Biomedical subjects
G Pioger
Publications and source records attributed to G Pioger.
Warning from Biotec and Medtronic.
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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).(ABSTRACT TRUNCATED AT 250 WORDS)
Improved dual chamber pacing mode in paroxysmal atrioventricular conduction disorders.
Dual chamber pacing may sometimes be directly indicated for carotid sinus hypersensitivity, vasovagal syndrome, and certain cases of sinoatrial block and intermittent atrioventricular (AV) block, although AV conduction is dominantly normal. At times of normal AV conduction, competition between ventricular pacing and spontaneous ventricular depolarization may occur, with its adverse hemodynamic effects on ventricular function and unnecessary drainage of pacemaker battery energy. A new mode of stimulation is described, called automatic DDD mode, which functions in 'pseudo-AAI' mode during normal AV conduction and reverts to classical DDD function during episodes of AV blocks. Furthermore, during pseudo-AAI function, the pacemaker measures certain physiological parameters that serve to automatically program certain parameters used in DDD mode. Preliminary clinical evaluation has shown that this new mode functions satisfactorily.
Relationship between heart rate and minute ventilation, tidal volume and respiratory rate during brief and low level exercise.
The correlation between heart rate (HR) and three respiratory parameters, minute ventilation (VE), tidal volume (Vt), and respiratory rate (RR), were studied. Four healthy subjects performed four exercise tests (duration 30 seconds at 50, 100, 150, or 200 W), in random order. Cardio-respiratory parameters were recorded respiratory cycle by respiratory cycle. The results of these low level exercise tests showed that oxygen consumption (VO2) was strongly correlated with VE (r = 0.91 +/- 0.10; P less than 0.01) (except in one test) and Vt (r = 0.91 +/- 0.07; P less than 0.001) (except in one test). There was no significant correlation between VO2 and RR. At exercise onset HR, VE, and Vt were modified in a matter of a few heart beats while RR varied depending on the subject and the level of exercise. During exercise average HR, VE, and Vt were significantly higher than at rest in most cases; but RR was not significantly changed by exercise. The correlations between HR and VE, Vt and RR varied from one individual to another. Nevertheless, the correlation coefficients were positive for VE and Vt, while they were negative for RR. Sensing respiratory rate thus appears to be insufficient for responsive pacing at exercise onset, but sensing respiratory volumes (Vt, VE) should give satisfactory results.
Clinical results of low energy unipolar or bipolar activated carbon tip leads.
Biocompatibility of carbon makes it a good candidate for a pacing electrode. Moreover, activation of the electrode creates microporosity, which increases the surface area and reduces polarization losses. Chronic thresholds noninvasively measured on a large population of patients implanted with vitreous carbon electrodes of one manufacturer are significantly lower than those caused by polished platinum tip electrodes of the same manufacturer with similar electrode design.
Detection and characteristics of retrograde P waves.
Clinical evaluation performed on an external prototype of a programmable VDD pacemaker showed a high risk of induction of pacemaker-mediated tachycardia. In these tests tachycardia was observed following magnet removal, premature atrial and ventricular complexes, myopotential oversensing, detection of electrical interference and other events. The high risk and poor predictability of pacemaker-mediated tachycardia suggest that VDD (or DDD) pacemakers should provide automatic means to control this kind of tachycardia without undue loss of the hemodynamic benefits which can be provided by these units.
[Ordistim 70 data processing system for the surveillance of patients with pacemakers].
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[Use of computers in the supervision of a large group of patients with a cardiac pacemaker].
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[Wear and breakdown of pacemakers].
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[1200 patients equipped by the Fernand-Widal Hospital team with internal pacemakers connected to endocavitary catheters].
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[Value and danger of electric, magnetic or electromagnetic fields in sentinel pacemaker control].
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Pacemaker electrodes and problems related to cardiac pacing and sensing: current solutions and future trends.
The current status of cardiac electrical stimulation requires electrodes improvements both in pacing and sensing features. A short overview of today's electrode problems and solutions is followed by the presentation of a new pyrocarbon tip lead. The new tip material and the conception of the lead allow an increase in energy transfer efficiency and a retention of good sensing properties. Clinical experience confirms theoretical expectations. New methods for tissue reaction limitation are under evaluation.