In certain circumstances, these same electrical features may be seen in a patient with normal pacemaker function. Physicians must recognize the potential for such "pseudomalfunction." This problem is minimized by careful interpretation of the paced electrocardiogram and knowledge of both the idiosyncrasies of the particular pacemaker and how it is programmed.

Several series have reviewed the incidence and types of pacemaker problems identified during long-term follow-up [1-6]. Sensing abnormalities, recognized as a lack of pacemaker artifacts or, conversely, as one or more inappropriate pacemaker artifacts, are the most common malfunction, occurring in approximately 3% of patients. Failure to capture occurs in 1% to 2% of patients; the remaining problems affect another 1%.

Although all pacemaker malfunctions can be related to problems with the pacemaker generator or the pacemaker lead (or both), it is useful to consider the differential diagnosis on the basis of the electrocardiographic signs listed in Table 1.

Failure to Output

The consequences of a pacemaker's failure to output Table 2 can be catastrophic for the pacemaker-dependent patient. Such failure can result from random component failure, which is rare, or from total battery depletion, which is avoidable if routine pacemaker follow-up is adequate and nonurgent battery replacement is planned when end-of-life indicators are reached. Lead fracture and disconnection of the lead from the pacemaker can also result in failure to output. Pacemaker lead fracture has become less common as lead technology has improved but must be part of the differential diagnosis for the patient with sudden failure to output. Disconnection of the lead from the pacemaker occurs only when the lead is not adequately secured within the connector block at the time of implantation; surgical intervention is required for correction.

The current lithium-powered pacemakers have a battery life that ranges from 4 to more than 12 years, depending on the current drain, which is determined by the percentage of time pacing is required, the thresholds necessary, whether single- or dual-chamber pacing is used, and whether a rate-modulating sensor or other features requiring additional current drain are included. Lithium iodine, currently the most commonly used battery, has shown predictable battery-depletion characteristics [7]. When a small voltage decrement occurs, end-of-life characteristics (such as a change in pacing rate) are triggered, signaling the need for pacemaker replacement. Once initial end-of-life changes appear, there is usually a period of months before the pacemaker battery reaches a critically low voltage and pacing fails. (Total battery depletion results in failure to output. Failure to capture can take place at a lesser degree of battery depletion.)

Oversensing is associated with the unexpected sensing of an intracardiac or extracardiac signal [8] (Figure 1). It may be intermittent, resulting in irregularly delayed pacemaker stimulation, or constant, leading to a decreased pacing rate or total inhibition of pacemaker output. Electrical signals that may cause oversensing include myopotentials, T waves, and P waves. Atrial-channel oversensing may occur when "far-field" R waves are sensed. Extrasystoles, which are nearly isoelectric in the monitored lead, may give the appearance of oversensing.

View larger version (81K): [in this window] [in a new window]   Figure 1. Example of oversensing. An electrocardiographic recording from a patient with a dual-chamber bipolar pacing system shows five atrial pacing artifacts followed by paced ventricular activity after the first, second, fourth, and fifth. Paced ventricular activity is absent after the third paced atrial beat because of oversensing; that is, activity other than intrinsic ventricular activity was sensed by the ventricular sensing channel and resulted in failure to output. Many signals could be responsible for the oversensing. In this patient, electrical noise arose within a ventricular pacing lead.

Oversensing of myopotentials in a single-chamber pacemaker may result in pauses, whereas oversensing of myopotentials by the atrial-sensing circuit of a dual-chamber pacemaker may result in rapid paced rhythms. Such myopotentials may be interpreted as atrial activity, and the pacemaker "tracks" the signals with ventricular pacing. Oversensing can frequently be corrected by reprogramming the sensitivity or, at times, by reprogramming the refractory period of the channel on which oversensing is occurring so that the event being inappropriately sensed occurs in the refractory period and therefore does not alter the timing cycle of the pacemaker. Oversensing of extracardiac events occurs much less commonly with bipolar sensing [9].

Although it is not a true malfunction of the pacing system, failure of output may also be the result of "cross talk"; that is, in a dual-chamber pacemaker, the pacemaker stimulus in one chamber is sensed in the other chamber [10, 11]. If the afterpotential of an atrial stimulus is sensed by the ventricular lead, ventricular output may be inhibited. For the pacemaker-dependent patient, inhibition could result in ventricular asystole. Most pacemakers have two methods of protection against such an occurrence. The first is interposition of a short period ("blanking") of refractoriness in the ventricular channel simultaneous with the atrial output stimulus. The second is adjustment of the response to sensed events on the basis of when, during the timing cycle, the event is sensed. One such response is ventricular "safety pacing," whereby any event sensed on the ventricular sensing circuit within a defined early portion of the atrioventricular delay (that is, the interval between the paced atrial event and the subsequent ventricular event) initiates the delivery of a ventricular pacing stimulus.

Another pseudomalfunction occurs when the monitor system does not display the pacemaker stimulus artifact when it is really present. This occurs more frequently with bipolar pacing, and the confusion can usually be resolved by magnet application, examination of a 12-lead electrocardiogram, or alteration of the configuration of the monitoring lead.

Failure to Capture

The most common cause of failure to capture Table 2 is dislodgment of the pacemaker lead from the endocardial surface; such dislodgment usually occurs in the first few weeks after implantation (Figure 2). The newer designs for active and passive fixation leads have been associated with a greatly decreased incidence of dislodgment [12]. Although the acceptable rate for lead dislodgment is difficult to define, it should be less than 2% for ventricular leads and less than 5% for atrial leads [13, 14].

View larger version (47K): [in this window] [in a new window]   Figure 2. Intermittent ventricular failure to capture in a patient with a dual-chamber pacemaker. The first two and last two ventricular pacing artifacts result in ventricular depolarization. The five ventricular pacing artifacts in between fail to result in ventricular capture, so that the patient remains asystolic during that period. Effective atrial depolarization can be seen throughout the tracing.

Failure to capture can also occur when a break in the insulation of the pacemaker catheter allows some of the current from the electrode to escape into the surrounding tissues. If the current leakage is sufficient, complete or intermittent failure of myocardial capture results.

If the pacing threshold required to depolarize the myocardium is greater than the programmed voltage amplitude and pulse duration, intermittent or total failure to capture may occur. Poor lead position is the most common cause of high thresholds, but exit block can also cause high thresholds in a few patients. Exit block, or high pacing thresholds without radiographic evidence of dislodgment, may be related to an inflammatory reaction or fibrosis at the electrode-myocardium interface [15]. In a patient with exit block, the risk for recurrent high thresholds can usually be minimized with the use of a steroid-eluting lead [16]. Failure to capture may also be induced by marked metabolic abnormalities, such as hyperkalemia, and some cardioactive drugs, such as flecainide, that alter the myocardial milieu [17].

Inappropriately low voltage-amplitude and pulse-duration settings may result in "true" failure to capture. A pacemaker artifact occurring within the myocardial refractory period Figure 3, functional loss of capture, results in a similar electrocardiographic appearance but is a pseudomalfunction.

View larger version (62K): [in this window] [in a new window]   Figure 3. Example of undersensing. The electrocardiographic recording was obtained from a patient with a ventricular pacemaker programmed to 50 beats per minute. The first pacing artifact occurs simultaneously with an intrinsic QRS complex and represents normal function (pseudofusion). However, the second and third pacing artifacts occur inappropriately close to the preceding QRS complex (that is, at less than 1200 ms the programmed rate of the pacemaker) and represent failure to sense or undersensing. The fourth pacemaker artifact is appropriate because it occurs 1200 ms after the preceding paced QRS complex. The second pacing artifact does not result in ventricular depolarization. This is not failure to capture, because the ventricular pacing artifact is occurring only 260 ms after the intrinsic QRS complex and the ventricle is refractory.

Undersensing

Failure to sense, or undersensing Table 2, whether intermittent or total, is rarely an urgent problem (Figure 4). Lack of sensing of intrinsic cardiac activity, a relatively common abnormality, results in pacemaker output that is undesirably competitive with the intrinsic rhythm. Competitive pacing can result in an unwanted rhythm. For example, atrial pacing that competes with normal sinus rhythm may result in atrial fibrillation. Competition in the ventricle is possible but is almost never a problem except when the fibrillation threshold has been altered by ischemia, electrolyte imbalance, or some other metabolic abnormality.

View larger version (73K): [in this window] [in a new window]   Figure 4. Example of functional undersensing. The electrocardiographic tracing was obtained from a patient with a ventricular pacemaker programmed to 70 beats/min. Of the five pacing artifacts shown, the first, fourth, and fifth result in effective ventricular depolarization. There is failure to capture with the second and third pacing artifacts. The third pacing stimulus occurs approximately 850 ms after the preceding intrinsic QRS complex. This timing represents normal sensing, that is, pacing at a rate of 70 beats/min. However, the fourth pacing stimulus occurs approximately 640 ms after the preceding intrinsic QRS complex, indicating that the preceding QRS complex was not sensed because it occurred during the pacemaker's ventricular refractory period. This is an example of functional undersensing; that is, undersensing was a function of the ventricular refractory period.

Undersensing is most likely caused by lead dislodgment, poor lead position at the time of implantation, or an interruption in the insulation of the pacing catheter. An insulation defect may be manifested as undersensing or oversensing, or both. Undersensing may also be the result of delivery of a low-amplitude P wave or QRS complex to a normally functioning pacing system. The size of the electrical signal can be determined only from the intracardiac electrogram. The size of the signal from the intracardiac electrogram may be influenced by many factors (for example, concomitant drug therapy, body position, myocardial infarction, and the cardiomyopathic process), so that an R-or P-wave amplitude that was initially acceptable may be diminished to a level that cannot be sensed by the pulse generator. Also, the size of the atrial signal may diminish with exercise [18]. Undersensing can frequently be corrected by reprogramming the sensitivity of the pacemaker.

Sensing is suspended as the result of magnet application, which disengages the sensing amplifiers. This is the expected response and should not be considered undersensing. Extraneous electrical noise sensed by the pacemaker may switch the unit to a nonsensing mode.

In dual-chamber pacemakers, apparent undersensing may occur during the initial portion of the atrioventricular interval, or the blanking period (Figure 5). The blanking period is programmable in most dual-chamber pacemakers and may range from 12 to 125 ms. During this interval, the ventricular channel of the pacemaker is refractory to avoid sensing of the atrial stimulus and depolarization. If an intrinsic ventricular event occurs during the blanking period, it is not sensed and will give the appearance of undersensing [19, 20]. This problem can often be corrected by shortening the blanking period. If an event occurs immediately after the blanking period, it occurs during the "cross-talk sensing window." An event that occurs during this period triggers ventricular safety pacing, as previously described (Figure 5).

View larger version (46K): [in this window] [in a new window]   Figure 5. The atrioventricular interval as a single interval with two subportions. The entire atrioventricular interval corresponds to the programmed value. The initial portion of the interval is the blanking period (crosshatched portion). If an intrinsic ventricular event occurs during this period, it will not be sensed; that is, functional undersensing occurs. This interval is followed by the cross-talk sensing window (gray portion). If an intrinsic ventricular event occurs during this period or if any other event is sensed on the ventricular sensing circuit during this period, ventricular safety pacing will occur. (Reprinted with permission of W.B. Saunders Company; From: Hayes DL. Timing cycles of permanent pacemakers. Cardiol Clin. 1992; 10:593-608.).

Functional undersensing may also occur when a P wave or QRS complex falls within the refractory period, that is, when a P wave occurs during the atrial refractory period or a QRS complex occurs during the ventricular refractory period (see Figure 4).

Care should be taken to avoid confusing what appear to be inappropriate pacemaker artifacts with artifacts caused by the monitoring equipment. These random occurrences, frequent in some older monitor systems, can be misleading.

Inappropriate Pacing Rates

Several causes for inappropriately rapid pacing rates have been identified Table 2, but few are true malfunctions of the pacing system [21]. One true malfunction that may be lethal for both pacemaker-dependent and non-pacemaker-dependent patients is "runaway pacemaker." Runaway pacemaker occurs infrequently with current pulse generators [22, 23]. However, when runaway pacemaker does occur, it qualifies as a true emergency because pacing rates may be very rapid and cause hemodynamic instability and collapse. The problem can result from battery failure, random component failure, or component failure induced by therapeutic radiation [24, 25]. Treatment aimed at disabling the faulty pacemaker output must be initiated promptly if there is hemodynamic compromise [22, 23].

Sensing abnormalities also may result in inappropriately rapid pacing rates by induction of tachydysrhythmias owing to undersensing and competitive pacing. Tracking of atrial fibrillatory or flutter waves and pacemaker re-entrant tachycardia are also inappropriate pacemaker-mediated tachycardias. (Pacemaker re-entrant tachycardia refers to a repetitive cycling that can be seen in dual-chamber pacemakers that can track atrial activity. Pacemaker re-entrant tachycardia occurs when sensing of a retrograde atrial depolarization initiates ventricular pacing, which in turn leads to retrograde conduction and repetition of the same cycle [26] (Figure 6).) Although these rhythms are pacing abnormalities that require correction, they are a function of the patient's intrinsic rhythm and the programming of the pacemaker, not true malfunctions of the pacing system.

View larger version (69K): [in this window] [in a new window]   Figure 6. Pacemaker re-entrant tachycardia shown by an electrocardiographic tracing from a patient with a dual-chamber pacemaker. Atrial and ventricular pacing stimuli precede the first three paced complexes at a rate of 80 beats/min, the programmed lower rate limit for the pacemaker. A premature ventricular complex follows the third paced ventricular complex. The premature ventricular complex is conducted in a retrograde fashion through the atrioventricular node and results in atrial activation. The retrograde atrial activation is in turn sensed by the pacemaker and initiates ventricular pacing. The pacing rate is limited to the programmed upper rate limit of 110 beats/min.

Electromagnetic interference from the patient's environment may cause the generator to be reset to a rate different from that programmed. Also, many pacemakers operate at a slower rate when battery depletion is imminent (end-of-life indicator).

During "safety pacing," the atrioventricular interval is shortened; therefore, the total interval is shortened from one paced ventricular complex to the next. Repetitive safety pacing results in a slight increment in pacing, but it is not clinically significant.

Pacemaker Lead Malfunction

A fracture or an insulation defect or, as previously discussed, lead dislodgment can cause lead malfunction. Lead fracture, common in the early years of cardiac pacing, has decreased in frequency as conductor technology has evolved [11]. The incidence of fracture of the pacing lead has been reported to be 0.1% to 4.2% per patient-year (< 2% per patient-year is the expected incidence with current pacing leads) [27]. Most often, lead fractures occur adjacent to the pulse generator or near the site of venous access [27], that is, at a stress point [28, 29], although fracture has also been reported at more distal portions of the pacing lead [30]. Although an uncommon cause, direct trauma may damage the pacing lead [31, 32].

Polyurethane and silicone are used as insulating materials for most permanent pacing leads. In the early 1980s, concern arose about the long-term performance of leads with polyurethane insulation because of the early failure of several specific polyurethane-insulated leads [33-35]. Failure of specific polyurethane leads appears to be attributable to difficulties in manufacturing these specific leads and is not representative of the overall experience with polyurethane leads. Insulation defects in polyurethane leads have also been detected at stress points, particularly at the costoclavicular space in leads placed using the subclavian puncture technique [36].

Environmental Causes of Pacemaker Malfunction

Many environmental factors can induce pacemaker malfunction, the most important of which are hospital related.

Electrocautery

The most common piece of medical equipment to affect pacemaker function is the electrocautery, which usually causes temporary sensing problems or reprogramming but rarely causes permanent alteration of the pacemaker circuits [37]. After electrocautery is used in a patient with a permanent pacemaker, the pacemaker should be checked to confirm proper function and expected programmed settings.

Transthoracic Defibrillation

Permanent or transient electrical damage to the pulse generator can occur during transthoracic defibrillation. The effects on the pacing system may be caused by myocardial thermal damage secondary to transmission of defibrillation discharge to the heart through the leads, inappropriate reprogramming of programmable pulse generators, or damage to the pacemaker circuitry [38, 39]. The potential for such damage is minimized by incorporating a zener diode into the pacemaker that will shunt excess energy away from the pacemaker [38]. Also, to minimize the chance of pacemaker malfunction occurring with defibrillation, the defibrillation paddles should be positioned anteroposteriorly and as far from the pacemaker or lead as possible.

Magnetic Resonance Imaging

The powerful static, time-varying magnetic, and radiofrequency fields of the magnetic resonance imaging (MRI) system can affect normal pacemaker operation and function. At the least, exposure to MRI causes all pacemakers to revert to an asynchronous mode because of reed-switch closure. This effect can be avoided only in pacemakers in which the magnet response can be programmed "off." Investigations of the interaction between MRI and the pacemaker have shown that MRI does not permanently damage the reed switch or other pulse generator components. The radiofrequency artifacts do not alter the acutely programmed variables, change the normal magnet rate, or induce pacing in most pacemakers tested. Certain single- and dual-chamber pacemakers implanted in animals and exposed to MRI can pace at the radiofrequency pulse period used during radiofrequency scanning [40]. Because the radiofrequency pulse period may be set at extremely short intervals for some diagnostic procedures (available range of 20 to 2000 ms), patients with susceptible pacemakers theoretically could be paced at rates as high as 3000 beats/min.

No generalizations can be made about which patients with pacemakers can be exposed safely to MRI. In general, MRI should be avoided in a patient with an implanted pacemaker. Several approaches have been used in patients with pacemakers who need MRI scanning and for whom alternative procedures cannot provide the necessary diagnostic information. Magnetic resonance imaging may be attempted in non-pacemaker-dependent patients if the device can be programmed to an output at which there is consistent failure to capture [41]. In this case, even if the pacemaker were susceptible to rapid pacing by the radiofrequency signals, the patient should be protected from effective rapid-pacing rates. If the pacemaker can be programmed to the OOO mode, or "off," the non-pacemaker-dependent patient can probably undergo MRI safely. Alternatively, the pacemaker can be explanted for the duration of the MRI scan, but this procedure is again obviously only applicable to the non-pacemaker-dependent patient and is not without risk. Even with strict sterile technique, the patient would be exposed to some increased risk for infection. It must be remembered that if the body area to be imaged is in close proximity to the pacemaker site, the pacemaker-induced artifact on MRI may obscure the images. Because MRI is generally thought to be contraindicated in patients with permanent pacemakers, the patient must be made thoroughly aware of the risks associated with MRI.

Extracorporeal Shock-Wave Lithotripsy

Lithotriptors may cause problems in permanent pacemakers [42, 43]. The shock waves produced by the lithotripsy device are usually synchronized to the patient's ventricular depolarization or to the output stimulus of the pacemaker. Testing of pacemakers in vitro and limited experience in vivo have shown that lithotripsy does not interfere with fixed-rate VVI pacing. In patients with dual-chamber pacemakers, synchronization of the lithotriptor with the atrial output can result in inhibition of ventricular output. Therefore, the pacemaker should be reprogrammed to the VVI or VOO mode for the duration of treatment. In patients with an activity-sensing, rate-adaptive pacemaker, sensing of the shock waves can result in increased pacing rates and in damage to the piezoelectric crystal if the focal point of the lithotriptor is placed near the pacemaker.

The following guidelines should be followed when lithotripsy is done in patients with pacemakers: 1) Program the pacemaker to the VVI or VOO mode; 2) keep the focal point of the lithotriptor at least 6 inches away from the pacemaker; and 3) monitor cardiac function throughout the procedure.

Transcutaneous Electrical Nerve Stimulation

Used frequently for several neurologic and musculoskeletal problems, transcutaneous electrical nerve stimulation appears to be safe in most patients with permanent pacemakers. One study showed no pacing abnormalities in 51 patients in whom 20 different pacemakers were evaluated [44]. Individual cases have been reported documenting pacemaker inhibition by transcutaneous electrical nerve stimulation [45]. It is not known how close to the pacemaker the transcutaneous nerve stimulator can be placed, and it is best to avoid applying the stimulator to a vector or path that would be parallel to the pacing lead. Pacemaker-dependent patients should be monitored during initial transcutaneous electrical nerve stimulation to be certain that no inhibition occurs. Most of the information on this procedure in patients with permanent pacemakers has been obtained in those with relatively modern pacemakers. It is possible that some older pacemakers with less sophisticated filtering capabilities are more susceptible to interference.

In patients with VD or DDD pacemakers, transcutaneous electrical nerve stimulation may result in an increased ventricular rate. If the noise created by transcutaneous electrical nerve stimulation were sensed as atrial activity, the pacemaker could track the noise and increase the ventricular rate.

Therapeutic Radiation

Diagnostic radiography does not interfere with pacemaker function. Therapeutic radiation can have a damaging effect on pacemaker function [46, 47]. Modern pacemakers contain complementary metal oxide semiconductors for their integrated circuits, whereas older generators had discrete components. Complementary circuits are more readily damaged by lower levels of radiation than were discrete components. Specifically, when the metal oxide semiconductor is exposed to ionizing radiation, damage occurs to the silicone and silicone oxide insulators within the semiconductors. Therapeutic radiation may be sufficiently intense to cause complete failure or random damage to circuit components. Sudden output failure or runaway may occur. Because the damage to the circuit is random and the radiation dose cumulative from one therapeutic exposure to the next, no specific prediction relative to dose can be made. Some reports have noted pacemaker damage in complementary metal oxide semiconductor devices from as small a radiation dose as 10 Gy, whereas in others, damage has resulted from doses of 30 to 150 Gy.

This effect is particularly important in patients undergoing radiation for thoracic or chest wall malignant disease. If the pacemaker is within the field of radiation—for example, in patients with carcinoma of the breast—moving the pulse generator to another site may be required. If the pulse generator is not in the field of radiation, it should nevertheless be shielded to prevent damage.

Other Medical Equipment

Diathermy, electroshock therapy for the treatment of depressive disorders, and radiofrequency ablation for the treatment of tachyarrhythmias may also cause pacemaker reprogramming or inhibition. From a practical standpoint, the pacemaker should be checked after the procedure or treatment to determine that programmed parameters remain accurate.

Nonmedical Equipment and Devices

Permanent damage to implanted pacemakers by electrical equipment normally encountered at home or at work has not been reported and is unlikely. The most frequent occurrence is temporary interference with pacemaker activity while the patient is in the field of sustained electrical interference. Interpreted by the pacemaker as cardiac electrical activity, this electrical interference may inhibit pacemaker function episodically but will not damage the pacemaker.

Potentially significant restrictions exist for a small subset of patients. Each circumstance is different and involves the mutual decision of the implanting physician and the patient. In patients who work in environments with equipment capable of causing significant electromagnetic interference—for example, heavy motors, such as internal combustion engines, or arc welding equipment—temporary interference with pacemaker activity can result in pacemaker inhibition. In these situations, patients may be required to change occupations or at least to avoid specific equipment. If the potential for such electromagnetic interference is known before implantation, the use of bipolar leads can minimize or eliminate the problem. When the patient's livelihood involves the use of equipment that may cause electromagnetic interference, it is helpful to have the patient, accompanied by another adult, return to the workplace with an ambulatory electrocardiographic monitor. Electrocardiographic recording during brief exposure to the potentially hazardous equipment at close proximity helps to determine whether a real problem exists. If the patient has a pacemaker with the capability of storing event records, examination of the stored records after exposure to the usual work environment may help to determine whether electromagnetic interference is a concern. Occasionally, it may even be necessary to request an engineer from the pacemaker company to visit the patient's workplace and determine potential exposure to electromagnetic interference.

Patients invariably ask whether a microwave oven or radar detectors of the type used in airports interfere with pacemaker function. With present-day pulse generators, microwaves should not cause any problem. Metal detectors could theoretically cause inhibition of a single beat, but significant clinical sequelae should not result.

Phantom Programming

Several categories of phantom or false programming have been defined, including misprogramming from faulty program emission signals, dysprogramming from anomalous sources, and, most commonly, purposeful programming by a health care provider who fails to inform the patient or to record the reprogramming for future reference. Faulty program emission signals were more common when programming was accomplished by magnetic reed switching. With radiofrequency transmission of programming signals, phantom programming is uncommon.

Several sources of phantom programming occur or are detected in a hospital setting. One is exposure to cold. The pulse generator may be exposed to severe cold in the cargo hold of an aircraft or in the trunk of an automobile during delivery. After exposure to severe cold, new microprocessor-based pulse generators revert to a back-up mode that is different for each pacemaker. A special programming sequence is usually necessary to restore normal operation. Reversion to the back-up mode could also be caused by cardioversion or electrocautery, as previously discussed. If the possibility of such reversion is not anticipated in each of these instances, pacemaker malfunction may be thought to be present.

When phantom programming occurs outside the hospital, a detailed analysis of possible sources of reprogramming should be discussed with the patient to determine and avoid the cause and to ascertain that pacemaker malfunction does not exist. With the electromagnetic interference shielding provided in current pacemakers, false programming caused by exposure to this interference is infrequent. When a patient's pacemaker is found to be programmed to parameters other than those on record, the following causes should be considered: 1) reprogramming by another physician without notification of the pacemaker center; 2) use of medical equipment in the hospital for diagnostic or therapeutic procedures [for example, electrocautery and magnetic resonance imaging]; and 3) close exposure to large internal combustion engines, welding equipment, or some form of external shock.

Conclusion

Top Conclusion Author & Article Info References

Prevention of pacing system malfunctions requires not only that the pacemaker and pacing lead be reliable but also that the implanter of the system be knowledgeable and have expertise in pacemaker implantation. In a survey conducted by Parsonnet and colleagues [48], the number of complications was proportional to the implanter's experience. Physician experience in interpreting electrocardiograms is essential to avoid mistakenly identifying pseudomalfunctions as true pacemaker malfunctions. When an experienced physician uses the reliable pacing devices now available, the number of pacemaker malfunctions is minimal.