling in this population. Thisimprovement in ventricular filling and reduction of theoutflow tract gradient can be optimized by adjustingthe AV interval using echo/Doppler guidance.2,16 Thebest outcomes are achieved by using dual-chamberpacing with a short AV interval (usually 50–125 ms)to allow for maximal ventricular preexcitation.2

Most recently, the indications for pacemakerimplantation have broadened to include biventricularpacing or cardiac resynchronization therapy toimprove hemodynamics, quality of life, and perhapsreduce morbidity for patients with class III–IV heartfailure and wide QRS.17–19 Approximately 25% to30% of patients with heart failure have intraventric-ular conduction delay (QRS � 120 ms), typically aleft bundle branch block, which leads to ventriculardyssynchrony. Ventricular dyssynchrony has beenshown to lead to a significantly increased risk ofmortality.20 Cardiac resynchronization or coordina-tion of ventricular activation is accomplished byadding a third lead, a left ventricular lead, placed viathe coronary sinus and positioned in a small vein offthe coronary sinus (posterolateral or anterolateral).In patients with ejection fraction less than 35%, wideQRS, and class III–IV heart failure, ventricular resyn-chronization with biventricular pacing significantlyimproves left ventricular emptying and ejection frac-tion, in addition to improving exercise tolerance, dis-tance walked in 6 minutes, and quality-of-life meas-urements.18,21 Importantly, cardiac efficiency isincreased because improvements in systolic functionis achieved at the same time that myocardial con-sumption is decreased.22 Moreover, a meta-analysisof several studies of cardiac resynchronization ther-apy showed a significant reduction in all-cause mor-tality for this group of patients.23

ComplicationsApproximately 4% to 5% of patients develop acomplication during or following pacemakerimplant,9 related to venous access, lead placement orpocket formation, and healing. As one of the pre-ferred sites of introduction for the transvenousleads, subclavian access can be complicated bycatheter needle or introducer injury to structures inthe vicinity of the vein, including the lung, subcla-vian artery, thoracic duct, and nerves. The 2 mostcommon complications that occur during access arepneumothorax or hemothorax. Likewise, the pacing

FIGURE 2. Second-degree heart block. Only every otheratrial beat (P wave) is conducted through the AV node.


lead itself can lead to complications. These mayinclude perforation of the myocardium leading tocardiac tamponade, lead dislodgement or poor leadpositioning leading to inadequate pacing, diaphrag-matic stimulation, or sensing problems.1,2,24–26

Arrhythmias can occur during lead manipulation,but repositioning the lead usually terminates theectopy. Device pocket–related complications canalso arise. These include development of ahematoma, infection, or skin erosion. Pacemakerpocket infections occur in less than 1% of thepatients undergoing pacemaker implantation.1

Troubleshooting Pacemaker ProblemsProblems in the immediate postoperative periodinclude tamponade, pneumothorax, and pacemakerwound problems. Immediate intervention and notifi-cation to the surgeon are needed. However, it isimportant to realize that pacemaker-related problemsmay be encountered at any time after implant:immediately or weeks, months, or years later. The cli-nician should be alert to these potential pacemakerproblems in any patient with a device, regardless ofthe diagnosis at admission. An astute clinician canidentify many pacemaker function problems by closeinspection of the EKG, comparing atrial and ventric-ular activity, and correlating that activity to patientsymptoms.

Inappropriate Sensing

The pacemaker may undersense intrinsic activity (a native P wave or QRS) and not inhibit pacing or,contrarily, it may oversense and inhibit pacing inap-propriately. Lead sensitivity is programmable andcan be adjusted as needed. Typically, intrinsic P andR waves are measured and then the sensitivity of therespective lead (atrial or ventricular) is programmedaccordingly to include a safety margin to allow forvariation in wave amplitude.

Undersensing that occurs within a short time afterdevice implantation may be due to lead dislodgementor malposition, or cardiac perforation. Undersensing

can also occur as the result of lead fracture, a changein native signal amplitude, disease progression,myocardial ischemia or infarction, inflammatorychanges of the lead-tissue interface, transient meta-bolic or electrolyte imbalance, or the appearance ofbundle branch block or ectopy. Undersensing resultsin overpacing, that is, pacing unnecessarily becauseintrinsic waves are not seen or sensed (Fig 3). Whenthe pacemaker is undersensing, the patient may expe-rience a sensation of extra beats, palpitations, orinappropriate tracking of atrial tachycardias. Onceidentified, undersensing should be evaluated by inter-rogation of the device. Appropriate intervention mayinclude reprogramming, lead reposition or replace-ment, or treatment of the underlying cause if tissue-related.

Oversensing can occur owing to the presence ofany electrical signal of sufficient amplitude and fre-quency that can be sensed during the pacemaker’salert period, which results in the pacing timingcycles being reset. Oversensing can be even moreproblematic if the patient is pacemaker-dependent(without an underlying rhythm) because oversens-ing results in underpacing (Fig 4). Often caused bythe same issues as those causing undersensing, over-sensing may also occur if the lead senses electricalstimulation from the muscles of the body (myopo-tentials), from the other lead, or from an externalsource of electromagnetic interference. Inhibition ofpacing by myopotentials occurs more often inunipolar systems because of the proximity of theanode (pulse generator house) to the pectoral mus-cles, diaphragm, or abdominal muscles dependingon pulse generator location. Examples of items thathave a strong enough electromagnetic field topotentially interfere with pacemaker function mayinclude surgical electrocautery, lithotripsy, radiationtherapy, arc welding, TENS units, internal combus-tion engines, and cellular telephones.26,27 Thepatient may experience a feeling of skips or pauses,or if inhibition is sustained, dizziness or syncopemay occur.

Oversensing requires evaluation with interrogationof the device. In many cases, such as with surgical

FIGURE 3. Intermittent under-sensing of ventricular impulse.


application of electrocautery or use of cellular phones,the following guidelines will prevent unwanted pacinginhibition.27 Patients who are pacemaker-dependentshould have their pacemakers reprogrammed to anasynchronous mode immediately before any surgicalprocedure involving electrocautery. In urgent instancesin which oversensing is causing profound bradycardia,a large magnet placed over the pacemaker pocket willtemporally reprogram the device to pace asynchro-nously until interrogation can occur.

Loss of Capture

Loss of capture occurs when the electrical impulsegenerated by the pacemaker does not result in depo-larization of the cardiac tissue. This may be causedby battery failure, lead dislodgement or poor posi-tion, lead fracture, or a rise in capture threshold dueto lead maturation or fibrosis, myocardial infarc-tion, or the initiation of certain antiarrhythmic medications (Bretylium, flecainide, moriazine,propafenone, and sotalol).5,28 The EKG will showpacing artifact without subsequent evidence of depo-larization and chamber capture, that is, a P wave fol-lowing the artifact for atrial pacing or a QRS fol-lowing the artifact for ventricular pacing (Fig 5).The patient may present with bradycardia, dizziness,or syncope. Reprogramming the pacemaker to ahigher-energy output is often sufficient to achieveconsistent capture until more definitive treatment(lead reposition or replacement) or resolution of tis-sue abnormalities occurs. Complete loss of capturerequires urgent evaluation and may require emer-gent intervention if there is no underlying rhythm,

such as external pacing, until the implanted devicecan be evaluated.

Loss of Biventricular Capture

For biventricular pacing to be most effective, the ven-tricles should be paced 100% of the time.Intermittent conduction through the AV node mayoccur and inhibit ventricular pacing. The AV delay isusually programmed sufficiently short to prevent thisfrom occurring frequently. Premature ventricularcontractions (PVCs) may also occur and inhibit pac-ing. Most commonly, however, biventricular pacingis compromised owing to loss of capture in one of theventricular leads. Because of the difficulty placingand securing the left ventricular or coronary sinus(CS) lead into the small venous branch, dislodge-ments may occur.29–32 Moreover, CS leads are notanchored within the vein as are the atrial and rightventricular leads, which can lead to dislodgement ormigration of the lead.

In the event of loss of biventricular capture, thepatient may present with worsening of symptoms ofcongestive heart failure. An EKG should be obtainedto look for biventricular capture (Fig 6). If frequentPVCs are noted along with biventricular capture, aconsult for device interrogation should be obtained.Increasing the lower pacing rate alone or combiningwith medication may effectively suppress the PVCsand increase the precentage of biventricular capturedbeats. Likewise, if single ventricular capture is seenon the EKG, the pacemaker team should evaluate forpossible lead dislodgement or rise in capture thresh-old. A chest x-ray may also be needed to determine

FIGURE 4. Ventricular pacing isinhibited because of oversensing ofmyopotentials from diaphragmresulting in asystole.

FIGURE 5. Intermittent loss of capture. Ventricular capture noted for beats 1–4. The fifth–ninth beats fail to cap-ture, only pacing artifact is seen. This was because of microdislodgement in the early postoperative period.


proper lead positioning. Repositioning may berequired if programming cannot solve the problem.

Special Management QuestionsWe are often faced with specific questions regardingthe management of patients with devices. These mayinclude questions about preparation for surgical ordental procedures, potential interactions between thepacemaker and other equipment, as well as questionsabout appropriate outpatient monitoring of thedevice.

Pacemakers present a few challenges when arrang-ing surgical procedures that involve electrocautery,because of the potential for inhibition of pacing, asdescribed earlier. When preparing a patient for a pro-cedure, determine the indication for the pacemaker,the patient’s current underlying rhythm, and the

manufacturer of the patient’s device (eg, Medtronic,Guidant, St. Jude). This information is invaluable tothe operating room team as they will use it to deter-mine if appropriate modification to electrocauterytechnique (bursts �4 seconds, bipolar configuration)is appropriate or if it will be necessary to have a rep-resentative from the company present for preproce-dure and postprocedure reprogramming.28 In somecases, the team may be instructed to secure a magnetover the device for the duration of the procedure toput it into an asynchronous mode. In general,patients are instructed to notify all healthcare per-sonnel that they have a pacemaker and to carry theirpacemaker identification card with them at all timesto facilitate appropriate planning for procedures.

Prophylactic antibiotic use is another questionoften asked when patients with devices prepare forsurgical, dental, or oral surgeries. Physicians may

FIGURE 6. 12-lead EKG biventri-cular capture.

FIGURE 7. 12-lead EKG showingright ventricular capture only.


have different protocols for antibiotic prophylaxisfor their patients such as prophylaxis only during thefirst few months after implant. However, accordingto accepted guidelines, patients with pacemakerimplants are not considered to be at a high risk forinfective endocarditis, and antibiotic prophylaxisprior to such procedures is not necessarily recom-mended.33–35 If, however, there is a suspicion ofinfective endocarditis in a patient with a permanentlyimplanted pacemaker, the system is generallyremoved, or in very rare cases, at least 4 to 6 weeksof antibiotic therapy may be prescribed.34 Patientsoften ask about possible equipment-pacemaker inter-action from electromagnetic interference (EMI). Inmost cases, the patient is able to carry out his or hernormal activities with only a few restrictions, such asavoiding close proximity (�2 feet) to strong magnetsor magnetic fields, running motors, and certainpieces of machinery. In rare circumstances, a patient’soccupation may require proximity to sources ofpotentially harmful EMI (eg, arc welding), and otherworking arrangements may be needed. The technicalservice departments of each pacemaker manufacturercan provide the clinician and patient with guidancein evaluating potential risk from the environment.

Patients and even healthcare professionals areoften confused about appropriate follow-up forpatients with pacemaker implants. These patientsshould be under the care of a cardiologist or electro-physiologist for device monitoring. Follow-up caretypically includes periodic remote telephonic trans-mission of pacemaker pulse/rhythm strip for moni-toring as well as a minimum of once- or twice-yearlyvisits to the clinic. During clinic visits, the device isintegrated with a special computer programmerusing telemetry communication with the device thatallows for noninvasive testing and reprogramming ofthe pacemaker. Such follow-up is necessary for ensur-ing the appropriate function and integrity of the sys-tem, and for monitoring battery life.

ConclusionWith expanding indications for pacemaker implanta-tion, most clinicians are likely to encounter a patientwho has a pacemaker. The advanced clinician shouldbe comfortable with answering the typical manage-ment questions that arise. When caring for a patientwith a pacemaker, be cognizant of the implications ofpacemaker malfunction on the patient’s condition,evaluate for appropriate device function, and identifypotential problems that may be contributing to orconfounding the patient’s diagnosis and treatment. Areview of the patient’s history allows for correlationof symptoms with potential pacemaker problems,and simple evaluation of an EKG provides important

information about the device function. The astute cli-nician, regardless of area of practice, should be ableto identify potential device-related problems, and ini-tiate appropriate interventions.

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