Biomedical subjects

P Lemetayer

Publications and source records attributed to P Lemetayer.

8 recordsLinked to original sources

PubMed1992

Elimination of atrioventricular nodal reentrant tachycardia using discrete slow potentials to guide application of radiofrequency energy.

BACKGROUND: Ablation of the slow pathway has been performed to eliminate atrioventricular (AV) nodal reentrant tachycardia (AVNRT) either by a surgical approach or by using radiofrequency catheter technique guided by retrograde slow pathway activation mapping. From previous experience of midseptal and posteroseptal mapping, we were aware of the existence of peculiar slow potentials in most humans. Postulating their role in AVNRT, we studied these potentials and the effects of radiofrequency energy. METHODS AND RESULTS: Sixty-four patients (mean age, 48 +/- 19 years) with the usual form of AVNRT were studied. Slow, low-amplitude potentials were recorded when using the anterograde AV conducting system. Slow potentials occupied all (giving a continuum of electrograms) or some of the time between the atrial and ventricular electrograms. Their most specific patterns were their progressive response to increasing atrial rates, which resulted in a dramatic decline in amplitude and slope, a corresponding increase in duration, and a separation from preceding atrial potentials until the disappearance of any consistent activity. Slow potentials were recorded along a vertical band at the mid or posterior part of the septum near the tricuspid annulus. Radiofrequency energy applied at the slow potential site resulted in interruption of induced tachycardia within a few seconds and rendered tachycardia noninducible in all patients. A median of two impulses was delivered to each patient. In 69% of patients, postablation atrial stimulation cannot achieve a long atrial-His interval, which previously was critical for tachycardia induction or maintenance. No patient had AVNRT over a follow-up period of 1-16 months, and all had preserved AV conduction. In all except two patients, the PR interval was unchanged. In 47 patients, long-term electrophysiological studies confirmed the efficacy of ablation and the nonreversibility of results by isoproterenol; however, echo beats remained inducible in 40% of patients. CONCLUSIONS: An area showing slow potentials is present at the perinodal region in humans. In patients with AVNRT, application of radiofrequency energy renders tachycardia noninducible through the preferential modification of the anterograde slow pathway. With present clinical methods, the exact origin and significance of these physiological potentials cannot be specified.

Cardiac Pacing, Artificial↗

PubMed1992

Radiofrequency catheter ablation of left lateral accessory pathways via the coronary sinus.

BACKGROUND: The purpose of this study was to describe a new technique for catheter ablation of left lateral accessory pathways (APs) by radiofrequency energy applied at the epicardium through the coronary sinus wall using a unipolar configuration. METHODS AND RESULTS: In an overall group of 212 patients with left lateral APs, multiple endocardial ablation attempts of the AP were unsuccessful in eight patients. The mean +/- SD cumulative duration of previous attempts was 12 +/- 9 hours, using DC shocks and/or radiofrequency energy applied both at the atrial and/or ventricular AP insertions. Epicardial AP insertion was determined by bipolar and unipolar unfiltered distal electrograms by scanning the coronary sinus with a steerable 6F or 7F catheter with a 4-mm distal electrode. The local atrial to ventricular electrogram amplitude ratio was 0.3-1.6. At the ablation site, the catheter tip was slightly deflected toward the annulus to increase both the ventricular component of electrograms and contact with the epicardium. In four patients, epicardial electrogram timings were earlier than endocardial ones. The AP was ablated in seven of the eight patients with 20-30 W applied for 10-60 seconds. No complications occurred except a marked nonspecific pain during radiofrequency energy application; however, the catheter remained adherent to the coronary sinus wall, and its withdrawal was performed during a new radiofrequency application to decrease the risk of coronary sinus rupture. After ablation, echocardiograms, coronary artery angiograms, and levophase coronary sinus angiograms showed no abnormality in all patients except two who had a probable mural thrombus in the coronary sinus. AP conduction remained abolished for 1-10 months of follow-up in seven patients. CONCLUSIONS: Radiofrequency catheter ablation of left lateral APs can be achieved effectively and relatively safely via the mid or distal coronary sinus when endocardial approaches are unsuccessful.

Catheter Ablation↗

PubMed1991

[Post-extrasystolic long QT: evaluation and significance].

The dynamic behaviour of the QT interval was studied in 13 patients with a prolongation of greater than 80 ms of the QT interval of the QRS complex following a post-extrasystolic pause. Normal repolarisation under basal conditions (QTc 410 +/- 30 ms) was significantly (p less than 0.001) prolonged after pauses (QTc 512 +/- 90 ms). The study protocol included the measurement of QT during a Holter recording, an exercise test, Valsalva's manoeuvre and the isoprenalin test. Hydroquidine 600-900 mg/d was given to evaluate its action on ventricular repolarisation. The longest sinus cycles seen on the night Holter tracing (mean: 1,395 +/- 666 ms) were accompanied by normal repolarisation (QTc 380 +/- 30 ms). In contrast, exercise or Valsalva's manoeuvre caused a prolongation of QTc (QTc greater than 460 ms) in 11 patients out of 13: exercise QTc 471 +/- 54 ms; Valsalva QTc 480 +/- 50 ms. No arrhythmia occurred during these dynamic manoeuvres nor during the isoprenalin test. Hydroquinidine (mean: 729 mg) induced a QTc of greater than 500 ms in 6 patients out of 13 (46%). A triplet suggestive of a "torsade de pointes" was seen in one patient only. In conclusion, patients with a post-extrasystolic T wave abnormality under basal conditions were shown to fail to appropriately adapt their QT interval during autonomic stimulation manoeuvres and the prescription of hydroquinidine at the usual dose induced a mean QTc of greater than 500 ms in 46% of them.

Adolescent↗

PubMed1990

[Interventional rhythmology].

Interventional cardiorhythmology was born with the invention of electrical catheter ablation of the common atrioventricular bundle of His as a palliative treatment of supraventricular arrhythmias refractory to medicinal treatment. This method is now used as a curative treatment. In Wolff-Parkinson-White syndrome, all accessory pathways, whatever their location, can be destroyed with a very high success rate (96 p. 100) and very low morbidity and mortality rates. Reentrant nodal tachycardias can also be treated by catheter ablation with, however, a low risk of atrioventricular block which, for the moment, limits its indications. In intractable ventricular tachycardias, its indications will certainly be extended and its efficacy will increase since numerous recent studies have identified a limited, slow-conduction area (arrhythmogenic substrate) as being the real target for ablation. Other sources of energy are also used for the same purposes, including radiofrequency currents with results that are promising but vary according to the type of arrhythmia treated. Thus, interventional cardiorhythmology is progressively replacing surgery.

Arrhythmias, Cardiac↗

PubMed1989

Closed-chest ablation of retrograde conduction in patients with atrioventricular nodal reentrant tachycardia.

We applied a new technique of catheter ablation to treat atrioventricular nodal reentrant tachycardia and preserve anterograde conduction, performing this procedure in 21 patients with repetitive episodes of tachycardia refractory to antiarrhythmic drugs. Using atrial activation in the His-bundle lead as a reference, we selected the optimal site of ablation by positioning an electrode catheter so that atrial activation occurred simultaneously with or earlier than the reference activation during tachycardia. At this site, the His-bundle deflection was completely absent or was present only at a low amplitude (less than 0.1 mV). In the majority of patients, these criteria could be met by withdrawing the catheter 5 to 10 mm from the site of the His-bundle recording (adjacent to the reference catheter). Shocks of 160 or 240 J were delivered at this site (cumulative energy [mean +/- SD], 689 +/- 442 J). Treatment resulted in preferential abolition or impairment of retrograde nodal conduction. Anterograde conduction, although modified, was preserved in 19 patients; complete heart block persisted in 2 patients. Sixteen patients remained free of arrhythmia, without medication or implantation of a pacemaker, for a mean follow-up period of 14 +/- 8 months (range, 7 to 42). Tachycardia was not inducible in 14 patients in a follow-up electrophysiologic study performed 3.6 +/- 6 months after the procedure. We conclude that catheter ablation is an effective alternative for the treatment of atrioventricular nodal tachycardia in patients with drug-resistant tachycardia.

Adult↗

PubMed1989

[Electrophysiologic study of syncope. Prediction of results].

In order to determine the factors predictive of dysrhythmia or disorders of conduction, 20 variables were analysed retrospectively in 201 patients who had undergone electrophysiological exploration. The electrophysiological abnormalities found to be significant were major sinus dysfunction (corrected post-stimulation atrial pause longer than 1 second), subnodal block (HV interval greater than 70 ms) or induction of sustained monomorphous ventricular tachycardia. The electrophysiological exploration gave abnormal results in 50 patients (25 per cent) with ventricular tachycardia in 36, subnodal block in 11 and sinus dysfunction in 5. Multivariate analysis brought out 4 independent variables that were predictive of electrophysiological study results. Presence of a cardiac disease (P less than 0.001), male sex (P less than 0.001), bundle branch block (P = 0.002) or injury consecutive to a syncope (P = 0.003) were associated with an abnormal exploration. The odd ratio of an abnormal electrophysiological exploration in the presence of a variable as compared with the reverse situation was 10, 6.25, 3.8 and 5 respectively. Postprandial syncopes were associated with a negative exploration (P = 0.06). Combining these variables and using a logistic regression model would provide an estimate of the probability of a positive or negative electrophysiological study. The selection of a high probability group would then indicate whether or not an electrophysiological study would be required.

Aged↗

PubMed1988

Catheter ablation of accessory pathways with a direct approach. Results in 35 patients.

Thirty-five consecutive patients with an overt accessory pathway, all but two suffering from arrhythmia (atrial fibrillation, reciprocating tachycardia, or both), underwent attempted transcatheter ablation (fulguration) of their accessory pathway. Thirty-three patients had been treated with a mean of 2.3 +/- 1.4 antiarrhythmic drugs. A standard bipolar catheter was positioned on the internal surface of the right or left atrioventricular anulus with 1) a subclavian approach of the right cardiac cavities in 29 patients with right-sided accessory pathway (n = 27) or left posteroseptal accessory pathway (n = 2), 2) a patent foramen ovale in five patients (two with a left posterolateral accessory pathway and three with a left parietal accessory pathway), and a transseptal catheterism (one patient with a left parietal accessory pathway). Cathodic shocks (mean, 4.3 shocks/patient) with a mean cumulative energy of 690 J enabled the ablation (disappearance of both anterograde and retrograde conduction) of the accessory pathway in 32 patients with a follow-up ranging from 1 to 32 months (mean, 10 +/- 8 months). Two of the remaining three accessory pathways were impaired: one pathway became intermittent, the anterograde effective refractory period of the second pathway increased from 260 to 410 msec, and the third pathway was slightly impaired. This latter patient is the only one who still requires therapy, with a single antiarrhythmic drug. All others are free of arrhythmias and require no therapy. Not using coronary sinus catheterism inclusive of its os has led to only a few, benign side effects. Only one third-degree atrioventricular block occurred in a posteroseptal accessory pathway ablation. Three cases of patients with incessant reciprocating tachycardia involving a further successful ablation occurred at the beginning of our experience. The best area for ablation is, in our opinion, the recording site for the Kent-bundle activity (18 of 35 patients), but a meticulous mapping of the atrioventricular anulus during orthodromic reciprocating tachycardia makes ablation possible when the shortest ventriculoatrial time (V-A') can be recorded with reliability (mean, 85 +/- 18 msec). Such a procedure is an alternative to surgical ablation regardless of the location of the accessory pathway--not only posteroseptally.

Adult↗

PubMed1988

[Predictive factors of the therapeutic result in the prevention of auricular fibrillation. Role of electrophysiological studies].

A population of 50 patients suffering from paroxysmal attacks of atrial fibrillation was studied prospectively to evaluate the prognostic value of 20 variables: 6 clinical variables: sex, age, cardiopathy, number of arrhythmic attacks, "vagal" triggering, failure of class IA antiarrhythmic agents; 3 echocardiographic variables: left ventricular diastolic diameter and percentage of fibre shortening, left atrial diameter; 6 basic electrophysiological data: threshold, refractory periods at 110 and 150/min, modalities of induction of a sustained arrhythmia; 4 results observed with an infusion of flecainide in doses of 2 mg/kg: arrest or persistence of the arrhythmia, whether or not it could be reinduced and value of refractory periods; doses of flecainide administered orally. With a mean +/- SD follow-up period of 7.7 +/- 7.3 months, preventive treatment with flecainide 233 +/- 7 mg failed in 16 patients (32 per cent) and succeeded in 34 patients (68 per cent). Analysis of Kaplan-Meier curves and use of Cox's multidimensional model showed that two electrophysiological data were of prognostic value: atrial effective refractory period, and non-inducibility of the arrhythmia after intravenous administration of flecainide. Thus, the probability of failure increases with the refractory period value and decreases with the non-inducibility of the arrhythmia.

Aged↗