Biomedical subjects
Publications and source records attributed to N Saoudi.
An 8-mm catheter does not appear superior to 4-mm tip electrode for atrial flutter ablation. The potential advantage of allowing higher energy delivery on a larger surface is compensated by the lack of consistent contact with the endocardial surface.
Typical atrial flutter ablation has become anatomically guided to 2 separate sites within the isthmus at the inferior right atrium: (1) between the inferior vena cava and the tricuspid annulus (anterior side of the isthmus [A]), (2) between the eustachian crest, the coronary sinus ostium and tricuspid annulus (posterior side of the isthmus [P]). We prospectively compared ablation results at these sites in 72 consecutive patients. Patients were randomized in group P or A according to the initial target site. If ablation failed at 1 site after 15 radiofrequency (RF) pulses, the other side of the isthmus was targeted. Before 15 RF pulses, complete bidirectional isthmus block was achieved in 30 of 36 group A patients and in 25 of 36 group P patients, with similar mean RF pulses number, procedure time, and fluoroscopy time. After shifting to the other target, success was finally obtained at P in 2 of 6 group A patients, and at A in 8 of 11 group P patients before a maximum of 30 RF pulses. Among successful patients, number of RF pulses, procedure time, and fluoroscopy time were significantly lower in group A (7.2 +/- 5.4 vs 11.0 +/- 8.1 pulses, p = 0.03; 131 +/- 44 vs 163 +/- 66 minutes, p = 0.03; 31 +/- 19 vs 46 +/- 24 minutes, p = 0.01, respectively). Impairment of atrioventricular (AV) nodal conduction occurred in 5 patients only during ablation at P. AV block was transient in 4 patients and permanent in 1. Although atrial flutter ablation is equally effective at P and A, success seems easier to obtain when A is first targeted. Ablation at P is associated with a significant risk of AV block.
The PIPAF trials are a set of randomized multicenter studies which seeks to evaluate the potential preventive effect of different modes of pacing in patients with drug refractory paroxysmal atrial fibrillation by means of a permanent pacemaker. The objective of the studies are (1) to significantly prolong the time to first recurrence of atrial arrhythmia and (2) to significantly reduce the cumulative arrhythmia duration. The role of the atrial pacing site (left or right), the overdriving of the sinus rate, and the suppression of the post extrasystolic compensatory pause are evaluated alone or in association, giving rise to four distinct pacing protocols. Over a period of 2 years, 220 patients will be included in 35 centers from 5 different countries.
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Fulguration, a widely used technique in the 80s, has been replaced by radiofrequency ablation. The limited and better controlled intra-cardiac lesions obtained by this method allowed the elimination of a large number of tachycardias with a high success rate. However, there are many arrhythmias, particularly at the atrial level, which are so complex that a limited analysis at a number of points of endocardial recording is inadequate. Recently, a number of systems has been introduced which considerably increased the acuity of observation of arrhythmias and the efficacy of their ablation. First of all, there are improved techniques of classical electrophysiological recording. Then, new systems of temporo-spatial recordings were developed and are described in this article. These use computer systems and enable particularly reliable and detailed approaches to cardiac anatomy and electrophysiology. However, the optimal use of these techniques can only be in specialised centres, by highly trained cardiologists in classical electrophysiology, for which they are complementary to rather than substitute for.
The concept of the "smart" pacemaker has been continuously changing during 40 years of progress in technology. When we talk today about smart pacemakers, it means optimal treatment, diagnosis, and follow-up for patients fitting the current indications for pacemakers. So what is smart today becomes accepted as "state of the art" tomorrow. Originally, implantable pacemakers were developed to save lives from prolonged episodes of bradycardia and/or complete heart block. Now, in addition, they improve quality of life via numerous different functions acting under specific conditions, thanks to the introduction of microprocessors. The devices have become smaller, with the miniaturization of the electrical components, without compromising longevity. Nevertheless, there are still some unmatched objectives for these devices, for example, the optimization of cardiac output and the management of atrial arrhythmias in dual-chamber devices. Furthermore, indications continue to evolve, which in turn require new, additional functions. These functions are often very complex, necessitating computerized programming to simplify application. In addition, the follow-up of these devices is time-consuming, as appropriate system performance has to be regularly monitored. A great many of these functions could be automatically performed and documented, thus enabling physicians and paramedical staff to avoid losing time with routine control procedures. In addition, modern pacemakers offer extensive diagnostic functions to help diagnose patient symptoms and pacemaker system problems. Different types of data are available, and their presentation differs from one company to the other. This huge amount of data can only be managed with automatic diagnostic functions. Thus, the smart pacemaker of the near future should offer high flexibility to permit easy programming of available therapies and follow-up, and extensive, easily comprehensible diagnostic functions.
BACKGROUND: Creation of a complete bidirectional inferior vena cava-tricuspid annulus isthmus block (CBIB) by radiofrequency catheter ablation is now a well-accepted criterion for prevention of common atrial flutter (AFl) recurrences. However, some patients still complain of palpitations after ablation, and it is not known whether these are related to AFl recurrences or to other arrhythmias. METHODS AND RESULTS: Among 100 consecutive patients referred to our institution for AFl ablation, CBIB was created in 83. There were 54 patients (group A) in whom AFl was the only documented arrhythmia before ablation and 29 patients (group B) in whom atrial fibrillation (AFib) had been documented in addition to AFl. An electrophysiological control study was performed in 40 patients 1 to 3 months after ablation. Arrhythmic events, medications, and functional status were evaluated at midterm follow-up (n=77; 14. 7+/-8.4 months; range, 4 to 34 months). The SF-36 questionnaire and the Symptom Checklist--Frequency and Severity Scale specific for cardiac arrhythmia were used to assess quality of life in 63 patients at long-term follow-up (27.1+/-8.5 months). Recurrence of AFl was documented in only 1 patient 6 months after ablation. AFib was recorded in 28 patients (36.4%), and atypical AFl was found in 3 patients. Thirty-two group A patients (66.7%) and 17 group B patients (58.6%) were still arrhythmia free at midterm follow-up. Even at long-term follow-up and in group B patients, AFl ablation was followed by a clear improvement in quality of life. CONCLUSIONS: Palpitations after creation of CBIB are due mostly to AFib but not to AFl recurrence. This technique provides a significant and persistent clinical benefit and may suppress all atrial arrhythmia in a subset of patients suffering from both AFl and AFib.
INTRODUCTION: Despite the ability to cure atrioventricular nodal reentrant tachycardia (AVNRT) by radiofrequency catheter ablation with a high success rate, the exact localization of the tachycardia circuit is still not well established. The presence of AV nodal tissue between the typical AVNRT circuit and the His bundle, constituting a lower common pathway (LCP), remains controversial. METHODS AND RESULTS: Entrainment of AVNRT during para-Hisian stimulation allows accurate measurement of the His- to- atrial (HA) interval which is part of the same circuit as that of the tachycardia. With an LCP, during tachycardia, there is simultaneous conduction from the low turnaround of the circuit to the atrium (via the fast pathway) and to the His bundle (via the LCP). However, during entrainment by para-Hisian pacing, the impulse has to retrogradely depolarize sequentially the LCP and the fast pathway. Therefore, in the presence of an LCP, the HA interval duration during tachycardia (HAt) should be shorter than that of during entrainment by para-Hisian stimulation (HAe). We considered an LCP present when Hae - HAt was > or = 10 msec. Entrainment of typical AVNRT with para-Hisian stimulation was performed in 23 consecutive patients (21 females) with a mean age of 45+/-17 years. LCP was considered to be present in 18 of 23 patients (78%). In addition, transient His-bundle dissociation from the ongoing tachycardia occurred in seven patients (30%). CONCLUSION: These results support the presence of a LCP during typical AVNRT.
Cardiologists are often confronted by the situation of discussing the indications for invasive electrophysiological procedures. In this field, the recommendations of American scientific societies have been published but they are relatively dated and require updating. These procedures require the introduction of one or more catheters by a femoral venous or arterial approach, or by the endoesophageal route for positioning at different sites in the heart. The first stage of the procedure is usually to evaluate the electrophysiological properties of the cardiac chamber under investigation; followed by provocative manoeuvres such as electrical stimulation, injection of a drug, the delivery of a CEE electrical shock percutaneously or by an intracardiac radiofrequency stimulation, according to the type of procedure or the centre concerned. Schematically, the indications of these procedures may be determined in different contexts according to the benefits that may be expected in a given clinical situation. This article is devoted to the principal rhythmological situations which may be encountered but, however, the indications of radiofrequency ablation are not discussed.
OBJECTIVES: We present three patients in whom atrial arrhythmia was treated by ablation of electrical conduction across a surgical suture line. BACKGROUND: Conduction across the suture line separating the donor and native right atria has recently been described after orthotopic heart transplantation. METHODS: Mapping and pacing of both grafted and recipient right atrium was performed to assess the relation between both atria and its relevance to clinical arrhythmia, prior to successful radiofrequency at the site of electrical communication. RESULTS: In cases 1 and 3, atrioatrial conduction was bidirectional. In both, two types of P waves were observed during sinus rhythm. In case 2, conduction from the recipient to the grafted atrium yielded a very particular surface ECG pattern of atrial extrasystole. The block being unidirectional, the recipient atrial sinus rhythm was not perturbed and behaved like an atrial parasystole. Ablation was performed during sinus rhythm in case 1, recipient right atrial pacing in case 2 and grafted right atrial pacing in case 3 at the site with the shortest conduction time to the other tissue. At the successful ablation site multiple component potentials were recorded. Respectively, 1, 4 and 2 radiofrequency pulses were followed by total atrioatrial conduction interruption. No tachycardia could be induced at the end of the procedure and late follow-up was event free. CONCLUSIONS: The existence of arrhythmogenic atrioatrial conduction should be taken into account when evaluating atrial arrhythmias in the transplanted heart because it is potentially curable by radiofrequency catheter ablation.
BACKGROUND: Until recently no clinical studies had reported precise right atrium (RA) mapping when performing induction of atrial flutter (AFl). We studied the mode of tachycardia initiation in 16 patients (pts) referred for radiofrequency (RF) AFl ablation. AFl induction was performed at the beginning of the procedure (n = 10), or after previous AFl termination during RF delivery (n = 6). Detailed analysis of AFl initiation was provided by duodecapolar (Halo) and multipolar catheters positioned in the peritricuspidian region at the lateral right atrial wall (LRA), the inferior vena cavatricuspid annulus (IVC-TA) isthmus and the interatrial septum. Induction was obtained during incremental pacing (IAP) (15 pts) or programmed stimulation (1 pt) from the proximal coronary sinus (PCS). RESULTS: Atrial flutter with counterclockwise (CCW) RA rotation was induced in all pts by PCS pacing. During PCS IAP, at long pacing cycle lengths, impulse propagated in a clockwise (CW) direction through the IVC-TA isthmus and then upward at low (L) LRA. This led to a collision at the mid LRA with another wave front propagating in a CCW direction at the septum. IAP from PCS induced a progressive delay of propagation at the IVC-TA isthmus resulting in a prolongation of the PCS-Mid Isthmus interval from 85 +/- 29 to 151 +/- 42 msec. At same pacing cycle lengths (CL), the PCS-HLRA interval was comparatively less prolonged, from 75 +/- 12 to 105 +/- 18 msec, p = 0.0007. This preferential slowing of conduction between PCS and mid isthmus, during IAP from PCS, was associated with a displacement of the zone of collision to the Low LRA. Finally a CW functional block occurred at the IVC-TA isthmus and CCW AFl was induced through a period of transient concealed entrainment. The paced CL required to initiate flutter ranged from 290 to 180 msec and the mean CL of induced atrial flutter was 254 +/- 27 msec. CONCLUSIONS: The IVC-TA isthmus has decremental properties and exhibits wenckebach phenomenon during incremental PCS pacing. Initiation of a counterclockwise flutter by PCS pacing is associated with appearance of a functional unidirectional block at the IVC-TA isthmus.
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The French translations of the word "gap" include "hole, breach, opening". In the Anglo-saxon literature, the conduction gap or the gap phenomenon is defined as the period of the cardiac cycle during which a premature beat is blocked whereas more delayed or more premature beats are conducted. This rare phenomenon, observed mainly during extrasystolic stimulation, was previously called supernormal conduction. The underlying mechanism is distal block in the conduction system occurring when more premature beats lead to delay in the proximal conduction which gives the distal site time to become excitable again. The excitability gap is one of the main characteristics of reentrant arrhythmias. Its presence in a reentrant circuit ensures the regularity and stability of the arrhythmia. It also allows penetration of the circuit by external stimuli. This different extrasystolic stimulation technique (resetting) or rapid fixed rate pacing (entrainment) may be used diagnostically and therapeutically. It enables the identification of the arrhythmia circuit and a critical zone (protected isthmus, zone of slow conduction) which may constitute a target for ablation. It also offers a possibility for terminating the arrhythmia by external stimulation. Finally, the duration of the excitable gap may guide the choice of antiarrhythmic agent during pharmacological cardioversion of a reentrant tachycardia.
BACKGROUND: Atrioventricular association is a key criterion for arrhythmia diagnosis. Its use in a defibrillator should significantly reduce the incidence of inappropriate shocks. Therefore, we evaluated the diagnostic accuracy of an algorithm that uses dual-chamber sensing and analysis of atrioventricular association to discriminate ventricular from supraventricular arrhythmias in a prototype of an implantable defibrillator. METHODS AND RESULTS: The algorithm performed a stepwise analysis of arrhythmias. The rhythm was first classified on the basis of cycle lengths. Each episode was then classified as supraventricular or ventricular in origin on the basis of the stability of cycle lengths and atrioventricular association. This algorithm was evaluated in 156 episodes of induced sustained tachycardias. Eighty-nine tachycardias were taken from the Ann Arbor electrogram library; the others were recorded in 50 patients during electrophysiological studies. The atrial and ventricular signals were stored on an external recorder and then injected into an external prototype of a defibrillator system. The algorithm correctly diagnosed 96% of ventricular tachycardia episodes, 100% of ventricular fibrillation episodes, and 92% of double-tachycardia episodes. The mean detection time for ventricular tachycardia was 2.6 +/- 0.8 seconds, and for ventricular fibrillation, it was 2.1 +/- 0.4 seconds. The positive predictive values for the diagnoses of atrial fibrillation and atrial flutter were 92% and 86%, respectively. For ventricular tachycardia and ventricular fibrillation, the values were 95% and 100%, respectively. CONCLUSIONS: Analysis of atrioventricular association promotes reliable differentiation between ventricular and supraventricular tachycardias and should enhance the diagnostic capabilities of implantable defibrillators.
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.
BACKGROUND: Radiofrequency ablation of type 1 atrial flutter (AF1) has recently evolved toward an anatomically guided procedure directed to isthmuses at the lower part of the right atrium (RA). However, different types of block at these isthmuses may be observed and potentially correlated with different late outcomes. In addition, because the ablation is anatomically guided, ablation should be possible during sinus rhythm. METHODS AND RESULTS: Forty-four patients underwent ablation of type 1 AF1 performed during ongoing tachycardia (33 patients) or sinus rhythm (11 patients). Evidence of inferior vena cava-tricuspid annulus isthmus block was assessed by changes in RA impulse propagation while pacing from both sides of the ablation site. Apparent complete isthmus block was achieved in 43 of 44 patients with 9 +/- 7 pulses. However, incomplete block mimicking complete block because of intra-atrial conduction delay but leading to a different low RA activation pattern was individualized. At the end of the procedure, isthmus block was complete in 35 patients and incomplete in 8, but since AF1 reinduction was no longer possible, patients were discharged. During a follow-up period of 12.1 +/- 5.5 months, 4 patients experienced AF1 recurrence; all had shown incomplete or no block. CONCLUSIONS: Detailed multiple-point low RA mapping is necessary to differentiate incomplete from complete isthmus block. Complete block is the best marker for long-term success of AF1 ablation, although incomplete block may be sufficient to prevent recurrence in a significant number of cases. Isthmus block is achievable during sinus rhythm, and AF1 induction is not mandatory.
Atrial tachycardias are frequently unresponsive to medical therapy. His bundle ablation has been proposed as a palliative treatment to treat symptoms and prevent development of tachycardia-mediated cardiomyopathy. Experience with catheter ablation directed at the atrial origin of the tachycardia remains limited. We reviewed the initial success rate and long-term follow-up of radiofrequency ablation of atrial tachycardias. Thirty-six patients underwent electrophysiologic study and radiofrequency ablation of atrial tachycardias, excluding atrial flutter. The suspected mechanism of the clinical arrhythmia was automatic in 16 patients, intraatrial reentrant in 15, sinoatrial reentrant in 3, and unknown in 2. One or two ablation catheters with a 4 mm distal electrode were used to find (1) the earliest local atrial activation time compared to P-wave onset in the bipolar recording mode and (2) a QS pattern in the unipolar mode. When two ablation catheters were used, an encircling approach was taken. Pace-mapping during sinus rhythm and entrainment techniques were occasionally used for mapping. Tachycardia rose from the right atrium in 33 of 36 patients and from the left atrium in the remaining three. Three patients showed multiple foci during the procedure. Successful ablation was obtained in 31 (86%) of 36 patients, with a median of two radiofrequency applications (range 1 to 32) at 10 to 50 W for 10 to 60 seconds. Failure occurred in 5 patients (including the 3 patients with multiple atrial foci). Late follow-up (18 +/- 15 months) showed recurrence of atrial tachycardia in 2 patients, each of whom underwent a successful second ablation. Emergence of another atrial tachycardia was noted in 2 other patients, and an uncommon atrial flutter was noted in 1 patient with repaired atrial septal defect. No late sinus or atrioventricular nodal dysfunction were observed. In conclusion, radiofrequency catheter ablation is a safe and reasonable alternative for atrial tachycardias that do not respond to drugs. However, as previously suggested by the surgical experience, the success rate of ablation appears less satisfactory in patients with multiple sites of origin of ectopic atrial tachycardia.