Remi Nitzsche

A New Pacing Algorithm for Overdrive Suppression of Atrial Fibrillation

Constant rapid pacing may suppress arrhythmias, but it is usually poorly tolerated in the long term. We report a pilot study of a new pacing algorithm for overdrive suppression of atrial premature complexes (APCs) and atrial fibrillation (AF), which prevents postextrasystolic pauses and varies the pacing rate in response to the frequency of APCs. The algorithm was tested in a multiple crossover study for 24 hours in dual chamber pacemakers implanted in 70 patients. Comparison was made on ambulatory recordings between the number of atrial arrhythmias commencing with the algorithm active and inactive. In all cases, the algorithm functioned as designed. No patient was aware of its operation, and no malignant arrhythmias were induced. The 36 recordings that showed atrial arrhythmia were included for analysis. The effects of the algorithm were: APCs (estimated from pacemaker statistics) reduced in 18 patients, increased in 8 (P = 0.02); atrial salvos reduced in 12, increased in 4 (P = 0.041); and AF reduced in 11, increased in 8 (P = NS). In all patients with frequent AF (> 5 episodes in total), fewer episodes occurred when the algorithm was active. We conclude that the algorithm is safe and well tolerated, reduces atrial ectopic activity, and may reduce the frequency of sustained atrial fibrillation.

Preliminary clinical experience with the first dual chamber pacemaker defibrillator.

The lack of specificity of VT detection is a significant shortcoming of current ICDs. In a French multicenter study, 18 patients underwent implantation of the Defender 9001 (ELA Medical), an ICD utilizing dual chamber pacing and arrhythmia detection. Over a mean follow‐up period of 7.1 ± 4.5 months, 176 tachycardia episodes recorded in the device memory were analyzed, and physician diagnosis was compared with that by the device. All 122 VT/VF episodes were correctly diagnosed, as were 51 of 53 supraventricular tachyarrhythmias. Two episodes of AF with rapid regular ventricular rates were treated as VT, and a third episode, treated as VT, could not be diagnosed with certainty. A dual chamber pacemaker defibrillator offers improved diagnostic specificity without loss of sensitivity, in addition to the hemodynamic benefit of dual chamber pacing. (PACE 1997;20

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.

AAIsafeR limits ventricular pacing in unselected patients.

Introduction: Dedicated pacing modes, such as AAIsafeR, prevent ventricular (V) pacing in selected patients. We report our experience in consecutive unselected patients.

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.

Diagnosis of Atrial Arrhythmias Using the Holter Function of a New DDD Pacemaker

The extension of random access memory now makes it possible to store electrocardiographic (ECG) information, referred to here as Holter function (HE), in the memories of new pacemakers, which can be used as diagnostic tools during long‐term follow‐up. This report describes our experience in 26 consecutive patients for whom the device was used to detect episodes of atrial arrhythmias (AA). An illustrative case is also presented to describe in detail the devices analytical method. Results: Fourteen AA profiles were successfully recorded in 10 patients by the pacemaker HF and correlated with confirmatory simultaneous surface ECG tracings. Three additional profiles were recorded in three other patients without simultaneous ECG recordings. A diagnosis of AA is established when the following findings are combined: (1) in all cases a large number of short interatrial inteivals (A INT); (2) in presence of AV block, interventricular intervals (VINT) stored between the lower programmed pacing rate and the upper rate limit or the fallback rate; (3) in absence of AV block, V INT stored between the basic rate and the AV node refractory period; (4) in case of fallback, (VVI function) no stored AV INT; and (5) in absence of fallback, great variability of AV INT (Wenckebach function). Conclusions: (1) Diagnoses of AA can be made with the pacemaker HE; (2) The homogeneity of the HF profiles makes them useful for long‐term follow‐up and will probably contribute and clarify the natural history of AA in DDD patients; (3) HF may also serve to monitor the safety and efficacy of antiarrhythmic drug therapy during long‐term follow‐up.

Use of a New Fallback Function to Prevent Endless-Loop Tachycardias: First Clinical Results

The methods used for preventing endless‐loop tachycardias (ELTs) most often consist of initiating a long postventricular atrial refractory period (PVARP) with the sensing of every event likely to induce ELTs, such as sensed premature ventricular contractions (PVCs). A new fallback function may be useful to prevent the initiation of ELTs. A window of atrial rate acceleration detection (WARAD) is initiated with the sensing of every sinus event and equals 75% of the preceding PP interval. If an atrial event is sensed during this period, as are premature atrial contractions (PACs), no atrioventricular (AV) delay is initiated, but an atrial puise output is delivered and a subsequent 31‐msec AV delay is started. Theoretically retrograde P waves are premature compared to sinus rhythm. They are therefore detected as PACs, and do not initiate AV delay, thus prohibiting the induction of ELTs. This function was tested in six patients, using external or implanted Chorus 2 pacemakers. Short PVARP (203 msec) and high atrial sensibility were programmed. Retrograde conduction was induced either by inefficient atrial pacing or a long programmed AV delay. Two different dual chamber settings were tested: dual chamber pacing with the fallback function On or Off. In every situation, the function proved effective in preventing ELTs: the number of tachycardia episodes went from 124 with the function programmed Off to 5 with the function programmed On for comparable durations. More than 75 ELTs effectively prevented by fallback have been recorded.

Very Low Ventricular Pacing Rates Can Be Achieved Safely in a Heterogeneous Pacemaker Population and Provide Clinical Benefits: The CANadian Multi-Centre Randomised Study-Spontaneous AtrioVEntricular Conduction pReservation (CAN-SAVE R) Trial

Background It is well recognized that right ventricular apical pacing can have deleterious effects on ventricular function. We performed a head-to-head comparison of the SafeR pacing algorithm versus DDD pacing with a long atrioventricular delay in a heterogeneous population of patients with dual-chamber pacemakers. Methods and Results In a multicenter prospective double-blinded randomized trial conducted at 10 centers in Canada, 373 patients, age 71±11 years, with indications for dual chamber DC pacemakers were randomized 1:1 to SafeR or DDD pacing with a long atrioventricular delay (250 ms). The primary objective was twofold: (1) reduction in the proportion of ventricular paced beats at 1 year; and (2) impact on atrial fibrillation burden at 3 years, defined as the ratio between cumulative duration of mode-switches divided by follow-up time. Statistical significance of both co-primary end points was required for the trial to be considered positive. At 1 year of follow-up, the median proportion of ventricular-paced beats was 4.0% with DDD versus 0% with SafeR (P<0.001). At 3 years of follow-up, the atrial fibrillation burden was not significantly reduced with SafeR versus DDD (median 0.00%, interquartile range [0.00% to 0.23%] versus median 0.01%, interquartile range [0.00% to 0.44%], respectively, P=0.178]), despite a persistent reduction in the median proportion of ventricular-paced beats (10% with DDD compared to 0% with SafeR). Conclusions A ventricular-paced rate <1% was safely achieved with SafeR in a population with a wide spectrum of indications for dual-chamber pacing. However, the lower percentage of ventricular pacing did not translate into a significant reduction in atrial fibrillation burden. Clinical Trial Registration URL: https://www.clinicaltrials.gov/ Unique identifier: NCT01219621.

Assistant Programming Software: A New Tool for an Improved Programming of Pacemakers

LASCAULT, G., ET AL.: Assistant Programming Software: A New Tool for an Improved Programming of Pacemakers. Programming the new DDD pacemakers is becoming increasingly difficult. One must take into, account the pacemakers complexity, the fact that some parameters are linked to others, and the clinical profile of the patient. This difficult problem will lead to the design of software to assist programming, which will help the implanting physicians in choosing adequate programmed settings adapted to the functioning of the device and to the physiology and pathology of the patient. These programming aides should meet certain basic requirements to make them safe, efficient, and easy to use. One such system designed by ELA Médical, “Programming Assistant” is herein described. The preliminary results of an initial study on the acceptance of this programming aide among physicians involved in cardiac pacing are given and discussed.

Incidence and Predictive Factors of Atrial Fibrillation in Paced Patients

We have designed a prospective observational study to analyze the incidence and predictive factors of atrial fibrillation (AF) during a long follow‐up, in a large population. Atrial fibrillation episodes were documented by the fallback mode switch (FMS) provided by implanted pacemakers. We have included 377 patients (61% men). The pacing indications were atrioventricular (AV) block (49%), sinus node disease (SND, 16%), bradycardia‐tachycardia syndrome (BTS, 5%), AV block + SND (19%), AV block + BTS (6%), and BTS + SND (5%). The mean age at implant was 75 ± 12 (range 28–95). Atrial fibrillation before inclusion was documented in 10% of patients. Drug therapy at first follow‐up included beta‐adrenergic blockers (17% of the patients), amiodarone (13%), and others (16%). The mean follow‐up was 30 ± 24 weeks. At least one AF episode was stored during follow‐up in the memory of 169 pacemakers (45%). Among patients without history of AF at implant, 46% had documented FMS during follow‐up. Patients with AF received more antiplatelet medications than patients without AF (P = 0.03). In patients with AF, New York Heart Association functional class was slightly higher, amiodarone and sotalol were more often prescribed, and the proportion of hypertension was higher than in patients without AF. However, these trends were not statistically significant. A significant higher incidence of premature atrial beats was observed in patients with AF than patients without AF (P < 0.0002). Patients with AF had a lower atrial percentage of paced events (55%) than patients without AF (63%, P < 0.02). These preliminary results confirm the high incidence of AF in paced patients and suggest a preventive effect of atrial pacing. The effects of other clinical variables may be confirmed with a longer follow‐up in a larger population.