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Biomedical subjects

G Fontaine

Publications and source records attributed to G Fontaine.

At least 127 records · Page 7Linked to original sources
PubMed1990

Better predictors of successful His-bundle ablation analysis of first shocks.

We have reported here that a longer HV interval in association with a larger His amplitude yields a high rate of success when used to position the ablating catheter for His-bundle ablation. Additionally, we have shown that double discharge shocks are more effective than single discharge shocks, and that negative polarity is more effective than positive polarity. The use of bipolar or tripolar, and not quadripolar catheters, was also associated with a higher success rate. In our institution, using a bipolar catheter, we attempt to record an HV interval greater than 55 msec and a His amplitude greater than 0.35 mV. When both of these criteria are fulfilled, we use 3 to 4 joules per kg, and a single discharge shock. When one or the other of these criteria are not fulfilled, we use the double discharge shock method. Using these techniques, we have achieved successful His-bundle ablation with only one shock in all but one of the most recent 21 consecutive patients.

Bundle of His↗
PubMed1990

Ablation of the slow-conduction area in chronic ventricular tachycardia.

The ablation techniques, which derive from surgical approach in the treatment of ventricular tachycardia, were originally based on the modification of conduction in the so-called site of origin of the arrhythmia. A reentrant tachycardia involves two areas of conduction, one which consists of normal tissue, and the other with slow-conduction properties isolated from the previous structure. We now think that a more appropriate place to deliver the shock should be the area of slow conduction. The purpose of this paper is to review the main electrophysiological characteristics of this tissue, which could be interesting markers to identify the site where the shock should be delivered.

Action Potentials↗
PubMed1990

[Electrophysiology in evaluating the treatment of sustained monomorphic ventricular tachycardia: criteria for efficacy].

The authors studied the influence on recurrence and mortality of induced ventricular arrhythmias during electrophysiological studies performed to assess the efficacy of treatment of sustained monomorphic ventricular tachycardia. One hundred and twenty-six consecutive patients investigated from 1981 to 1988 were included. The underlying pathology was chronic myocardial infarction (N = 56), dilated cardiomyopathy (N = 24), right ventricular dysplasia (N = 31) and there were 15 idiopathic cases. All these tachycardias could be induced during the control study. A second test was performed after instituting treatment. This was maintained whatever the result of the electrophysiological study except in patients in whom the tachycardia rate was over 130/mn and/or poorly tolerated. Recurrences were defined as the observation of tachycardia with the same morphology and/or the occurrence of sudden death. Follow-up averaged 29 +/- 21 months. The absence of recurrence and survival were assessed by the Kaplan-Meier method and Logrank's test. It was not possible to induce any arrhythmia after treatment in 52 patients (41%). The prevalence of absence of recurrence in this group was 0.863. If the induction of ventricular fibrillation, doublets or short runs of VT (N less than 6 with no recurrences) are included, the value increased to 0.877. These patients were considered to be non-inducible. The prevalence of absence of recurrence of arrhythmia in patients in whom it was possible to induce sustained ventricular tachycardia of the same morphology as the clinical arrhythmia was 0.512 (p = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

[Congenital and acquired right ventricular dysplasia].

Arrhythmogenic right ventricular dysplasia has been described as a developmental malformation occurring during foetal life. This explains a number of familial cases of this condition where dysplasia was the result of a genetic abnormality transmitted in an autosomal dominant mode with incomplete penetrance. Histological data of peroperative or post-mortem specimens of 27 cases showed a large number of grape-like lymphoplasmocytic infiltrations. These appearances suggest an inflammatory origin of the disease, most probably related to an infective etiology. The authors suggest that in addition to the congenital form there may also be a possibility of acquiring arrhythmogenic right ventricular dysplasia after an episode of myocarditis.

Adult↗
PubMed1990

[Value and limitations of Holter monitoring and electrophysiologic testing in the evaluation of the treatment of sustained monomorphic ventricular tachycardia].

The authors studied the value and limitations of Holter monitoring and electrophysiological investigation in the evaluation of treatment of sustained monomorphic ventricular tachycardia (VT). One hundred and twenty-four consecutive patients were included in the study from January 1981 to February 1988. The etiologies were chronic myocardial infarction (N = 54), dilated cardiomyopathy (N = 24), right ventricular dysplasia (N = 31), and idiopathic VT (N = 15). All the tachycardias could be induced during baseline electrophysiological investigations and presented as complex ventricular arrhythmias on the Holter recordings. The investigations were repeated after treatment which was maintained irrespective of the results, unless the tachycardia which was induced or recorded was over 130 cycles/min and/or poorly tolerated. Recurrence was defined as the recording of VT in the absence of a change of treatment and/or the occurrence of sudden death. The follow-up period averaged 29 +/- 21 months. The Kaplan-Meier method was used to study the prevalence of absence of recurrence and survival rates. We observed 28 recurrences of VT and there were 21 deaths. Eighty-five per cent of patients had normal Holter monitoring after treatment. The prevalence of absence of recurrence was 0.751 when the Holter was normal and 0.485 when an arrhythmia was recorded (p = 0.03). The sensitivity was 25 per cent and the specificity 88 per cent. The survival rates were 0.66 and 0.585 respectively (p = 0.008). Fifty-three per cent of patients remained inducible after treatment with a prevalence of absence of recurrence of 0.572. This value rose to 0.877 when VT could not be induced (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1990

[Physical and biophysical aspects of high energy intracardiac electrical discharges. II. Correlations between the physical and electrical effects of liminal and infraliminal shocks].

The electrical phenomena produced during the fulguration impulses are analyzed using a digital oscilloscope which enables the calculation, with precision, of the energies consumed all along the curve or between chosen times. Moreover, it enables the calculation of the corresponding impedance values and shows that the latter varies during all the discharge. The explanation for these impedance variations is obtained thanks to rapid cinematography, showing the formation of the fulguration bubble. Hence, one can observe an impedance variation which is quite distinctive from the one which would correspond to the simple passage of an electrical current in saline solution. Particularly at the end of the impulse, an important increase in the impedance corresponds to the loss of ionization of the bubble. Therefore, by simply reading these electrical parameters, it is possible to know the main stages of the fulguration phenomenon for impulses situated around the deflagration threshold.

Algorithms↗
PubMed1990

[Physical and biophysical aspects of high-energy intracardiac electric discharges. III. Correlation between physical and electric effects for the use of supraliminal shocks].

Using the same methods as for the measurement of electrical parameters by means of an oscilloscope with a wave shape calculator to determine at all points the energy and impedance values, as well as high speed cinematography, the analysis of the behavior of these parameters for shocks with energies close to those used in clinical medicine can be carried out. It shows namely an important decrease in the impedance at the current peak due to an important ionization of the fulguration bubble. It underlines the different behavior of the anode and cathode bubbles, in relation with the size of the bubbles obtained thanks to rapid cinematography. Comparative measurements concerning the polarity, the size of the indifferent electrode, the medium used in vitro and in vivo have supplied the elements to enable the precise determination of the adequate electrical parameters for the good use of fulguration.

Animals↗
PubMed1990

[Revision of criteria for locating the accessory pathway by electrocardiogram in Wolff-Parkinson-White syndrome. A new algorithm].

A new algorithm has been developed for locating the anomalous conduction pathway from the ECG which is based on 62 cases of Wolff-Parkinson-White syndrome with a single anomalous conduction pathway, located by epicardial mapping, i.e. 28 on the free edge of the left ventricle (FL), 22 posterior septal, including 11 left (LPS) and 11 right (RPS), 8 right lateral (RL) and 4 right anterior septal (RAS). Criteria use the orientation of the delta wave and the QRS complex in the right precordial leads and the frontal plane, combined with the presence or absence of left or right ventricular hypertrophy. The algorithm is worked out in 15 steps, each criterion being applied only if the preceding criterion has not been observed. It identifies 100 per cent of the study population. This high specificity has been checked on independent series which include 55 FL pathways, 9 LPS, 17 RPS, 10 RL and 5 RAS. Only 2 LPS pathways were identified as FL and 1 RPS pathway as RL corresponding, perhaps, to "borderline" cases. The ECG thus remains the simplest non invasive examination for locating the ventricular origin of anomalous conduction pathways.

Algorithms↗
PubMed1990

[Physical and biophysical aspects of high-energy intracardiac electric discharges. I. The discharge bubble].

Endocavitary discharge produces an electrical spark at the end of the probe. This in turn produces a plume of steam which lasts for about ten milliseconds and which subsequently acts like a cavitation bubble. This phenomenon is well known in the branch of physics dealing with dynamics and fluids, and should be subjected to rapid kinetic recording. It may make it possible to explain various barotraumas which are observed during the discharge. However, the plumes of steam produced by the discharge have some highly specific features which are due to the fact that the discharge is usually produced using a monopole in an electrolyte. In addition, the shape of the electrode also affects the formation of the bubble. This results in a description of the cavitation bubble produced by the discharge as the "discharge bubble".

Biophysical Phenomena↗
PubMed1990

[Effect on atrioventricular conduction of a new calcium antagonist: lacidipine. Evaluation by the Holter method].

The modification of AV conduction induced by 4 mg b.i.d. of lacidipine (L), a new calcium antagonist, was assessed by studying the changes in ventricular rhythm in 10 patients with stable chronic atrial fibrillation (mean age 71 +/- 15) by daily Holter recordings. The study was single blind versus placebo (P), nifedipine (N) 10 mg b.i.d. and for five patients diltiazem (D) 120 mg b.i.d. Five or seven consecutive 24 hours Holter were recorded in the following order: P, P, N or L, P, N or L, D, D. For each hour, an RR histogram was drawn and the 10 per cent and 90 per cent values of the cumulative cycle length curve were computed, as were the total number of QRS, and the mean value of RR intervals. The correlation coefficient between the number of QRS from the same hour on different days, the Student t test between the mean hourly RR interval values and the comparison between the histograms did not demonstrate a significant difference between the placebo, the nifedipine and the lacidipine periods. The only significant changes were induced by diltiazem (p less than 0.01), with a significant prolongation of the RR intervals. This suggests that lacidipine, like nifedipine, has no effect on AV conduction.

Aged↗
PubMed1989

Treatment of rhythm disorders by endocardial fulguration.

The fulguration procedure was originally introduced for the treatment of supraventricular arrhythmias by a pervenous interruption of His bundle conduction. This procedure has been extended to the treatment of almost any cardiac arrhythmia resistant to antiarrhythmic drug therapy. Recent results suggest that ablation could be selectively applied to the site of abnormal conduction. Overall results obtained at the Jean Rostand Hospital are reported for a series of 104 patients ranging in age from 14 to 83 years with atrial, junctional and ventricular tachycardias. The follow-up extends up to 65 months. Clinical efficacy, defined as a control of the arrhythmias by fulguration used alone or in association with drug therapy that was previously ineffective, lead to a success rate ranging from 80 to 85%. Mortality was less than 10% in the worst situation (chronic resistant ventricular tachycardia). Mortality was always related to inappropriate protocols. Therefore, fulguration, which was originally reserved to treat the most difficult cases, is now considered for non-life-threatening but incapacitating arrhythmias. Despite these results the technique is not simple. Fulguration should be performed by groups knowledgeable in electrophysiology and with expertise in high voltage electricity and biophysics.

Arrhythmias, Cardiac↗
PubMed1989

[Treatment of ventricular tachycardia using endocavitary fulguration. 5 years' experience with 53 cases].

53 patients, between the ages of 14 and 76 years, presented a ventricular tachycardia which was treated by the fulguration method. 19 resulted from a complication of an old myocardial infarction, 15 from a right arrhythmogenic ventricular dysplasia, 8 from a dilated myocardiopathy. 10 patients presented idiopathic tachycardias: 3 originated in the infundibulum of the right ventricule and 7 from the left ventricle. One case originated from a surgical scar of the infundibulum. These tachycardias were continuous or occurred daily in half of the cases, or presented monthly recurrences. 1 to 17 shocks were delivered at each session, 143 on the right, 112 on the left and 2 transseptal. Four patients died from haemodynamic deterioration prior to the shock. The other 49 patients are considered as clinical successes. Three died within the first three months of low cardiac output without any recurrence of the tachycardia. 26 did not longer present any recurrent tachycardia and were not given any preventive anti-arrhythmic treatment. 19 developed recurrence or could be triggered off again, but the anti-arrhythmic medications which were ineffective, become effective. One female patient again developed slavos of ventricular tachycardia after a few months. Seven patients died 4 to 18 months after fulguration, and three presented a sudden death. They belong to the group with medically treated recurrences. This technique is a major factor in the therapeutic strategy of ventricular tachycardias, either used alone or associated with a pharmacological treatment.

Adolescent↗
PubMed1989

Electrode catheter ablation of resistant ventricular tachycardia in arrhythmogenic right ventricular dysplasia: experience of 13 patients with a mean follow-up of 45 months.

Electrode catheter ablation (fulguration) is a new technique for the treatment of ventricular tachycardia resistant to medical treatment. It proved effective in our hands in a series of 65 cases of ventricular tachycardia of varied origin. This paper reports the early results in a subgroup of 13 patients suffering from arrhythmogenic right ventricular dysplasia in whom shocks ranging from 160 to 280J, single or multiple, in one or up to three sessions were delivered. In the 11 patients surviving the DC ablation procedure single or multiple monomorphic sustained VT was brought under control. However, four patients (36%) required therapeutic antiarrhythmic treatment following the fulguration therapy. During the learning phase one case of death was related to poor catheter selection and the other to poor protocol. The post-mortem study of the effect of shocks depends on the anatomical structure to which the shocks have been delivered.

Adult↗
PubMed1989

Assessment of the optimal atrio-ventricular delay in DDD paced patients by impedance plethysmography.

The beneficial haemodynamic effects of sequential atrioventricular (AV) pacing have been clearly established and are dependent on the AV delay and pacing rate. However, the optimal AV delay is difficult to determine in each particular patient. We used a modified impedance plethysmographic method to assess variations in stroke volume for different AV delay and pacing rate settings. Impedance measurements showed a good correlation with CO2 rebreathing stroke volume measurements in VVI patients. Impedance variations were then used to set the optimal AV delay at different pacing rates in DDD patients. The inverse relationship between the optimal AV delay and the pacing rate has been accurately identified in most of the patients but is not predictable. In all cases, the cardiac output was higher in DDD mode at the optimal AV delay than in VVI mode. In some patients with a damaged myocardium, the stroke volume appeared to be highly sensitive to multiple AV delay settings. Impedance plethysmography can permit such repetitive non-invasive quick measurements, increasing the accuracy of optimal AV delay determination and is well suited for routine examination of patients with cardiac dual chamber pacemakers.

Atrioventricular Node↗
PubMed1989

Non-invasive study of dual chamber pacing by pulsed Doppler. Prediction of the haemodynamic response by echocardiographic measurements.

The increase in stroke volume with DDD compared with VVI pacing was measured at rest using pulsed Doppler echocardiography in 23 patients at a pacing rate of 70 beats min-1. Stroke volume was assessed by measuring the velocity integral of the flow at the aortic annulus using the apical five-chamber window. Pulsed Doppler echocardiography allowed determination of the least and most favourable AV delay haemodynamically. TVI was also measured at each nominal value of AV delay. The percentage increase in stroke volume was determined in every patient changing from VVI to optimum DDD pacing and was used as a measurement of the 'sensitivity' to optimum DDD pacing; the mean increase was 27 +/- 19%. The increase in stroke volume accompanying the change from DDD pacing with the least favourable to the optimum AV delay was also measured, and used as a measurement of 'sensitivity' to changes in AV delay; the mean increase was 23.7 +/- 16.3%. Clinical and standard echocardiographic parameters were studied in order to determine which variable might best identify the patients more likely to benefit from DDD pacing, and to identify those more sensitive to the AV delay setting. With respect to sensitivity to DDD pacing, three echocardiographic variables were selected by linear discriminant analysis from 11 clinical and echocardiographic variables. These were, in order of importance, left ventricular systolic diameter (LVSD), left ventricular wall thickness (LVWT) and left atrial size (LAS) which allowed the prediction of a good or a bad response to optimal DDD pacing with an accuracy of 91.3%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗