Europace (2002) 4, 55–59 doi:10.1053/eupc.2001.0210, available online at http://www.idealibrary.com on
Pacemaker troubleshooting: improved efficacy using a new diagnostic digital Holter recording system J. P. Moak, B. Gunderson1, V. Freedenberg and C. Ramwell Department of Cardiology, Children’s National Medical Centre, Washington, DC, and 1Medtronic Inc, Fridley, Minnesota, U.S.A.
Asymptomatic dysfunction of cardiac pacing systems is not uncommonly detected using long-term ambulatory monitoring techniques. We report two patients with atrial and ventricular sensing abnormalities noted only on Holter monitoring. Multiple empirical attempts at pacemaker reprogramming based on deductive analysis of the pacing anomaly were unsuccessful. Through the use of a new digital recording system that allowed collection of surface electrocardiographic data, intracardiac electrograms, and
Marker Channel data a correct diagnosis was made (pacing lead insulation failure). This new recording system has the advantage of significantly improving diagnostic sensitivity and resulting in cost savings. (Europace 2002; 4: 55–59) 2002 The European Society of Cardiology
Introduction
Methods
Previous studies have suggested a high incidence of clinical pacemaker dysfunction, despite the lack of correlation with patient symptoms[1–4]. Long-term ambulatory recordings (Holter monitoring) can be a useful adjunctive technique for assessing pacemaker function post-implantation and aid in determining the need for device reprogramming. On rare occasion, inappropriate pacing can elicit proarrhythmic responses, and fatal arrhythmias[5]. Sometimes related to poor quality surface electrocardiographic (ECG) tracings or patient motion artefacts, interpretation of aberrant pacing behaviour may be difficult. Increasingly sophisticated pacing algorithms further make deductive analysis of the surface ECG provisional at best. With increasing automation, simple interpretation of the ambulatory tracings becomes impossible without access to the internal operation of the pacemaker. Further, present generation pacemakers have enhanced diagnostic functions that provide some monitoring features, however, the accuracy of these monitoring tools have been shown to be limited[6].
We report two cases highlighting the diagnostic usefulness of a prototype digital ambulatory recording system in the detection of pacemaker dysfunction secondary to occult pacing lead insulation failure. This prototype recording system provides the reviewer with multiple channels of data to interpret complex pacing responses (two surface ECG leads, intracardiac electrograms, and Marker Channels (Medtronic, Fridley, MN, U.S.A.)). The Holter recording system is a modified 5-lead digital recorder that uses 80 megabits of flash memory storage. Data is sampled at 369 samples/s. An antenna is placed over the pacemaker to receive telemetry (intracardiac electrograms and Marker Channel data), and two surface ECG leads are also simultaneously recorded. The data are reviewed using standard Holter software.
Manuscript submitted 12 December 2000, accepted after revision 20 October 2001. Correspondence: Dr Jeffrey P. Moak, Department of Cardiology, Children’s National Medical Centre, Washington, DC 20010, U.S.A. E-mail:
[email protected] 1099–5129/02/010055+05 $35.00/0
Key Words: Pacemaker troubleshooting, sensing abnormalities, Holter monitoring, pacing lead fracture.
Case 1 RB, a 16·5-year-old adolescent male, underwent pacemaker implantation for high degree AV block. Transvenous pacemaker implantation was performed using two CPI (Cardiac Pacemakers, Inc., St Paul, MN, U.S.A.) model 4269 bipolar active fixation leads inserted through a lateral subclavian vein puncture, and a Medtronic (Medtronic, Fridley, MN, U.S.A.) model 7960i pulse generator. Pacemaker interrogation 19 months post-implantation revealed excellent atrial/ ventricular sensing and capture thresholds, with stable 2002 The European Society of Cardiology
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Figure 1 Holter monitor recording (3-channel) demonstrating pacemaker dysfunction. Evident on the Holter strip are two sinus rhythm complexes not followed by appropriate ventricular paced events, but rather conducted sinus complexes. An atrial pacing spike is highlighted by the arrow, suggesting possible atrial undersensing. The following P wave, again not followed by appropriate ventricular pacing, represents either an atrial-undersensed event or a ventricular oversensed event. Programmed pacemaker settings: DDD mode; lower rate limit=60/min; upper rate limit 180/min; AV delay: paced=170 msec; sensed=120 msec, with rate adaptive AV delay programmed on; post-ventricular atrial refractory period=220 msec; ventricular refractory period=360 msec; atrial blanking period=220 msec; sensing and pacing mode=bipolar; PVC response=on; PMT intervention=off, and mode switch=off. lead impedance measurements. A 24-h Holter monitor revealed occasional periods of either atrial undersensing or ventricular oversensing, Fig. 1. The pacemaker was reprogrammed on two occasions without eliminating the erratic pacing behaviour. Attempts to reproduce the abnormal Holter findings in the clinic were unsuccessful. A Medtronic DR 180 digital Holter system (Northeast Monitoring, Inc, Sudbury, MA, U.S.A.) was applied in order to gain insight into the aberrant pacing behaviour. Evidence for ventricular oversensing with ‘apparent’ or pseudo atrial undersensing were observed (Fig. 2), the primary anomaly being ventricular oversensing. One of the ventricular oversensed events resulted in ventricular pacing into the T wave. Fortunately, no ventricular arrhythmias resulted. Reprogramming the ventricular sensing polarity from bipolar to unipolar corrected the ventricular oversensing, and also corrected the ‘apparent’ atrial undersensing. A chest X-ray failed to reveal any evidence for subclavian crush Europace, Vol. 4, January 2002
injury or distortion of the pacing leads. The implication of the findings suggested an outer conductor insulation fracture.
Case 2 SH is a 34-year-old woman with d-transposition of the great arteries, status post-Mustard repair. A transvenous dual chamber pacing system was placed for sinus and AV node dysfunction. Prior to transvenous pacemaker implantation, balloon dilation and placement of a stent in the superior vena cava was performed. Transvenous pacemaker implantation was performed using two CPI (Cardiac Pacemakers, Inc., St Paul, MN, U.S.A.) model 4269 bipolar active fixation leads inserted through a lateral subclavian vein puncture, and a Medtronic (Medtronic, Fridley, MN, U.S.A.) model 7940B pulse generator. Pacemaker interrogation at 3·5 years
Pacemaker troubleshooting with digital recorder
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Figure 2 Two tracings from digital Holter recorder provide an explanation of the pacing anomaly observed in Fig. 1. Three channels of data are displayed in the following order: surface ECG, atrial electrogram, and Marker Channel . Programmed pacemaker settings are the same as in Fig. 1. (A) Ventricular oversensing noted on starred complex. The two ventricular sensed events result in an atrial refractory sensed event (atrial refractory period extension following PVC=400 msec). Subsequently, the lower rate limit times out and evokes an atrial paced/ ventricular paced event. The atrial pacing spike can be seen to follow the surface P wave. The ventricular pacing spike is concealed in the surface QRS. (B) ‘Apparent’ atrial undersensing which is secondary to PVC response, extending the PVARP. Ventricular oversensing noted prior to the ninth QRS complex. The subsequent atrial sensed event is in the atrial refractory period. Subsequently, the lower rate limit times out evoking an atrial paced/ ventricular paced event. This time the ventricular paced event occurs in the T wave. Marker Channel annotation:
AR=atrial refractory, AS=atrial sense, AP=atrial paced, VR= ventricular refractory; VS=ventricular sense, VP=ventricular paced. The low amplitude biphasic markers signify the end of the post ventricular atrial refractory period. The arrows highlight atrial paced/ventricular paced complexes.
post-implantation revealed good to excellent atrial/ ventricular sensing and capture thresholds, with stable lead impedance measurements. A 24-h Holter monitor revealed occasional periods of atrial undersensing and oversensing, along with periods of ventricular undersensing of PVCs. Outpatient evaluation in the clinic revealed normal pacemaker behaviour, despite attempts at upper extremity exercise. Three attempts at empirical
reprogramming failed to correct the abnormal sensing function. In order to understand the pacing anomaly better, the Medtronic DR 180 digital Holter system was applied. Evidence for both atrial under and oversensing, in addition to ventricular oversensing, resulting in inappropriate pacing was seen, Fig. 3. A chest X-ray did not reveal any evidence for subclavian crush injury or distortion of the pacing leads. Europace, Vol. 4, January 2002
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Figure 3 Atrial oversensing noted predominantly in Case 2. Three channels of data are displayed in the following order: surface ECG, atrial electrogram, and Marker Channel . Atrial oversensing highlighted by arrows. Evidence against this being a real episode of atrial tachycardia include: (1) the ‘atrial’ electrogram precedes QRS complex without any P wave visible on the surface ECG, (2) ventricular rate remains constant, in a patient not known to have advanced AV block, and (3) true atrial electrogram is visible during the fifth complex and occurs with respect to timing as expected. Observed during the seventh junctional complex is an atrial paced/ventricular paced event, resulting from the lower rate limit timing out. The pacing spikes are concealed in the QRS complex. Prominent U waves may be mistaken for pseudo P waves. Programmed pacemaker settings: DDD mode; lower rate limit= 50/min; upper rate limit=180/min; AV delay: paced=250 msec, sensed=250 msec; post-ventricular atrial refractory period=300 msec; ventricular refractory period=300 msec; atrial blanking period=250 msec; ventricular output programmed to non-capture, atrial sensitivity=0·35 mV; ventricular sensitivity=8 mV; PVC response=on; PMT intervention=off, and mode switch=off. Marker Channel annotation same as in Fig. 2.
Discussion Our two patients initially proved difficult diagnostic challenges. Multiple empirical attempts to reprogramme atrial and ventricular sensing functions were unsuccessful. Only by obtaining simultaneous surface ECG, intracardiac electrograms, and marker annotations were we able to appreciate the sensing dysfunction responsible for the aberrant pacing behaviour and properly reprogramme the pacemaker. These evaluations ultimately identified a lead integrity problem that was not apparent during clinic assessment of pacing lead impedance or physical exercises. Sensing abnormalities have been the commonest pacing anomaly detected during ambulatory Holter monitoring, mostly in patients with unipolar pacing systems, much less so when bipolar leads were Europace, Vol. 4, January 2002
implanted[1,4]. An incidence as high as 240 pacemaker malfunctions per 24 h was found by Brandes et al. during ambulatory monitoring of 100 consecutive adult patients with ventricular demand pacemakers[1]. Secemsky et al. performed 24-h Holter monitoring in 228 patients implanted with unipolar ventricular demand pacing systems[2]. Overall, 38% exhibited ventricular oversensing secondary to myopotentials, and 17% of patients were found to display ventricular undersensing. Wiegand et al. studied the incidence of atrial sensing anomalies in 100 patients implanted with dual chamber pacemakers[3]. Atrial oversensing was discovered in 56% of patients programmed to the unipolar mode. No instances of oversensing were noted in the bipolar atrial sensing mode. Atrial undersensing occurred in 35% and 22% of patients programmed to the unipolar and bipolar sensing mode, respectively.
Pacemaker troubleshooting with digital recorder Gillis et al. followed 261 patients with pacemaker leads on safety alert using ambulatory monitoring and intensified outpatient pacemaker clinic evaluations[4]. Ambulatory monitoring detected pacing lead failures in 31% of the study population, in contrast to only a 4% detection rate during clinic assessment. Pacing lead failure documented during ambulatory monitoring could subsequently be confirmed during outpatient assessment in only 25% of these patients, emphasizing the greater diagnostic sensitivity of ambulatory Holter monitoring in detection of pacing system dysfunction. Several other attempts at developing an improved Holter monitoring technique for pacemaker evaluation have been previously reported. Kelen et al. described a system that incorporated pacing spike detection circuitry on a separate channel from the ECG data[7]. This system facilitated better recognition of pacing artefacts that can be intermittently difficult to observe during long-term recordings. Nowak et al. developed a recording system that allowed the continuous transfer of marker annotations from the pulse generator to one of the unused recording tracks on the Holter tape[8]. The advantage of the Medtronic DR 180 ambulatory monitoring system used in this study was its ability to provide not only marker annotation but also intracardiac electrogram data. Better recognition of pacing lead failures may in the future be also allowed through long-term measurement of intracardiac pacing lead impedances. Accurate detection of pacemaker sensing abnormalities can be facilitated using digital Holter recording systems
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that incorporate surface electrocardiographic data, intracardiac electrograms, and marker annotations.
References [1] Brandes A, Bethge KP, Gonska BD, Diederich KW. Transient pacemaker dysfunction and spontaneous arrhythmias in symptomatic and asymptomatic patients with demand pacemakers. Z Kardiol 1996; 85: 237–47. [2] Secemsky SI, Hauser RG, Denes P, Edwards LM. Unipolar sensing abnormalities: incidence and clinical significance of skeletal muscle interference and undersensing in 228 patients. Pacing Clin Electrophysiol 1982; 5: 10–9. [3] Wiegand UK, Schier H, Bode F, Brandes A, Potratz J. Should unipolar leads be implanted in the atrium? A Holter electrocardiographic comparison of threshold adapted unipolar and high sensitive bipolar sensing. Pacing Clin Electrophysiol 1998; 21: 1601–8. [4] Gillis AM, Hillier KR, Rothschild JM, McDonald M, Simpson CA, Wyse DG. Ambulatory electrocardiography for the detection of pacemaker lead failure. Pacing Clin Electrophysiol 1997; 20: 1274–82. [5] Bohm A, Pinter A, Preda I. Pacemaker induced torsade-depointe tachycardia. Heart 1998; 80: 466–7. [6] Wiegand UK, Bode F, Schneider R, et al. Diagnosis of atrial undersensing in dual chamber pacemakers: impact of autodiagnostic features. Pacing Clin Electrophysiol 1999; 22: 894–902. [7] Kelen GJ, Bloomfield DA, Hardage M, et al. A clinical evaluation of an improved Holter monitoring technique for artificial pacemaker function. Pacing Clin Electrophysiol 1980; 3: 192–7. [8] Nowak B, Middeldorf T, Housworth CM, et al. Holter recordings with continuous marker annotations: a new tool in pacemaker diagnostics. Pacing Clin Electrophysiol 1996; 19: 1791–5.
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