Effect of adenosine triphosphate on left atrial electrogram interval and dominant frequency in human atrial fibrillation.

BACKGROUND: Complex fractionated atrial electrograms (CFAEs) and high dominant frequency (DF) are targets for atrial fibrillation (AF) ablation. Although adenosine triphosphate (ATP) is known to promote AF by shortening the atrial refractory period, its role in the pathogenesis of CFAEs and DF during AF is not fully understood. METHODS: We recorded electrical activity from a 64-electrode basket catheter placed in the left atrium (LA) of patients with paroxysmal AF (PAF, n=18) or persistent AF (PerAF, n=19) before ablation. Atrial electrogram fractionation intervals (FIs) and DFs were measured from bipolar electrograms of each adjacent electrode pair. Offline mean atrial FIs and DFs were obtained before bolus injection of 30 mg ATP. Peak effect was defined as an R-R interval >3 s. RESULTS: With ATP, the mean FI decreased (from 110.4±29.1 ms to 90.5±24.7 ms, P<0.0001) and DF increased (from 6.4±0.6 Hz to 7.1±0.8 Hz, P<0.0001) in all patients. There was no difference in the FI decrease between the two groups (-20.3±20.5 ms vs. -19.6±14.5 ms, P=0.6032), but the increase in DF was significantly greater in PAF patients (1.1±0.8 Hz vs. 0.3±0.6 Hz, P=0.0051). CONCLUSIONS: ATP shortens atrial FIs and increases DFs in both PAF and PerAF patients. The significant increase in DF in PAF patients suggests that pathophysiologic characteristics related to the frequency of atrial fractionation change as atrial remodeling progresses.

Right atrial tachycardia with 2:1 intra-atrial conduction.

In a case of atrial tachycardia (AT) originating from the inferolateral right atrium, cycle length (CL) alternans was observed. Conduction at the longer CL was to the high right atrium (HRA), His bundle electrogram region (HBE), and coronary sinus (CS). Conduction at the shorter CL was to the HRA, with that to the HBE and CS blocked.

Spatial and temporal variability of the complex fractionated atrial electrogram activity and dominant frequency in human atrial fibrillation.

BACKGROUND: The presence of complex fractionated atrial electrograms (CFAEs) and high dominant frequencies (DFs) during atrial fibrillation (AF) have been demonstrated to be related to AF maintenance. Therefore, sequential mapping of CFAEs and DFs have been used for target sites of AF ablation. However, such mapping strategies are valid only if the CFAEs and DFs are spatiotemporally stable during the mapping procedure. We obtained spatially stable multi-electrode recordings to assess the spatiotemporal stability of CFAEs and DFs. METHODS: We recorded electrical activity during AF for 10 min with a 64-electrode basket catheter (48 bipole electrode pairs) placed in the left atrium in 36 patients with AF (paroxysmal AF [PAF], n=16; persistent AF [PerAF], n=20). The spatial and temporal distribution of the CFAEs (fractionation interval <120 ms) and high DFs (>8 Hz) at 1-min intervals for 10 min were compared for each of the 48 bipoles. RESULTS: The baseline CFAEs were located at 68.5±14.0% (32.9±6.7) of the 48 bipoles; however, the high DF sites were fewer (9.6±8.6% [4.6±4.1 bipoles]). The CFAEs sites did not change significantly during the 10-min recording period (kappa statistic: 0.71±0.24); however, the high DF sites changed significantly (kappa statistic: 0.07±0.19). These spatiotemporal changes in the CFAEs and high DFs did not differ between patients with PAF and PerAF. CONCLUSIONS: Regardless of the AF type, CFAEs sites, but not high DF sites, showed a high degree of spatial and temporal stability.

Tissue velocity imaging-based atrial fibrillatory cycle length and wall motion for predicting atrial structural remodeling in patients undergoing catheter ablation.

BACKGROUND: Atrial fibrillation (AF) causes atrial electrical and structural remodeling, which are linked to recurrence of AF after ablation. Atrial fibrillatory cycle length (AFCL) and AF wall motion velocity (AFW-V) obtained by tissue velocity imaging (TVI) might characterize such atrial electrical and structural remodeling. The purpose of this study was to assess the clinical and electrophysiologic correlates of these parameters and their relation to ablation outcomes. METHODS AND RESULTS: The study group comprised 80 patients who underwent transthoracic echocardiography followed by AF ablation. Atrial TVI traces were used to determine AFCL-tvi and AFW-V-tvi at the left atrial septal wall. AFCL that was measured from intracardiac electrograms correlated well with AFCL-tvi (R=0.6094; P=0.0002). AFW-V-tvi was significantly lower and AFCL-tvi was significantly shorter in patients with non-paroxysmal AF than in those with paroxysmal AF (1.63±0.76 cm/s vs. 2.85±1.00 cm/s, respectively, P<0.0001; and 118.2±23.0 ms vs. 145.0±35.0 ms, respectively, P=0.0001). These findings held true for patients with and without post-ablation recurrence. Upon multivariate analysis, a reduced AFW-V-tvi remained the strongest predictor of post-ablation recurrence (hazard ratio for +1-cm/s change, 0.573; 95% confidence interval, 0.337-0.930; P=0.0234). CONCLUSIONS: TVI of atrial fibrillatory wall motion might enhance the non-invasive characterization of atrial remodeling in patients with AF and thus be used for predicting AF recurrence after ablation.

Rate-dependent electrophysiologic effects of the class III antiarrhythmic drugs nifekalant, amiodarone, and ibutilide on the atrium in patients with persistent atrial fibrillation.

Persistent atrial fibrillation (AF) is characterized by electrical remodeling, ie, marked decreases in the atrial effective refractory period (ERP), ERP rate adaptation, and atrial conduction velocity. Little information is available on the effects of class III antiarrhythmic drugs on the remodeled atrium. We studied the effects of the class III antiarrhythmic drugs nifekalant, ibutilide, and amiodarone on rate-dependent changes in atrial action potential duration in patients with persistent AF. Right atrial (RA) monophasic action potential duration (MAPD) and intra-atrial conduction time (IACT) were measured at pacing cycle lengths (CLs) of 800, 700, 600, 500, 400, 350, 300, and 250 ms before and after administration of nifekalant (0.4 mg/kg + 0.3 mg/kg/hr, iv), amiodarone (5 mg/kg, iv), or ibutilide (0.01 mg/kg, iv) in 31 patients after successful internal cardioversion of chronic AF of > 2 months duration. Nifekalant and ibutilide significantly increased RA MAPD and the ERP at each CL in a reverse rate-dependent manner. Amiodarone did not affect RA MAPD. Nifekalant did not affect IACT, whereas amiodarone increased IACT at each CL in a rate-dependent manner, and ibutilide increased IACT at CLs ≤ 350 ms. The atrial electrophysiologic effects of the class III antiarrhythmic drugs nifekalant, amiodarone, and ibutilide differ, depending on the degree of electrical and structural remodeling and the effects of the drugs on the depolarizing and repolarizing currents.

Three-dimensional high-density bipolar contact mapping of left atrial endocardial activation during sinus rhythm in patients with atrial fibrillation.

Non-contact array mapping studies have demonstrated the existence of a line of conduction block along the septopulmonary bundle area and the posterior left atrial (LA) roof during sinus rhythm (SR). However, little is known of the global LA activation pattern during SR using a high-density contact bipolar mapping system. High-density contact bipolar isochronal mapping (bipolar mapping sites: 292 [IQR 250-348] points) of the LA was performed during SR with the NavX mapping system in 20 patients with paroxysmal atrial fibrillation (AF) and 11 patients with non-paroxysmal AF. The earliest endocardial breakthrough in the the LA from the right atrium (RA) during SR occurred in the anterosuperior LA (77%) or anterior to the right pulmonary veins (23%), and the breakthrough site did not differ between patients with paroxysmal and non-paroxysmal AF. Regardless of the site of breakthrough, the LA activation pattern was homogeneous, and no line of functional block was observed in any patient. Total LA activation time was significantly longer in non-paroxysmal AF patients than in paroxysmal AF patients (95.1 ± 4.3 ms versus 78.3 ± 3.2 ms, P = 0.0040). Contact-based bipolar LA endocardial activation mapping revealed a homogeneous LA activation pattern during SR, regardless of the between-group difference in activation time and the between-patient difference in sites of earliest LA endocardial breakthrough from the RA.

Potential anatomic substrate of peri-atrioventricular nodal atrial tachycardia ablated from the noncoronary sinus of Valsalva.

INTRODUCTION: Although focal atrial tachycardia (AT) is known to sometimes be ablated from the noncoronary aortic cusp (NCC), the electro-anatomic characteristics of NCC-AT are not well known. METHODS: We compared the clinical, 12-lead electrocardiogram (ECG), and transthoracic echocardiogram characteristics of 6 women (median age, 66.5 years) with NCC-AT and 12 age-matched women (median age, 64.0 years) with atrioventricular nodal reentrant tachycardia (AVNRT) as the control group. RESULTS: There was no difference in the prevalence of hypertension between the two groups (67 vs. 33 %, respectively, P = 0.3213). The resting ECG of the NCC-AT group vs. that of the AVNRT group showed a significantly longer PQ interval (170.0 (interquartile range (IQR), 157.5-180.0 ms) vs. 140.0 ms (IQR, 122.5-147.5 ms), P = 0.0010) and leftward shifting of the QRS axis (4° (IQR, -26.0° to 24.0°) vs. 57° (IQR, 43.0-70.2°), P = 0.0087). The upper interventricular septum (IVS) thickness was significantly greater (15.6 (IQR, 11.9-18.7 ms) vs. 11.7 mm (IQR, 10.2-12.9 ms), P = 0.0393), and the angle formed by the aortic roof and IVS (AS angle) was significantly steeper (103.0° (IQR, 94.2-119.2°) vs. 122.5° (IQR, 108.5-128.5°), P = 0.0343) in the NCC-AT group than in the AVNRT group. CONCLUSIONS: Our data suggest that NCC-AT is characterized by a longer atrioventricular (AV) conduction time, steeper AS angle, and thicker IVS than are seen with AVNRT. These electrocardiographic and echocardiographic characteristics from the IVS to the peri-AV nodal regions may have some effect on the development of NCC-AT.

Effect of catheter tip-tissue surface contact on three-dimensional left atrial and pulmonary vein geometries: potential anatomic distortion of 3D ultrasound, fast anatomical mapping, and merged 3D CT-derived images.

UNLABELLED: Anatomic Distortion of 3D Mapping. BACKGROUND: Although catheter tip-tissue contact is known as a reliable basis for mapping and ablation of atrial fibrillation (AF), the effects of different mapping methods on 3-dimensional (3D) map configuration remain unknown. METHODS AND RESULTS: Twenty AF patients underwent Carto-based 3D ultrasound (US) evaluation. Left atrium (LA)/pulmonary vein (PV) geometry was constructed with the 3D US system. The resulting geometry was compared to geometries created with a fast electroanatomical mapping (FAM) algorithm and 3D US merged with computed tomography (merged 3D US-CT). The 3D US-derived LA volumes were smaller than the FAM- and merged 3D US-CT-derived volumes (75 ± 21 cm(3) vs 120 ± 20 cm(3) and 125 ± 25 cm(3) , P < 0.0001 for both). Differences in anatomic PV orifice fiducials between 3D US- and FAM- and merged 3D US-CT-derived geometries were 6.0 (interquartile range 0-9.3) mm and 4.1 (0-7.0) mm, respectively. Extensive encircling PV isolation guided by 3D US images with real-time 2D intracardiac echocardiography-based visualization of catheter tip-tissue contact generated ablation point (n = 983) drop-out at 1.9 ± 3.8 mm beyond the surface of the 3D US-derived LA/PV geometry. However, these same points were located 1.5 ± 5.4 and 0.4 ± 4.1 mm below the FAM- and merged 3D US-CT-derived surfaces. CONCLUSIONS: Different mapping methods yield different 3D geometries. When AF ablation is guided by 3D US-derived images, ablation points fall beyond the 3D US surface but below the FAM- or merged 3D US-CT-derived surface. Our data reveal anatomic distortion of 3D images, providing important information for improving the safety and efficacy of 3D mapping-guided AF ablation. (J Cardiovasc Electrophysiol, Vol. 24, pp. 259-266, March 2013).

Comparative distribution of complex fractionated atrial electrograms, high dominant frequency (HDF) sites during atrial fibrillation and HDF sites during sinus rhythm.

PURPOSE: Complex fractionated atrial electrograms (CFAEs) and high dominant frequency sites during atrial fibrillation (AF-HDF) are related to the maintenance of atrial fibrillation (AF). HDF sites in sinus rhythm (SR-HDF; as defined by frequencies of >70 Hz) are suggested to be abnormal atrial tissue. Relations between these electrophysiologic signals have not been elucidated. METHODS: We investigated the relations between SR-HDF and CFAE and AF-HDF sites during AF. NavX-based maps of CFAE and left atrium (LA)/pulmonary vein (PV) dominant frequency (DF) during AF and DF maps during SR were created for 23 patients with AF (paroxysmal AF (PAF), n = 14; persistent AF (PerAF), n = 9). RESULTS: The extent of overlap between SR-HDF and CFAE sites was 51 ± 18 % (as calculated by the LA/PV segments containing both an SR-HDF site and a CFAE site/total LA/PV segments containing an CFAE site) and the extent of overlap between SR-HDF and AF-HDF sites was 50 ± 35 % (P = 0.7464). However, statistically poor agreement was noted for both (kappa values, 0.07 ± 0.19 and 0.08 ± 0.24, P = 0.8794). The extent of overlap did not differ between PAF and PerAF patients (SR-HDF and CFAE, 52 % (interquartile range (IQR), 42-59) versus 57 % (IQR, 33-67), P = 0.5842; SR-HDF and AF-HDF, 43 % (IQR, 25-85) versus 55 % (IQR, 13-83), P = 0.9465). The bipolar voltage amplitudes of SR-HDF, CFAE, and AF-HDF sites revealed normal voltage areas (1.6 mV (IQR, 0.8-2.7), 1.9 mV (IQR, 1.1-2.8), and 1.5 mV (IQR, 1.7-2.7), respectively). CONCLUSIONS: In both PAF and PerAF, most CFAE and AF-HDF sites did not correspond to the SR-HDF sites or low-voltage area during SR. Thus, most CFAE and DF signals during AF represent functional electrical activities rather than structural remodeling of the atria.

Linear catheter ablation of the right atrium for rapid atrial pacing-induced sustained atrial fibrillation in dogs.

Catheter ablation of persistent/long-persistent atrial fibrillation (AF) has been shown to be less effective by pulmonary vein isolation (PVI) and additional left atrial (LA) complex fractionated atrial electrograms and long linear lesions are often required. Recent reports have demonstrated right atrial (RA) ablation increases the success rate of maintaining sinus rhythm in persistent/long-persistent AF. The aim of this study was to investigate whether effective RA linear lesions can terminate AF and render it noninducible in a canine model of rapid atrial pacing-induced sustained AF. Sustained AF was induced by rapid atrial pacing in 20 dogs. AF duration was 21-126 days (median, 50 days). Four RA linear lesions (superior vena cava-inferior vena cava, septal line, transverse line, and cavo-tricuspid line) were created with the use of 1 of 3 different ablation catheters (large-tip [8-mm tip], coil-tip, and cooled-tip catheters). AF was terminated with the large-tip catheter in 4/7 dogs (1 dog died of ventricular fibrillation [VF]), with the coil-tip catheter in 3/7 dogs (1 dog died of VF), and with the cooled-tip catheter in 1/6 dogs. In 6 dogs in which AF could not be terminated acutely by RA ablation, AF terminated spontaneously at 7-78 days (median, 14 days) after ablation. RA linear ablation terminated AF with limited success in our dog model of rapid atrial pacing-induced AF, but late AF termination was noted in the surviving dogs. Therefore, RA linear lesions in addition to the PVI and LA lesions may have additional effects on the catheter ablation for the persistent AF.

Does location of epicardial adipose tissue correspond to endocardial high dominant frequency or complex fractionated atrial electrogram sites during atrial fibrillation?

BACKGROUND: Although increased epicardial adipose tissue (EAT) volume is known to be associated with increased prevalence of atrial fibrillation (AF), the exact mechanisms are unclear. Therefore, we investigated whether EAT locations were associated with high dominant frequency (DF) sites or complicated fractionated atrial electrogram sites during AF. METHODS AND RESULTS: Three-dimensional reconstruction computed tomography images depicting EAT volumes (obtained by 320-detector-row multislice computed tomography) were merged with NavX-based DF and complicated fractionated atrial electrogram maps obtained during AF for 16 patients with paroxysmal AF and for 18 patients with persistent AF. Agreement between locations of the EAT, especially EAT surrounding the left atrium, and of high DF or complicated fractionated atrial electrogram sites was quantified. In addition, serum biomarker levels were determined. EAT surrounding the left atrium volumes was significantly greater in patients with persistent AF than in patients with paroxysmal AF (52.9 cm(3) [95% CI, 44.2-61.5] versus 34.8 cm(3) [95% CI, 26.6-43.0]; P=0.007). Serum high-sensitivity C-reactive protein and interleukin-6 levels were significantly higher in persistent AF patients than in paroxysmal AF patients (median high-sensitivity C-reactive protein, 969 ng/mL [interquartile range, 307-1678] versus 320 ng/mL [interquartile range, 120-660]; P=0.008; median interleukin-6, 2.4 pg/mL [interquartile range, 1.7-3.2] versus 1.3 [interquartile range, 0.8-2.4] pg/mL; P=0.017). EAT locations were in excellent agreement with high DF sites (κ=0.77 [95% CI, 0.71-0.82]) but in poor agreement with complicated fractionated atrial electrogram sites (κ=0.22 [95% CI, 0.13-0.31]). CONCLUSIONS: Increased EAT volume and elevation of inflammatory biomarkers are noted in persistent AF rather than paroxysmal AF patients. High DF sites are located adjacent to EAT sites. Thus, EAT may be involved in the maintenance of AF.

Effects of the antianginal drug trapidil on atrioventricular conduction disturbances during acute myocardial ischemia.

Adenosine and related compounds have been shown to produce atrioventricular (AV) conduction block during acute myocardial ischemia. We investigated the effects of the antianginal drug trapidil, which has been shown to inhibit phosphodiesterase, on AV conduction disturbances in a canine model of acute myocardial ischemia. In 35 anesthetized dogs, the AV node artery was cannulated and perfused with arterial blood. Adenosine (300 µg, 650 µg, or 1000 µg) was injected into the AV node artery. With administration of adenosine at 300 µg, 650 µg, or 1000 µg, the atrio-His (AH) interval was increased by 14.6 ms, 22.3 ms, and 29.7 ms, respectively. The effects of adenosine were potentiated by pretreatment with intravenous dipyridamole (250 µg/kg), an inhibitor of adenosine uptake, but the effects of adenosine were attenuated with intravenous trapidil (3 mg/kg), an inhibitor of phosphodiesterase. AV node artery occlusion resulted in prolongation of the AH interval in 4 of 12 dogs. The ischemia-induced AH prolongation was potentiated with intravenous dipyridamole and attenuated with intravenous trapidil. AV conduction disturbances associated with inferior myocardial infarction may be related in part to endogenously released adenosine, and trapidil may be useful in treating AV block associated with acute AV node ischemia.

Pharmacologic atrial defibrillation by drug delivery into the temporarily occluded coronary sinus. A canine study.

Venous blood draining from the left atrium (LA) flows into the coronary sinus (CS) through the Marshall vein which has no valvular apparatus, thus allowing LA retroperfusion if reflow in the right atrium is hindered. We investigated pharmacologic atrial defibrillation via the CS in dogs with chronic atrial fibrillation (AF). Chronic AF was induced by rapid atrial pacing for 4-16 weeks in 6 mongrel dogs. A 7F occlusion balloon catheter was introduced into the proximal CS. Boluses of low doses of the class Ic antiarrhythmic drug, pilsicainide (2, 4, 6, and 8 mg as needed) or class III antiarrhythmic drug, nifekalant (0.5, 1, 2, and 4 mg) were infused directly within 3-4 seconds at 10 minute intervals into the temporarily balloon occluded CS near its orifice. In 4 of the 5 dogs (balloon catheter could not be placed in the CS in 1 dog), the cumulative dose of 11.5 ± 7.4 mg of pilsicainide was effective in restoring sinus rhythm; the venous concentration of pilsicainide was 1.23 ± 0.79 µg/mL. A cumulative dose of 7.5 mg nifekalant restored sinus rhythm in only 1 of the 6 dogs. Our results in dogs with sustained AF indicate that delivery of a class Ic or III antiarrhythmic drug near the CS ostium via the temporarily occluded CS is feasible and effective for pharmacologic atrial defibrillation; however, the effect may be related to the elevation of the serum concentration of the drug to the therapeutic range rather than to the delivery method itself.

A novel technique for improved lesions in the coronary sinus. comparison of bipolar and unipolar ablation.

The stepwise approach to radiofrequency (RF) ablation of atrial fibrillation (AF) can include ablation of the coronary sinus (CS) by RF delivery at the left atrium (LA) and/or within the CS. In both cases, the energy is applied between the tip electrode of a percutaneous catheter and a dispersive electrode on the body surface. We explored the feasibility of using the electrode rings of a diagnostic catheter placed in the CS as dispersive electrode(s) for RF delivery within the LA and compared this technique to an established CS ablation method.Excised pig hearts were superfused with a pulsatile saline flow. Bipolar ablation was performed between a saline-irrigated (20 mL/minute) 4-mm tip electrode placed in the LA adjacent to the CS and 7 electrode rings of a 6F, septapolar, 4-mm nonirrigated electrode placed within the CS adjacent to the LA endocardial electrode. Unipolar ablation was performed between the endocardial electrode and dispersive electrode. A continuous transmural lesion was produced in 6/8 (75%) attempts with bipolar ablation, but in 0/6 (0%) attempts with unipolar ablation. However, the incidence of steam pop tended to be increased with bipolar ablation.Bipolar ablation of the CS appears to be highly effective for creating a transmural LA-CS lesion.

Prevalence of prominent J waves in patients presenting with ventricular fibrillation without structural heart disease: a single-center study.

Association between sudden cardiac arrest and early repolarization (QRS slurring in the inferolateral leads) has drawn recent attention. We retrospectively assessed the prevalence of electrocardiographic J waves in 19 men aged 46.5±13.7 years who, between 1979 and 2011, were resuscitated after cardiac arrest due to ventricular fibrillation. There was no structural heart disease in this group. The J wave is an elevation of the QRS-ST junction of at least 0.1mV from baseline in the inferior or lateral leads, manifested as QRS slurring or notching. Eleven patients (age, 37.3±13.9 years) showed J waves in the inferior leads (n=8) or in both the inferior and lateral leads (n=3). Brugada syndrome was diagnosed in 5 patients (age, 46.4±15.7 years). The QRS complex was normal in the remaining 3 patients (age, 44.3±9.5 years). Ventricular fibrillation was induced by programmed ventricular stimulation with up to 3 extrastimuli from the right ventricular apex or outflow tract in 7 of the 10 J-wave syndrome patients tested, in all 5 Brugada syndrome patients, and in all 3 patients with a normal electrocardiogram. There appears to be an increased prevalence of J-wave syndrome among patients with a history of idiopathic ventricular fibrillation.

Effects of inter-electrode spacing on complex fractionated atrial electrograms and dominant frequency detection.

BACKGROUND: The influence of inter-electrode spacing (IES) on complex fractionated atrial electrograms (CFAEs) and dominant frequency (DF) detection was assessed. METHODS: Bipolar electrograms were recorded via an octapolar catheter (2-mm electrode spacing) from left atrial CFAEs sites in 17 atrial fibrillation patients. The CFE-mean was calculated at IES of the electrode pairs 1-2, 1-3, 1-4, 1-5, and 1-6. The DF, regularity index (RI), and organization index (OI) were simultaneously analyzed. RESULTS: The CFE-mean decreased as the IES increased (from 71 ± 15 ms of IES 1-2 to 61 ± 8 ms of IES 1-3, 57 ± 6 ms of IES 1-4, 57 ± 8 ms of IES 1-5, and 58 ± 9 ms of IES 1-6, respectively; IES 1-2 vs. 1-3 to 1-6, P < 0.01). The DF was unchanged (6.6 ± 1.6 Hz for all; P > 0.99). However, the RI decreased as the IES increased (from 0.30 ± 0.11 to 0.26 ± 0.11, 0.23 ± 0.11, 0.22 ± 0.12, and 0.20 ± 0.12; IES 1-2 vs. 1-3 to 1-6, P < 0.01), as did the OI (from 0.39 ± 0.14 to 0.34 ± 0.12, 0.32 ± 0.13, 0.29 ± 0.13, and 0.28 ± 0.13; IES 1-2 vs. 1-3 to 1-6, P < 0.01). CONCLUSIONS: A wider IES might detect dyssynchronous activations, leading to a reduced CFE-mean and RI and OI. Therefore, bipolar signals recorded with a narrower IES might be preferable to more precisely localizing CFAEs and DF sites.

Epicardial ablation with irrigated electrodes: ­ effect of bipolar vs. unipolar ablation on lesion formation ­.

BACKGROUND: Ablation of ventricular tachycardia originating from the left ventricular (LV) epicardium is often limited by the radiofrequency power delivery. We compared the effect of bipolar vs. unipolar epicardial ablation on lesion size. METHODS AND RESULTS: Eleven excised pig hearts were superfused with saline (2 L/min). Unipolar ablation (25 or 30 W for 120 s) was performed between the LV epicardial saline-irrigated electrode and an indifferent electrode (n = 33 lesions). Bipolar ablation (25 or 30 W for 120 s) was performed between a 4-mm saline-irrigated-tip (20 ml/min) electrode on the LV epicardium and an opposing 10-mm non-irrigated-tip electrode on the LV endocardium (n = 38 lesions). Wall thickness did not differ between experiments (15.4 ± 2.4 vs. 15.3 ± 2.1 mm). Impedance was lower at the beginning and end of unipolar ablation than at the beginning and end of bipolar ablation (163.2 ± 20.3Ω and 109.9 ± 16.0Ω vs. 194.6 ± 23.3Ω and 127.1 ± 16.4Ω, respectively) (P<0.001). Epicardial lesion width did not differ between unipolar and bipolar ablation (10.1 ± 2.7 vs. 10.2 ± 2.4 mm), but lesion depth was greater with bipolar ablation (10.6 ± 2.7 vs. 7.5 ± 1.0 mm) (P<0.001). Unipolar ablation produced no transmural lesion, but bipolar ablation produced 15 (46%) (P<0.001). Steam pop occurred in 11 (29%) and 3 (9%) cases, respectively (P = 0.036). CONCLUSIONS: Bipolar ablation of the LV free wall is highly effective at creating an appropriately deep epicardial lesion.

Characteristics and distribution of complex fractionated atrial electrograms and the dominant frequency during atrial fibrillation: relationship to the response and outcome of circumferential pulmonary vein isolation.

BACKGROUND: Although sites of complex fractionated electrograms (CFAEs) and dominant frequency (DF) are known to be critical for the maintenance of atrial fibrillation (AF), spatial distribution of CFAEs and DF and their impact on the outcome of AF ablation remain unclear. METHODS: We created CFAE and DF maps of the left atrium (LA), right atrium, and pulmonary veins (PVs) with a NavX mapping system and simultaneously calculated the DF values with a Bard LabSystem Pro in 40 patients with AF (nonparoxysmal, n = 16). RESULTS: In 19 patients in whom circumferential PV isolation (CPVI) terminated AF, there was a high DF in the PVs (Bard-based DF value, 6.70 ± 1.01 Hz), low DF in the LA body (5.94 ± 0.75 Hz), and a significant PV-to-LA body DF gradient (0.76 ± 0.65 Hz), and the CFAEs were located mainly in the PV antrum. In the 21 patients not responding to CPVI, a high DF was located in both the PVs (7.04 ± 0.81 Hz) and LA body (6.75 ± 0.81 Hz), and therefore, the PV-to-LA body DF gradient was smaller than that in the CPVI responders (0.29 ± 0.52 Hz, P = 0.0160), and the CFAEs extended to the LA body. The higher DF in the LA body, nonparoxysmal AF, and longer AF duration remained as independent predictors of a post-ablation AF recurrence by using a multivariate analysis. CONCLUSIONS: A higher LA-DF value, smaller PV-to-LA DF gradient, and wider LA-CFAE distribution were noted more often in the nonresponders to CPVI than in the responders. This suggested the presence of an arrhythmogenic substrate in the LA beyond the PVs in patients whose AF persisted after CPVI, which was further associated with post-ablation AF recurrence.