Biomedical subjects
J Mugica
Publications and source records attributed to J Mugica.
Effect of different body-exercise modes on the rate response of the temperature-controlled pacemaker Nova MR.
In order to evaluate the effect of different modes of physical exercise on the rate response of the temperature-controlled Nova MR, parameters such as temperature behaviour and correlation of work load to pacing rate were investigated using different types and protocols of stress testing. This study considered 21 patients (age: 66 +/- 12 y). The indications for the Nova MR were AV block (n: 14) and sick sinus syndrome (n: 7). The patients performed two different types of exercise (treadmill n: 13, bicycle n: 14) based on different protocols. We registered the surface ECG, pacing rate, exercise time, and (via data transmission by the RX 2000 programmer) blood temperature and pacing rate. An adequate rate response could be achieved with all the different types of exercise and protocols using more sensitive program settings. The type of stress testing used to adjust or evaluate the Nova MR seems to be secondary, although cycling as compared with treadmill exercise resulted in a slightly weakened reaction of temperature and pacing rate. Our investigations revealed a good correlation between work load and pacing rate independent of the type of stress testing. The initial DIP (48%) is not a constant phenomenon and showed inter- and intraindividual variations. Impressive psychological influences also exhibited an effect on temperature and pacing rate, sometimes preventing a DIP response. During exercise at lower work loads (under 50 watts, shorter than 3-4 min) the rate response of the Nova MR--without any detected DIP--is often delayed due either to a decrease or to a late and flat increase in temperature. An additional fast-reacting sensor could be advantageous in triggering the initial rate response in such cases.
Progress and development of cardiac pacing electrodes.
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Pre- and postnatal aminopeptidase activities in the rat brain.
Research concerning the functional role of brain peptides is performed, in part, by studying peptidase enzymes which might be involved in brain peptide processing or inactivation. Aminopeptidase (AP) activity has been proposed as a candidate regulator of the degradation of these peptides. In this paper, changes in Lys- and Leu-aminopeptidase activities in rat brain hemispheres, cerebellum and medulla were examined in 20 day fetuses and one day postnatal subjects. Aminopeptidase activities were studied by measuring the rate of hydrolysis of the artificial substrates Lys- and Leu-2-naphthylamides (fluorimetrically detected in triplicate). Both enzyme activities increase from the last fetal stage up to the first day of birth in all the brain areas examined except for the case of Leu-AP activity in the medulla. It is suggested that these activities play a part in the neurochemical changes that take place during rat brain maturation, possibly by regulating the activity of several neuroactive peptides.
DDD pacing: an effective treatment modality for recurrent atrial arrhythmias.
We performed atrial EP studies (atrial substrate evaluation) on 10 patients. These patients had evidence of paroxysmal, sustained, recurrent atrial arrhythmias (7 men and 3 women with a mean age of 64 +/- 15 years). All patients combined a brady-tachy syndrome; 7 patients had a sick sinus syndrome (SSS) and 3 patients a typical vagally induced atrial arrhythmia. No anti-arrhythmic drug was allowed in 3 patients with SSS, 1 drug failed in 4 patients and the combination of 2 drugs failed in 3 patients during the first to eighth years prior to pacemaker implantation. Atrial substrate evaluation was feasible in all these patients off anti-arrhythmic therapy and showed important abnormalities of atrial loco-regional conduction parameters and long refractory periods (RP). The remarkable point was, in 7 patients, a paradoxical improvement in intra-atrial conduction delay at rapid pacing rate. The DDD pacing mode was chosen in all patients. No technical problem occurred during implantation. Atrial pacing rate was programmed to be slightly higher than the mean diurnal heart rate calculated on Holter monitoring. After implantation, the mean follow-up period was 18 +/- 25 months with an average of one Holter every 4 months during the first 2 years. The 7 patients who improved intra-atrial conduction at rapid pacing rate were controlled without drugs, 2 patients were controlled with 1 drug, and 1 patient with 2 drugs. Atrial pacing in the DDD mode in a selected group of patients prevents paroxysmal and drug-resistant atrial arrhythmias. Atrial substrate evaluation is a sensitive tool for assuring the long-term benefit of atrial pacing.(ABSTRACT TRUNCATED AT 250 WORDS)
Clinical experience with new leads.
Recent developments in cardiac pacemaker electrodes have resulted in significant benefits to the group of pacemaker patients as a whole. The results of analysis of 2,818 chronic pacemaker electrodes are presented. These electrodes are divided into major categories according to their particularities: platinum iridium, elgiloy, carbon-tip, anodized platinum and granulated iridium-platinum. All leads were in the ventricular position. The results of acute and chronic threshold measurements reveal that carbon-tipped electrodes appear to have the most favorable overall characteristics. This will have a major influence on long-term pacing practices.
Direct diaphragm stimulation.
Direct diaphragmatic stimulation is effective without discomfort to the patient and without muscular fatigue. However, some quadriplegic patients may require synchronous expiratory stimulation in order to obtain complete and permanent respiratory autonomy. Now it will be necessary to undertake further studies of the indications for direct diaphragm stimulation.
[Midazolam-fentanyl for implantation of an intracavitary cardiac pacemaker].
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Importance of atrial electrophysiology in the work-up of cerebral ischemic attacks.
Recent data suggest that a large proportion of ischemic strokes are due to embolic phenomena from the heart. Atrial fibrillation appears to be one of the principal causes of embolization. If electrophysiologic parameters are considered as determining factors, the existence of atrial hypervulnerability in patients with embolic strokes is significant, when arrhythmia has been excluded as an etiology. This study suggests that an aggressive approach to early diagnosis and management through electrophysiologic studies might aid in preventing future neurologic attacks.
Clinical experience with 910 carbon tip leads: comparison with polished platinum leads.
Since 1980, we have implanted 910 carbon tip leads from three different manufacturers. The pacing thresholds from these leads were compared to those of standard polished platinum electrode configurations. Our major findings are that while acute voltage thresholds are not significantly different, two of the three carbon tip leads that we used in the study have statistically lower chronic thresholds then polished platinum leads (p less than or equal to 0.01).
The clinical utility of pacemaker follow-up visits.
Because of the increased complexity of modern pacemakers, pacemaker follow-up visits in specialized centers become more and more indispensable. In this study, the results of 15,000 outpatient visits to the cardiac pacing center between the years 1983-1985 are presented. In most cases (92.8%), verification of normal function was made; however, mandatory reprogramming was required in 1.2%, and hospitalization for various reasons was required in 6% of visits. Careful outpatient monitoring of pacemakers is therefore very important for detecting early or late pacemaker complications.
Survival and mortality in 3,701 pacemaker patients: arguments in favor of pacemaker reuse.
This study analyzed the results of 3,701 patients implanted with cardiac pacemakers at the Centre Chirurgical du Val d'Or between 1976 and 1981. Two pacemaker populations were compared: those having a new pacemaker and those implanted with a reused pacemaker. There were no statistically significant differences between the two groups, either in terms of indications for implantation or in terms of actuarial survival of patients. In addition, there was no significant change in survival of the pulse generator. The reutilization of pacemakers appeared to be in no way detrimental to patients.
[Assisted respiration by stimulation of the diaphragmatic muscle. A case].
Direct electrical stimulation of the diagram has resulted in physiological functioning in a quadriplegic patient. Mechanical ventilation could be partly withdrawn with 13-hour periods of "respiration". During the 2-month stay in hospital, 90 hours of respiration were obtained by stimulation. The patient died 8 weeks after the operation.
How should the software pacemaker be programmed during manufacturing and after implantation?
The different possibilities for programming modern pacemakers are discussed. A pacemaker based on hardware alone provides highly reliable pacing within narrow limits. On the other hand, a totally software-based pacemaker would provide maximum flexibility in terms of programming but would remain more susceptible to errors in software. A middle solution might be one that divides the program between passive ROM and active RAM memories. This alternative may provide sophistication without sacrificing safety.
[Flunitrazepam-fentanyl for the intracavitary placement of pacemakers].
Eight hundred pacemaker have been placed under general anaesthesia associating flunitrazepam-fentanyl, with a good comfort and safety for those patients old and often weak.
Electrode-heart interface: definition of the ideal electrode.
In dual-chamber pacing in order to maintain the advantages of small pulse generator size and volume, and increased longevity, it becomes necessary to reduce pulse generator output. This may be accomplished by optimizing the electrode-heart interface. New electrode designs may reduce polarization losses; perhaps even newer materials should be considered. The results of accumulated data must be applicable to long-term pacing.
Long-term prevention of vagal atrial arrhythmias by atrial pacing at 90/minute: experience with 6 cases.
Six patients (5 men, 1 woman) with a history ranging from 3-16 years of resistant vagal atrial arrhythmias were treated by atrial pacing at a rate of 90/Min. These patients have been followed up for an average of 5.5 years (range 2-11 years) with favorable results. The arrhythmias were characterized by daily or weekly attacks of typical atrial flutter and atrial fibrillation occurring mainly or exclusively at night, at rest, or in the digestive periods in otherwise normal hearts of middle-aged patients (first attack between 25 and 54, mean 40). The arrhythmias were resistant to quinidine, and were usually aggravated by digitalis, beta-blockers and verapamil. Amiodarone is usually the only effective drug in this syndrome, but was not used before pacing in the 2 first cases, and was ineffective in the other 4 cases. Electrophysiologic studies confirmed the absence of sick sinus syndrome, and the close relationship between relative bradycardia and the onset of the arrhythmia. Atrial pacing alone totally controlled the arrhythmia in 1 patient; amiodarone was used in conjunction with pacing in 3 patients. In 1 patient the improvement was clear but incomplete, and in 1 patient permanent atrial fibrillation occurred shortly after pacemaker implantation.
[Long-term monitoring of a patient with a cardiac pacemaker--complications].
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