Marcel Limousin

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.

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.

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.

Mode Switch Despite Undersensing of Atrial Fibrillation in ODD Pacing

Mode switching algorithms are commonly used to protect the ventricles against high rates induced by atrial tachycardia. In the case of atrial fibrillation (AF), the response of these algorithms depends on the quality of atrial sensing. The Chorum 7234 DDDR pacemaker uses a new mode switching algorithm, based on a statistical analysis of the atrial rhythm. It includes two criteria of diagnosis: “high” if more than 28 of 32 cycles are abnormally accelerated; and “low” if more than 36 of 64 cycles are abnormally accelerated. Methods: From a taped database of electrophysiological studies, episodes of AF lasting more than 2 minutes were selected. A tape recorder replayed the atrial signals into an external Chorum device. Each episode was replayed eight times with a programmed atrial sensitivity increasing from 0.4 –2.0 mV. For each criterion of diagnosis and each programmed sensitivity, the percentage of atrial sensing, the time to switching, and the mean ventricular rate were measured. Ten episodes of AF from 10 patients (9 men and 1 woman; ages 62 ± 16 years) were included: 1.95 ± 0.97 mV and 196 ± 64 ms. The sensitivity of the algorithm to diagnose atrial tachycardia reached 100%, for an atrial sensitivity set between 0.4 and 1.0 mV. The mean percentages of atrial sensed events were 74%± 18% and 46%± 9% for the “high” and “low” criteria, respectively. The mean diagnostic times were 28 ± 26 seconds and 68 ± 27 seconds, respectively. Sensing of < 23% of AF events resulted in failure to diagnose the arrhythmias by both algorithms. In the event of diagnostic failure, the mean ventricular pacing rate was 79 ± 9 ppm. Conclusion: Up to an atrial sensitivity of 1 mV, 100% of AF episodes were diagnosed. The Chorum mode switching algorithms are 100% reliable if > 45% of the AF waves are sensed. In the event of switching failure, the ventricle is protected by an average rate remaining below 80 ppm. (PACE 1996;

A New Algorithm for a High Level of Protection Against Pacemaker-Mediated Tachycardia

Pacemaker‐mediated tachycardia (PMT) is a well‐known complication of DDD pacing. PMT needs a permeable V‐A conduction and is usually initiated by a premature ventricular or atrial systole, artifact sensing, or misprogramming (long AV delay [AVD]). Today, protection against PMT is expected from pacemaker multiprogrammability. Unfortunately, this prevention is often ineffective; postventricular atrial refractory period (PVARP) must be prolonged, which limits the upper tracking rate and the patient capacity. The new Chorus ELA Medical DDD pacemaker provides classic protection against PMT (PVARP prolongation after premature V or A complex, magnet application, noise sensing), hut also automatically reduces an eventual PMT and adjusts AVD or PVARP for a high level of protection. The process is divided in four steps: (1) a sensing step for 16 cycles, with V‐P conduction analysis; (2) confirmation of the presence of the PMT and analysis of V‐A conduction time; (3) a termination step, by extending the PVARP after the following ventricular heart beat; and (4) in case of immediate recurrence of the tachycardia, reprogramming of the AVD and eventually of the PVARP. By first reducing AVD, before reprogramming PVARP, the pacemaker preserves point 2:1, providing a higher exercise capacity. This algorithm was successfully tested in three patients who had a permeable V‐A conduction, without any adverse effect.

Carotid Sinus Syndrome: Acute Hemodynamic Evaluation of a Dual Chamber Pacing Mode

Cardiac pacing is the treatment of choice in patients with carotid sinus syndrome (CSS), Three different pacing modes were tested in 20 patients (16 males, 4 females; mean age 75 ± 9 years) with documented symptomatic CSS, Three carotid sinus massages (CSM) were performed in each supine patient successively paced in random order in: DDI—the reference pacing mode; DDD—automatic mode conversion (DDD/AMC) allowing automatic switching from AAI to DDD when AV block occurs; DDD/AMC plus a trial acceleration (DDD/AMC + ace); and OOO (CSM without pacing) to determine whether the vasodepressive effect was still present 10 minutes after the preceding CSM. Intraarterial blood pressure was continuously monitored. Results were expressed as the value of the mean systolic BP at TO + 3 s + 6 s … TO + 30 s divided by the value of the mean systolic blood pressure prior to onset of CSM. The drop in arterial blood pressure was more severe in the DDI mode than in DDD/AMC (P < 0,001) and DDD/AMC + acc (P < 0.0001) in 20 patients. In the OOO mode, the drop in arterial blood pressure was most marked and greater than in the DDI mode (P < 0.0001). The average time between start of the CSM and onset of the drop in blood pressure was the same in the three dual chamber modes. We conclude that the DDD/AMC mode significantly improves the vasodepressor response to CSM compared to the DDI mode. There is a current trend favoring DDD/AMC + acc over DDD/AMC.

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.

Automatic Adaptation of the Basic Pacing Rate in Response to Minute Ventilation

Rate responsive pacing based on minute ventilation (VE) correlates highly with metabolic demand. This type of sensing also recognizes extended periods of rest. The Chorum pacemaker includes a rate responsive algorithm that modulates the basic rate according to phases of activity versus sleep. Forty‐six patients (mean age 78 ± 15), received a Chorum pacemaker for atrioventricular block in 17 cases, sick sinus syndrome in 25, and mixed disorders in 4. Holter monitoring was performed to analyze heart rate and to examine the circadian adaptation of the minimal pacing rate. The mean basic rate was programmed at 63 ± 5 beats/min, and the sleep rate at 52 ± 4 beats/min. Seventeen patients had spontaneous heart rates consistently above the programmed basic rate, and 6 had sustained supraventricular tachyarrhythmias. One‐half of the patients had periods of pacing at the programmed sleep rate. The mean diurnal pacing rate was 68 ± 5 beats/min compared to a mean nocturnal rate of 60 ± 4 beats/min (P < 0.0001). The average time spent at the basic rate was 37 ± 30 min (0–110) during daytime (4%), versus 242 ± 153 min (20–477) at night (45%, P < 0.0001). No adverse effect was observed in this patient population. VE allows a reliable detection of the sleeping periods as well as an adjustment of the basic rate in accordance. Caution is advised in cases of bradycardia dependent tachyarrbythmias.

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.

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.