Domenico Caponi

Radiofrequency catheter ablation of atrial fibrillation: A cause of silent thromboembolism? Magnetic resonance imaging assessment of cerebral thromboembolism in patients undergoing ablation of atrial fibrillation

Background— Radiofrequency left atrial catheter ablation has become a routine procedure for treatment of atrial fibrillation. The aim of this study was to assess with preprocedural and postprocedural cerebral magnetic resonance imaging the thromboembolic risk, either silent or clinically manifest, in the context of atrial fibrillation ablation. The secondary end point was the identification of clinical or procedural parameters that correlate with cerebral embolism. Methods and Results— A total of 232 consecutive patients with paroxysmal or persistent atrial fibrillation who were candidates for radiofrequency left atrial catheter ablation were included in the study. Pulmonary vein isolation or pulmonary vein isolation plus linear lesions plus atrial defragmentation with the use of irrigated-tip ablation catheters was performed. All of the patients underwent preprocedural and postablation cerebral magnetic resonance imaging. A periprocedural symptomatic cerebrovascular accident occurred in 1 patient (0.4%). Postprocedural cerebral magnetic resonance imaging was positive for new embolic lesions in 33 patients (14%). No clinical parameters such as age, hypertension, diabetes mellitus, previous history of stroke, type of atrial fibrillation, and preablation antithrombotic treatment showed significant correlation with ischemic cerebral embolism. Procedural parameters such as activated clotting time value and, in particular, electric or pharmacological cardioversion to sinus rhythm correlated with an increased incidence of cerebral embolism. Cardioversion was also associated with an increased risk of 2.75 (95% confidence interval, 1.29 to 5.89; P=0.009). Conclusions— Radiofrequency left atrial catheter ablation carries a low risk of symptomatic cerebral ischemia but is associated with a substantial risk of silent cerebral ischemia detected on magnetic resonance imaging. Independent risk factors for cerebral thromboembolism are the level of activated clotting time and, in particular, the electric or pharmacological cardioversion to sinus rhythm during the procedure.

Long-Term Clinical Results of 2 Different Ablation Strategies in Patients With Paroxysmal and Persistent Atrial Fibrillation

Background—Data regarding the long-term efficacy of atrial fibrillation (AF) ablation are still lacking. Methods and Results—Two hundred four consecutive patients symptomatic for paroxysmal or persistent/permanent AF were randomly assigned to 2 different ablation schemes: pulmonary vein isolation (PVI) and PVI plus left linear lesions (LL). Primary end point was to assess the maintenance of sinus rhythm (SR) after procedures 1 and 2 in the absence of antiarrhythmic drugs in a long-term follow-up of at least 3 years. Paroxysmal AF—With a single procedure at 12-month follow-up, 46% of patients treated with PVI maintained SR, whereas at 3-year follow-up, 29% were in SR; using the “PVI plus LL” at the 12-month follow-up, 57% of patients were in SR, whereas at the 3-year follow-up, 53% remained in SR. After a second procedure, the long-term overall success rate without antiarrhythmic drugs was 62% with PVI and 85% with PVI plus LL. Persistent/Permanent AF—With a single procedure at the 12-month follow-up, 27% of patients treated with PVI were in SR, whereas at the 3-year follow-up, 19% maintained SR; using the PVI plus LL with a single procedure at the 12-month follow-up 45% of patients were in SR, whereas at the 3-year follow-up, 41% remained in SR. After a second procedure, the long-term overall success rate without antiarrhythmic drugs was 39% with PVI and 75% with PVI plus LL. Conclusions—A long-term follow-up of AF ablation shows that short-term results cannot be considered permanent because AF recurrences are still present after the first year especially in patients who have had “PVI” strategy. PVI isolation plus LL is superior to the PVI strategy in maintaining SR without antiarrhythmic drugs after procedures 1 and 2 both in paroxysmal and persistent AF.

Linear Cryoablation of the Left Atrium Versus Pulmonary Vein Cryoisolation in Patients With Permanent Atrial Fibrillation and Valvular Heart Disease. Correlation of Electroanatomic Mapping and Long-Term Clinical Results

Background—The aim of this study was to clarify the role of pulmonary vein isolation (PVI) alone versus left atrial linear lesions in the treatment of permanent atrial fibrillation (AF) in patients with left atrial dilatation and valvular disease. The primary end point was to assess the persistence of sinus rhythm (SR) off antiarrhythmic drugs (AADs) at 2-year follow-up and to correlate clinical outcome with surgical results validated with electroanatomic mapping (EAM). Methods and Results—A total of 105 patients with permanent AF undergoing valve surgery were assigned to 3 different groups: in groups “U” and “7,” left atrial linear cryoablation was performed, whereas in group “PV” patients, anatomic cryoisolation of pulmonary veins only was performed. In groups U and 7, SR was achieved in 57% of patients, whereas it was achieved in 20% of PV patients during 2-year follow-up. In the first 51 patients, the ablation schemes were validated with EAM. The EAM showed that the U lesion was never obtained: in 59% of these patients, a complete 7 lesion was achieved instead; in the 7 group, a complete 7 lesion was present in 65% of patients, whereas a complete PVI was obtained in 71% of patients. Considering patients in whom a complete 7 lesion was demonstrated with the EAM, SR without AADs was achieved in 86% of patients, whereas only 25% of patients with complete PVI were in SR without AADs. Conclusions—In patients with permanent AF, left atrial dilatation and valvular heart disease linear lesions in the posterior region of the left atrium are more effective than PVI alone. With cryoablation, the surgical intent is fulfilled in only approximately 65% of the cases. Knowing the real anatomic and electrophysiological effects of surgical ablation is necessary to correctly interpret the clinical outcome.

Limited posterior left atrial cryoablation in patients with chronic atrial fibrillation undergoing valvular heart surgery

OBJECTIVES We sought to evaluate whether a limited surgical cryoablation of the posterior region of the left atrium was safe and effective in the cure of atrial fibrillation (AF) in patients with associated valvular heart disease. BACKGROUND Extensive surgical ablation of AF is a complex and risky procedure. The posterior region of the left atrium seems to be important in the initiation and maintenance of AF. METHODS In 32 patients with chronic AF who underwent heart valve surgery, linear cryolesions connecting the four pulmonary veins and the posterior mitral annulus were performed. Eighteen patients with AF who underwent valvular surgery but refused cryoablation were considered as the control group. RESULTS Sinus rhythm (SR) was restored in 25 (78%) of 32 patients immediately after the operation. The cryoablation procedure required 20 +/- 4 min. There were no intraoperative and perioperative complications. During the hospital period, one patient died of septicemia. Thirty-one patients reached a minimum of nine months of follow-up. Two deaths occurred but were unrelated to the procedure. Twenty (69%) of 29 patients remained in SR with cryoablation alone, and 26 (90%) of 29 patients with cryoablation, drugs and radiofrequency ablation. Three (10%) of 29 patients remained in chronic AF. Right and left atrial contractility was evident in 24 (92%) of 26 patients in SR. In control group, two deaths occurred, and SR was present in only four (25%) of 16 patients. CONCLUSIONS Linear cryoablation with lesions connecting the four pulmonary veins and the mitral annulus is effective in restoration and maintenance of SR in patients with heart valve disease and chronic AF. Limited left atrial cryoablation may represent a valid alternative to the maze procedure, reducing myocardial ischemic time and risk of bleeding.

Different patterns of atrial activation in idiopathic atrial fibrillation: simultaneous multisite atrial mapping in patients with paroxysmal and chronic atrial fibrillation

OBJECTIVES We aimed to evaluate: 1) the behavior of electrical activity simultaneously in different atrial regions during atrial fibrillation (AF); 2) the difference of atrial activation between paroxysmal and chronic AF; 3) the atrial refractoriness dispersion; and 4) the correlation between the effective refractory periods (ERPs) and the FF intervals. BACKGROUND Little data exist on the electrophysiologic characteristics of the different atrial regions in patients with AF. A more detailed knowledge of the electrical activity during AF may provide further insights to improve treatment of AF. METHODS Right and left atria were extensively mapped in 30 patients with idiopathic AF (18 paroxysmal and 12 chronic). In different atrial locations, we analyzed 1) the FF interval duration; and 2) the grade of organization and, in case of organized electrical activity, the direction of atrial activation. Furthermore, in patients with paroxysmal AF, we determined the atrial ERP, evaluated the ERP dispersion and assessed the presence of a correlation between the ERPs and the FF intervals. RESULTS In patients with chronic AF, we observed a shortening of the FF intervals and a greater prevalence of disorganized activity in all the atrial sites examined. In patients with paroxysmal AF, a significant dispersion of refractoriness was observed. The right lateral wall showed longer FF intervals and more organized atrial activity and, unexpectedly, the shortest mean ERPs. In contrast, the septal area showed shorter FF intervals, greater disorganization and the longest mean ERPs. CONCLUSIONS Electrical activity during AF showed a significant spatial inhomogeneity, which was more evident in patients with paroxysmal AF. The mean FF intervals did not correlate with the mean ERPs.

Acute and long-term outcome of transvenous cryothermal catheter ablation of supraventricular arrhythmias involving the perinodal region.

Objective Cryoenergy is a new valuable treatment option to perform ablation close to the atrioventricular (AV) node in the cure of supraventricular tachycardias because of its favourable properties, such as the possibility of creating reversible lesions. The aim of this study was to report our experience on the effectiveness and safety of catheter cryoablation performed in “critical areas” to treat a large cohort of patients with supraventricular arrhythmias. Methods One hundred and thirty-one patients suffering from supraventricular tachycardias underwent catheter cryoablation using a 7F catheter. Eighty-seven patients presented with AV nodal re-entrant tachycardia (AVNRT), 39 had accessory pathways (APs) either manifest or concealed (15 midseptal, 24 parahissian), three had ectopic right atrial tachycardia (AT), and two patients had a permanent junctional reciprocating tachycardia (PJRT). When the optimal parameters were recorded, ice mapping at −30°C was performed for 80 s to validate the ablation site. If the expected result occurred, cryoablation was carried out by lowering the temperature to −75°C for 4 min. Results In two patients cryoablation was not performed because of technical reasons. Cryoablation was acutely successful in 84 out of 85 patients with AVNRT, in 37 of 39 with APs and in all patients with AT and PJRT. No complications occurred in any patient. Transient AV conduction impairment occurred in seven patients with midseptal APs and in two patients with AVNRT. In particular, in these patients no late permanent AV block was observed at follow-up. At a mean follow-up of 27 ± 12.9 months, clinical success rate was 87%. Conclusions Cryoablation is a safe and effective technique with a high success rate in the long term. It may be particularly useful when performing ablation close to the AV node or His bundle owing to the possibility of validating the ablation site with ice mapping, which creates only a reversible lesion, mainly in the midseptal APs.

Should stimulation therapy for congestive heart failure be combined with defibrillation backup

Biventricular pacing has been proposed to resynchronize ventricular contraction in patients with congestive heart failure (CHF) and interventricular conduction delay. However, the sudden death rate is still high despite the improvement in cardiac performance. Devices combining biventricular pacing with implantable cardioverter defibrillator (ICD) backup are now under clinical investigation to demonstrate whether they can decrease sudden death. From the first implant of an ICD with biventricular transvenous pacing on August 1998 to April 2000, 96 patients underwent such implants: 67 (70%) received pacemakers alone and 29 (30%), who had class I ICD indications, received combined pacemaker/ICD systems. During a mean follow-up of 283 +/- 170 days, 13 (14%) patients died: 5 of 29 (17%) in the ICD group and 8 of 67 (12%) in the pacemaker group. A total of 15 patients (52%) had ICD shocks and 6 patients (21%) had 113 episodes of ventricular tachyarrhythmias, of which 96 (85%) were converted to sinus rhythm with antitachypacing. The echocardiograms showed a narrowing of the delay between the onset of right and left ventricular outflow from 40 +/- 37 msec to 17 +/- 16 msec (p = 0.03) and a reduction of the mitral regurgitation area from 7 +/- 3.8 cm2 to 5 +/- 4 cm2 (p = 0.04) at 3 months. Functional class improved from 2.8 +/- 0.7 to 1.6 +/- 0.5 (p <0.001) 3 months after implant. Thus, ischemic patients with reduced left ventricular ejection fraction and ventricular tachyarrhythmias seem good candidates for biventricular pacing with ICD backup. The sudden death risk for those with idiopathic dilated cardiomyopathy, however, is difficult to stratify, and the choice of ICD backup has to be considered on the basis of patient safety, as well as of costs.

Cardiac resynchronization and implantable cardioverter defibrillator therapy: Preliminary results from the InSync implantable cardioverter defibrillator italian registry

GASPARINI, M., et al.: Cardiac Resynchronization and Implantable Cardioverter Defibrillator Therapy: Preliminary Results From the InSync Implantable Cardioverter Defibrillator Italian Registry. The aim of this study was to evaluate ventricular arrhythmias occurring in recipients of the InSync ICD for the primary and secondary prevention of sudden death. The InSync ICD was implanted in 142 patients (128 men; mean age65 ± 10years) with heart failure (mean NYHA functional Class3.0 ± 0.7) and wide QRS (mean159 ± 33ms). The underlying etiology was ischemic in 55%, idiopathic in 33%, and valvular or hypertensive cardiomyopathy in 12% of patients. The numbers of arrhythmic episodes/100 patient‐months was computed with their 95% CI, assuming a Poisson distribution. Implants were performed in 48 (34%) patients who did not have an ACC/AHA guidelines Class I indication for ICD therapy. A total of 104 patients were compliant for follow‐up visits. During a 9‐month median (range 0.1–24) follow‐up of 104 compliant patients, 19 experienced a total of 94 ventricular arrhythmias, all successfully interrupted or selfterminated, with a median number of two separate episodes, corresponding to a rate of 10 episodes/100 person‐month (95% CI 8–12). A rate of 12 episodes/100 person‐months (95% CI 10–15) was measured in the subgroup of patients with ACC/AHA class I indications, versus two episodes/100 person‐months (95% CI 1–5) in the remainder of the population. Among 12 deaths, 9 were due to heart failure, 1 to a noncardiovascular cause, and 2 to unknown causes. The implantation of ICD in heart failure patients has been prominently extended to primary prevention. Patients without standard ICD indications experienced life‐threatening arrhythmic events. The impact of ICD combined with cardiac resynchronization therapy on arrhythmic profile, mortality, and costs in this subgroup of patients need to be more precisely studied, with a particular focus on the various types of underlying heart disease. (PACE 2003; 26:[Pt. II]:148–151)

Atrial Electrical Remodeling by Rapid Pacing in the Isolated Rabbit Heart: Effects of Ca++ and K+ Channel Blockade

Introduction: Electrical remodeling describes atrial electrophysiologic changes that occur following atrial fibrillation. The mechanism(s) responsible for this phenomenon is not well understood. The purpose of this study was to examine the effects of rapid atrial pacing on atrial action potential duration, conduction time and refractoriness in the isolated rabbit heart. The effects of Ca++ and K+ blockade in this model were also studied.Methods and Results: Monophasic action potential recordings were made from 12 epicardial atrial sites in 50 isolated perfused rabbit heart preparations. These recordings were analyzed for activation time (AT), 90% action potential duration (APD) and conduction times (CT) measured at a 250 msec cycle length. Atrial effective refractory periods (ERP) were determined at a 200 msec cycle length. All measurements were made at baseline and repeated after 2 hours of biatrial pacing at 250 msec (control group, n = 10) or 2 hours of rapid biatrial pacing (≊80 msec) in 4 groups: rapid pacing alone (rapid pacing group); rapid pacing in the presence of 0.1mM verapamil (verapamil group) for L-type Ca++ channel blockade; rapid pacing with 1 mM 4-aminopyridine (4-AP group) for K+ channel blockade; and rapid pacing with 50 μM nickel chloride (Ni++ group) for T-type Ca++ channel blockade (n = 10 each group). All baseline and post pacing measurements were taken in the presence of Ca++ or K+ blockers for the respective groups.After rapid atrial pacing alone the average APD shortened by 8.2±10.4 msec compared to 3.6±12.5 msec shortening for control group (p = 0.002). The shortening of APD was uniform at all recording sites. For the rapid pacing group, CT was unchanged for right to left atrial conduction but shortened significantly for left to right atrial conduction (26.8±1.9 msec at baseline to 22.3±4.1 msec post pacing, p = 0.005). Conduction times were unchanged in the control group. The dispersion of repolarization was unchanged by rapid pacing alone. The decrease in APD from baseline to post rapid pacing was similar to the control group for those hearts treated with verapamil and 4-AP (1.5±12.3 and 4.7±10.4 msec, respectively, both p ≤ 0.18 vs control group). The decrease in APD was significantly greater for the Ni++ group (11.8± 14.3 msec) than for either the control group or rapid pacing group (both p ≤ 0.023). The dispersion of repolarization was increased only in the 4-AP group post rapid pacing (41.7±6.2 msec at baseline to 53.5±9.6 msec post pacing, p = 0.01). ERPs were unchanged in any of the 5 groups except for a decrease in left atrial ERP in the Ni++ group after rapid pacing (98±14 msec at baseline to 88±8 msec post rapid pacing, p = 0.005).Conclusions: In the isolated rabbit heart model: 1) atrial APD is shortened after rapid pacing; 2) the shortening of APD is attenuated by verapamil and 4-AP but exaggerated by Ni++ 3) atrial conduction times are shortened in a direction specific manner after rapid pacing; and 4) shortening of ERP in this model is measured only in the presence of Ni++. These findings suggest that both L-type Ca++ and 4-AP sensitive channels may participate in atrial electrical remodeling.

Delaying cardioversion following 4-week anticoagulation in case of persistent atrial fibrillation after a transcatheter ablation procedure to reduce silent cerebral thromboembolism: a single-center pilot study.

Background Symptomatic cerebral thromboembolism occurs in 0.4% of transcatheter atrial fibrillation ablation procedures. Silent cerebral events, instead, have recently been reported in up to 14%, especially clustered within patients undergoing cardioversion at the end of the procedure. The present study reports the incidence of silent cerebral thromboembolism, assessed by cerebral MRI, delaying electrical cardioversion, in case of lack of sinus rhythm restoration at the end of the procedure, after 4 weeks of effective anticoagulation. Methods and results Ninety-five consecutive patients with antiarrhythmic drug refractory atrial fibrillation were referred for transcatheter ablation and enrolled in the study. All patients underwent pre-ablation and post-ablation cerebral MRI. Overall, post-ablation cerebral MRI registered new thromboembolism in six (6%) patients. Fifty-five (58%) patients remained in sinus rhythm throughout the procedure and 40 (42%) reported persistent atrial fibrillation, yielding a silent thromboembolism incidence of 5 and 8%, respectively. In particular, silent thromboembolism was registered in one (4%) of the 25 patients achieving sinus rhythm by catheters, in two (18%) of the 11 patients spontaneously restoring sinus rhythm shortly following the procedure and in none of the four patients cardioverted following 4-week anticoagulation. In a matched reference population, a significantly higher percentage of patients (15, 16% vs. 6, 6%; P = 0.03) suffered from a new post-ablation thromboembolism; particularly within patients terminating the procedure in atrial fibrillation. Delaying cardioversion reduced silent cerebral thromboembolism from 38 to 13%. Conclusion Delaying electrical cardioversion after a 4-week anticoagulation period reduced the risk of silent cerebral thromboembolism and is a viable and safer option in patients terminating a transcatheter ablation procedure in atrial fibrillation.