A New Algorithm for Minimizing Pacemaker Polarization Artifact: Universally Applicable in Permanent Pacing Systems

Polarization artifacts that result from pacing may interfere with analysis of paced evoked responses during, e.g., automatic threshold tracking. We have developed a method for reduction of such artifacts that relies on the introduction of pacing stimuli during the refractory period of unipolar or bipolar paced captured beats after previous identification of a refractory period "template" or baseline. The refractory pacing stimuli cannot capture the heart, and thus any deviation from the template is due to polarization artifact alone. The artifact amplitude is measured and the precharge duration of the triphasic stimulus waveform is changed each time until artifact is minimized, as detected by repeated reversals in the polarily of the polarization artifact. In a series of 11 patients with unipolar and bipolar permanent pacing leads, mean initial artifact before balancing was 1.44 ± 0.84 mV, which was reduced to 0.44 ± 0.30 mV after balancing (P = 0.001). Initial precharge duration was 3.2 msec by design; mean final precharge duration was 3.30 ± 0,34 msec. This algorithm is universally applicable in permanent pacing systems, as it is valid in unipolar and bipolar pacing and it does not require an intrinsic cardiac rhythm.     

A most unusual pacemaker

We present a case of pacemaker artifact on 12-lead electrocardiogram that was initially interpreted as malfunction of the patient's dual-chamber cardiac pacemaker. It was ultimately determined to arise from an extracardiac gastric pacemaker, which had been inserted for refractory, severe diabetic gastroparesis. Proper functioning of both devices was confirmed, and settings were adjusted to test for interdevice interference. This is a report of a patient with both cardiac pacemaker and a gastric pacemaker. We review the literature on patients with multiple pacemaker devices, and conclude with several practical considerations for their care.     

New onset of pacemaker dependency after permanent pacemaker implantation

Pacemaker dependency has dangerous consequences under conditions of electromagnetic interference, unrecognized lead dysfunction, and battery depletion, and has been associated with cardiovascular and overall mortality. The aim of this study was to examine the incidence of new onset of pacemaker dependency during long-term follow-up after pacing system implantation. The study included 518 patients (mean age 72.9 +/- 10.4 years) who presented with intrinsic rhythms at the time of implantation. Indications for pacing were sick sinus syndrome (SSS) in 275 (53%) patients, AV block in 209 (40%), and AF with bradycardia in 34 (7%) patients. The mean follow-up was 3.7 +/- 2.7 years (range 1-17). Pacemaker dependency was defined as the absence of an intrinsic rhythm during backup pacing at 30 beats/min for 30 seconds. New onset of pacemaker dependency was observed in 23 (4.4%) of the 518 patients at a mean of 3.1 +/- 2.7 years of follow-up. Pacing indications were SSS in 6 (2.2%) of 275 patients, AV block in 15 (7.2%) of 209, and AF with bradycardia in 2 (5.9%) of 34. Patients with AV block had a significantly higher incidence of pacemaker dependency than patients with SSS (odds ratio 3.51; 95% CI 1.3 to 9.3; P = 0.012). The average annual rate of new pacemaker dependency was 1.6% during an 8-year follow-up. The incidence of new onset of pacemaker dependency varied among pacing indications, and was significantly higher in patients with AV block than patients with SSS.     

Delayed complications following pacemaker implantation

Acute complications resulting from permanent pacemaker implantation are well known and include perforation of the right atrium or right ventricle. Recently, several reports have described the occurrence of perforation and pericarditis as late complications following pacemaker implantation. These complications may occur days to weeks following uncomplicated pacemaker implantation and may lead to death if they are not recognized early. Five patients with late complications caused by active-fixation leads are reported and the clinical features of their presentation and management are reviewed. Late perforation of the right atrium or right ventricle is an uncommon complication after pacemaker implantation but should be suspected by the general cardiologist in a patient who has a device implanted within a week to several months prior to the development of chest pain.     

Upgrade of a chronic unipolar pacemaker to a biventricular pacemaker system

With the development of cardiac resynchronization for patients with symptomatic heart failure and electrical dyssynchrony, there are patients with chronic pacemakers that meet the indications for biventricular pacing. Typically, this involves placement of the left ventricular lead with generator change to a dual chamber biventricular pacemaker, maintaining use of the right-sided leads. There are patients with older pacemaker systems that have unipolar leads with 5/6-mm pin connectors. These patients present challenges to upgrade that are separate from typical IS-1 system upgrades. Currently there are no pacemakers manufactured that accept the chronic 5/6-mm unipolar leads directly with the additional IS-1 left heart lead. This report presents one such case in which a combination of adaptor and lead replacement resulted in upgrade to a biventricular system.     

Pseudo SVT in the pacemaker patient

This is an interesting report of a supraventricular tachycardia in a paced patient with intermittent atrioventricular nodal block. Only electrophysiology testing revealed the correct diagnosis. Images explain how pacemaker timing cycles and refractory periods can confuse an otherwise straightforward diagnosis.     

The autodiagnostic pacemaker.

Loss of normal pacemaker stimulation and/or sensing functions requires prompt detection, automatic correction, and automatic and continuous "marking" of the intermittent failure. The autodiagnostic pacemaker (ADP) detects "failure to capture" (FC) by distinguishing, at its single stimulating and sensing electrode, between the normal biphasic cardiac response evoked by an adequate stimulus (corresponding to the QRS and T waves on the surface cardiogram) and the monophasic pseudo-response generated by electrotonic spread of a subthreshold stimulating current. Detection of "failure to sense" (FS) spontaneous cardiac activity requires two amplifiers: a "timing control" amplifier of standard fidelity and standard (approximately 250 ms) refractory period, and a second amplifier which has negligible refractoriness and provides high fidelity amplification of all evoked and spontaneous activity. Failure to sense (FS) is defined as a specified number of consecutive failures to recycle correctly the pacemaker's timing circuits. Similarly, a specified number of consecutive failures of the stimulus to evoke an active cardiac response is defined as a failure to capture (FC). When FC is detected, the ADP doubles the applied stimulus voltage and generates marker pulses which follow every subsequent stimulus by 40 ms. The marker pulses appear on the surface electrocardiogram, serving as an externally detectable "memory" of the earlier, possible corrected, failure. When FS is detected, non-stimulating marker pulses, of a different time relation (80 ms delay) to each stimulus, are generated continually and can also be detected externally. The ADP has been tested in 14 anesthetized, open-chest dogs. Unipolar rather than bipolar electrodes were used as they rpovided more reliable stimulation and more satisfactory electrograms for detection.     

Temporary transvenous pacemaker placement in the Emergency Department

Emergency Department placement of a temporary transvenous cardiac pacemaker offers potential life-saving benefits, as the device can definitively control heart rate, ensure effective myocardial contractility, and provide adequate cardiac output in select circumstances. The procedure begins with establishment of central venous access, usually by a right internal jugular or left subclavian vein approach, although the femoral vein is an acceptable alternative, especially in patients who are more likely to bleed should vascular access become complicated. The indications for the procedure, as well as the equipment needed, are reviewed. Both blind and ECG-guided techniques of insertion are described. Methods of verification of pacemaker placement and function are discussed, as are the early complications of the procedure.     

双腔起搏器治疗严重缓慢性心律失常

目的 :评价双腔起搏器治疗严重缓慢性心律失常的临床疗效及价值。方法 :5 2例双腔起搏器 ,其中 41例DDD起搏器 ,11例DDDR起搏器。病态窦房结综合征 (sicksinussyndrome,SSS) 39例 ,房室传导障碍 13例 ,其中包括Ⅲ度房室传导阻滞 (thirddegreeAVblock ,Ⅲ°AVB) 3例 ,高度房室传导阻滞 (highdegreeAVblock ,HDAVB) ,Ⅱ度Ⅱ型房室传导阻滞 (typeⅡseconddegreeAVblock ,Ⅱ°Ⅱ型AVB) ,三分支传导阻滞 (threefascicularblock ,TFB)病人 ,以上病人均伴有昏厥、黑朦或严重头晕。电极植入途径为锁骨下静脉或头静脉。结果 :5 2例术后随访 1 78个月 ,临床疗效显著 ,不仅防止心博骤停发生 ,脑缺血症状消失 ,而且生活质量明显提高。 3例SSS者阵发房颤 (atrialfibrillation ,Af)术后消失 ,10例SSS者结合药物治疗Af发作次数减少。 1例扩张性心肌病死于左心衰竭。并发症 :心房感知过度 2例 ,心房感知不足 1例 ,心室电极阈值升高 1例 ,囊袋感染 1例 ,血肿 1例。结论 :双腔起搏器为较理想的生理性起搏 ,本研究证实能有效地治疗严重SSS和房室传导障碍的病人     

Criteria for pacemaker explant in patients without a precise indication for pacemaker implantation

Unnecessary pacemaker implantation may cause significant social and psychological consequences, the inconvenience of periodic office visits, and the expense of pulse generator replacement. Establishing adequate criteria for explantingpacemakers is crucial and has notyet been described. This study presents the results of a study protocol for explanting the pacemaker in patients without a clear indication for pacemaker implantation. Seventy pacemaker users without a clear reason for the implantation were included in the study conducted from August 1986 to November 1998 and were prospectively followed. The investigation consisted of clinical and neurological evaluations, echocardiogram, exercise testing, and tilt table testing. When these tests were negative, the pulse generator energy and stimulation rates were reprogrammed to the lowest values. Periodic Holter monitoring was conducted during follow-up. When asymptomatic for 1 year, patients underwent an electrophysiological evaluation of sinus and atrioventricular junction function and ventricular vulnerability. When the electrophysiological study was negative, pacemaker explantation was performed. Of the 70 patients, 35 had their pacemaker explanted; 3 were excluded due to a positive tilt table test and electrophysiological study, and 3 are waitingfor pacemaker explantation. Mean follow-up after pacemaker explantation was 30.3 months, and all patients remained asymptomatic, exceptfor one patient who died of a noncardiac cause. Critical analysis of pacemaker users without a well-established indication is justified because it may allowpacemaker explant in a significant proportion of these patients, and it may bring considerable social, economic, and psychological benefits.     

Venous obstruction after pacemaker implantation

BACKGROUND: Central vein leads are known to predispose to venous obstruction. Although usually asymptomatic, obstruction may render electrode removal difficult. This study aimed at quantifying changes in venous calibers in a prospective fashion by intravenous contrast venography (ICV) before and after pacemaker (PM) or cardioverter-defibrillator implantation. METHODS: One hundred and fifty (mean age 67; 61% male) consecutive patients were enrolled, and followed for 6 months. A successful ICV was done at baseline prior to implantation and at 6-month follow-up in 136 (91%) patients. Minimum (D(min)) and maximum (D(max)) vessel diameters were obtained from both ICVs. A new stenosis was defined as a 50% diameter reduction in a venous segment when compared to baseline. We implanted a total of 230 electrodes: 47 (34.6%) single lead, 84 (61.8%) 2-lead, and 5 (3.7%) 3-lead systems. RESULTS: At baseline ICV, 10 patients (7%) were found to have venous anomalies, including 8 patients with obstructive lesions, 1 patient with a persistent left superior vena cava, and 1 patient with double axillary vein. At 6 months, a new obstructive venous lesion had developed in a total of 19 (14%) patients, none of whom exhibited any local symptoms. Of these patients 14 (10%) had a stenosis (mean D(min) 4.6 mm and diameter 38% of baseline), and 5 (3.6%) had a complete venous occlusion. In most cases the new stenosis developed in a location where the vessel was narrowest at baseline. Clinical predictors for the development of stenosis were atrial fibrillation at baseline and biventricular PM implantation. CONCLUSIONS: This is the first systematic study to quantify venous changes after PM or ICD implantation. Our study shows that venous anomalies rendering PM implantation difficult are not infrequent. The incidence of new venous obstruction was 14%. Atrial fibrillation and biventricular PM implantation were independent predictors of venous obstruction.     

Reticulated telangiectatic erythema of the pacemaker

Reticulated telangiectatic erythema is a rare entity; it has been reported to occur following the placement of implanted cardiac devices and drug delivery systems. Histologically, reticulated telangiectatic erythema of the pacemaker is characterized by slight spongiosis and increased dermal telangiectasias. We describe a patient that developed reticulated telangiectatic nonpruritic patches on the left chest after the placement of a pacemaker. The patient responded favorably to the removal of the pacemaker.     

Asystole during pacemaker magnet application

Pacemaker magnet application during surgery for patients who are pacemaker‐dependent is often utilized to avoid perioperative inhibition from electromagnetic interference. We present a case during which such routine magnet use resulted in an unexpected response and discuss the limitations and nuances of this common practice.     

A rare case of "runaway" pacemaker in a modern CPU-controlled pacemaker

"Runaway" pacemaker is a rare entity that occurs when a malfunctioning artificial cardiac pacemaker abruptly accelerates its pacing rate above the set upper rate limit. This can result in life-threatening dysrhythmia. Runaway pacemaker used to occur more frequently in older model pacemakers, but now with newer pacemaker generators, runaway pacemaker is a rare entity. We report the case of a runaway pacemaker in a modern CPU-controlled pacemaker in a 79-year-old man presenting with lightheadedness and review the literature regarding this rare entity.     

Multiple pulse generator malfunctions with a dual chamber pacemaker

The aim of this study was to evaluate the dual chamber uni/bipolarpacemaker Minidual 50, manufactured by Sorin Biomedica. Between 1995 and 1998, 66 Minidual 50 models were implanted at the Heart Institute. During the follow-up period of 33 +/- 12.8 months (range 0-50 months), total function loss in seven (10.6%) units and false threshold measurement of sensing and pacing in three (4.5%) patients were observed. Average time from implantation to malfunction was 37 months (range 28-42). Malfunction was unrelated to battery status and could not be predicted by any measures obtained during the pacemaker follow-up period. Kaplan Meyer survival curve predicted a 70% 4-year malfunction-free survival of that pacemaker model. Given this high rate of total malfunction and the unpredictable nature of its occurrence, the authors recommend the replacement of all remaining Minidual 50 units at risk, at least in dependent patients.     

Sleep syncope: treatment with a permanent pacemaker

Vasovagal syncope usually occurs during upright posture, but Jardine et al. have described a variant that occurs at night. During "sleep syncope" patients are awakened from sleep with nausea, abdominal cramping, or a sense of impending diarrhea; get up; and faint in the bathroom. We report on a patient with recurrent sleep syncope (with physical injury) in whom an asystolic pause was documented during one of her "sleep syncope" spells. Implantation of a dual chamber pacemaker (5-year follow-up) "cured" her of further syncope. This is a report of pacemaker use for this unusual form of reflex syncope.     

Runaway pacemaker syndrome and intermittent nonoutput as manifestations of end of life of a VVI pacemaker

A case of a runaway pacemaker with intermittent nonoutput failure of a VVI Intermedics pacemaker is presented. This is the first report of such a phenomenon in that type of pacemaker with no apparent reason other than approaching battery end-of-life. The reported case warrants a close follow-up of patients with the same type of device.