Guy Pioger

Value of automatic processing and reliability of stored data in an implanted pacemaker: initial results in 59 patients.

Stored data in implantable pacemakers have rarely been used as a diagnostic tool because of the complexity. Our group bas developed software called AIDA, providing an automatic interpretation of data stored in memories of the Chorus (ELA medical) pacemaker. We com pared the results of AIDA analysis to surface ECG Holter interpretation in 59 patients (age 75 ± 9 years). In 33 cases, neither AIDA nor the Holter found any anomaly. Eleven patients demonstrated episodes of supraventricular tachycardia (SVT), confirmed by AIDA in ten patients; AIDA failure was due to nonsustained episodes of SVT not inducing mode switch. Loss of atrial sensing, pacemaker‐mediated tachycar dia, and ventricular extrasystoles were detected by AIDA in ten patients. Traditional Holter missed three cases. This initial study confirms that stored pacemaker data, automatically interpreted can provide reli able information over a 24‐hour period.

Failure Rates of Leads, Pulse Generators, and Programmers Have Not Diminished Over the Last 20 Years: Formal Monitoring of Performance is Still Needed

Formal Monitoring of Performance is Still Needed. In order to detect trends in the number of device or component failures that have occurred among permanent pacemaker systems since the 1970s, we reviewed the data of the five largest pacemaker manufacturers from the Bilitch Registry of permanent pacemaker pulse generators, the Stimarec failure registry, the general accounting office summaries of the United States Veterans Administration (VA) Registry of Pacemaker Leads, and the Implantable Lead Registry, from the Cleveland Clinic Lead registry, and the recalls and safety alerts issued by the United States Food and Drug Administration (FDA) over the last 20 years. The definition of failure followed the criterion, or criteria, developed within each registry and differed significantly between the registries. The 20‐year period between 1976 and 1995 was divided into 5‐year quartiles (QT): QT 1 = 1976–1980; QT2 = 1981–1985; QT 3 = 1986–1990; and QT4 = 1991–1995. For pulse generators, the number of models with failures in each quartile in the Bilitch Registry were: QT 1 = 9; QT 2 = 11; QT 3 = 17; QT 4 = 13. In Stimarec, the number of units reported as having reached a dangerous condition were: QTl = 710; QT2 = 212; QT3 = 114; QT4 = 310. From the FDA reports, the number of units included in recalls or safety alerts were: QT 3 = 6,085; QT4 = 135, 766. For permanent pacemaker leads, the numbers of failed or dangerous leads recorded in Stimarec were: QT 3 = 16; QT 4 = 32. In the VA Registry, the number of models having a below average survival was 2/92 (2.7%). In the Implantable Lead Registry, the number of models having a below average survival was 3/21 (14%). In the Cleveland Clinic series, 6/13 (46%) of lead models were recognized to have some failure involving the conductor, insulation, or connector. In the FDA reports, the number of leads involved in either recall or safety alert were: QT3 = 20,354; QT 4 = 332,105. For programmers, the number of units involved either in a recall or safety alert were: QT 3 = 11,124; QT 4 = 3,528. In all of these series, each of the five largest manufacturers had some models or units involved in each time period. This review of programs has revealed: 1. The incidence of failures, recalls, or safety alerts did not decline over time; and 2. Despite changes in technology, formal monitoring of pacemaker systems is still warranted.

Measurement of Minute Ventilation with Different DDDR Pacemaker Electrode Configurations

A rate responsive minute ventilation (VE) pacemaker was implanted in 49 patients (70.8 ± 40.0 years). A Chorus RM 7034 pacemaker was implanted in 43 patients and an Opus RM 4534 in six patients. Four sensor configurations were compared: atrial configuration (bipolar atrial lead) in 34 patients; ventricular configuration (bipolar ventricular lead) in 6 patients; unipolar configuration (double unipolar leads) in 6 patients; and floating configuration (VDD single‐pass lead) in 3 patients. The patients carried out 57 exercise tests in all with cardiopulmonary recording (CPX). Real VE and oxygen consumption (VO2) were recorded by the CPX, the VE measured by the sensor (VEsensor) was recorded in the pacemaker memory. The mean correlation between VE and VEsensor was 0.90 ± 0.08 (P < 0.001) and between VO2 and VEsensor was 0.86 ± 0.10 (P < 0.001). The mean correlation between VE and VEsensor by configuration type were as follows: atrial configuration = 0.89 ± 0.08; ventricular configuration = 0.95 ± 0.05; unipolar configuration = 0.87 ± 0.14; and floating configuration = 0.88 ± 0.05. In conclusion, VE may be reliably measured using different electrode configurations. A study conducted in a larger population should allow one to conclude that uniploar electrodes can be used in VDDR, AAIR, VVIR, or DDDR modes to measure VE.

Endless-loop tachycardias: description and first clinical results of a new fully automatic protection algorithm.

NITSCHÉ, R., ET AL.: Endless‐Loop Tachycardias: Description and First Clinical Results of a New Fully Automatic Protection Algorithm. Endless‐loop tachycardia ELT) is one of the most common pacemaker mediated tachycardia. An innovative ELT protection algorithm has proven to be clinically effective. A new improved version that will eliminate the need to program any parameter is now under clinical evaluation. Nine patients entered the study: six men and three women, aged 52 ± 22 years. This automatic algorithm needs only 10 cycles to detect and confirm an ELT. Three hundred thirty‐three ELTs lasting more than 9 cycles have been induced and analyzed. The total results are the following: mean duration: 6.7 sec ± 3.1; mean ELT rate: 137 ± 21.9 bpm, mean programmed upper rate limit (URL): 142.5 ± 26.5 bpm (Only 70% of ELTs presented rates equal to programmed URL). (1) ELTs reduced by postventricular atrial refractory period (PVARP) extension on one cycle: 291 ELTs (87%). ELT rate: 128.5 ± 18.2 bpm. (2) Retrograde block: algorithm operation may induce a retrograde block due to a short atrioventricular delay AVD) applied during the confirmation phase to discriminate an ELT from a stable sinus rhythm. Thirty‐two ELTs (10%) have been reduced and detected on a retrograde block occurrence. (3) Algorithm failure due to an unstable ventriculoatrial conduction time VACT) even at fixed rate or to a retrograde Wenckebach behavior on AVD reduction during the confirmation phase. A total of 10 algorithms failed to detect or confirm an ELT have been recorded 3%). Mean duration: 8.2 ± 4.2 sec, mean ELT rate: 148.9 ± 14.3 bpm. This new fully automatic algorithm has reduced 97% of ELTs, including high rate episodes (100–175 bpm). It allows 1:1 tracking adapted to the needs of the patient, by programming a short PVARP and a physiological AVD.

Spontaneous Versus Extraction Related Injuries Associated With Accufix J‐wire Atrial Pacemaker Lead: Tracking Changes in Patient Management

To make recommendations for management of potentially fatal failure of the Accufix series of atrial J‐wire permanent pacemaker leads, we closely monitored the number of injuries and fatalities resulting either from spontaneous fracture of the J‐wire or from attempts to extract the lead. In a population of 30,357 patients, 2,298 patients are enrolled in a prospective follow‐up Multicenter Study, the remainder are patients with known clinical status from voluntary reporting, and 2,992 patients died following implant. In the remaining 27,365 patients, 6 deaths have been attributed to J‐wire related injury (J‐inj) while 13 were complications (E‐inj) associated with 4,076 lead extraction procedures (3,974 intravascular (intra)/ 102 primary thoracotomy (PT). The date of occurrences were from 1994 to November 1997. Conclusions: (1) Since lead extractions were not conducted in a controlled study, it is not known whether the deaths associated with lead extraction is in excess of what would have occurred if these leads had not been removed in this specific subset.

Circadian Variations in Minute Ventilation Can Be Reproduced by a Pacemaker Sensor

Special software allowing the memorization of 24‐hour minute ventilation can be loaded into the memoiy of the Chorus RM, a DDDR pacemaker driven by minute ventilation. This feature was tested in the postimplant period in 13 patients. Measurements of minute ventiiation, respiratory rate, and respiratory amplitude were analyzed according to prospectively defined diurnal and nocturnal time periods. Minute ventilation decreased by 39% (P < 0.001) from the diurnal to the nocturnal phase, while respiratory rate and amplitude decreased by 18% and 28%, respectively (P < 0.001 each). Thus, minute ventilation allowed discrimination between sleep and waking hours. This information could be utilized to modulate the backup rate of the pacemaker.

Kaplan-Meier analysis of freedom from extraction or death in patients with an Accufix J retention wire atrial permanent pacemaker lead: A potential management tool

Morbidity (36 cases) and mortality (6 cases) have been reported in patients with Accufix J retention wire atrial leads. This has resulted in ongoing patient fluoroscopic monitoring as well as lead extractions. The estimated implanted worldwide population is 40,860. Estimating the size of the remaining population at risk is an important tool for assessing patient management guidelines. Results: The Kaplan‐Meier method can be used to calculate the cumulative probability of remaining free of extraction and death for patients based on implant duration. The individual Kaplan‐Meier curves for lead extraction and patient survival can also be computed. Based on the Multicenter Study (MCS) population of 2,298 patients, the probability that a patient is alive with the lead still implanted at 5 years implant duration is 52.5%. The event‐free survival rate at 5 years implant duration is 81.3%. The corresponding probability of remaining free from injury due to the J‐wire is 99.9% at 5 years implant duration. Assuming similar rates of death and extraction, these results can be extrapolated to the world wide population. Conclusions: The management of Accufix patients must consider patient longevity, the probability of J‐wire morbidity/mortality, and the probability of extraction complication morbidity/mortality. The probability of remaining at risk as a function of time from implant can be calculated from the events known in the MCS patient population. These event‐free survival estimates can be used to identify subsets of the population at greater or lesser risk based on various clinical parameters.

Improved Dual Chamber Pacing Mode in Paroxysmal Atrioventricular Conduction Disorders

GIRODO, S., ET AL.: Improved Dual Chamber Pacing Mode in Paroxysmal Atrioventricular Conduction Disorders.Dual chamber pacing may sometimes be directly indicated for carotid sinus hypersensitivity, vasovagal syndrome, and certain cases of sinoatrial block and intermittent atrioventricular (AV) block, although AV conduction is dominantly normal. At times of normal AV conduction, competition between ventricular pacing and spontaneous ventricular depolarization may occur, with its adverse hemodynamic effects on ventricular function and unnecessary drainage of pacemaker battery energy. A new mode of stimulation is described, called automatic DDD mode, which functions in ‘pseudo‐AAI’ mode during normal AV conduction and reverts to classical DDD function during episodes of AV blocks. Furthermore, during pseudo‐AAI function, the pacemaker measures certain physiological parameters that serve to automatically program certain parameters used in DDD mode. Preliminary clinical evaluation has shown that this new mode functions satisfactorily.

Ventricular Protection Against Atrial Arrhythmias in DDD Pacing Based on a Statistical Approach: Clinical Results

Atrial arrhythmias (AA) are commonly encountered in DDD paced patients. Newer dual chamber pacemakers (PM) possess mode switching functions that convert pacing to an asynchronous mode when AAs are detected. The lack of a reliable mode switch leading to rapid, irregular ventricular responses may result from AA undersensing. To avoid this, the DDDR PM Chorum 7234 Eta Medical AA diagnosis is based on a statistical approach: the PM constantly compares arrhythmic and sinus cycles and, based on “strong” and “weak” criteria, provides for rapid or slower mode switch. The aim of the study was to evaluate the efficiency and reliability of these two criteria. Thirty‐one patients with a Chorum 7234 implanted for AV block (11), sinus dysfunction (10), both (5), or hypertrophic obstructive cardiomyopathy (5) were evaluated at 24 hours and 1 month using the internal memory (IM) of the PM, surface 24‐hour Holter recordings, and exercise testing. Interrogation of the IM on the first day of study showed that 8 patients had mode switching episodes, based only on the strong criterion confirmed by the surface Holter recording. At I month, the IM revealed mode switching episodes in 12 patients, 6 of whom had used the weak criterion. No inappropriate mode switching episode was recorded during exercise testing at the 1‐month follow‐up. These results confirm the reliability and efficiency of this algorithm as well as the requirement for a specific algorithm to compensate for transient loss of sensing during AA.

Cumulative Hazard Analysis of J‐Wire Fracture in the Accufix Series of Atrial Permanent Pacemaker Leads

To permit a more complete analysis of J‐wire fracture in the Accufix series of atrial permanent pacemaker leads, the time to occurrence of all known fractures and injuries has been redefined relative to the duration of risk exposure, that is, according to the interval of time between implant and occurrence of the event. This redefinition permits application of a cumulative hazards model to the data, which previously has not been explored. Predictors of J‐wire fracture can be tested using this method. This also permits parametric curve‐fitting for determination of linearity or constancy of risk of events over time. Results: Among 2,063 Multicenter Study (MCS) leads analyzed, 381 fractures of the J‐wire were identified. Stratified analysis based on cumulative hazard curves identified a more open shape of the J‐wire as predictive of fracture, which supports the results previously reported based on logistic regression analysis. Fitting a Weibull curve to the cumulative hazard of J‐wire fracture gives a shape parameter equal to 0.85. This value indicates that the instantaneous hazard of J‐wire fracture decreased over time from implant. Conclusions: (1) The cumulative hazard function can be used to examine predictors of J‐wire fracture and preliminary findings support the previously identified predictor of J shape; (2) Based on these analyses, the rate of J‐wire fracture appears to decrease slightly as time from implant increases.