Retrograde (Ventriculoatrial) Conduction

Ľinterêt dans la conduction VA rétrograde a été renouvelé depuis la découverte de tachycardies induites par les stimulateurs cardiaques de type physiologique qui incorporent le recueil des potentiels auriculaires. Seule ľétude de la conduction VA rétrograde associée à une parfaite connaissance de son comportement électrophysiologique dans dif-ferents cos, permettra de dépister les malades susceptibles de faire une tachycardie induite par le stimulateur.
Interest in retrograde VA conduction has been renewed with the advent of tachycardias induced by physiologic pacemakers with atrial sensing capabilities. Accurate representation of ventriculoatrial conduction requires detailed electrophysiologic analysis during sinus rhythm, during tachycardias whether or not associated with accessory pathways, and during ventricular pacing studies. Retrograde conduction should be assessed in patieifts considered for implantation of atrial sensing and tracking pacemakers (VAT, VDD, DDD), until technologic advances overcome the problems of endless loop tachycardias.     

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.     

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.     

Holter Functions of the Implantable Cardioverter Defibrillator: What is Still Missing?

The technology of the implantable Cardioverter defibrillator (ICD) offers the opportunity to overcome the present limits of the invasive and noninvasive approaches of clinical electrophysiology. The invasive approach enables us to reproduce severe arrhythmias if they are inducible, but does not give information concerning the way they spontaneously arise. The noninvasive approach (Holter) gives this information, but it usually concerns only trivial arrhythmias with different therapeutic targets. One hopes in the future, by means of an important extension to ICD technology, which is not technically possible for the time being, to have access to pertinent information and to a better understanding of the circumstances leading to severe spontaneous arrhythmias, potentially lethal. For the moment, we only have the diagnostic certainty leading to the therapeutic intervention. It is based on an ECG and on the sequence of cardiac cycles preceding the rhythmic controlled accident. These data allow verification of but not explanation of the events. To have a chance to be understood and explained, these "events" must be replaced in the context of the "nonevents." Ideally, one should have all the gross information concerning the last 24 hours and subsequently analyze them. It is already a big step, thanks to the defibrillators the right to therapeutic error has been gained, a unique and fatal accident has been transformed into a repeatable event, and therefore, access is gained to the evolution of the responsible disease. I PACE 1995; 18[Pt. II].560–568)     

Hereditary complement factor I deficiency

We describe four cases (from three families) of hereditary factorI deficiency, bringing the total number of cases now reportedto 23. In one family there are two affected siblings: one hassuffered recurrent pyogenic infections; the other is asymptomatic.In the second family, the patient had recurrent pyogenic infectionsand a self-limiting vasculitic illness; in the third family,the patient suffered recurrent pyogenic and neisserial infections.All four patients had markedly reduced concentrations of C3in the serum (family 1 propositus: 28%; family 1 asymptomaticsibling: 15%; family 2: 31%; and family 3: 31 % normal humanserum) which was in the form of C3b. Low lgG₂ levels may occurin primary C3 deficiency, and reduction in lgG₂ concentrationto 1.14 g/l (normal: 1.30–5.90 g/l) was found in the patientfrom family 2. Using radioligand binding assays, we demonstratedincreased binding of C3b to erythrocytes in a patient with factorI deficiency. This C3b could not be cleaved by autologous serumbut could be cleaved by normal serum or purified factor I. Wereview and compare the published cases of C3, factor H and factorI deficiency.     

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 pacemaker's 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.     

Artificial Circus Movement Tachycardias: Incidence, Mechanisms, and Prevention

In a group of 45 patients treated with Medtronic 7000 and 7100 pulse generators for sick sinus syndrome or second or third degree atrioventricular block, an atrial synchronous mode of pacing was programmed in 34 cases and spontaneously occurring artificial circus movement tachycardios (ACMTs) were observed in nine. An analysis of conditions of occurrence, triggering mechanisms and patterns of ACMT, is presented. Various modalilies of prevention are discussed. They resulted in suppression of ACMT in five patients and decrease of incidence in a sixth; the three remaining subjects were managed by definitive reprogramming in the DVI mode. Our conclusion is that correct prevention of ACMT requires the use of dual chamber pulse generators with programmable atrial refractory periods. For patients in whom a unit has already been implanted, careful observation of the triggering mechanism and pattern of ACMT may help in determining the most suitable way to prevent and suppress the arrhythmia.     

Abnormal Nocturnal Heart Rate Variability and QT Dynamics in Patients with Brugada Syndrome

Background: In Brugada syndrome (BSY), most of the ventricular arrhythmic events are nocturnal, suggesting an influence of the autonomic nervous system.
Methods: In 46 patients (mean age = 41 ± 14 years, 43 men) with electrocardiograms (ECG) consistent with BSY and structurally normal hearts, we measured heart rate variability (HRV) and QT dynamics (QT/RR slopes) on 24-hour ambulatory ECG. Type 1 BSY-ECG was spontaneous in 23 (50%) and induced in 23 patients.
Results: History of syncope was present in 23 patients (50%). Programmed ventricular stimulation induced ventricular tachyarrhythmias (VTA) in 13 patients (28%). A single patient developed ventricular tachycardia during a mean follow-up of 34 months. Compared to a control group matched for age and sex, HRV was decreased over 24 hours and during nighttime in patients with BSY (SDNN 122 ± 44 vs 93 ± 36 ms, P = 0.0008 and SDANN 88 ± 39 vs 54 ± 24 ms, P < 0.0001). QTend /RR slopes were decreased over 24 hours in patients with BSY (0.159 ± 0.05 vs 0.127 ± 0.05, P = 0.003) and particularly at night (0.123 ± 0.04 vs 0.089 ± 0.04, P = 0.0001). QTend /RR slopes were significantly decreased during nighttime in patients with spontaneous versus provoked BSY-ECG patterns. By contrast, HRV and QT/RR slopes were similar in symptomatic and asymptomatic patients, whether VTA were induced or not.
Conclusions: Patients with a BSY-ECG pattern had lower HRV and QT/RR slopes than control subjects during nighttime. High-risk patients with spontaneous BSY-ECG patterns had the lowest nocturnal QTend/RR slopes. These unique repolarization dynamics might be related to the frequent nocturnal occurrence of VTA in BSY.