Jean-Luc Bonnet

Evaluation of a Dual Sensor Rate Responsive Pacing System Based on a New Concept

The minute ventilation is known to be one of the most physiological indicators of exercise. A curvilinear relationship between VE and the normal sinus rhythm (NSR) has been demonstrated in healthy patients. The aim of this study is to show that a pacemaker based on a VE sensor can reproduce such a relationship. Eighty‐one patients received a Talent DR 213 (ELA Medical, Montrouge, France) pacemaker with a third‐generation rate responsive algorithm. At 1‐month follow‐up, the patients underwent a treadmill exercise test, after which three groups were defined: group 1 had 6 patients who were 100% paced throughout the exercise test; group 2 had 10 patients who maintained NSR throughout the test; and group 3 had 12 patients who had cardiopulmonary recording during the exercise test. In group 1 patients, the simulation function computed the simulated rate (sim‐rate), which was compared to the sensor‐driven rate (SDR). In group 2 patients, sim‐rate was compared to the NSR. In group 3 patients, cardiac and metabolic reserves were compared to determine the appropriateness of the rate response to exercise (HRR% vs MR%). The results showed that the mean correlation coefficient between sim‐rate and SDR was 0.983 ± 0.005 (P < 0.001); the mean correlation coefficient between NSR and SDR was 0.92 ± 0.07 (P < 0.001); and a linear relationship was found between HRR% and MR%, with a mean slope of 1.1 ± 0.2 that was significantly equal to the theoretical value of 1 (P = NS). In conclusion, combining an activity‐driven sensor with a physiological sensor allows the preservation of a physiological rate response during exercise.

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.

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;

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.

Comparison of Metabolic Expenditure During CAEP Versus a Test Adapted to Aerobic Capacity (Harbor Test) in Elderly Healthy Individuals

Cardiopulmonary exercise tests are frequently used to test rate responsive pacemakers. The chronotropic assessment exercise protocol (CAEP) has been specifically proposed for the evaluation of rate responsive pacing systems. A mathematical method, based on CAEP measurements, was developed with a view of normalizing the exercise induced metabolic response. CAEP was compared to a tailored protocol (Harbor), adapted to the metabolic capacity of each patient. Harbor was set to keep the exercise duration within 10 minutes and achieve a workload as linear as possible. Metabolic parameters were continuously recorded by a cardiopulmonary system. Those data were used in the construction of slopes by the normalization method. The results of the tests performed in 16 elderly healthy patients showed no differences in metabolic or functional parameters. Slopes of the mathematical model were comparable (1.09 ± 0.16 for CAEP vs 1.07 ± 0.17 for Harbor), though both were higher than the value of 1, defined as normal. In both cases, linearity was confirmed by the coefficient of correlation (0.98 ± 0.02 for CAEP and Harbor). In conclusion, no significant differences were found in the outcomes of the two protocols. Higher values of the slopes with the normalization method can be explained by the definition of the maximal predicted heart rate as 220 — age, which is probably not appropriate for elderly, healthy, active subjects.

Comparison of the Cardiopulmonary Response to Exercise in Recipients of Dual Sensor DDDR Pacemakers Versus a Healthy Control Group

PAGE, E., et al.: Comparison of the Cardiopulmonary Response to Exercise in Recipients of Dual Sensor DDDR Pacemakers Versus a Healthy Control Group. The authors previously have shown in healthy subjects that age related loss of muscular strength did not alter the chronotropic response during treadmill exercise, whether with sudden onset of effort, as in the chronotropic assessment exercise protocol (CAEP) or more gradual effort as in the Harbor exercise protocol. This study was performed to verify that in patients suffering from chronotropic insufficiency, and in absence of other effort‐limiting disorders, “physiologic” pacing enables a cardiorespiratory response comparable to that of age‐matched healthy subjects. Furthermore, the aim of the study was to confirm that the response of a new dual sensor‐based pacing system was properly adapted to the metabolic demand, whether during CAEP or during Harbor test, by subjecting patients to both protocols. All study participants were able to undergo treadmill exercise testing, had normal cardiopulmonary function tests at rest, and no cardiac, muscular, or pulmonary disease. A healthy group (control) included 16 subjects (mean age 70.4 ± 3.9 years), and the test group (pacemaker [PM]) included 9 subjects (mean age 67.1 ± 10.8 years) permanently paced for isolated chronotropic insufficiency with a dual sensor pacing system. All subjects underwent CAEP and Harbor tests with measurements of gas exchange, 24 hours apart, in randomized order. All subjects reached an appropriate level of exercise, as expressed by mean lactate plasma concentrations, which were slightly higher in the control than the PM group during CAEP (4.9 ± 1.9 vs 3.7 ± 1.9 mmol/L, NS) and Harbor (5.3 ± 1.9 vs 3.8 ± 1.8 mmol/L, P < 0.05) tests. No statistical difference was observed in VO2 and VE at peak exercise between the two groups during either test. In the PM group, heart rate at peak exercise and metabolic reserve slope were higher during the CAEP than the Harbor protocol. These two measurements were significantly lower than in the control group. The PM group also had lower plasma lactate concentrations and dyspnea/fatigue scores. The Harbor test seems less suitable than the CAEP test to study the chronotropic response of pacemakers with dual sensors during exercise. A high performance of the new dual sensor‐based pulse generator was confirmed in this physically fit patient population, whose peak heart rate was considerably higher than in other similar studies. (PACE 2003; 26[Pt. II]:239–243)

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.

A minute-ventilation single-sensor can provide a fast response at the onset of exercise

EFFICACY OF TRANSCATHETFR CARDIOVFRSION FOR CHRONIC UNTOLERATFD ATRIAL FIBRILLATION Fiorenzo Acquati MD, Fortunato Forgione MD, Salvalore Caico MD, Cecilia Saveri MD, Luca Tagliagambe MD. Gianni Cecchin MD, Giovanni Binaghi MD Division of Cardiology, Regional Hospital of Varese ITALY Internal electrical cardioversion (IKC) was recently proposed as a new method to restore sinus rhythmn chronit atrial fibrillalion (CAF). Between .August 1991 and May 1993 14 pts (3 valvular. 4 dilated cardiomyopathy, 5 hypertensive and 2 without heart disease) underwent lEC for CAF (mean duration 17 1+24 4 months) resistant lo external eleetrical cardioversion (mean 2 . I±I2 attempts) and badly tolerated despite the use of many antiarThythmic drugs (mean 2 8+1.0) All pts had a poor haemodynamic status due to loss of atria! apport (5 pts NYHA class II and 5 pts class HI) or lo high ventricular rate (4 pts NYHA class I!) An electric shock was given between an internal electrode positioned in the right atrium cavity and an external dorsal plate. A single 200 J synchronized shock was sufficient to restore sinus rhythm in all pts (acute success rate = 100%) No traumatic complication due to energy shock was observed, ihe only complications being transient complete AV block in 5 pts (36%) and transient RBB block in 2 pts (M%). Sinus rhythm was present at hospital discharge in 11/14 pts (78%) and during follow up in 8/14 pts (57%) at 1 month, in 5/11 pts (45%) at 6 months and in 3/5 pis (60%) at i year In conclusion, lEC is a safe and effective method to restore sinus rhythm in pts affected by chronic untoleraied AF, maintaining it long term in almost half of them Therefore [EC may be considered an alternative to AV node ablation procedures in selected patients SHORT LOW ENERCY TEST SHOCKS ARE MORE ACCURATE THAN LONG SHOCKS FOR ESTIMATING DEFIBRILLATION IMPEDANCES TP Adams, MS, MW Kroll, PhD, KC Kroll, BS, RS Lueders, JS Perttu, BS, AngeMed subsidiary of Angeion, Minneapolis, MN, USA. It bas been reported that low energy (LE) lest shocks overestinriate the high energy (HE) impedance of implanted defibrillalion electrodes. We hypothesized tbat this difference was actually due to tbe decreased electrocbemical activation with Ibe lower eleclrical fields of LE shocks and not due to the lower energy per se. We furlher hypothesized that, because of electrode capacitance effects, shortening the duration of the LE shock would fend to compensate (by decreasing tbe impedance) and give a more accurale impedance estimate. Titanium screens (3x5 cm) were slilched to swine hearts (n= 4) weighing 193 ±44 gm wblch were then placed in a saline bath. HE shocks and LE shocks of conventional and shorl duration were given. Results: Delivered EnerRy Inilial Voltage duration Z HiRb Energv 30,7 ± 0.26 J 750 V 8 ms 46.8 ± 1.3 Q Standard LE 0,6 ± 0.03 ! 100 V 8 ms 54,6 ± 2.5 n Short LE 0,056 ± 0,0016] 100 V 0.3 ms 51.3 ± 0.4 iJ The short LE shock had less error (4.5 ± 1.4 « vs 7.8 ± 2.8 il. p< 0.0001) than did the standard duration shock in predicting the HE shock impedance. This was in spite of Ihe fact that it had about 1/10 of the energy of the standard duration lest shock. We conclude that it is not true in general that low energy test shocks have higher impedances than high energy shocks. A very low energy, short duration, shock can give a more accurate impedance estimate than a higher energy test shock of standard duration. The use of short duration test shocks in clinical implant procedures may warrant further exploration. EVMUATKH VTm ffl flCtHHOtHHi-Bflar mAPnVf> «̂3E ITALIAN MJl.TKIKreB SlUff CN TIE (PI EMEL VB. ntUO ADim>I (W)) et al . Serw. elettrtBtirajlazimD od elettroriaiol&gia cffldiasa Cep. Sai Canillo de Lellis, Ifctne, Italy SUxfy objecUves: t ie cbjecUve of the clinical s t u^ nee to eiraluate tlie ^ e t y axl efficay of the Excel VB pulse esErator (PG). Fran Fehruffly to October 1992. 53 inite wure inplalted in 17 itaiiai centos. Pri<r to ftxir the t»=^ital, postural ari acUvity tests urere poicnted in to tte sti t^ tfesigi ae weLl ae ai ibltfr mcnitcrliig wae pafar^ ned ai 3 nrrAh foUot-iV (FU)As a axsetfatx of a medical dewice adiriao i^ rciUce relevait ID a pcesible irre&O^ saBcr b*auicw, a fi«-ther FTJ w^ perfcnred in c i * r to verify the ircper po^trmaTce of tJie PG. : dirirg prediadHTge poetural testing die rate in5.336 fi-cm aiding to sitting a i i 9.3« ftxm sitting to B e fast telk fa-otoool Hie rate increasijig see a .3a t ari 40.36 respectively. AU patiarts {pts) after 3 min. of rest relumed at a b»al fEart rate. As a reault of the preliminary <bta mLy 2 pts required a rew fr<Brannii« of raninal se t t ing. Ttiree imrth HI: pte caipleted d« 3 rrentti tV with a 24 hour ttaltsrecording inclnling natlaXixy excotige; ^ g)i,^ Lp a d donn tJie stairs ari gjii^ ty ca-, cbtainiig the followiig results: t r i * iiiBlk:t33.175t-faBt iialk:+48.23t-g)iie nBtairs: 44?.rflt-»)iiB (fc»«wtaira:t31.seSt-g)iie tff ca-:tl7». PijihCTTO: pta r^jeated the prediadEn^ tests cbtaining the SEme results. Iftl PG raaUictio; data dHioBtrated a gpod aaeitivity of ctoraved. tte axKleroietsaenacr acotrding to the bacV notloi (pocr rate increaair^ ( ir lr« pcstural d»B2s aid ocngmciE rate increeeirg ( i r i ig activity tests). Wth refs-ace to qiecificity a mre hcmo^KOB behavioir »BB ctwrvEd in canwiam to traditicnal piezoelectric aeiecrs. Ma fUictionii^ va-iatiCTB ( i r i te >^> ^^^ repsrted. OOy cne uii t shcuod at inplarta.ticn a fixed polite rate at (he nrat aerearate. Tte event nee the init,. ;OMPARATIVE EVALUATION OF DDDR AND DDD PACING MODES IN THE PREVENTION OF ATRIAL FIBRILLATION. Wornato E.*M.D.-Monea P. M.D.-AdornaCo E.M.F.M.D.-De Seta , PH.D.Consolo A. M.D. •Dpt. of Cardiology,Regional Hospital,Reggio Calabria-Italy .trial Fibrillation (AF) can occur In Pta with implanted DDE Ms because of chronotropic incompetence of sino-atrial node CI), or because of atrial competition. The new sensor modu.aCed dual chamber PMs (DDDR) allow to obviate the limita:ionB of DDD pacing that derive from Cl. However the antirrhythmic advantages of DDDR compared DDD pacing are conroversial and not sufficiently documented. For this instance we have performed a study to evaluate the efficacy of DDDR and DDD pacing modes in preventing AF episodes In 10 Pts with Sick Sinus Syndrome and CI (Group I)an< in ID Pts with A-V conduction disturbances and normal sinus function (Group II). All Pts had a history of pre-existing AF during repeated Holter monitoring (HM). A dual chamber DDDR Pacemaker (Medtronic model Synergyst II) was implanted in all Pts. Th PM was random:^ programmed in DDDR for 1 montti and in DDD mode at the same basic rate for another month; HM (24 or 48 h) was performed at the end of every evaluation period. Results-Group I: at last one AF episode occurred in 3 Pts (30J) during DDD pacing mode, while no incidence of AF was noted during DDDR pacing mode. Group 11: in these PEs AF occurred only in one patient during DDD pacing mode. Conclusions: in comparing DDDR to DDD pacing in the main difference in the prevention of aCrial fibrillation has bee seen in Pts who exibit Cl. Nevertheless an accurate programmation of DDDR PM is necessary to optimize the potential advantages of this pacing mode. PACE, Vol. 16 September 1993 1911