M. Haissaguerre

Spectral Analysis Identifies Sites of High-Frequency Activity Maintaining Atrial Fibrillation in Humans

Background—The identification of sites of dominant activation frequency during atrial fibrillation (AF) in humans and the effect of ablation at these sites have not been reported. Methods and Results—Thirty-two patients undergoing AF ablation (19 paroxysmal, 13 permanent) during ongoing arrhythmia were studied. Electroanatomic mapping was performed, acquiring 126±13 points per patient throughout both atria and coronary sinus. At each point, 5-second electrograms were obtained to determine the highest-amplitude frequency on spectral analysis and to construct 3D dominant frequency (DF) maps. The temporal stability of the recording interval was confirmed in a subset. Ablation was performed with the operator blinded to the DF maps. The effect of ablation at sites with or without high-frequency DF sites (maximal frequencies surrounded by a decreasing frequency gradient ≥20%) was evaluated by determining the change in AF cycle length (AFCL) and the termination and inducibility of AF. The spatial distribution of the DF sites was different in patients with paroxysmal and permanent AF; paroxysmal AF patients were more likely to harbor the DF site within the pulmonary vein, whereas in permanent AF, atrial DF sites were more prevalent. Ablation at a DF site resulted in significant prolongation of the AFCL (180±30 to 198±40 ms; P<0.0001; &kgr;= 0.77), whereas in the absence of a DF site, there was no change in AFCL (169±22 to 170±22 ms; P=0.4). AF terminated during ablation in 17 of 19 patients with paroxysmal and 0 of 13 with permanent AF (P<0.0001). When 2 patients with nonsustained AF during mapping were excluded, 13 of 15 (87%) had AF termination at DF sites (54% at the initially ablated DF site): 11 pulmonary veins and 2 atrial. In addition, AF could no longer be induced in 69% with termination of AF at a DF site. There were no significant differences in the number or percentage of DF sites detected (5.4±1.6 versus 4.9±2.1; P=0.3) and ablated (1.9±1.0 versus 2.4±1.0; P=0.3) in those with and without AF termination. The duration of radiofrequency ablation to achieve termination was significantly shorter than that delivered in those with persisting AF (34.8±24.0 versus 73.5±22.9 minutes; P=0.0002). All patients with persisting AF had additional DF sites outside the ablated zones. Conclusions—Spectral analysis and frequency mapping identify localized sites of high-frequency activity during AF in humans with different distributions in paroxysmal and permanent AF. Ablation at these sites results in prolongation of the AFCL and termination of paroxysmal AF, indicating their role in the maintenance of AF.

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

BackgroundAblation 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 ResultsSixty-four patients (mean age, 48±19 years) with the usual form ofAVNRT 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%1 of patients. ConclusionsAn 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.

Outcome After Implantation of a Cardioverter-Defibrillator in Patients With Brugada Syndrome A Multicenter Study

Background— Implantable cardioverter-defibrillator indications in Brugada syndrome remain controversial, especially in asymptomatic patients. Previous outcome data are limited by relatively small numbers of patients or short follow-up durations. We report the outcome of patients with Brugada syndrome implanted with an implantable cardioverter-defibrillator in a large multicenter registry. Methods and Results— A total of 378 patients (310 male; age, 46±13 years) with a type 1 Brugada ECG pattern implanted with an implantable cardioverter-defibrillator (31 for aborted sudden cardiac arrest, 181 for syncope, and 166 asymptomatic) were included. Fifteen patients (4%) were lost to follow-up. During a mean follow-up of 77±42 months, 7 patients (2%) died (1 as a result of an inappropriate shock), and 46 patients (12%) had appropriate device therapy (5±5 shocks per patient). Appropriate device therapy rates at 10 years were 48% for patients whose implantable cardioverter-defibrillator indication was aborted sudden cardiac arrest, 19% for those whose indication was syncope, and 12% for the patients who were asymptomatic at implantation. At 10 years, rates of inappropriate shock and lead failure were 37% and 29%, respectively. Inappropriate shock occurred in 91 patients (24%; 4±4 shocks per patient) because of lead failure (n=38), supraventricular tachycardia (n=20), T-wave oversensing (n=14), or sinus tachycardia (n=12). Importantly, introduction of remote monitoring, programming a high single ventricular fibrillation zone (>210–220 bpm), and a long detection time were associated with a reduced risk of inappropriate shock. Conclusions— Appropriate therapies are more prevalent in symptomatic Brugada syndrome patients but are not insignificant in asymptomatic patients (1%/y). Optimal implantable cardioverter-defibrillator programming and follow-up dramatically reduce inappropriate shock. However, lead failure remains a major problem in this population.

Interventricular and intra-left ventricular electromechanical delays in right ventricular paced patients with heart failure: implications for upgrading to biventricular stimulation

Objective: To correlate, in patients with right ventricular pacing (RVP), the QRS width with electromechanical variables assessed by pulsed Doppler tissue imaging echocardiography. Secondly, to find reliable parameters for selecting RVP patients who would respond to biventricular pacing (BVP). Methods: 26 randomly selected control patients with RVP (mean (SD) ejection fraction 74 (3)%) (group A) were matched on sex and age criteria with 16 RVP patients with drug resistant heart failure (mean (SD) ejection fraction 27 (5)%) (group B). All patients were pacemaker dependent and all underwent pulsed Doppler tissue imaging echocardiography. This technique provided the intra-left ventricular (LV) electromechanical delay and the interventricular electromechanical delay. The Gaussian curve properties of data from group A patients provided the normal range of ECG and echographic parameters. Design: Prospective study. Setting: University hospital (tertiary referral centre). Results: Data from the control group showed that an interventricular electromechanical delay or an intra-LV electromechanical delay > 50 ms would identify patients with a significantly abnormal ventricular mechanical asynchrony (p < 0.05). In the same manner, a QRS width > 190 ms was considered significantly larger in group B patients (p < 0.05) than in controls. In Group B patients, there was no correlation between the QRS width and the interventricular electromechanical delay (r  =  −0.23, NS) or the intra-LV electromechanical delay (r  =  0.19, NS). Seven group B patients (44%) were misclassified by ECG criteria for ventricular mechanical asynchrony identification: four patients (25%) had a QRS width similar to that of controls but with a significantly prolonged intra-LV electromechanical delay and interventricular electromechanical delay; and three patients (19%) had a QRS width significantly larger than that in controls but without significant ventricular mechanical asynchrony. Conclusions: The QRS width is not a reliable tool to identify RVP patients with ventricular mechanical asynchrony. In RVP patients, an interventricular electromechanical delay or intra-LV electromechanical delay > 50 ms reflects a significant ventricular mechanical asynchrony and should be required to select patients for upgrading to BVP.

Electrocardiographic characteristics and catheter ablation of parahissian accessory pathways.

BackgroundAccessory pathways may be located in close proximity to the His bundle, resulting in a high risk of heart block during attempted surgical or electrical interruption of these pathways. This study reports the prevalence, ECG characteristics, and results of catheter ablation of parahissian accessory pathways. They were defined on the basis of both the presence of a high amplitude (>0.1 mV) of His bundle potential at the ablation site and an exclusion of anteroseptal or midseptal location of the accessory pathway. Methods and ResultsEight patients with a parahissian accessory pathway were identified among 582 consecutive patients who underwent radiofrequency ablation of an acces-sory pathway. They were six males and two females with a mean age of 21±9 years. During maximal preexcitation, the ECG showed a positive delta wave in leads I, II, and aVF in all patients: six had a negative delta wave in leads V1 and V2 instead of the positivity usually observed in anteroseptal accessory pathways. This pattern had a sensitivity of 75%, a specificity of 96%, a positive predictive value of 86%, and a negative predictive value of 93% for a parahissian location in comparison with a group of 28 patients with anteroseptal accessory pathways. At the successful ablation site, the mean amplitude of the His bundle potential was 0.2±0.1 (0.12 to 0.4 mV). All accessory pathways were successfully ablated without causing heart block using 5 to 20 W of radiofrequency energy. ConclusionsParahissian accessory pathways have a preexcitation pattern that is distinctive from that of anteroseptal accessory pathways. Catheter ablation of these pathways is feasible using low energy with preservation of normal atrio-ventricular conduction.

Catheter ablation of Mahaim fibers with preservation of atrioventricular nodal conduction.

Three patients with refractory preexcited tachycardia implicating Mahaim fibers underwent attempted catheter ablation of the accessory pathway. In the absence of demonstrable retrograde conduction in Mahaim fibers, we located the accessory pathway ventricular insertion site using the criteria of concordance between paced and spontaneous QRS morphologies during pace-mapping and earliest onset of local electrogram relative to surface preexcited QRS. At this site, a QS-like pattern of unfiltered unipolar electrograms with steep downstroke was recorded. The optimal site appeared radiologically at the right ventricular anterior wall or the adjacent septum, 2-4 cm from the tricuspid anulus. Three to six 160-J shocks were delivered at this site using an anterior chest wall plate as anode. After fulguration, conduction through the Mahaim tract was absent. A right bundle branch block persisted in two patients. All patients remained free of preexcited tachycardia during 12-16 months of follow-up. Postablation electrophysiological assessment showed no preexcitation in any patient. No reciprocating tachycardia was inducible, even during isoproterenol infusion. Atrioventricular nodal conduction parameters were unchanged from baseline study. Catheter ablation of Mahaim fibers is an effective alternative method for the treatment of tachycardias that include the accessory pathway in the circuit.

Prevalence, characteristics, and prognosis role of type 1 ST elevation in the peripheral ECG leads in patients with Brugada syndrome

BACKGROUND Despite isolated reports of Brugada syndrome (BrS) in the inferior or lateral leads, the prevalence and prognostic value of ST elevation in the peripheral electrocardiographic (ECG) leads in patients with BrS remain poorly known. OBJECTIVE To study the prevalence, characteristics, and prognostic value of type 1 ST elevation and ST depression in the peripheral ECG leads in a large cohort of patients with BrS. METHODS ECGs from 323 patients with BrS (age 47 ± 13 years; 257 men) with spontaneous (n = 141) or drug-induced (n = 182) type 1 ECG were retrospectively reviewed. Two hundred twenty-five (70%) patients were asymptomatic, 72 (22%) patients presented with unexplained syncope, and 26 (8%) patients presented with sudden death (12 patients) or appropriated implantable cardioverter-defibrillator therapies (14 patients) at diagnosis or over a mean follow-up of 48 ± 34 months. RESULTS Thirty (9%) patients presented with type 1 ST elevation in at least 1 peripheral lead (22 patients in the aVR leads, 2 in the inferior leads, 5 in both aVR and inferior leads, and 1 in the aVR and VL leads). Patients with type 1 ST elevation in the peripheral leads more often had mutations in the SCN5A gene, were more often inducible, had slower heart rate, and higher J-wave amplitude in the right precordial leads. Twenty-seven percent (8 of 30) of the patients with type 1 ST elevation in the peripheral leads experimented sudden death/appropriate implantable cardioverter-defibrillator therapy, whereas it occurred in only 6% (18 of 293) of other patients (P < .0001). In multivariate analysis, type 1 ECG in the peripheral leads was independently associated with malignant arrhythmic events (odds ratio 4.58; 95% confidence interval 1.7-12.32; P = .0025). CONCLUSIONS Type 1 ST elevation in the peripheral ECG leads can be seen in 10% of the patients with BrS and is an independent predictor for a malignant arrhythmic event.

Pulmonary vein isolation using a circular, open irrigated mapping and ablation catheter (nMARQ): a report on feasibility and efficacy

AIMS Pulmonary vein isolation (PVI) is the mainstay of interventional treatment of paroxysmal atrial fibrillation (PAF). We report on the feasibility and efficacy of a novel, open-irrigated mapping and radiofrequency (RF) ablation catheter. METHODS AND RESULTS Thirty-nine consecutive patients (pts; age 60 ± 10 years, 8 females) suffering from drug-refractory PAF referred for PVI were included in this prospective study. Pulmonary vein isolation was performed with the use of a novel 10-pole circular, open-irrigated mapping and ablation catheter (nMARQ, Biosense Webster). Outcome parameters were the acute success rate in establishing complete PVI and the rate of sustained sinus rhythm (SR) during follow-up (FU). Ten patients underwent a repeat procedure for recurrent AF. Ninety-eight percent of the PVs could be acutely isolated using solely the nMARQ catheter by applying a mean total of 10.0 ± 4.6 min of RF energy. The mean total procedure duration was 86 ± 29 min, and the mean fluoroscopy time was 22.2 ± 6.5 min, respectively. Transient reconnection provoked by adenosine was observed in 10 of 24 patients, most frequently in the right superior PV. Cardiac tamponade related to transseptal puncture occurred in one patient. Reconnected PVs could be identified as a source of recurrent AF in 9 of 10 patients undergoing a repeat procedure. Single and multiple procedure success rates during a mean FU of 140 ± 75 days were 66 and 77%, respectively. CONCLUSION Irrigated multi-electrode RF ablation is fast and effective, providing a high rate of isolated PVs without the need of touch-up lesions. Success rates were comparable with other techniques with a low complication rate. Recurrences of AF were mainly due to recovered pulmonary vein/left atrium conduction.

Characteristics of Ventricular Tachycardia Ablation in Patients With Continuous Flow Left Ventricular Assist Devices

Background—Left ventricular assist devices (LVADs) are increasingly used as a bridge to cardiac transplantation or as destination therapy. Patients with LVADs are at high risk for ventricular arrhythmias. This study describes ventricular arrhythmia characteristics and ablation in patients implanted with a Heart Mate II device. Methods and Results—All patients with a Heart Mate II device who underwent ventricular arrhythmia catheter ablation at 9 tertiary centers were included. Thirty-four patients (30 male, age 58±10 years) underwent 39 ablation procedures. The underlying cardiomyopathy pathogenesis was ischemic in 21 and nonischemic in 13 patients with a mean left ventricular ejection fraction of 17%±5% before LVAD implantation. One hundred and ten ventricular tachycardias (VTs; cycle lengths, 230–740 ms, arrhythmic storm n=28) and 2 ventricular fibrillation triggers were targeted (25 transseptal, 14 retrograde aortic approaches). Nine patients required VT ablation <1 month after LVAD implantation because of intractable VT. Only 10/110 (9%) of the targeted VTs were related to the Heart Mate II cannula. During follow-up, 7 patients were transplanted and 10 died. Of the remaining 17 patients, 13 were arrhythmia-free at 25±15 months. In 1 patient with VT recurrence, change of turbine speed from 9400 to 9000 rpm extinguished VT. Conclusions—Catheter ablation of VT among LVAD recipients is feasible and reasonably safe even soon after LVAD implantation. Intrinsic myocardial scar, rather than the apical cannula, seems to be the dominant substrate.

Characterization of contact force during endocardial and epicardial ventricular mapping.

Background—The optimal contact force (CF) for ventricular mapping and ablation remains unvalidated. We assessed CF in different endocardial and epicardial regions during ventricular tachycardia substrate mapping using a CF-sensing catheter (Smartouch; Biosense-Webster) and compared the transseptal versus retroaortic approach. Methods and Results—In total, 8979 mapping points with CF, and force vector orientation (VO) were recorded in 21 patients, comprising 13 epicardial, 12 left ventricular (6 transseptal and 6 retroaortic approach), and 12 right ventricular endocardial maps. VO was defined as adequate when the vector was directed toward the myocardium. During epicardial mapping, 46% of the points showed an adequate VO and a median CF of 8 (4–13) g, however, with significant differences among the 8 regions. When VO was inadequate, median CF was higher at 16 (10–24) g (P<0.0001). During left ventricular and right ventricular endocardial mapping, 94% of VO were adequate. Median CF of adequate VO was higher in the left ventricular and right ventricular endocardium than in the epicardium (15 [8–25] and 13 [7–22] g versus 8 [4–13] g, respectively; both P<0.001). Global median left ventricular CF with transseptal approach was not statistically different from retroaortic approach, but CF in the apicoinferior and apicoseptal regions was higher with transseptal approach (P<0.001). Conclusions—Ventricular mapping demonstrates important regional variations in CF, but in general, CF is higher endocardially than epicardially where poor catheter orientation is associated with higher CF. A transseptal approach may lead to improved contact particularly in the apicoseptal and inferior regions.