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Biomedical subjects

M Chauvin

Publications and source records attributed to M Chauvin.

At least 91 records · Page 5Linked to original sources
PubMed1994

[Role of the conditions of recording and analysis of the atrial signal on the results of ECG signal averaged P wave].

Several studies have shown that high amplification and averaging of the electrocardiographic P wave may soon enable better identification of people at high risk of paroxysmal atrial fibrillation. The results of this technique are closely dependent on the conditions of recording and analysis of the atrial signal but this factor has not been widely appreciated. The authors, therefore, undertook a study of the reliability of the manual method of measuring P wave duration, the influence of the filters used and the level of background noise on the 3 parameters of analysis: the duration of the P wave (DUR), the root mean square of the amplitude of the terminal 20 milliseconds (RMS20) and the integral under the P curve (IN). The recorder was a Predictor II 5.0 (Corazonix) with a special programme to identify and analyse the P wave in 3 bipolar non-orthogonal leads. DUR was determined manually after amplification and averaging; RMS20 and IN were calculated automatically. In order to assess the reliability of manual determination of the P wave, 48 consecutive patients were studied: two analyses were made with a least a 2 months' interval by entering the data through two filters (unidirectional and FIR). The role of the filters was then studied by passing the preceding 48 recordings to an analysis with three filters: unidirectional, bidirectional and FIR, and comparing the results.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Fibrillation↗
PubMed1994

[Lesions caused by techniques of endocavitary ablation using high frequency currents: anatomo-pathological aspects].

Anatomopathological studies have considerably increased our understanding of the ablative technique by radiofrequency current. They have provided information on the nature, extent and time dependency of the lesions induced. Despite variable results according to whether the experiments were performed in vitro or in vivo, a correlation has been observed between the volumes of the lesions and the energies used. One factor is unquestionable: monitoring the temperature allows better control of the lesion size than monitoring current intensity. However, other technical points are essential for this control such as ensuring good contact between the catheter and the endocardium and the definition of the optimal surface area of the electrode. Now that the conditions of efficacy and security of ablation by high frequency currents are known, anatomopathological studies in man have become rare. These studies, which will take a long time to perform due to the very nature of the technique and pathologies treated, should provide interesting anatomo-electrical comparisons to increase our understanding of certain arrhythmias.

Animals↗
PubMed1994

[Peridural morphine or intravenous patient-controlled (PCA) morphine: which is the best choice?].

Postoperative analgesia must be adapted to each case. When postoperative course is moderately painful, as in day case surgery, non opioid analgesics are sufficient. In case of a more painful surgery, opioids are necessary. Morphine by intravenous PCA is the technique of choice for it provides an optimal comfort in most cases. Nevertheless, when an intensive analgesia is needed, as for active physiotherapy in a risk patient after an important surgery, an epidural combination of opioids and local anaesthetics is much more suitable.

Analgesia, Epidural↗
PubMed1993

[Antiarrhythmic treatment after reduction of atrial fibrillation by external shock].

Among the drugs recommended to prevent recurrences of atrial fibrillation after external electric shock, antiarrhythmic agents of classes Ia (quinidine, disopyramide), Ic (cibenzoline, flecainide, propafenone) and III (sotalol) seem to have the same effectiveness in maintaining the sinus rhythm in about 50 percent of the cases after 6 months and one year. Amiodarone, seldom used as first-line treatment, appears to be the most effective drug. The percentage of side-effects requiring discontinuation of treatment is the same for all drugs (about 10 percent). All these drugs have potential proarrhythmic effects. In case of recurrence electric shocks can be repeated in some special cases. The therapeutic strategy according to the clinical context (atrial fibrillation of vagal nerve or catecholergic origin, normal or altered left ventricular function) is discussed.

Amiodarone↗
PubMed1993

Equivalence of postoperative analgesia with patient-controlled intravenous or epidural alfentanil.

The analgesia and the frequency and severity of oxyhemoglobin desaturation related to alfentanil administration were compared in 32 patients randomly selected to receive patient-controlled analgesia (PCA) by either the epidural (EPI) or intravenous (i.v.) route for a mean period of 16 h after major abdominal surgery. Bolus increments of 250 micrograms of alfentanil with a lockout interval of 5 min for i.v. and of 10 min for EPI route were administered by a programmable pump. Oxygen saturation (SpO2) was monitored for 16 h, using a pulse oximeter; data were collected continuously and stored every 30 s via an interface connected to a computer. For the purpose of analysis, SpO2 was divided into six categories: 95%-100%, 90%-94%, 85%-89%, 80%-84%, 75%-79%, and 70%-74%. Both routes provided similar degrees of analgesia at rest and on coughing. Maximum pain relief was obtained earlier in the i.v. group (P < 0.01). The total consumption of alfentanil was 13,141 +/- 3471 micrograms (mean +/- SD) in the i.v. group and 8000 +/- 4213 micrograms in the EPI group (P < 0.001). The effects on SpO2 were not statistically different between the two groups. Cumulative time spent in each saturation category was similar for the EPI and i.v. groups. Severe desaturation episodes, defined as SpO2 < or = 85% for at least 60 s, occurred in 69% of patients in the EPI group and 56% in the i.v. group.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1993

[Signal averaged electrocardiogram of the P wave after reduction of permanent atrial fibrillation. A comparison with results obtained in healthy subjects and in patients with atrial fibrillation].

Signal averaging of the ECG P wave is a recent technique used for obtaining predictive and prognostic information in atrial arrhythmias. There have been few publications of its evaluation in this setting. The authors report their results of temporal analysis of the P wave of patients who had undergone electrical cardioversion of atrial fibrillation (group 3, n = 22 patients) and compared them with those of a control group without atrial arrhythmias (group 1, n = 25 patients). After recording signals in three bipolar leads (Predictor 5.0 II Corazonix recorder-analyser), the total duration of the P wave, the root mean square of the P wave amplitude (RMSt) and of the last 20 milliseconds (RMS 20) and the integral under the curve of the P waves (IN) were determined. The comparison was continued with data obtained from a population of patients with paroxysmal atrial fibrillation (group 2, n = 22). All patients had normal left atria on echocardiography, had no valvular heart disease, had no myocardial infarction or signs of cardiac failure. Results showed that the most discriminating parameter was the P wave duration (Group 3: 159.45 +/- 15.1 ms; group 1: 123 +/- 8.5 ms; group 2: 144.6 +/- 12.03 ms; group 1 versus group 2, p < 0.001, group 2 versus group 3, p < 0.01; group 1 versus group 3, p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Amplifiers, Electronic↗
PubMed1993

[Ventricular tachycardia of dilated cardiomyopathies].

Patients with dilated cardiomyopathy often have unsustained VT (15 to 60% of cases) but sustained VT is much less common (0 to 10% of cases). The predictive value of sudden death of VT in Holter monitoring is not unanimously accepted. Therefore, it appears that, in patients with non-symptomatic VT, it is the degree of left ventricular dysfunction which is the best predictive factor of mortality because Holter monitoring, signal averaged ECG and programmed stimulation have a low positive predictive value although their cumulated negative predictive value seems to be very good. Programmed ventricular stimulation should be proposed to patients considered to be at high risk of sudden death, presenting with symptomatic unsustained VT or sustained VT. Approximately 3 out of 4 of these arrhythmias will be inducible and benefit from this method for orientating the choice of treatment. In these high risk subjects about 1 in 3 will be satisfactorily protected by antiarrhythmic drug therapy: non-inducible patients from the outset and those remaining inducible despite antiarrhythmic therapy remain at high risk of sudden death. This group of patients probably represents the best indication of implantable cardioverter defibrillators.

Action Potentials↗
PubMed1993

[Simultaneous prescription of digoxin and an anti-arrhythmia agent, is it dangerous?].

Many anti-arrhythmic drugs modify the pharmacokinetics of digoxin and increase serum levels. This possibility is considered for the majority of main anti-arrhythmics on the basis of a review of the literature. Quinidine, propafenone, flecainide, amiodarone and verapamil increase blood digoxin levels, sometimes to twice their baseline values. Suggested mechanisms involve above all a decrease in clearance of digoxin and changes in its volume of distribution. Reported accidents considered to be a direct consequence of these interactions are nevertheless rare in the literature, and the need for modifying dose and increased cardiological surveillance in the case of such a combination is essentially a question of precaution. Disopyramide, procainamide and mexiletine do not appear to have any reported effects on the pharmacokinetics of digoxin, their combined prescription never having had any effect on blood digoxin levels.

Anti-Arrhythmia Agents↗
PubMed1992

[Paraplegia after spinal anesthesia].

A case of paraplegia occurring after a spinal anaesthetic is reported. The 79-year-old man was admitted for a fractured neck of femur. Twenty years previously, he had had pharyngeal surgery and a tracheostomy. He had also undergone a prostatectomy for prostate cancer, and had been on oestrogen therapy for two years. He complained of dyspnoea at rest and his chest film showed diffuse pulmonary opacities. In order to avoid possible intubation and respiratory complications, spinal anaesthesia was performed without any problems in the L4 space. After the surgery, the patient recovered all his motor and sensory functions in the lower limbs. On the second postoperative day, he suffered from a motor paralysis of the right leg, which spread to the left leg on the fourth day. NMR imaging showed several vertebral metastases, together with anterior and lateral epidural invasion responsible for cord compression. Treatment with tetracosactide was begun, but the patient died six weeks later in his home, not having recovered any neurological function at all in his lower limbs. In fact, it was only after the procedure that the anaesthetist was informed that, at the time the prostate cancer had been diagnosed, vertebral body metastases, of which the patient had not been informed, were already present. The part played by the spinal anaesthetic in the occurrence of the paraplegia is not clear. It is reminded that such a technique should be used with extreme care in patients having a neoplasm with a very often high incidence of vertebral metastases.

Aged↗
PubMed1992

Interaction between permanent cardiac pacing and electrocautery: the significance of electrode position.

The danger in utilizing electrocautery during a surgical procedure on a pacemaker patient depends, to a great extent, on the position of the electrodes. We have studied this influence in an experimental model consisting of a plexiglass tank filled with a saline solution. Seven pacemakers were successively attached to an immersed and fixed frame and connected to a lead whose tip remains in the same location throughout the experiments. An ERBOTOM T 400 C generator (450 kHz) was used in an unmodulated unipolar mode at a maximum output (400 W). The high frequency current was delivered between a patch located successively at six preset positions in the tank and another electrode applied to 176 surface locations. For each position, we measured the currents in the lead with a separate measurement circuit connected in parallel on the same lead. Results were displayed on a map. Regardless of the patch position, currents were: (1) at a maximum when high frequency was delivered close to the pacemakers and around the tip of the lead; (2) negligible when applied to the path followed by the lead; and (3) a function of the distance between electrodes. These results may help to formulate recommendations to prevent accidents when using electrocautery in pacemaker patients.

Animals↗
PubMed1992

[Effects of electrocautery on the threshold values of permanent pacing. An experimental study].

One of the hazards of high frequency electrical interference (electrocautery) with cardiac pacing is thought to be related to an increase in the threshold values leading to loss of pacing. This hypothesis was examined in an experimental study performed on 5 dogs. A pacing catheter was introduced via the right jugular vein and positioned at the apex of the right ventricle and connected successively to several stimulators implanted in a latero-cervical subcutaneous pocket. A Bovie 400 CT generator was used to deliver a high frequency 1.75 MHz current between a probe applied near to the pacemaker pocket and an electrode placed under the right leg. One or two 5 second bursts were applied for each make of pacemaker, making a total of 3 to 6 applications per animal. A detecting circuit enabled the measurement of the currents in the catheter during the application. The thresholds of pacing were measured before and after each manipulation for several pacing impulse durations. At the maximal output of the generator, the highest recorded current was 117 mA (modulated) and 141 mA (unmodulated). The thresholds of stimulation did not change significantly and the pacing catheter impedance was also stable. This study suggests that high frequency current does not modify the threshold of stimulation in cardiac pacemaker patients. The loss of pacing sometimes observed after the use of electrocautery is probably related to pacemaker dysfunction.

Animals↗
PubMed1992

[Drug treatments of atrial fibrillation].

Atrial fibrillation is a daily cardiological problem which poses three types of questions, which, though old, are only partially mastered: anticoagulation, reduction and prevention of recurrence. It is a potent source of embolism. The risk is the greatest in patients with rheumatic valvular disease when the fibrillation is recent and when underlying cardiac disease is uncompensated. Long term anticoagulation is mandatory when the cause is rheumatic heart disease. In other pathologies, though anticoagulation has not been shown to reduce mortality, it significantly reduces the number of cerebrovascular accidents, including in the elderly and with low-dose vitamin K antagonist drugs. The efficacy of anticoagulation in preventing arterial embolism has not been established. Reduction of atrial fibrillation is not essential if the arrhythmia is well tolerated, chronic, especially in elderly patients and when several recurrences have occurred despite preventive therapy. In other cases, medical reduction is to be preferred to cardioversion if the fibrillation is recent and well tolerated. Of the oral and injectable preparations, amiodarone seems to be the drug with best benefit/risk ratio. Prevention of recurrence of fibrillation is unnecessary for many after a first episode, especially when idiopathic. In other cases, there are many available drugs but results are uncertain except in those observed in atrial fibrillation related to the autonomic nervous system. Strictly controlled and statistically exploitable studies show comparable efficacy of quinine and other Class I drugs. Beta-blockers are not very useful and the excellent long term results with amiodarone require confirmation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1992

[Predictive factors of regularization and maintenance of sinus rhythm in chronic atrial fibrillation].

The aim in treating chronic atrial fibrillation, is not limited to simply achieving immediate regularization. What matters, is sustaining the sinus rhythm. The various methods of regularization, using either medical procedures or cardioversion, involve constraints and risks. Investigation of the relapse predicting factor is of great value in evaluating the benefit/risk ratio. For regularization, the absence ultrasound signs of heart disease, an undilated left atrium, recent atrial fibrillation and all forms of heart disease which are curable, albeit surgically, are indicative of success. With regard to prophylaxis, relapses occur more frequently in cases involving mitral valve disease, long-standing atrial fibrillation or a dilated left atrium.

Age Factors↗
PubMed1992

[Study of intraocular diffusion of ofloxacin in humans and rabbits].

The diffusion of ofloxacin in infected and healthy human and rabbit eyes was investigated. In the human study, cataract surgery patients were given intravenous ofloxacin either as a single 200 or 400 mg dose or as two 400 mg infusions 12 hours apart. Samples of aqueous humor and plasma were collected between 1 and 12 hours after the end of the infusion. Levels in the anterior chamber increased with the dose; peak levels, which occurred after three hours, were 0.33 mg/l after 200 mg and 1.24 mg/l after two 200 mg doses given 12 hours apart. In the rabbit study, 16 hours after experimental infection of the left eye by injection of S. epidermidis into the vitreous, animals were given an intraperitoneal injection of 20 or 50 mg/kg ofloxacin. Dosages in the various ocular tissues showed that penetration into the eye varied with race (albinos greater than pigmented) and dose. Intraocular ofloxacin levels, including in the vitreous, increased two fold when the eye was infected; however, penetration into the sclera, choroid, and retina was comparable in infected and noninfected eyes. These findings in humans and animals suggest that ofloxacin in a dose of a least 400 mg is a useful agent for the treatment of prophylaxis of ocular infections.

Aged↗
PubMed1992

[Embolic complications of chronic atrial fibrillation].

Systemic embolism secondary to chronic atrial fibrillation usually affect the cerebral circulation. The risk of a cerebrovascular accident in patients with chronic atrial fibrillation, irrespective of the aetiology, is 1.8 to 7.5 times that of the general population. The embolic risk is 18 times greater in patients with atrial fibrillation related to the rheumatic heart disease. The risk of patients under 60 years of age with idiopathic atrial fibrillation does not seem to be different to that of the general population. The risk of early recurrence of embolism in the first 30 days ranges from 8 to 15%. The risk of late recurrence varies but seems to be higher than that of the general population. The prognosis of embolic cerebrovascular accidents is poor with a 20% mortality rate. The benefits of preventive therapy of embolism with oral anticoagulants have been clearly established in rheumatic atrial fibrillation and in other indications. In non-valvular atrial fibrillation the benefits have to be compared with the risks of treatment. The incidence of hemorrhage due to anticoagulant therapy is between 3 and 5% per year per patient (about 1% of severe haemorrhage). Three randomised studies of primary prevention have shown a significant reduction of the embolic risk in non-valvular atrial fibrillation treated by warfarin compared to patients on placebo. Only one study has shown a significant reduction of the embolic risk in patients under 75 years of age with non-valvular atrial fibrillation treated with 325 mg/day of aspirin. However, anticoagulant therapy does not seem necessary in carefully selected patients under 60 years of age with idiopathic atrial fibrillation (less than 5% of all patients).

Aspirin↗