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T Lavergne

Publications and source records attributed to T Lavergne.

At least 37 records · Page 2Linked to original sources
PubMed2000

[Heart rate and mortality: review of the literature].

A great number of studies focussed on a wide variety of subjects have been concerned with the subject of morbi-mortality and the effect of heart rate. These studies show that there is a connection between high heart rate and arterial hypertension, and a significant coronary, cardiovascular, non-cardiovascular and overall mortality risk. Two explanations are possible for this. The increase in heart rate together with associated sympathetic hyperactivity can be considered a cardiovascular risk factor: or it could be viewed as an independent risk factor, associated with an increase in mechanical constraints.

Cardiovascular Diseases↗
PubMed1999

Efficacy and safety of septal and left-atrial linear ablation for atrial fibrillation.

Atrial fibrillation (AF), the most common of all sustained cardiac arrhythmias, is frequently resistant to antiarrhythmic drugs, and physicians have seen limited success with catheter ablation limited to the right atrium. As a result, the safety and efficacy of systematic biatrial linear ablation for drug resistant AF was investigated. Forty-four patients (54 +/- 7 years) underwent catheter ablation of daily drug-resistant AF. Two right-atrial lines (1 septal and 1 cavotricuspid) and 3-4 left-atrial lines were transseptally performed: 2 joining each superior pulmonary vein to the posterior mitral annulus and 1 interconnecting them. An additional left-atrial septal line from the right superior pulmonary vein (RSPV) to the foramen ovalis was performed in 23 patients. Radiofrequency was delivered with a conventional thermocouple-equipped ablation catheter or with an irrigated tip ablation catheter for resistant cases and for sparing the endocardium. Of the 44 patients, 25 (57%) were successfully treated without antiarrhythmic drugs. Twelve patients (27%) improved (<6 hours of AF per trimester under a previously ineffective drug) and 7 (16%) were considered treatment failures. Multiple sessions were required to ablate new left-atrial macro-reentry and initiating foci (2.7 +/- 1.3 procedures per patient). Five patients had a pericardial effusion and 1 each a pulmonary embolism, an inferior myocardial infarction, and a reversible cerebral ischemic event. One patient had thrombosis of the 2 left pulmonary veins. Despite a relatively high success rate, this procedure is too long, and the safely and efficacy need to be improved and applied to a broader range of patients.

Adult↗
PubMed1998

Successful irrigated-tip catheter ablation of atrial flutter resistant to conventional radiofrequency ablation.

BACKGROUND: Catheter ablation of typical right atrial flutter is now widely performed. The best end point has been demonstrated to be bidirectional isthmus block. We investigated the use of irrigated-tip catheters in a small subset of patients who failed isthmus ablation with conventional radiofrequency (RF) ablation. METHODS AND RESULTS: Of 170 patients referred for ablation of common atrial flutter, conventional ablation of the cavotricuspid isthmus with >21 applications failed to create a bidirectional block in 13 (7.6%). An irrigated-tip catheter ablation was performed on identified gaps in the ablation line according to a protocol found to be safe in animals: a moderate flow rate of 17 mL/min and temperature-controlled (target, 50 degrees C) RF delivery with a power limit of 50 W. Bidirectional isthmus block was achieved in 12 patients by use of a mean delivered power of 40+/-6 W with a single application in 6 patients and 2 to 6 applications in the other 6. No side effects occurred during or after the procedure. CONCLUSIONS: Irrigated-tip catheter ablation is safe and effective for achieving cavotricuspid isthmus block when conventional RF energy has failed.

Adult↗
PubMed1998

Segment by segment linear ablation with an articulated bilimb catheter: initial experimental results.

Transcatheter radiofrequency (RF) ablation of atrial fibrillation or flutter requires the creation of linear lesions. However, conventional catheters are not predictably effective because of poor endocardial contact, and limited lesion size and penetration. The purpose of the study was to assess in the right atrium, the efficacy and safety of a new catheter designed to create long myocardial tissue lesions using RF energy. The main characteristics of this 8 Fr deflectable RF ablation catheter were: (1) a perpendicularly contacting articulated bilimb electrodes ensuring stable and firm endocardial firm contact; and (2) an irrigated planar interface. Three different electrode prototypes were tested. Fourteen anesthetized sheep weighing 61 +/- 7 kg underwent RF ablation in the right atrium using three incremental power levels (25 to 45, 50, 55 to 75 W) with the aim of creating fully transmural (FT) lesions, defined as continuous and complete epicardial and endocardial lesion imprints. The animals were euthanized 1 hour later for macroscopic and histologic examinations. Forty-three of the 80 right atrial lesions created, in smooth as well as in trabeculated areas, were FT. The percentage of FT lesions increased with the applied power from 37% with 25-45 W, to 49% with 50 W, and up to 86% for 55-75 W. In all but two cases, histologic examination showed no discontinuity between FT lesions produced by both limbs resulting in 19 coalescent linear lesions with an average size of 25 x 6 x 4 mm (length x width x depth). In situ bipolar electrograms after ablation in the FT group showed split potentials and/or a marked decrease in amplitude from 2.85 +/- 1.79 to 0.33 +/- 0.14 mV (P = 0.001) accompanied by near complete disappearance of unipolar electrograms. There was no perforation due to RF ablation. In conclusion, continuous and FT lesions can be achieved in various areas of sheep atria, including the trabecular right atrium, with a perpendicularly contacting bilimb electrode catheter. It represents a promising tool for catheter ablation of atrial fibrillation and flutter.

Animals↗
PubMed1998

[Management of arrhythmias in patients with heart failure].

Cardiac failure is a common cause of arrhythmia. Many factors predispose to the genesis of arrhythmias in these patients. A number of non-invasive methods allow stratification of the risk of arrhythmia in cardiac failure. Approximately half the deaths of these patients are due to arrhythmia. Unfortunately, most of the investigations for risk evaluation have a high negative predictive value but a lower positive predictive value. The treatment of supraventricular arrhythmias, mainly atrial fibrillation, is complex in cardiac failure. Class I antiarrhythmics are contraindicated. The only remaining options are Class II, especially Sotalol, and Class III drugs, especially Amiodarone. In some cases, non-pharmacological methods such as ablation, pacing or an implantable atrial defibrillator must be considered. The treatment of ventricular arrhythmias is also difficult. In this indication, Class I antiarrhythmic agents must also be avoided. Non-sustained ventricular tachycardia may be treated by betablockers or amiodarone. The use of an implantable defibrillator is increasingly recommended after the results of several controlled large scale trials. The indication is obvious in patients resuscitated from sudden death and these devices are also beneficial in sustained ventricular tachycardia in patients with cardiac failure. Many studies are currently under way to determine the value of this therapeutic modality in indications now considered to be "prophylactic".

Adrenergic beta-Antagonists↗
PubMed1997

Preliminary clinical experience with the first dual chamber pacemaker defibrillator.

The lack of specificity of VT detection is a significant shortcoming of current ICDs. In a French multicenter study, 18 patients underwent implantation of the Defender 9001 (ELA Medical), an ICD utilizing dual chamber pacing and arrhythmia detection. Over a mean follow-up period of 7.1 +/- 4.5 months, 176 tachycardia episodes recorded in the device memory were analyzed, and physician diagnosis was compared with that by the device. All 122 VT/VF episodes were correctly diagnosed, as were 51 of 53 supraventricular tachyarrhythmias. Two episodes of AF with rapid regular ventricular rates were treated as VT, and a third episode, treated as VT, could not be diagnosed with certainty. A dual chamber pacemaker defibrillator offers improved diagnostic specificity without loss of sensitivity, in addition to the hemodynamic benefit of dual chamber pacing.

Adolescent↗
PubMed1997

[Radiofrequency ablation of accessory atrioventricular pathways].

Since its introduction at the beginning of the 1980s, radiofrequency ablation of accessory atrioventricular pathways has become method because of its excellent results and the indications have increased to cases in which only symptomatic improvement is the objective. These advances have been made possible by technical innovations to the generators of the radiofrequency current and, above all, to the ablation catheters which enable mapping nearly all the perimeter of the atrioventricular rings and reach all the accessory pathways irrespective of their site. The approach depends on the localisation of the accessory pathway but the criteria of mapping are the same: detection of a specific accessory pathway potential, precession or concordance (depending on the topography) of the initial peak of the endocavitary ventriculogramme and the onset of the delta wave on the surface ECG, QS morphology of the ventriculogramme on monopolar recording, shortest VA' interval in orthodromic reciprocating tachycardia for latent kent bundles. In specialised centres, the global success rate is 90 to 98% but certain sites, especially the right lateral pathways, are more difficult to attain. The complication rate is about 4% but it tends to decrease with the experience of the operating teams and close monitoring of the patients. However, there persists an uncertainty concerning potentially arrhythmogenic effects of the lesions induced which justifies restricting the indications in young children.

Arrhythmias, Cardiac↗
PubMed1997

Study of muscular and ventricular function in dynamic cardiomyoplasty: a ten-year follow-up.

BACKGROUND: The basic physiologic principle underlying cardiomyoplasty is long-term electrostimulation of a latissimus dorsi muscle (LDM) wrapped around the heart to obtain a phasic activity that could be integrated with ventricular kinetics. The aim of cardiomyoplasty is to prolong survival and to improve the quality of life of patients with severe chronic and irreversible myocardial failure by improving systolic contraction and correcting diastolic dysfunction. METHODS: To evaluate the long-term outcome of cardiomyoplasty, we investigated 82 patients electively undergoing this procedure in-our hospital. All patients had severe chronic heart failure that did not respond to optimal medical treatment. Patients had a mean age of 50 +/- 12 years (84% males). The cause of heart failure was ischemic (55%), idiopathic cardiomyopathy (34%), ventricular tumor (6%), and other (5%). The mean follow-up was 4.3 years. RESULTS: The mean New York Heart Association functional class improved after operation from 3.2 to 1.8. Average radioisotopic left ventricular ejection fraction increased from 17% +/- 6% to 28% +/- 3% (p < 0.05). Stroke volume index increased from 35 +/- 9 to 46 +/- 8 ml/beat/m2 (p < 0.05). The heart size remained stable at long term (evaluated by echo and computed tomography scanning). After cardiomyoplasty the number of successive hospitalizations resulting from congestive heart failure was reduced to 0.4 hospitalizations/patient/year (before operation 2.5, p < 0.05). Computed tomography scans showed at long-term a preserved LDM structure in 82% of patients who underwent operation. Survival probability at 7 years was 54% for the totality of patients, and 66% for patients who underwent operation in New York Heart Association functional class 3. Five patients underwent heart transplantation after cardiomyoplasty (mean delay 29 months), principally as a result of the natural evolution of their underlying heart disease, without major technical difficulties. CONCLUSIONS: Our 10-year clinical experience demonstrates that cardiomyoplasty increases ejection fraction, improves functional class, and ameliorates quality of life. Ventricular volumes and diameters remain stable long term. LDM structure is maintained long term if electrostimulation is performed avoiding excessive myostimulation. Patient selection is the most important determinant for early and late outcome. Late death in patients undergoing cardiomyoplasty is principally due to sudden death. Our future aim is to incorporate a cardioverter-defibrillator in the cardiomyostimulator, thus improving long-term results. Cardiomyoplasty may delay or prevent end-stage heart failure and the need for heart transplantation.

Adolescent↗
PubMed1997

[Auricular vulnerability: what information can be obtained from the study of auricular vulnerability? How to perform this study?].

The factors involved in atrial vulnerability are the presence of intra-atrial conduction disorders and abnormalities of refractory periods which are short, dispersed and poorly adapted to heart rate. All these factors are arrthythmogenic. The main value of the study of atrial vulnerability consists of investigation of unexplained ischaemic cerebrovascular accidents in young subjects. In practice, atrial vulnerability can be measured in the context of a classical endocavitary electrophysiological investigation. The stimulation and recording parameters must be standardized. Latent atrial vulnerability can be considered to be present when at least one of the following elements are found: significant inducibility, very short and poorly adapted effective refractory periods, decreased latent atrial vulnerability index.

Atrial Fibrillation↗
PubMed1996

[Mechanisms of atrial fibrillation. Recent progress and therapeutic implications].

Atrial fibrillation is usually due to multiple microreentry circuits. However, in some cases, the initial arrhythmia inducing the atrial fibrillation may be an abnormal automatism, or a macroreentry. The initial abnormalities may induce a desynchronization due to multiple macroreentry circuits. The main factors of atrial vulnerability are intraatrial conduction disturbances and changes in refractory periods. Critical mass and effects of autonomic nervous system may also play a role. Shortened refractory periods and decreased conduction velocity imply a short wavelength and an important arrhythmogenic risk. On the other hand, the longer the duration of atrial fibrillation, the more refractory periods will shorten and the more atrium will become vulnerable: atrial fibrillation tends to beget atrial fibrillation because of an electrophysiologic remodelage. In some cases atrial fibrillation, if its duration is long and if its rate is high, may be responsible for the development of a tachycardiomyopathy. The knowledge of atrial fibrillation mechanism may have interesting therapeutic implications such as resynchronization of the atria by stimulation or ablation, for example in the approaches comparable to the maze operation.

Arrhythmias, Cardiac↗
PubMed1996

Ventricular protection against atrial arrhythmias in DDD pacing based on a statistical approach: clinical results.

Atrial arrhythmias (AA) are commonly encountered in DDD paced patients. Newer dual chamber pacemakers (PM) possess mode switching functions that convert pacing to an asynchronous mode when AAs are detected. The lack of a reliable mode switch leading to rapid, irregular ventricular responses may result from AA undersensing. To avoid this the DDDR PM Chorum 7234 Ela Medical AA diagnosis is based on a statistical approach: the PM constantly compares arrhythmic and sinus cycles and, based on "strong" and "weak" criteria, provides for rapid or slower mode switch. The aim of the study was to evaluate the efficiency and reliability of these two criteria. Thirty-one patients with a Chorum 7234 implanted for AV block (11), sinus dysfunction (10), both (5), or hypertrophic obstructive cardiomyopathy (5) were evaluated at 24 hours and 1 month using the internal memory (IM) of the PM, surface 24-hour Holter recordings, and exercise testing. Interrogation of the IM on the first day of study showed that 8 patients had mode switching episodes, based only on the strong criterion confirmed by the surface Holter recording. At 1 month, the IM revealed mode switching episodes in 12 patients, 6 of whom had used the weak criterion. No inappropriate mode switching episodes was recorded during exercise testing at the 1-month follow-up. These results confirm the reliability and efficiency of this algorithm as well as the requirement for a specific algorithm to compensate for transient loss of sensing during AA.

Algorithms↗
PubMed1996

Initial and long-term evaluation of escape rhythm after radiofrequency ablation of the AV junction in 50 patients.

Between 1986 and 1994, 50 patients (mean age 63 +/- 13 years), 25 of whom had organic heart disease and presenting with atrial arrhythmias refractory to 5.6 +/- 1.6 antiarrhythmic drugs, underwent radiofrequency ablation (5 +/- 3 pulses by procedure; duration of pulses 50.5 +/- 32 s) of the proximal AV junction to create complete and permanent AV block. The escape rhythm was studied immediately after the procedure and during long-term follow-up. Immediately after the procedure, an escape rhythm was observed in 80% of the patients (junctional in 92%). Over a mean follow-up of 36 +/- 16 months in 47 patients (2 patients died before assessment of escape rhythm and 1 was lost to follow-up), an escape rhythm was present in 39 patients (83%) and absent in the remaining 8 (17%). The only significant difference between the two groups was the initial presence of an escape rhythm (P = 0.008). However, three patients with an initial escape rhythm had none during long-term follow-up. The initial presence of an escape rhythm as a predictive factor of its presence during follow-up had a sensitivity of 87%, specificity of 63%, positive predictive value of 92%, and negative predictive value of 50%. Thus, the absence of an escape rhythm during long-term follow-up causing pacemaker dependency was noted in 1 of 6 patients. This represents a limitation to this palliative treatment, which should be reserved for patients suffering from supraventricular tachycardias refractory to other treatments.

Adult↗
PubMed1996

Correlation between time-domain measures of heart rate variability and scatterplots in postinfarction patients.

Heart rate variability (HRV) is usually measured in time or frequency domains. Beat-to-beat variability, which cannot be assessed by frequency-domain analysis, and can only be assessed globally by time-domain analysis, provides information concerning the nonlinear behavior of heart rate. This beat-to-beat variability can be displayed on scatterplots, where each RR interval is plotted against the preceding RR interval. However, the relationship between scatterplots and other measures of HRV is unknown. We studied the correlations between time-domain measures and scatterplot length, width, and area in 50 postinfarction patients. Scatterplot length and width were measured after printing. Scatterplot area was calculated from length and width, assimilating the plot to an ellipse. Long-term variability indexes (SDNN and SDANN) were strongly correlated with scatterplot length (r > 0.9, P < 0.0001), and short-term variability parameters (pNN50 and variability index) with scatterplot width (r > 0.9; P < 0.0001). Scatterplots are, therefore, a simple way of providing information concerning long- and short-term HRV. Furthermore, measurement of scatterplot width at different given RR intervals could be an approach to the evaluation of short-term HRV for different heart rates. This could provide a simple way of assessing cardiac parasympathetic modulation at different heart rates.

Adult↗
PubMed1996

[Radiofrequency ablation: physical bases and principles].

Radiofrequency currents are the reference physical agent for endocavitary ablation, especially of supraventricular tachycardias. They are delivered in a continuous mode or sinusoidal waves. Because of the high frequency between 200 and 3,000 kHz there is no stimulation of the neuromuscular cells. The mechanism of the resulting lesion is essentially related to heating of the biological surroundings of the active electrode. The temperature increase remains localised around the active electrode and its kinetics are progressive, which implies close and stable contact between the active electrode and the tissues. The lesional effect is obtained 60 to 90 degrees C in order to avoid the deleterious effects induced by temperatures of over 100 degrees C: boiling, coagulation, vaporization and carbonization of the tissues leading to an increase in impedence. The volume of lesions depends on many factors which are sometimes difficult to control in vivo. It is more closely correlated to the temperature of the active electrode than to the parameters of delivery (power, duration ...). The histological lesions correspond to scar tissue which respects the surrounding architecture. The major technological innovations of this method have resulted in an increase in the volume of the lesions produced, a reduction in the frequency of undesirable effects such as the formation of coagulum and in an immediate evaluation of the anatomic lesional effect. They have consisted in the introduction of specific electrodes and of systems of monitoring the electrical and thermal effects with the use of imaging techniques such as endovascular and transoesophageal echocardiography and angioscopy. New indications will require development of specific catheter-generator equipment to create lesions of size and shape adapted to the arrhythmogenic substrate.

Animals↗
PubMed1995

Radioisotopic pacemaker: long-term clinical results.

In order to prolong the service life of the generator, the isotopic pacemakers, powered by Pu238, have been developed and implanted since 1970. We report the follow-up of 325 patients (mean age 39 +/- 18 years) implanted with an isotopic pulse generator (Medtronic 9000/9090) between April 1970 and July 1982. The mean follow-up was 12 years (range 6 days to 18.5 years). The generator was highly reliable; the mean value of pacing rate between implantation and last follow-up decreased significantly but no more than 1 beat/min (72.7 vs 71.8 beats/min; P < 0.001) and the pulse width did not change significantly. The actuarial survival of the device was 97% at 18.5 years. During the follow-up period, 122 reoperations were performed in 85 patients: 88 explanations of the entire pacing system and 34 modifications of the lead system. Lead dysfunction accounted for 68% of the 122 reoperations, generator failure for 6%, and miscellaneous reasons for 26%. However, 72% of patients remain free of intervention during the follow-up period and 61 patients (20%) died during this period. Most deaths (52%) were of nonsudden cardiovascular origin, 17% were related to cancer, and 13% to sudden death. After 5, 10, and 18.5 years, 94%, 89%, and 73% of the patients were alive, respectively. No side effect could be attributed to the radioisotope. We conclude that this isotopic pacemaker demonstrated its reliability for long-term cardiac pacing.

Actuarial Analysis↗
PubMed1995

[Impact of controlling risk factors after myocardial infarction].

The relative risks of each factors and the benefits of their reduction after myocardial infarction are comparable to those observed in primary prevention. However, because of an overexposure to the risk, the absolute gains are five times greater. The impact of diet is one of the most important: in addition to the limitation of polyunsaturated fats and global calory intake, especially in cases of central obesity, the increase in dietary alpha-linolenic acid and in omega-3, has been shown to reduce the risk of myocardial infarction and mortality by up to 70%. Supplements of vitamins A and E could be useful. After infarction, the risks of an ex-smoker decrease rapidly by half and become comparable to those of non-smokers in 2 to 3 years. Physical exercise reduces cardiovascular mortality by 20-25% and contributes to better control of risk factors. The management of some psycho-physiological factors (reaction to stress, hostility) also gives encouraging results). A 10% reduction in total cholesterol leads to a 20% or more decrease in coronary events and a 10% reduction in mortality with a marked dose-response effect inciting to the reduction of its level to under 2 g/l. The progression of atherosclerosis delayed; early lesions, with the greatest risk of rupture and thrombosis, are stabilised and may even regress. A low HDL-c concentration should lead to more energetic reduction of LDL-c and control of smoking, obesity and sedentarity. Its association with hypertriglyceridaemia, glucose intolerance, hypertension and central obesity defines the syndrome of insulin resistance which multiplies cardiovascular risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗