Search

OBJECTIVESThe purpose of this study was to determine the characteristics of double potentials (DPs) that are helpful in guiding ablation within the cavo-tricuspid isthmus.BACKGROUNDDouble potentials have been considered a reliable criterion of cavo-tricuspid isthmus block in patients undergoing radiofrequency ablation of typical atrial flutter (AFL). However, the minimal degree of separation of the two components of DPs needed to indicate complete block has not been well defined.METHODSRadiofrequency ablation was performed in 30 patients with isthmus-dependent AFL. Bipolar electrograms were recorded along the ablation line during proximal coronary sinus pacing at sites at which radiofrequency ablation resulted in incomplete or complete isthmus block.RESULTSDouble potentials were observed at 42% of recording sites when there was incomplete isthmus block, compared with 100% of recording sites when the block was complete. The mean intervals separating the two components of DPs were 65 ± 21 ms and 135 ± 30 ms during incomplete and complete block, respectively (p < 0.001). An interval separating the two components of DPs (DP1-2interval)

Signie cance of Atrial Tachycardia. Introduction: The purpose of this prospective study was to determine the prevalence and clinical signie cance of inducible atrial tachycardia in patients undergoing slow pathway ablation for AV nodal reentrant tachycardia who did not have clinically documented episodes of atrial tachycardia. Methods and Results: Twenty-seven (15%) of 176 consecutive patients who underwent slow pathway ablation for AV nodal reentrant tachycardia were found to have inducible atrial tachycardia with a mean cycle length of 351 6 95 msec. The atrial tachycardia was sustained in 7 (26%) of 27 patients and was isoproterenol dependent in 20 patients (74%). The atrial tachycardia was not ablated or treated with medications, and the patients were followed for 9.7 6 5.8 months. Six (22%) of the 27 patients experienced recurrent palpitations during follow-up. In one patient each, the palpitations were found to be due to sustained atrial tachycardia, nonsustained atrial tachycardia, recurrence of AV nodal reentrant tachycardia, paroxysmal atrial e brillation, sinus tachycardia, and frequent atrial premature depolarizations. Thus, only 2 (7%) of 27 patients with inducible atrial tachycardia later developed symptoms attributable to atrial tachycardia. Conclusion: Atrial tachycardia may be induced by atrial pacing in 15% of patients with AV nodal reentrant tachycardia. Because the vast majority of patients do not experience symptomatic atrial tachycardia during follow-up, treatment for atrial tachycardia should be deferred and limited to the occasional patient who later develops symptomatic atrial tachycardia. (J Cardiovasc Electrophysiol, Vol. 12

Background Many patients with previously implanted ventricular defibrillators are candidates for an upgrade to a device capable of atrial-ventricular sequential or multisite pacing. The prevalence of venous occlusion after placement of transvenous defibrillator leads is unknown. The purpose of this study was to determine the prevalence of central venous occlusion in asymptomatic patients with chronic transvenous defibrillator leads. Methods Thirty consecutive patients with a transvenous defibrillator lead underwent bilateral contrast venography of the cephalic, axillary, subclavian, and brachiocephalic veins as well as the superior vena cava before an elective defibrillator battery replacement. The mean time between transvenous defibrillator lead implantation and venography was 45 ± 21 months. Sixteen patients had more than 1 lead in the same subclavian vein. No patient had clinical signs of venous occlusion. Results One (3%) patient had a complete occlusion of the subclavian vein, 1 (3%) patient had a 90% subclavian vein stenosis, 2 (7%) patients had a 75% to 89% subclavian stenosis, 11 (37%) patients had a 50% to 74% subclavian stenosis, and 15 (50%) patients had no subclavian stenosis. Conclusions The low prevalence of subclavian vein occlusion or severe stenosis among defibrillator recipients found in this study suggests that the placement of additional transvenous leads in a patient who already has a ventricular defibrillator is feasible in a high percentage of patients (93%). (Am Heart J 2001;141:813-6.)

Background: Ibutilide may result in chemical cardioversion of atrial fibrillation and facilitates transthoracic cardioversion by lowering the defibrillation energy requirement. Whether routine pretreatment with ibutilide increases or decreases the cost of cardioversion is unknown. The purpose of this study was to compare the cost of outpatient transthoracic cardioversion of atrial fibrillation with and without ibutilide pretreatment. Methods: Using a model based on published literature and hospital accounting information, a hypothetical group of 100 patients with atrial fibrillation and a left ventricular ejection fraction >0.30 underwent 2 strategies of outpatient cardioversion: transthoracic cardioversion with and without routine pretreatment with 1 mg ibutilide, and with and without involvement of an anesthesiologist for sedation. If transthoracic cardioversion was unsuccessful in patients who did not receive ibutilide, transthoracic cardioversion was repeated after administration of ibutilide. Results: If an anesthesiologist was involved, transthoracic cardioversion with ibutilide was associated with incremental cost-savings as the efficacy of ibutilide alone in restoring sinus rhythm increased above the critical values of 20%, 27%, and 35% when the efficacy of transthoracic cardioversion alone was 60%, 80%, and 100%, respectively. In the absence of an anesthesiologist, routine pretreatment with ibutilide increased the cost of cardioversion at all success rates of transthoracic cardioversion. Conclusions: In the presence of an anesthesiologist, whether or not routine pretreatment with ibutilide lowers the mean cost of cardioversion is determined by the success rates of chemical cardioversion with ibutilide and transthoracic cardioversion. In the absence of an anesthesiologist, ibutilide pretreatment increases the cost of cardioversion.

The purpose of this double-blind study was to determine the effect of intravenous ethanol administration on defibrillation efficacy in 18 patients with an implantable defibrillator. The equivalent of 60 ml of 100 proof ethanol did not impair defibrillation efficacy.

Background —Atrial fibrillation (AF) shortens the atrial effective refractory period (ERP) and predisposes to further episodes of AF. The acute changes in atrial refractoriness may be related to tachycardia-induced intracellular calcium overload. The purpose of this study was to determine whether digoxin, which increases intracellular calcium, potentiates the acute effects of AF on atrial refractoriness in humans. Methods and Results —In 38 healthy adults, atrial ERP was measured at basic drive cycle lengths (BDCLs) of 350 and 500 ms after autonomic blockade. Nineteen patients had been treated with digoxin for 2 weeks. After a several-minute episode of AF, atrial ERP was measured serially at alternating BDCLs. Compared with pre-AF ERPs, the first post-AF ERPs were significantly shorter in both the digoxin and the control groups ( P P P Conclusions —After a brief episode of AF, digoxin augments the shortening that occurs in atrial refractoriness and predisposes to the reinduction of AF. These effects occur in the setting of autonomic blockade and therefore are more likely to be due to the effects of digoxin on intracellular calcium than to its vagotonic effects.

OBJECTIVES The purpose of this prospective study was to quantitate the diagnostic value of several tachycardia features and pacing maneuvers in patients with paroxysmal supraventricular tachycardia (PSVT) in the electrophysiology laboratory. BACKGROUND No study has prospectively compared the value of multiple diagnostic tools in a large group of patients with PSVT. METHODS One hundred ninety-six consecutive patients who had 200 inducible sustained PSVTs during an electrophysiology procedure were included. The diagnostic values of four baseline electrophysiologic parameters, nine tachycardia features and five diagnostic pacing maneuvers were quantified. RESULTS The only tachycardia characteristic that was diagnostic of atrioventricular (AV) nodal reentry was a septal ventriculoatrial (VA) time of

Postdefibrillation Ventricular Arrhythmias. Background: The relationship between postdefibrillation ventricular arrhythmias and shock strength is poorly understood in patients with implantable defibrillators. The purpose of this study was to characterize the relationship between postdefibrillation ventricular arrhythmias and shock strength. Methods and Results: Forty-three patients with an implanted defibrillator underwent six separate inductions of ventricular fibrillation (VF) after a step-down defibrillation energy requirement (7.3 ± 4.6 J) was determined. For each of the first three inductions of VF, the first two shocks were low energy and equal to approximately 75 % of the defibrillation energy requirement (5.4 ± 3.3 J), or to the defibrillation energy requirement plus 10 J (17.5 ± 4.3 J). After the first two shocks, subsequent shocks were programmed to the maximum available energy (29.0 ± 2.5 J). The alternate technique was used for the subsequent three inductions of VF. Post defibrillation ventricular arrhythmias were noted. Post defibrillation ventricular arrhythmias with a cycle length ≤ 300 msec were more frequent after a low-energy shock (19%), than after a high-energy shock (1.5 %; P = 0.005). Postdefibrillation ventricular arrhythmias with a cycle length > 300 msec were more frequent after a high-energy shock (32%), than after a low-energy shock (7.1%; P = 0.002). A relationship between the cycle length of the post defibrillation ventricular arrhythmias and the absolute defibrillation energy was observed (P 300 msec were uncommon after shocks ≤ 10 J (P = 0.001). The characteristics of ventricular arrhythmias after maximum-energy shocks were similar to those that occurred after high-energy shocks. Conclusions: Post defibrillation ventricular arrhythmias with a cycle length ≤ 300 msec are more common after shocks of strength associated with a low probability of successful defibrillation. Postdefibrillation ventricular arrhythmias with a cycle length of > 300 msec are more common after high- and maximum-energy shocks, and are directly related to the absolute defibrillation energy.

Defibriiiation Energy Requirements. Introduction: Defibrillation energy requirements in patients with nonthoracotomy defibrillators may increase within several months alter implantation. However, the stability of the defibrillation energy requirement beyond I year has not heen reported. The purpose of this study was to characterize the defihrillation energy requirement during 2 years of clinical follow-up. Methods and Results: Thirty-one consecutive patients with u biphasic nonthoracotomy defihrillation system underwent defibrillation energy requirement testing using a step-down technique (20, 15, 12. 10, 8, 6, 5, 4, 3, 2, and I J) during defibrillator implantation, and then 24 hours, 2 months, 1 year, and 2 years after implantation. The mean defihrillation energy requirement during these evaluations was 10.9 ± 5.5 J, 12.3 ± 7.3 J, 11.7 ± 5.6 J, 10.2 ± 4.0 ,|, and 11.7 ± 7.4 J, respectively (P = 0.4). The defibrillation energy requirement was noted to have increased hy 10 J or more after 2 years of follow-up in five patients. In one of these patients, the defihrillation energy requirement was no longer associated with an adequate safety margin, necessitating revision of the defihrillation system. There were no identifiahle clinical characteristics that distinguished patients who did and did not develop a 10-J or more increase in the defihrillation energy requirement. Conclusion: The mean defibrillation energy requirement does not change significantly after 2 years of hiphasic nonthoracotomy detihrillator system implantation. However, approximately 15% of patients develop a 1((-J or greater elevation in the defihrillation energy requirement, and 3% may require a defihrillation system revision. Therefore, a yearly evaluation of the defibrillation euergy requirement may he appropriate. (J Cardiovasc Electrophysiol, Vol. 9, pp. 916-920. Septemtwr 1998)

have shown that the fast pathway is more responsive to adenosine than the slow pathway in patients with AV nodal reentrant tachycardia. Little information is available regarding the effect of adenosine on anterograde and retrograde fast pathway conduction. Methods and Results: The effects of adenosine on anterograde and retrograde fast pathway conduction were evaluated in 116 patients (mean age 47 ± 16 years) with typical AV nodal reentrant tachycardia. Each patient received 12 mg of adenosine during ventricular pacing at a cycle length 20 msec longer than the fast pathway VA hlock cycle length and during sinus rhythm or atrial pacing at 20 msec longer than the fast pathway AV block cycle length. Anterograde block occurred in 98% of patients compared with retrograde fast pathway block in 62% of patients (P < 0.001). Unresponsiveness of the retrograde fast pathway to adenosine was associated with a shorter AV hlock cycle length (374 ± 78 vs 333 ± 74 msec, P < 0.01), a shorter VA hlock cycle length (383 ± 121 vs 307 ± 49 msec, P < 0.001), and a shorter VA interval during tachycardia (53 ± 23 vs 41 ± 17 msec, P < 0.01). Conclusion: Although anterograde fast pathway conduction is almost always blocked by 12 mg of adenosine, retrograde fast pathway conduction is not blocked hy adenosine in 38% of patients with typical AV nodal reentrant tachycardia. This indicates that the anterograde and retrograde fast pathways may be anatomically and/or functionally distinct. Unresponsiveness of VA conduction to adenosine is not a reliable indicator of an accessory pathway. (J Cardiovasc Electrophysiol, Voi 9. pp. 820-824, August 1998)

A patient is described in whom severe cardiac dysfunction developed from amyloid deposited entirely in the walls and lumens of intramural coronary arteries, underwent cardiac transplantation, survived another 69 months, died suddenly, and at necropsy had amyloid again limited to the walls and lumens of the intramyocardial coronary arteries in the donor heart. The rather lengthy survival in this patient and the 118-month survival in a similar previously reported patient suggests that cardiac transplantation may be an appropriate procedure for some patients with cardiac amyloidosis.

SESSION 32: CATHETER ABLATION V: New Techniques and Approaches Friday, May 6, 2005 10:45 a.m.–12:15 p.m.

Asymptomatic Atrial Fibrillation. Introduction: The long-term efficacy of radiofrequency catheter ablation of atrial fibrillation (AF) has been based on patient-reported symptoms suggestive of AF. However, asymptomatic recurrences of AF may remain undetected. The aim of this study was to determine the prevalence of asymptomatic recurrences of AF after an apparently successful catheter ablation procedure for AF. Methods and Results: Among 244 consecutive patients (mean age 53 ± 11 years) who underwent a pulmonary vein isolation procedure for symptomatic paroxysmal AF and who reported no symptoms of recurrent AF at ≥6 months after the procedure, 60 patients with a history of ≥1 episode of AF per week were asked to participate in this study. Preablation, these patients had experienced 19 ± 13 episodes of AF per month. The patients were provided with a patient-activated transtelephonic event recorder for 30 days, a mean of 642 ± 195 days after the ablation procedure, and were asked to record and transmit recordings on a daily basis and whenever they felt palpitations. Seven patients (12%) felt palpitations during the study, although they had not experienced symptoms previously. Each of these 7 patients had an episode of AF documented with the event monitor during symptoms. In these 7 patients, the mean number of episodes per month decreased from 19 ± 14 preablation to 3 ± 1 postablation (P < 0.001). Among the 53 asymptomatic patients, an episode of AF was captured in 1 (2%) patient during the study period. Conclusion: Asymptomatic recurrences of AF after an apparently successful catheter ablation procedure for symptomatic paroxysmal AF are infrequent. (J Cardiovasc Electrophysiol, Vol. 15, pp. 920-924, August 2004)

Objectives The aim of this study was to define the role of papillary muscles (PAPs) in post-infarction ventricular arrhythmias. Background Papillary muscles have been implicated in arrhythmogenesis; however, their role in post-infarction ventricular arrhythmias has not been well-defined. Methods In a series of 9 patients (age 65 ± 9 years, ejection fraction 0.36 ± 0.1) with post-infarction ventricular arrhythmias, electroanatomic mapping in conjunction with intracardiac echocardiography demonstrated that 1 of the PAPs was involved in the arrhythmia. Magnetic resonance imaging with delayed enhancement (DEMRI) was performed in all patients without contraindications. A consecutive series of 9 patients (age 64 ± 8 years, ejection fraction 0.32 ± 0.14) with ventricular arrhythmias that did not originate from the PAP served as a control group and also underwent DEMRI. Results Heterogeneous uptake of gadolinium during magnetic resonance imaging was observed more frequently in arrhythmogenic PAPs than in PAPs that were not involved in ventricular arrhythmias (p = 0.01). The PAPs in the control patients did not take up contrast or show homogeneous contrast uptake. Radiofrequency ablation eliminated all arrhythmias originating from PAPs. Echocardiography after the ablation showed no new or worsened mitral regurgitation. Conclusions Papillary muscles that lie within an infarct zone might give rise to ventricular arrhythmias. Heterogeneous uptake of gadolinium in magnetic resonance images might be predictive of arrhythmogenic PAPs. Radiofrequency catheter ablation of ventricular tachycardia and ventricular ectopy arising in a PAP has a high success rate.

Objectives The purpose of this study was to identify ventricular tachycardia (VT) isthmus sites by pace-mapping within scar tissue and to identify electrogram characteristics that are helpful in identifying VT isthmus sites during sinus rhythm (SR). Background Pace-mapping has been used in the scar border zone to identify the exit site of post-infarction VT. Methods In 19 consecutive patients (18 men, mean age 66 ± 9 years, mean ejection fraction 0.24 ± 0.12) with post-infarction VT, a left ventricular voltage map was generated during SR. Pace-mapping was performed at sites with abnormal electrograms or isolated potentials. Radiofrequency ablation was performed at isthmus sites as defined by pace-mapping (perfect pace-map = 12/12 matching electrocardiogram leads; good pace-map = 10/12 to 11/12 matching electrocardiogram leads) and/or entrainment mapping. Results A total of 81 VTs (mean cycle length 396 ± 124 ms) were inducible. In 16 of the 19 patients, a total of 41 distinct isthmus areas of 41 distinct VTs were identified and successfully ablated. All but one displayed isolated potentials during SR. Furthermore, 22 of the 81 VTs (27%) for which no isthmus was identified became noninducible after ablation of a targeted VT. The 16 patients in whom ≥1 isthmus was identified and ablated were free of arrhythmic events during a mean follow-up of 10 months. Conclusions During SR, excellent or good pace-maps at sites of isolated potentials within areas of scar identify areas of fixed block that are protected and part of the critical isthmus of post-infarction VT. Shared common pathways might explain why non-targeted VTs might become noninducible after ablation of other VTs.

Objectives The purpose of this study was to determine whether the response to ventricular pacing during tachycardia is useful for differentiating atypical atrioventricular node re-entrant tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT) using a septal accessory pathway. Background Although it is usually possible to differentiate atypical AVNRT from ORT using a septal accessory pathway, a definitive diagnosis is occasionally elusive. Methods In 30 patients with atypical AVNRT and 44 patients with ORT using a septal accessory pathway, the right ventricle was paced at a cycle length 10 to 40 ms shorter than the tachycardia cycle length (TCL). The ventriculo-atrial (VA) interval and TCL were measured just before pacing. The interval between the last pacing stimulus and the last entrained atrial depolarization (stimulus-atrial [S-A] interval) and the post-pacing interval (PPI) at the right ventricular apex were measured on cessation of ventricular pacing. Results All 30 patients with atypical AVNRT and none of the 44 patients with ORT using a septal accessory pathway had an S-A-VA interval >85 ms and PPI-TCL >115 ms. Conclusions The S-A-VA interval and PPI-TCL are useful in distinguishing atypical AVNRT from ORT using a septal accessory pathway.

OBJECTIVES The purpose of this randomized study was to evaluate the prevalence of pocket hematomas in patients treated with heparin 6 h or 24 h after pacemaker or defibrillator implantation. BACKGROUND The risks of pocket hematoma and need for evacuation after device implantation have not been defined in patients who require anticoagulation. METHODS Forty-nine consecutive patients with an indication for anticoagulation with heparin after implantable defibrillator or pacemaker implantation were randomized to receive intravenous heparin either 6 h (n = 26) or 24 h (n = 23) postoperatively. Both groups also received warfarin on a daily basis starting the evening of surgery. Twenty-eight patients who received postoperative warfarin alone and 115 patients who did not receive anticoagulation were followed up in a study registry. RESULTS A pocket hematoma developed in 6 of 26 patients (22%) who were treated with intravenous heparin 6 h postoperatively, as compared with 4 of 23 patients (17%) who were treated with intravenous heparin 24 h postoperatively (p = 0.7). In total, a pocket hematoma developed in 10 of 49 patients (20%) treated with heparin, 1 of 28 patients (4%) treated with warfarin alone and 2 of 115 (2%) patients who received no anticoagulation (p < 0.001). CONCLUSIONS Intravenous heparin initiation 6 h or 24 h after pacemaker or defibrillator implantation is associated with a 20% prevalence of pocket hematoma formation. Warfarin therapy or no anticoagulation is associated with only a 2% to 4% risk of pocket hematoma formation.

Objectives This study was designed to determine the prevalence and clinical significance of atrial flutter (AFL) that occurs during catheter ablation for atrial fibrillation (AF). Background Atrial flutter frequently occurs in patients with AF. Methods Pulmonary vein isolation was performed in 133 consecutive patients (age 52 ± 11 years) for paroxysmal (n = 112) or persistent (n = 21) AF. A clinical episode of AFL was documented in 40 of the 133 patients (30%). During the ablation procedure, AFL occurred in 86 patients (65%), either spontaneously (n = 36) or by rapid atrial pacing (n = 50), with AFL being typical in the majority (80%). Cavo-tricuspid isthmus ablation was performed in 28 of the 133 patients. Results Among the 105 patients who did not undergo isthmus ablation, 25 patients (24%) were documented to have symptomatic AFL during a mean follow-up of 609 ± 252 days. Among the clinical variables of age, gender, history of clinical AFL, ejection fraction, left atrial diameter, duration of AF, and occurrence of AFL during ablation, only a history of clinical AFL (p = 0.05) and occurrence of typical AFL during the ablation (p = 0.01) were independent predictors of symptomatic AFL during follow-up. The incidence of symptomatic AFL during follow-up was similar among patients who did and did not have long-term freedom from recurrent AF. Conclusions In patients with AF who have either a history of AFL or an episode of typical AFL during an electrophysiologic study, symptomatic AFL is common after pulmonary vein isolation. Therefore, cavo-tricuspid isthmus ablation is appropriate during pulmonary vein isolation if AFL has been observed clinically or in the electrophysiology laboratory.

OBJECTIVES The purpose of this study was to determine the outcome of patients with nonischemic dilated cardiomyopathy, unexplained syncope and a negative electrophysiology test who are treated with an implantable defibrillator. BACKGROUND Patients with nonischemic cardiomyopathy and unexplained syncope may be at high risk for sudden cardiac death, and they are sometimes treated with an implantable defibrillator. METHODS This study prospectively determined the outcome of 14 consecutive patients who had a nonischemic cardiomyopathy, unexplained syncope and a negative electrophysiology test and who underwent defibrillator implantation (Syncope Group). Nineteen consecutive patients with a nonischemic cardiomyopathy and a cardiac arrest who were treated with a defibrillator (Arrest Group) served as a control group. RESULTS Seven of 14 patients (50%) in the Syncope Group received appropriate shocks for ventricular arrhythmias during a mean follow-up of 24 ± 13 months, compared with 8 of 19 patients (42%) in the Arrest Group during a mean follow-up of 45 ± 40 months (p = 0.1). The mean duration from device implantation until the first appropriate shock was 32 ± 7 months (95% confidence interval [CI], 18 to 45 months) in the Syncope Group compared to 72 ± 12 months (95% CI, 48 to 96 months) in the Arrest Group (p = 0.1). Among patients who received appropriate shocks, the mean time from defibrillator implantation to the first appropriate shock was 10 ± 14 months in the Syncope Group, compared with 48 ± 47 months in the Arrest Group (p = 0.06). Recurrent syncope was always associated with ventricular tachyarrhythmias. CONCLUSIONS The high incidence of appropriate defibrillator shocks and the association of recurrent syncope with ventricular arrhythmias support the treatment of patients with nonischemic cardiomyopathy, unexplained syncope and a negative electrophysiology test with an implantable defibrillator.

OBJECTIVEThe purpose of this study was to evaluate the value of activation mapping for radiofrequency modification of the sinus node and the long-term success rate of the procedure in a series of patients with inappropriate sinus tachycardia.BACKGROUNDThe results of radiofrequency ablation of inappropriate sinus tachycardia have been reported in only a small number of patients.METHODSThe subjects of this study were 29 consecutive drug-refractory patients who underwent catheter ablation of inappropriate sinus tachycardia. Target sites were selected by activation mapping during sinus tachycardia.RESULTSThe ablation procedure was successful acutely in reducing the baseline sinus rate to 20% in 22 of 29 patients (76%). In 13 of 22 patients (59%) with a successful acute outcome, successive applications of radiofrequency energy at the site of earliest endocardial activation resulted in a cranial-caudal migration of earliest endocardial activation from the high lateral right atrium, along with a step-wise reduction in heart rate. In the other nine patients (41%) with a successful acute outcome, the reduction in sinus rate occurred abruptly, unaccompanied by migration of the site of earliest activation. Symptoms due to inappropriate sinus tachycardia recurred at a mean of 4.4±; 3 months after the ablation procedure in 6 of 22 patients (27%). After additional procedures in three patients, symptoms of inappropriate sinus tachycardia ultimately were successfully eliminated over the long-term in 19 of 29 patients (66%).CONCLUSIONSIn conclusion, radiofrequency ablation is at best only modestly effective for managing patients with inappropriate sinus tachycardia. The two different responses of heart rate to radiofrequency ablation may reflect differences in the number and/or multicentricity of subsidiary sites of impulse generation within the sinus node and/or atrium in patients with inappropriate sinus tachycardia.

OBJECTIVES The purpose of this study was to describe a computerized mapping system that utilizes a noncontact, 64 electrode balloon catheter to compute virtual electrograms simultaneously at 3,360 left ventricular (LV) sites and to assess the clinical utility of this system for mapping and ablating ventricular tachycardia (VT). BACKGROUND Mapping VT in the electrophysiology laboratory conventionally is achieved by sequentially positioning an electrode catheter at multiple endocardial sites. METHODS Fifteen patients with VT underwent 18 electrophysiology procedures using the noncontact, computerized mapping system. A 9F 64 electrode balloon catheter and a conventional 7F electrode catheter for mapping and ablation were positioned in the LV using a retrograde aortic approach. Using a boundary element inverse solution, 3,360 virtual endocardial electrograms were computed and used to derive isopotential maps. An incorporated locator system was used in conjunction with or instead of fluoroscopy to position the conventional electrode catheter. RESULTS A total of 21 VTs, 12 of which were hemodynamically-tolerated and 9 of which were not, were mapped. Isolated diastolic potentials, presystolic areas, zones of slow conduction and exit sites during VT were identified using virtual electrograms and isopotential maps. Among 19 targeted VTs, radiofrequency ablation guided by the computerized mapping system and the locator signal was successful in 15. CONCLUSIONS The computerized mapping system described in this study computes accurate isopotential maps that are a useful guide for ablation of hemodynamically stable or unstable VT.

Objectives The aim of this study was to determine the effects of circumferential pulmonary vein ablation (CPVA) and electrogram-guided ablation (EGA) on the spectral characteristics of atrial fibrillation (AF) and the relationship between changes in dominant frequency (DF) and clinical outcome. Background Circumferential pulmonary vein ablation and EGA have been used to eliminate AF. Spectral analysis may identify high-frequency sources. Methods In 84 consecutive patients, CPVA (n = 42) or EGA (n = 42) was performed for paroxysmal (n = 49) or persistent (n = 35) AF. During EGA, complex electrograms were targeted. Lead V1and electrograms from the left atrium and coronary sinus were analyzed to determine the DF of AF before and after ablation. Results The left atrial DF was higher in persistent (5.83 ± 0.86 Hz) than paroxysmal AF (5.33 ± 0.76 Hz, p = 0.03). There was a frequency gradient from the left atrium to the coronary sinus (p = 0.02). Circumferential pulmonary vein ablation and EGA resulted in a similar decrease in DF (18 ± 17% vs. 17 ± 15%, p = 0.8). During a mean follow-up of 9 ± 6 months, the change in DF after CPVA was similar among patients with and without recurrent AF. An acute decrease in DF after EGA was associated with freedom from recurrent AF only in patients with persistent AF (19 ± 14% vs. 3 ± 6%, p = 0.02). Conclusions Both CPVA and EGA decrease the DF of AF, consistent with elimination of high-frequency sources. Whereas the efficacy of EGA is associated with a decrease in DF in patients with persistent AF, the efficacy of CPVA is independent of changes in DF. This suggests that CPVA and EGA eliminate different mechanisms in the genesis of persistent AF.

ObjectivesTo identify and characterize ablation lesions after radiofrequency (RF) catheter ablation of ventricular arrhythmias in patients without prior myocardial infarction and to correlate the ablation lesions with the amount of RF energy delivered and the clinical outcome.BackgroundVisualization of RF energy lesions after ablation of ventricular arrhythmias might help to identify reasons for ablation failure.MethodsIn a consecutive series of 35 patients (19 women, age: 48 ± 15 years, ejection fraction: 0.56 ± 0.12) without structural heart disease who were referred for ablation of ventricular arrhythmias, cardiac magnetic resonance imaging with delayed enhancement was performed before and after ablation. Ablation lesions were sought in the post-ablation cardiac magnetic resonance images. The endocardial area, depth, and volume of the lesions were measured. Lesion size was correlated with the type of ablation catheter used and the duration of RF energy delivered.ResultsIn 25 of 35 patients (71%), ablation lesions were identified by delayed enhancement a mean of 22 ± 12 months after the initial ablation procedure. The mean lesion volume was 1.4 ± 1.4 cm3, with a mean endocardial area of 3.5 ± 3.0 cm2. The largest lesions (mean volume of 2.9 ± 2.1 cm3 with an endocardial area of 6.4 ± 3.4 cm2) were identified in patients in whom the arrhythmias originated in the papillary muscles. Ablation duration correlated with lesion size (r = 0.67, p < 0.001). There was no difference in lesion volume with irrigated versus nonirrigated ablation catheters (1.0 ± 0.73 vs. 2.0 ± 2.1 cm3, p = 0.09). Identification of ablation lesions in patients with a failed procedure identified the sites where ineffective RF energy lesions were created.ConclusionsRF ablation lesions can be detected long term after an ablation procedure targeting ventricular arrhythmias in patients without previous infarction. Lesion size correlates with the amount of RF energy delivered and is largest when a targeted arrhythmia originates in a papillary muscle.

Results: Mortality was higher (P