[Non-valvular cardiac devices endocarditis]. / L'endocardite sur matériel de stimulation intracardiaque.

The risk of infective endocarditis on pacemaker or ICD is not negligible and has increased in recent years. Several host-related, procedure-related, or device-related risk factors have been recognized. Owing to its potential severity, the possibility of infective endocarditis should be envisaged in patients with repeated pulmonary infections or documented bacteremia and transesophageal echocardiography should then be used. The most common germs causing pacemaker endocarditis are staphylococci. Treatment requires prolonged antibiotic therapy and retrieval of the pacemaker and leads.

DDD pacing in hypertrophic cardiomyopathy: a multicentre clinical experience.

BACKGROUND: DDD pacing has been advocated as an effective treatment for drug refractory obstructive hypertrophic cardiomyopathy. This study reports the outcome of pacing in 56 patients with refractory symptoms referred to four tertiary centres. METHODS: Core data on symptoms, drug burden, and left ventricular outflow tract gradient were recorded. Patients underwent a temporary pacing study with optimisation of the atrioventricular (AV) delay for greatest gradient reduction without haemodynamic compromise. Patients were assessed after implantation in terms of changes in symptoms, drug load, and outflow tract gradient. RESULTS: 56 patients underwent pacing assessment. The mean (SD) left ventricular outflow tract gradient before pacing was 78 (31) mm Hg. At temporary study the mean (SD) left ventricular outflow tract gradient was 38 (24) mm Hg with a median (range) optimised sensed AV delay of 65 (25-125) ms. Fifty three patients were implanted and followed up for a mean (SD) of 11 (11) months. The median (range) programmed sensed AV delay was 60 (31-200) ms. Left ventricular outflow tract gradient at follow up was 36 (25) mm Hg. Forty four patients had improved functional class. Although a correlation (r = 0.69) was shown between acute and chronic left ventricular outflow tract gradient reduction, there was no correlation between magnitude of gradient reduction and functional improvement, and no appreciable change in pharmacological burden. CONCLUSION: This series confirms symptomatic improvement after DDD pacing in hypertrophic cardiomyopathy. There remains, however, a discrepancy between perceived symptomatic benefit and modest objective improvement. Furthermore, the optimal outcome has been achieved only with continued pharmacological treatment. Current methods of temporary evaluation do not predict functional outcome which seems to be independent of the magnitude of gradient reduction.

Influence of high-energy photon beam irradiation on pacemaker operation.

In this paper, we determine the influence of high-energy photon beam irradiation used for external radiotherapy on pacemakers, at different doses and dose rates. Ninety-six pacemakers of various origins and ages underwent in vitro high-energy photon irradiation under technical conditions close to external radiotherapy, using a linear accelerator delivering photons of high energy (18 MV). Various dose levels (up to 200 Gy for certain particularly resistant pacemakers) were delivered to pacemakers located in a water-equivalent phantom with several dose rates (from 0.05 to 8 Gy min(-1)). Observed failures were sorted into eight classes of progressive harmfulness, some of them possibly lethal. One irradiated pacemaker exhibited an important defect at a dose rate of 0.2 Gy min(-1), for a cumulative dose of 0.15 Gy. Two pacemakers showed an important defect at a cumulative dose of 1 Gy, while nine pacemakers failed at a cumulative dose lower than or equal to 2 Gy and 13 failed at a cumulative dose lower than or equal to 5 Gy. The most important failure probability (70% of irradiated pacemakers) is observed for 8 Gy min(-1), whereas no pacemakers failed at a dose rate lower than or equal to 0.2 Gy min(-1). In conclusion, warnings given by manufacturers about the maximum tolerable cumulative radiation doses for safe operation of irradiated pacemakers (5 Gy), even reduced to 2 Gy, are not reliable. The spread of cumulative doses inducing failures is very large since our observations show an important failure at 0.15 Gy, while ten pacemakers withstood more than 140 Gy of cumulative dose. The safe operation of pacemakers under irradiation depends mainly on type and model. It depends also on dose rate. From our observations, for the safe operation of pacemakers, a recommendation of a maximum dose rate of 0.2 Gy min(-1) rejecting direct irradiation of the pacemaker at a standard dose rate for tumour treatment (2 Gy min(-1)) is made.

Effects of radiofrequency catheter ablation on patients with permanent pacemakers.

The objective of this study was to assess the effects of radiofrequency energy application on implanted pacemaker functions. Radiofrequency (RF) catheter ablation may cause pacemaker dysfunction due to electromagnetic interferences. The effects of RF on pacemaker behavior were studied in a series of 38 pacemakers, implanted 18 +/- 26 months prior to a RF procedure using either a right ventricular approach (AV node ablation, n = 35) or a left ventricular approach (left concealed accessory pathway ablation, n = 1; VT ablation, n = 2). The 38 patients (mean age 65 +/- 9 years) included 20 men and 18 women. Before energy applications, the 23 different pacemaker models were programmed to the VVI mode at the lowest available rate. The continuous surface ECG was recorded throughout the procedure. Thorough testing of the devices was performed before and after each RF delivery. Unusual pacemaker responses occurred in 20 of the 38 cases studied (53%). The impact of RF delivery was unpredictable, and variable dysfunctions were observed at different times for a given patient or could vary for a given model. Unusual pacemaker responses included pacemaker inhibition (n = 8), untoggled backup mode (n = 3), electromagnetic interference noise mode (n = 3), temporary RF-induced pacemaker tachycardia (n = 2), erratic behavior (n = 1), oversensing of RF onset and offset (n = 8), and transient loss of ventricular capture, (n = 1). Postablation, most devices automatically toggled back to full functionality. The three devices in the untoggled backup mode had to be reprogrammed to obtain normal operations. At the end of the procedure, pacing thresholds remained unchanged in all but one patient, in whom the increase in ventricular threshold was due to a nicked lead. In conclusion, implanted pacemakers frequently exhibit transient, unpredictable responses to RF energy application. Although all pacemaker functions were restored postablation, some devices had to be reset manually. The anomalies observed during the RF application argue for the simultaneous use of an external pacemaker in pacing-dependent patients.

[Pacemakers 16 years later]. / Les pacemakers seize ans après

In 1976, 10 years after the first successful implantations, the pacemaker technique is perfectly well accepted. Transvenous placement of the electrode is preferred in 95 % of the cases. Besides the 15 years nuclear power pacers (1970), conventional mercury pacemakers may reach a longevity of 4 to 5 years because of the reduction of the current drain. Lithium iodine seems a very promising source of energy. The mini-pacemakers with various iodine anodes are particularly attractive. The future is probably a well designed medium sized lithium pacemaker lasting more than 7 years. Patient follow-up is very much improved. All pacemakers exhibit an obvious rate reduction when their source of energy runs down. Therefore general practitioner and even the patients may detect this symptom. The main problem remains the lead resistance. The reduction of the frequency of pacemaker replacements and of the medical check-up makes life more simple for the pacemaker patient.

[Interferences in the everyday life of the patient with a cardiac pacemaker or an implantable defibrillator]. / Interférences de la vie quotidienne chez le patient avec stimulateur cardiaque ou défibrillateur implantable.

The electromagnetic sources of interferences being able to deteriorate the operation of cardiac pacemakers or implantable defibrillators are numerous. This potential risk has been known since the release, 40 years ago, of pacemakers incorporating a detection circuit. Many papers, reviewed in this article, have been published about these conflicts. In daily practice, the risk of dangerous interference is weak, but it seems obvious that the implantable defibrillators are much more sensitive to the external environment than the cardiac pacemakers. With some precautions to eliminate manifest risk situation, it is possible to carry out a strictly normal life. Diagnostic memories increasingly sophisticated included in the new prostheses make possible the identification of asymptomatic conflicts, and the specification of the mechanism of a real problem. Provided information may also be useful to find solutions (adjustment, precautions) to decrease, even to remove the risks.

[French evaluation of cardiac stimulation]. / Bilan francais de la stimulation cardiaque.

A national enquiry into the problems related to definitive cardiac pacemakers, carried out in 1975, has yielded certain essential findings: the number of first-time implantations of pacemakers has been increasing by about 20% per annum; 92% of electrodes are currently implanted by an endocavitary technique, thoracotomy having now practically been abandoned; 90% of pacemakers implanted in 1975 were threshold models, inhibited by a QRS complex; the indications have become progressively wider, and are essentially related with the various forms of bradycardia, most frequently those due to atrio--ventricular block. In 1976, we have now reached a figure of about 200 new implantations of pacemakers per million inhabitants; those using lithium are increasingly superceding the mercury and isotope models.

[Clinical aspects of implantable defibrillators: indication]. / Le défrillateur implantable aspects cliniques: indication.

The rapidity of technological progress has now made available a device which was only a dream a few years ago, a nearly ideal implantable defibrillator. Despite the persistence of a number of technical and clinical problems, the fourth generation defibrillators are multiprogrammable, with antitachycardia and antibradycardia functions, implantable by the endocavitary approach in most cases thanks to the introduction of biphasic shocks, fitted with constantly improving systems of telemetry, and are progressively smaller in size. The selection of a defibrillator device requires consideration of the patient's needs and the technical characteristics of the defibrillator. Apart from special situations in which the indications of the implantable defibrillator are generally accepted, it is only possible in the absence of results of prospective clinical trials, to use data accumulated on the place of defibrillation compared with other forms of management of severe ventricular arrhythmias. As there is a wide choice of treatment of these ventricular arrhythmias, the role of each must be defined for each individual patient. With regards to the implantable defibrillator, it is essential to take into consideration a number of clinical and paraclinical factors such as the clinical preservation of the arrhythmia, the underlying cardiac disease, left ventricular function and the type of arrhythmia induced by programmed ventricular stimulation.

[Left-sided His bundle ablation after failure of right-sided approach: technique and initial results]. / Ablation du faisceau de His par voie gauche après échec d'un abord droit: technique et résultats préliminaires.

Although interruption of atrioventricular conduction has been widely used over the last decade in patients with supraventricular arrhythmias and rapid conduction resistant to antiarrhythmic therapy, the incidence of atrioventricular block obtained by delivering the energy at the tricuspid ring ranges from 45 to 92%. Failure of this technique is usually related to the inhability to record endocavitary electrogrammes compatible with probable success by the right-sided approach. The authors report four cases of interruption of atrioventricular conduction in 4 men (average age 61.5 +/- 10 years) by the retrograde arterial catheterisation after one or more (1 to 3) failures by the right-sided approach. After arterial puncture, the ablation catheter is positioned against the interventricular septum below the aortic cusps to record the His bundle electrogram. His bundle ablation was obtained after an average of 2 radio frequency energy applications (range 1 to 3). At the time of effective application, the average amplitude of the endocavitary electrogram was as follows: auriculogram 0.09 mV (range 0.05 to 0.2 mV), His bundle electrogram 0.19 mV (0.15-0.22 mV), ventriculogram 1.36 mV (1.0 to 1.7 mV). No complications were observed. After an average follow-up of 4 months, the 4 patients were still in complete atrioventricular block. This preliminary series shows that left-sided interruption of atrioventricular conduction is effective and safe. It may be proposed after failure of a right-sided attempt.

[Relevance of in vitro studies for the immunity of cardiac implants in an electromagnetic field environment]]. / Intérêt des études in vitro de l'immunité des implants cardiaques en environnement électromagnétique basse fréquence.

The object of this article is to show the contribution of the vitro experimental approach, based on the basic rules of electromagnetic compatibility (EMC), as a complementary tool to the clinical studies. Results can be obtained by a experimental approach in vitro with electromagnetic phantoms associated to a bench of "standard" test to allow a possible comparison between various studies. After describing the protocol developed for the cardiac implants (pacemakers and defibrillators), examples of partial results are presented by way of illustration.

[Cardiac stimulation in children. 20 years' experience]. / La stimulation cardiaque infantile. Expérience de vingt ans.

Between July, 1967 and December, 1987, 71 children and adolescents (43 boys, 28 girls) aged from 9 days to 20 years (mean 7.8 years) underwent pacemaker implantation. In 91 p. 100 of the cases this treatment was performed for complete atrioventricular block (CAVB). Surgical CAVB was the reason for 59 p. 100 of implantations (correction of tetralogy of Fallot and, more recently, of complex cardiopathies), the second main reason (16.9 p. 100) being nonsurgical CAVB associated with heart disease; the children in this group were young (mean age 4.2 years), and the prognosis mainly depended on the heart disease. Isolated congenital CAVB accounted for only 8.5 p. 100 of pacemaker implantations; these were older children (mean age 13.7 years), and the decision to implant was often difficult to reach in the absence of major functional disorders; following implantation, it was frequently found that isolated congenital CAVBs regarded as being well tolerated in fact were unrecognized handicaps. Acquired CAVB (7 p. 100) mostly consisted of Kearns' syndrome (4/5 cases). In addition, 3 children with sinus node disease and 1 with Romano-Ward syndrome benefited from cardiac pacing. Seven children died; death was in no case due to pacing but to the heart disease associated with CAVB. Endocardial pacing (68.2 p. 100 of primary implantations during the last decade) was preferred to epicardial pacing. Since 1985 we have been using exclusively screwed endocardial monopolar electrodes. The pacemakers were usually of the single-chamber ventricular type (85.9 p. 100 of primary implantations), but since 1987 dual-chamber pacemakers have been increasingly preferred for children with permanent CAVB or for replacement of pacemaker cases. Single-chamber noncompetitive ("demand") pacemakers were implanted in only 2 children: one pacemaker was connected to a ventricular electrode (atrial paralysis), the other to an atrial electrode. Whatever the type of electrode used, the pacemakers were implanted in the abdominal region in very young infants and in the pectoral region in children older than 3 or 4 years. Breakage of the wire was the main complication. Rises in threshold are the major drawback of epicardial pacing, as they require reoperation when the energy delivered cannot be effectively programmed. Endocardial pacing, preferably with a dual-chamber instrument, seems to be the best method, being the least aggressive, with minimal complications in short and very long term; it is justified as first-line treatment of permanent or predominant CAVB.(ABSTRACT TRUNCATED AT 400 WORDS)

[Hemocynamic role of atrial contraction in the acute phase of myocardial infarct]. / Rôle hémodynamique de la contraction auricularie dans l'infarctus du myocarde ó la phase aiguë

The authors have studied the haemodynamic role of atrial systole in patients in the acute stage of a myocardial infarction, usually with left ventricular failure. Their main comparison is between the results obtained with stimulation of the right ventricle at a fixed rate and those obtained with bifocal stimulation, thus restoring the atrio-ventricular sequence. The authors discuss their results, and especially their findings of improvement in cardiac output and systemic arterial blood pressure. They raise the question of synchronous stimulation in cases of infarction with heartblock complicated by left ventricular failure, and also of re-establishing sinus rhythm in cases of arrhythmia of supraventricular origin.

[Isolated congenital complete atrio-ventricular block]. / Blocs auriculo-ventriculaires complets congénitaux isolés. Suivi à long terme d'une série consécutive de 54 patients.

The objective of this work was to study the long term evolution of a retrospective series of 54 patients affected with congenital isolated complete atrio-ventricular block (CAVB) and to analyse the value of the different methods used for surveillance. Our series included 54 patients affected with isolated CAVB, without associated cardiopathy, diagnosed at an average age of 5.3 +/- 5.5 years, of which 9 were in utero. The average duration of follow up was 14.5 +/- 9.6 years. During the evolution, a cardiac stimulator was placed in 41 patients (76%) at a relatively late average age of 13.3 +/- 9 years, significantly lower for CAVB diagnosed before the age of 1 year (9.6 +/- 7.4 years) than for those diagnosed after the age of 1 year (16.2 +/- 9.2 years) (p < 0.02). The approach was endocavitary in 39 cases and epicardial in 2 cases. The only 2 deaths in our series (4%) concerned 2 patients of 18 and 26 years already fitted with a stimulator. Three patients progressed to severe dilated cardiomyopathy despite implantation of a stimulator. The decisive arguments for implantation of a PM were clinical (11 patients), Holter ECG (25 patients), stress test (17 patients), electrophysiological investigation (5 patients), echocardiography (3 patients) and surgical intervention (2 patients). In conclusion, our study confirms the good prognosis of isolated congenital complete atrio-ventricular block, but underlines the possible progression in rare cases in spite of stimulation towards dilated cardiomyopathy for which the aetiology remains uncertain. Three quarters of the patients required a stimulator at a somewhat late age.

[Value of permanent cardiac pacing in hypertrophic and obstructive cardiomyopathies resistant to medical treatment]. / Intérêts de la stimulation cardiaque permanente dans les myocardiopathies hypertrophiques et obstructives rebelles au traitement médical.

The authors report their experience of long-term dual-chamber pacing in the treatment of hypertrophic and obstructive cardiomyopathy. Between August 1990 and March 1993, 16 patients (8 men, average age 53.5 +/- 18.9 years, range 21 and 79 years) with symptomatic hypertrophic obstructive cardiomyopathy resistant to medical therapy underwent electrophysiological investigation to assess atrioventricular conduction and the effects of temporary atrioventricular pacing on the intraventricular pressure gradient before implantation of a dual-chamber pacing system. The decision to implant was taken if the endocavitary studies showed severe atrioventricular conduction defects and/or if temporary pacing reduced the systolic pressure gradient by more than 30%. Temporary dual-chamber pacing led to a decrease of 48% of the systolic pressure gradient from 78.6 +/- 21.3 to 40.1 +/- 23.6 mmHg (p < 0.0005), a regression observed in 15 of the 16 patients. After an average follow-up period of 18.7 +/- 9.5 months (range 6 and 37 months), all 15 patients who received a dual-chamber pacing system were alive and were clinically improved. The systolic pressure gradient continued to decrease during the follow-up period (24.4 +/- 17.2 mmHg at the 6th month compared with 36.5 +/- 18.6 mmHg at the time of implantation; p = 0.014). The clinical improvement was dependent on careful adjustment of the atrioventricular delay which was programmed at relatively short values (65.6 +/- 14 ms, range 47 and 75 ms) to obtain permanent right ventricular capture. The authors conclude that dual-chamber pacing is an effective means of treating symptomatic hypertrophic obstructive cardiomyopathy resistant to medical therapy, even in the absence of preexisting conduction defects.

[Results, complications and long-term follow-up of percutaneous ablation of atrioventricular conduction. Apropos of 85 cases]. / Résultats, complications et suivi au long cours de l'ablation percutanée de la conduction auriculo-ventriculaire. A propos de 85 observations.

This retrospective study reports the immediate and long-term results of percutaneous ablation of atrioventricular conduction. Between July 1983 and January 1992, 85 consecutive patients (51 men, age 64 +/- 10 years, range 43-84 years) presenting with supraventricular arrhythmias (atrial fibrillation n = 53; atrial flutter n = 50; atrial tachycardia n = 17; junctional tachycardia n = 6) resistant to antiarrhythmic therapy (number of drugs used: 4 +/- 1.3, range 1-6) underwent interruption of atrioventricular conduction by fulguration (n = 65) or radiofrequency energy (n = 13) or by an association of the two methods (n = 7). The 75 pacemakers implanted (10 patients had pacemakers before the procedure) comprised 55 VVIR, 11 VVI, 5 DDD and 4 DDDR units. The immediate results included two sudden deaths at the 4th and 7th day in patients undergoing fulguration and three complications with a favourable outcome (staphylococcal septicaemia, pulmonary embolism and haematoma at the site of implantation of the pacemaker). None of the patients was lost to follow-up and the average follow-up was 31 +/- 18 months (range 2-108 months). During follow-up, 15 patients died and there was a recurrence of symptoms in 11 patients after 1 to 9 months requiring a repeat procedure. In the 68 survivors, the follow-up is now 38 +/- 18 months (range 12-108 months). Sixty one patients have 2nd (2) or 3rd (59) degree atrioventricular block, giving 90% good electrocardiographic results.(ABSTRACT TRUNCATED AT 250 WORDS)

[Characteristics and causes of death in 283 patients with implanted defibrillators]. / Caractéristiques et causes de décès chez 283 patients implantés d'un défibrillateur automatique.

UNLABELLED: The implantable automatic defibrillator has proved its superiority over pharmacological treatments for preventing mortality by serious ventricular arrhythmia. We studied the cause of death in a population of 283 consecutive patients implanted between February 1988 and December 2000 (age at implantation: 58 +/- 14.7 years; extremes: 15-78 years, 45 females, ejection fraction: 0.39 +/- 0.15) and followed up over a median of 25 months (extremes = 1 day-163 months). RESULTS: At the end of follow up, 55 patients had died (average age: 62.7 +/- 12.6 years, extremes: 15-79 years, 7 females). All except 2 had a cardiopathy: ischaemic cardiopathy (n = 38, 36 IDDM), dilated cardiomyopathy (n = 14), arrhythmogenic dysplasia of the right ventricle (n = 1). The median interval between implantation and death was 35 months (extremes = 1 day-137 months). The causes of death were the following: cardiac insufficiency (n = 24), refractory arrhythmias (n = 13), other cardiac causes (n = 8), extra-cardiac pathologies (n = 10). The deceased patients had presented an average of 86.6 +/- 23.4 ventricular arrhythmias (extremes = 0-1309) but 18 of them (33%) did not present any during follow up. CONCLUSIONS: Cardiac insufficiency is the prime cause of death in refractory arrhythmias; on patient in 4 dies from ventricular arrhythmia, despite the defibrillator and one deceased patient in 3 had no arrhythmia during follow up.

[Implantable defibrillator using epicardial and endocardial leads. Results of 36 implantations]. / Défibrillateur implantable par système épicardique et endocardique. A propos de 36 implantations.

The authors report their experience of implantable defibrillators over a 5 year period. Between February 1988 and July 1992, 36 patients (25 men, 11 women, average age 51 +/- 11 years, range 18 +/- 71 years) underwent implantation of an automatic defibrillator with epicardial (n = 13, Group I) or endocardial leads (n = 23, Group II) without patch electrodes (n = 7), with subcutaneous patch electrodes (n = 12) or epicardial patch electrodes (n = 4). Three serious early complications were observed: 2 cardiogenic shocks in Group I, one of which died on Day 1 and one case of infection which required explanation of the defibrillator on Day 23 in Group II. Late complications in Group I included one case of disactivation of the defibrillator, 2 losses of output, one of which required replacement of the defibrillator and 2 increases of threshold treated by implantation of an endocardial lead. In Group II, 2 patients had inappropriate shocks due to overdetection (n = 1) and double counting (n = 1). During an average follow-up period of 28.5 +/- 9 months in group I and 13 +/- 6 months in Group II, 4 patients died, 2 from sudden death. Ninety seven shocks were delivered in 19 patients (56%), 5.1 shocks per patient. In the 17 patients with an antitachycardia function, 14 (82%) developed 947 episodes of VT treated successfully by antitachycardia pacing in 917 cases. This retrospective study confirms the efficacy of implantable defibrillators in the treatment of malignant ventricular arrhythmias. The efficacy of endocardial and epicardial leads seems to be the same but there seems to be a lower immediate mortality and morbidity with the endocardial system.

[Cardiac stimulation in the infant and young child]. / Stimulation cardiaque chez le nourrisson et le jeune enfant. Avantages et inconvénients respectifs de la voie endocavitaire et de la voie épicardique.

This study evaluates the problems and the evolution of cardiac stimulation in infants (aged < 3.5 years) by comparing the endocavity and epicardial routes in a retrospective series of 37 patients. Thirty seven patients aged 1.2 +/- 0.9 years treated with epicardial (n = 19) or endocavity (n = 18) stimulation were followed for 10.9 +/- 6.4 years (0.75-24). The 2 patient groups did not differ in age or weight. Four patients were lost to follow up, and 1 died. The functional duration of the first stimulator was not significantly different if the initial approach was epicardial or endocavity. The endocavity probes were introduced by venous denudation in 15 cases and by subclavian puncture in 3 cases. Fourteen of the 19 children fitted by the epicardial route went on to endocavity stimulation, of which 10 were at the first replacement. None of the 18 patients fitted by the endocavity route went on to epicardial stimulation. Out of 11 endocavity probe replacements and 9 atrialisations, the homolateral venous approach was always possible except in 2 cases. In conclusion, the results for the epicardial and endocavity routes are comparable. For technical reasons (calibre of the veins, size of the stimulator) it would appear reasonable if the endocavity route was used, making do initially with a mono chamber stimulation. The advances in the epicardial electrodes abolishes the major handicap (threshold elevation) of this approach which can be advocated when double chamber stimulation seems preferable.

[New pacemaker functions: which ones represent real progress and which are only gadgets?]. / Les nouvelles fonctions des stimulateurs cardiaques: lesquelles relèvent du gadget? Lesquelles ont un réel intérêt?

Modern pacemakers, and particularly dual chamber models, include a broad array of therapeutic and diagnostic features. Some are designed to increase safety, whereas others are either designed to avoid unnecessary pacing, reduce the current drain and increase the pacemaker longevity, or to improve the hemodynamics. Diagnostic features are more elaborate, more or less automatic, and easier to extract from the pacemaker memory. Some of these new algorithms represent a real advantage, while others appear to be more like gadgets than real advances. Several new algorithms should be improved in order to avoid possibly dangerous side effects. Most of these new features are of little value in the absence of postoperative programming by a well trained physician.

[Rate-responsive cardiac pacing]. / Stimulation cardiaque à freéquence asservie.

The term "synchronous pacemaker (SPM)" is used to describe all pacemakers of which the frequency can be accelerated by means of a sensor other than the sinus node. The most commonly used system is the detection of changes in physical activity by means of a quartz crystal included in the casing. Changes in respiratory volume, the respiratory rate, the QT interval or central temperature have been less successfully used. Single and double-chamber (DC) synchronous pacemakers exist. Ventricular single-chamber synchronous pacemakers (VVIR) are primarily intended for active patients in a state of chronic atrial fibrillation or, secondarily, in cases in which the insertion of an atrial electrode raises difficulties. The single-chamber atrial synchronous pacemaker (AAIR), or preferably the double-chamber equivalent (DDDR) is intended for the correction of chronotropic failure, whether this is primary or induced by bradycardiac antiarrhythmic medication. AVB should be treated by double-chamber simulation designed to pick up P waves. The value of the synchronous pacemaker in these patients is that it makes it possible to partially offset the loss of atrial systole in cases of ventricular fibrillation by a synchronous pacemaker (pacemaker programmed to shift from DDD to VVIR). The setting of the SPM is fairly complex and calls for exercise tests. Iatrogenic acceleration is not unusual and must be identified by long-term recordings. All these pacemakers will here include a "synchronous" option, which may be of variable efficacy. It is up to the clinician to use them appropriately, and not automatically, remembering that the best sensor is the sinus node and that synchronous pacemakers are only second best.