Effect of empagliflozin on ventricular arrhythmias in patients with type 2 diabetes treated with an implantable cardioverter-defibrillator: the EMPA-ICD trial.

BACKGROUND: Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce the risk of hospitalization for heart failure and cardiovascular death with type 2 diabetes; however, their effect on arrhythmias is unclear. The purpose of this study was to investigate the effects of empagliflozin on ventricular arrhythmias in patients with type 2 diabetes. METHODS: A total of 150 patients with type 2 diabetes who were treated with an implantable cardioverter-defibrillator or cardiac resynchronization therapy defibrillator (ICD/CRT-D) were randomized to once-daily empagliflozin or placebo for 24 weeks. The primary endpoint was the change in the number of ventricular arrhythmias from the 24 weeks before to the 24 weeks during treatment. Secondary endpoints included the change in the number of appropriate device discharges and other values. RESULTS: In the empagliflozin group, the number of ventricular arrhythmias recorded by ICD/CRT-D decreased by 1.69 during treatment compared to before treatment, while in the placebo group, the number increased by 1.79. The coefficient for the between-group difference was - 1.07 (95% confidence interval [CI] - 1.29 to - 0.86; P < 0.001). The change in the number of appropriate device discharges during and before treatment was 0.06 in the empagliflozin group and 0.27 in the placebo group, with no significant difference between the groups (P = 0.204). Empagliflozin was associated with an increase in blood ketones and hematocrit and a decrease in blood brain natriuretic peptide and body weight. CONCLUSIONS: In patients with type 2 diabetes treated with ICD/CRT-D, empagliflozin reduces the number of ventricular arrhythmias compared with placebo. Trial registration jRCTs031180120.

Occlusion and catheter ablation using a large-size cryoballoon for various pulmonary veins: a case series.

Background: It is established that pulmonary vein isolation using the POLARx™ (Boston Scientific, Marlborough, MA, USA) cryoballoon is a rapid, safe, and effective approach. The new POLARx™ FIT (Boston Scientific), which is expandable from 28 to 31 mm in diameter, is currently available. However, there is limited evidence available regarding the treatment of atrial fibrillation in this setting. In this article, we report a case series of cryoballoon ablation in patients with atrial fibrillation using POLARx™ FIT. Case summary: This case series describes a comparison of obstruction in three patients with pulmonary veins of different shapes and diameters undergoing cryoballoon ablation and pulmonary vein isolation with a 31 mm diameter balloon. Discussion: Cryoballoon ablation using the 31 mm mode of POLARx™ FIT has the potential to provide safe and stable pulmonary vein isolation with good occlusion for a variety of pulmonary vein geometries. In this case series, the 31 mm mode of the POLARx™ FIT resulted in better pulmonary vein occlusion than the 28 mm mode in patients with large left atria and large pulmonary veins, including the left common pulmonary vein. This approach may be considered a first-line therapy option of cryoballoon ablation in patients with atrial fibrillation.

Successful removal of a circular mapping catheter which perforated the pulmonary vein during cryoballoon ablation by lateral thoracotomy: a case report.

BACKGROUND: Serious complications may occur during cryoballoon ablation (CBA). However, pulmonary vein (PV) perforation by a circular mapping catheter and the strategy for removing the catheter remain poorly understood. CASE SUMMARY: A 40-year-old male presented with palpitations 2 years ago and was diagnosed with paroxysmal atrial fibrillation 5 months ago. He underwent CBA for paroxysmal atrial fibrillation. After isolation of the left PV, a circular mapping catheter was advanced in the right inferior pulmonary vein (RIPV), and single freeze was performed. After isolation of the PV, the catheter tip was immobile and could not be withdrawn with significant resistance. Computed tomography showed that the catheter tip perforated the posterior basal vein (V10) of the RIPV and remained in the right lower lobe, along with intrapulmonary haemorrhage. The patient underwent surgery via right lateral thoracotomy to remove the catheter. The RIPV was peeled to the periphery to expose the V10. The catheter perforated the vessel wall in the middle of the V10 and entered the pulmonary parenchyma. A microincision on the lung parenchyma covering the surface of the catheter tip was performed, and the circular distal portion of the catheter was cut. The entire catheter (i.e. shaft and proximal portion) was successfully removed from the transseptal catheter. DISCUSSION: Surgical approach was performed for the management of PV perforation caused by a circular mapping catheter. This case may assist in troubleshooting and problem-solving in case such an event occurs again during procedures in the future.

Radiofrequency catheter ablation for inappropriate sinus tachycardia in a patient with systemic lupus erythematosus: a case report.

BACKGROUND: Systemic lupus erythematosus (SLE) is known to cause inappropriate sinus tachycardia (IST). However, there is limited evidence available with regard to the treatment of IST in this setting. In this article, we report a case of drug refractory IST in a patient with SLE treated with radiofrequency catheter ablation (RFCA) using a non-contact mapping system. CASE SUMMARY: A 33-year-old woman had been diagnosed with SLE in 2001. She presented with complaints of persistent palpitations for 1 month and persistent sinus tachycardia. She underwent RFCA using a non-contact mapping system for drug refractory IST. The voltage and activation maps did not show obvious differences in the earliest activation site at heart rates (HRs) 90-150 b.p.m. In contrast, the areas of breakout sites were clearly distinguished between those from the normal P-wave zones at HR <140 b.p.m. and those from higher rate sites at HR >140 b.p.m. Radiofrequency catheter ablation was performed in those areas as the target for ablation. Thereafter, the symptoms steadily disappeared and the maximum HR-using 24-h Holter monitoring-decreased from 156 to 120 b.p.m. DISCUSSION: Radiofrequency catheter ablation using a non-contact mapping system was applied to the treatment of drug refractory IST in a patient with SLE. Of note, IST in such patients may be left untreated. This approach may be considered as a first-line therapy option for drug refractory IST in patients with SLE.

Relationship between Impairment of the Vascular Endothelial Function and the CHA2DS2-VASc Score in Patients with Sinus Rhythm and Non-valvular Atrial Fibrillation.

Objective and methods There is little information concerning the influence of the heart rhythm on the vascular endothelial function in patients with non-valvular atrial fibrillation (AF) compared with studies concerning sinus rhythm (SR). The present study included paroxysmal (n=184) or chronic (n=53) AF patients without heart failure and control subjects with SR (n=79) matched for age, gender and the CHA2DS2-VASc score. Paroxysmal AF was defined as episodes that terminated spontaneously within 7 days, while chronic AF was defined as longstanding AF that was refractory to cardioversion for 12 months or longer. There were no significant differences in the numbers of patients receiving renin-angiotension-aldosterone system inhibitors or statins among the three groups. Results Among the 237 AF patients (155 men, mean age 64±9 years, mean CHA2DS2-VASc score 1.8±1.4), the flow-mediated dilatation (FMD) was 5.4%±2.6% in the paroxysmal AF group, 4.3%±2.1% in the chronic AF group and 6.5%±3.5% in the SR group. There were significant differences among the 3 groups (all, p<0.05). Nitroglycerin-induced dilatation (NMD) was noted in 14.6%±6.5% of the paroxysmal AF group, 16.5%±9.1% of the chronic AF group and 12.7%±5.9% of the SR group, with no significant differences among the 3 groups. There was a significant negative correlation between the CHA2DS2-VASc scores and the FMDs value in all 3 groups (paroxysmal AF group:r=-0.322, p<0.01; chronic AF group:r=-0.291, p<0.05; SR group:r=-0.326, p<0.01). Conclusion In comparison with SR, the frequency and duration of AF episodes appear to cause deterioration of the vascular endothelial function.

Long Postpacing Interval After Entrainment of Tachycardia Including a Slow Conduction Zone Within the Circuit.

BACKGROUNDS: Postpacing interval (PPI) measured after entrainment pacing describes the distance between pacing site and reentrant circuit. However, the influential features to PPI remain to be elucidated. METHODS AND RESULTS: This study included 22 cases with slow/fast atrioventricular (AV) nodal reentrant tachycardia (AVNRT), 14 orthodromic AV reciprocating tachycardia (AVRT) using an accessary pathway, 22 typical atrial flutter (AFL), and 18 other macroreentrant atrial tachycardia (atypical AFL). Rapid pacing at a pacing cycle length (PCL) 5% shorter than tachycardia cycle length (TCL) was done from a site on or close to the reentry circuit. Pacing sites included the coronary sinus ostium in AVNRT, earliest atrial activation site in AVRT, and cavotricuspid isthmus in typical AFL. In atypical AFL, tachycardia circuit was determined on the basis of CARTO mapping, and then the pacing site was. TCL was significantly longer in AVNRT and AVRT than in typical AFL and atypical AFL (both P < 0.05). PCL minus TCL value was similar among the 4 groups. PPI minus TCL value (milliseconds) was significantly longer in AVNRT (median, 40 [IQR, 29-60.8]) and AVRT (34 [20-47]) than in typical AFL (0 [0-4]) and atypical AFL (3.5 [0-8]) (both P < 0.05). Furthermore, PPI minus TCL was prolonged with shortening of PCL in AVNRT and AVRT (both P < 0.05), whereas it was unchanged in typical AFL (P = 0.50). CONCLUSION: PPI after concealed entrainment is prolonged compared with TCL when the reentry circuit involves a slow conduction zone with a decremental conduction property such as the AV node.

Reduced residual conduction gaps and favourable outcome in contact force-guided circumferential pulmonary vein isolation.

AIMS: Although contact force (CF)-guided circumferential pulmonary vein isolation (CPVI) for paroxysmal atrial fibrillation (PAF) is useful, AF recurrence at long-term follow-up still remains to be resolved. The purpose of this study was to assess safety and efficacy of CF-guided CPVI and to compare residual conduction gaps during CPVI and long-term outcome between the conventional (non-CF-guided) and the CF-guided CPVI. METHODS AND RESULTS: We studied the 50 consecutive PAF patients undergoing CPVI by a ThermoCool EZ Steer catheter (conventional group, mean age 61 ± 10 years) and the other 50 consecutive PAF patients by a ThermoCool SmartTouch catheter (CF group, 65 ± 11 years). The procedure parameters and residual conduction gaps during CPVI, and long-term outcome for 12 months were compared between the two groups. Circumferential pulmonary vein isolation was successfully accomplished without any major complications in both groups. Total procedure and total fluoroscopy times were both significantly shorter in the CF group than in the conventional group (160 ± 30 vs. 245 ± 61 min, P < 0.001, and 17 ± 8 vs. 54 ± 27 min, P < 0.001, respectively). Total number of residual conduction gaps was significantly less in the CF group than in the conventional group (2.7 ± 1.7 vs. 6.3 ± 2.7, P < 0.05). The AF recurrence-free rates after CPVI during 12-month follow-up were 96% (48/50) in the CF group and 82% (41/50) in the conventional group (P = 0.02 by log rank test). Multivariate Cox regression analysis further supported this finding. CONCLUSION: Contact force-guided CPVI is safe and more effective in reducing not only the procedure time but also the AF recurrence than the conventional CPVI, possibly due to reduced residual conduction gaps during CPVI procedure.

CHA2DS2-VASc and HAS-BLED scores and activated partial thromboplastin time for prediction of high plasma concentration of dabigatran at trough.

INTRODUCTION: Although dabigatran, an oral direct thrombin inhibitor, does not require routine monitoring, high plasma concentration of dabigatran (PDC) at trough level is shown to be a high risk for bleeding in patients with nonvalvular atrial fibrillation (NVAF). As dabigatran prolongs the activated partial thromboplastin time (APTT), we examined relationships of PDC at trough with APTT and clinical features to identify patients at high risk for major bleeding during dabigatran treatment. MATERIALS AND METHODS: In the consecutive 48 patients with NVAF taking dabigatran at a daily dose of 220mg (n=32) or 300mg (n=16), we measured PDC using HEMOCLOT Thrombin Inhibitor assay and APTT ratio to control before (trough) and 2hours after taking dabigatran. RESULTS: PDC was positively correlated with APTT ratio (R(2)=0.64, p<0.0001). Using this regression equation and values of median trough PDC 116 (46.7-269) ng/mL observed in patients with major bleeding in the RE-LY trial, we calculated the expected value of APTT ratio corresponding to the 10th percentile of trough PDC (46.7). It was 1.20. There was a significant increase in trough PDC with increasing CHA2DS2-VASc score (p=0.01) and with increasing HAS-BLED score (p=0.01), especially in CHA2DS2-VASc score ≥4 and in HAS-BLED score ≥3, respectively. The highest trough PDC was obtained in patient group with CHA2DS2-VASc score ≥4, HAS-BLED score ≥3, or creatinine clearance ≤80, each combined with trough APTT ratio ≥1.20. CONCLUSIONS: This study provides an important clinical implication for identifying patients at high risk for major bleeding during dabigatran treatment in clinical practice.

Comparison of lesion formation between contact force-guided and non-guided circumferential pulmonary vein isolation: a prospective, randomized study.

BACKGROUND: Contact force (CF) monitoring could be useful in accomplishing circumferential pulmonary vein (PV) isolation (CPVI) for atrial fibrillation (AF). OBJECTIVE: The purpose of this study was to compare procedure parameters and outcomes between CF-guided and non-guided CPVI. METHODS: Thirty-eight consecutive AF patients (mean age 60 ± 11 years, 28 paroxysmal AF) undergoing CPVI were randomized to non-CF-guided (n = 19) and CF-guided (n = 19) groups. CPVI was performed with the ThermoCool SmartTouch catheter in both groups. The end-point was bidirectional block between the left atrium (LA) and PV. In the CF group, CF was kept between 10 and 20 g during CPVI, whereas in the non-CF group, all CF information was blanked. Radiofrequency energy at 30 W in the anterior and 25 W in the posterior LA wall was applied for 20-25 seconds at each point. RESULTS: CPVI was successfully accomplished without any major complications in both groups. Mean CF in the non-CF and CF groups were 5.9 ± 4.5 g and 11.1 ± 4.3 g, respectively, for left-side CPVI, and 9.8 ± 6.6 g and 12.1 ± 4.8 g, respectively, for right-side CPVI (both P <.001). The procedure and fluoroscopy times for CPVI in the non-CF and CF groups were 96 ± 39 minutes and 59 ± 16 minutes, respectively (P <.001), and 22 ± 63 seconds and 9 ± 20 seconds (P = NS), respectively. Total number of residual conduction gaps was 6.3 ± 3.0 in the non-CF group and 2.8 ± 1.9 in the CF group (P <.001). During 6-month follow-up, 84.2% of patients in the non-CF group and 94.7% in the CF group were free from any atrial tachyarrhythmias (P = .34). CONCLUSION: CF-guided CPVI is effective in reducing procedure time and additional touch-up ablation and may improve long-term outcome.

High correlation of estimated local conduction velocity with natural logarithm of bipolar electrogram amplitude in the reentry circuit of atrial flutter.

BACKGROUND: Low conduction velocity (CV) in the area showing low electrogram amplitude (EA) is characteristic of reentry circuit of atypical atrial flutter (AFL). The quantitative relationship between CV and EA remains unclear. We characterized AFL reentry circuit in the right atrium (RA), focusing on the relationship between local CV and bipolar EA on the circuit. METHODS AND RESULTS: We investigated 26 RA AFL (10 with typical AFL; 10 atypical incisional AFL; 6 atypical nonincisional AFL) using CARTO system. By referring to isochronal and propagation maps delineated during AFL, points activated faster on the circuit were selected (median, 7 per circuit). At the 196 selected points obtained from all patients, local CV measured between the adjacent points and bipolar EA were analyzed. There was a highly significant correlation between local CV and natural logarithm of EA (lnEA) (R(2) = 0.809, P < 0.001). Among 26 AFL, linear regression analysis of mean CV, calculated by dividing circuit length (152.3 ± 41.7 mm) by tachycardia cycle length (TCL) (median 246 msec), and mean lnEA, calculated by dividing area under curve of lnEA during one tachycardia cycle by TCL, showed y = 0.695 + 0.191x (where: y = mean CV, x = lnEA; R(2) = 0.993, P < 0.001). Local CV estimated from EA with the use of this formula showed a highly significant linear correlation with that measured by the map (R(2) = 0.809, P < 0.001). CONCLUSION: The lnEA and estimated local CV show a highly positive linear correlation. CV is possibly estimated by EA measured by CARTO mapping.

Validation of accuracy of three-dimensional left atrial CartoSound™ and CT image integration: influence of respiratory phase and cardiac cycle.

BACKGROUND: CartoSound™ (CS) module is useful in integrating 3-dimensional (3D) left atrial (LA) image with CT image. Integration method, however, has not been established. We reported the accuracy of LA electroanatomical (EA) and CT image integration by registering LA roof (LAR) and posterior wall (LAPW). METHODS: The consecutive 56 atrial fibrillation patients undergoing pulmonary vein isolation were studied. In the initial 29 patients, before the transseptal puncture, 3D CS LAR and LAPW image was created by registering a mean of 10 contour lines between the right and left pulmonary veins. After transseptally inserting a mapping catheter into LA, 3D EA image of LAR and LAPW was obtained by sampling a mean of 40 points. LA CT image was taken at the full-inspiratory position and 0% of R-R interval. After visual alignment of CS or EA and LA CT image, the 2 images were integrated with surface registration program. In the latter 27 patients, both CT and CS images were taken while matching the respiratory phase at the end-tidal position and cardiac cycle at 50% of R-R interval. RESULTS: In the initial 29 patients, the mean distances between EA and CT images and between CS and CT images were 1.53 ± 0.27 and 1.59 ± 0.23 mm, respectively (P = NS). In the latter 27, the mean distance was decreased to 1.08 ± 0.14 mm (P < 0.0001). CONCLUSIONS: CS system is useful in image integration with 3D CT. Matching both respiratory phase and cardiac cycle between CS and CT image acquisition improves the image integration accuracy.

Revisit of typical counterclockwise atrial flutter wave in the ECG: electroanatomic studies on the determinants of the morphology.

BACKGROUND: Cavotricuspid isthmus-dependent counterclockwise atrial flutter (typical AFL) is characterized by negative saw-tooth morphology flutter wave (F-wave) in the inferior leads, which is classified as type 1 with purely negative F-wave without positive terminal deflection (PTD), type 2 with small PTD, and type 3 with broad PTD. The determinants of these morphological differences remain to be elucidated. METHODS AND RESULTS: Of 72 patients (58 males, 65 ± 13 years) with typical AFL, 19 were classified as type 1 and 53 as types 2 and 3. We created an electroanatomic map of the right atrium (RA) during AFL and determined which RA site activation corresponded to which F-wave component by analyzing the activation map. It was revealed that F-wave component from the nadir to terminal deflection point coincided with the cranio-caudal activation of the RA free wall (RAFW) in all types. The bipolar voltage map showed that type 1 had the greater extent of low voltage (<0.5 mV) area (LVA) in RAFW (39 ± 24%) than types 2 and 3 (4 ± 3%) (P < 0.0001), explaining the absence of PTD in type 1. In types 2 and 3, F-wave amplitude determining the PTD magnitude was highly correlated with the longitudinal distance between two points on RAFW corresponding to the nadir and peak of F-wave (r = 0.73, P < 0.0001). CONCLUSIONS: Terminal positivity and amplitude of F-wave in typical AFL are primarily related to the RAFW activity: negatively by the extent of LVA and positively by the longitudinal vector of activation.

Three-dimensional cardiac image integration of electroanatomical mapping of only left atrial posterior wall with CT image to guide circumferential pulmonary vein ablation.

BACKGROUND: CARTO merge™ is used in integrating left atrial (LA) CARTO and computed tomography (CT) images, but the integration method is not established. The relative anatomic position and configuration of the LA posterior wall (LAPW) between the right and left pulmonary veins (PVs) are not greatly affected by respiration, LA contraction or hydration state. LAPW and adjacent roof area has an anatomically curved structure which is geometrically amenable to integration using a surface registration software. METHODS: We examined the accuracy of surface registration using only the LAPW CARTO image constructed by mapping of a mean of 101 ± 34 points in 108 consecutive AF patients before PV isolation. After visual alignment of CARTO LAPW and LA CT images using one anatomically defined position in each image, the two images were integrated with an installed surface registration program. Points with differences ≥ 4.0 mm between the two images were deleted (mean, 17 points/patient) and a second surface registration was performed. RESULTS: The mean distance between CARTO and CT images was 1.37 ± 0.23 mm, with mean minimum and maximum values of 0.03 and 3.99 mm, respectively. The accuracy of integration was verified in 34 patients by measuring the gaps between the catheter tip on the LA wall and the design line delineated for PV isolation on the integrated image. The gaps (mm) at the superior, inferior, anterior and posterior sites on the right PV side were 0.8 ± 0.5, 0.9 ± 0.7, 1.3 ± 1.0, and 0.8 ± 0.7, respectively, and those on the left side were 0.8 ± 0.5, 0.9 ± 0.7, 1.0 ± 0.5, and 1.0 ± 0.6, respectively. Thus, the gaps were all <1.0 mm, except for the right anterior aspect. CONCLUSIONS: These results show that surface registration using only the LAPW image can accurately integrate CARTO and CT images.

Effect of pilsicainide on dominant frequency in the right and left atria and pulmonary veins during atrial fibrillation: association with its atrial fibrillation terminating effect.

Dominant frequency reflects the peak cycle length of atrial fibrillation. In 34 patients with atrial fibrillation, bipolar electrograms were recorded from multiple atrial sites and pulmonary veins and the effect of pilsicainide, class Ic antiarrhythmic drug, on dominant frequency was examined. At baseline, mean dominant frequencies (Hz) in the right and left atria, coronary sinus and right and left superior pulmonary veins were 5.87 +/- 0.76, 6.08 +/- 0.60, 5.65 +/- 0.95, 6.12 +/- 0.88 and 6.59 +/- 0.89, respectively (P < 0.05, left superior pulmonary vein vs right atrium and coronary sinus). After pilsicainide (1.0 mg/kg/5 min), dominant frequency decreased at all sites in all patients. Atrial fibrillation was terminated at 5.9 +/- 2.2 min in 16 patients (Group A) with a decrease in the average of mean dominant frequencies at all sites from 5.80 +/- 0.72 to 3.57 +/- 0.63 Hz, was converted to atrial flutter at 7.3 +/- 1.4 min in 5 (Group B) with a decrease in the average dominant frequency from 5.83 +/- 0.48 to 3.08 +/- 0.19 Hz, and was not terminated in the other 13 (Group C) despite the average dominant frequency decrease from 6.59 +/- 0.76 to 4.42 +/- 0.52 Hz. In 14 of the 21 Groups A and B patients (67%), mean dominant frequencies at all recording sites were < 4.0 after pilsicainide, while they were < 4.0 in 1 of the 13 Group C patients (8%, P < 0.01). In conclusion, the degree of dominant frequency decrease by pilsicainide is closely related to its atrial fibrillation terminating effect: When dominant frequency in the atria decreases to < 4.0 Hz, atrial fibrillation is terminated with 93% positive and 63% negative predictive values.

Effects of amiodarone on electrical and structural remodeling induced in a canine rapid pacing-induced persistent atrial fibrillation model.

Structural in addition to electrical remodeling may be induced by persistent atrial fibrillation per se and make atrial fibrillation refractory to antiarrhythmic drug therapy. Matrix metalloproteinases (MMPs) contribute to structural remodeling in the interstitial space. Amiodarone is effective in treating persistent atrial fibrillation compared with other antiarrhythmic drugs. In mongrel dogs, right atrial pacing at 540 beats/min (bpm) was performed along with ventricular pacing at 100 bpm for 6 weeks after atrioventricular node ablation. Right atrial pacing at 400 bpm was continued for 4 weeks with (n=5) or without (n=5) oral amiodarone (30 mg/kg/day). In sham dogs, only ventricular pacing was done with (n=4) or without (n=6) amiodarone. In atrial pacing without amiodarone group, electrical remodeling characterized by monophasic action potential duration shortening, loss of action potential duration-rate adaptation and depressed conduction velocity and structural remodeling characterized by slightly but significantly increased interstitial fibrosis and enhanced MMP-2 activity compared with sham group were observed, and sustained atrial fibrillation was easily induced. In atrial pacing with amiodarone group, both electrical and structural remodeling were reversed and sustained atrial fibrillation was not induced. In sham group with amiodarone, action potential duration prolongation and depressed conduction velocity compared with sham without amiodarone were observed, but either increased fibrosis or enhanced MMP-2 activity was not observed. Not only electrical but structural remodeling were induced in a canine persistent atrial fibrillation model. Amiodarone reversed both of them, which may be related to its high efficacy in preventing recurrence of persistent atrial fibrillation.

"V-H-A Pattern" as a criterion for the differential diagnosis of atypical AV nodal reentrant tachycardia from AV reciprocating tachycardia.

BACKGROUND: During ventricular extrastimulation, His bundle potential (H) following ventricular (V) and followed by atrial potentials (A), i.e., V-H-A, is observed in the His bundle electrogram when ventriculo-atrial (VA) conduction occurs via the normal conduction system. We examined the diagnostic value of V-H-A for atypical form of atrioventricular nodal reentrant tachycardia (AVNRT), which showed the earliest atrial activation site at the posterior paraseptal region during the tachycardia. METHODS: We prospectively examined the response of VA conduction to ventricular extrastimulation during basic drive pacing performed during sinus rhythm in 16 patients with atypical AVNRT masquerading atrioventricular reciprocating tachycardia (AVRT) utilizing a posterior paraseptal accessory pathway and 21 with AVRT utilizing a posterior paraseptal accessory pathway. Long RP' tachycardia with RP'/RR > 0.5 was excluded. The incidences of V-H-A and dual AV nodal physiology (DP) were compared between atypical AVNRT and AVRT. RESULTS: V-H-A was demonstrated in all the 16 patients (100%) in atypical AVNRT and in only 1 of the 21 (5%) in AVRT (P < 0.001). DP was demonstrated in 10 patients (63%) in atypical AVNRT and in 4 (19%) in AVRT (P < 0.05). The sensitivity of V-H-A for atypical AVNRT was higher than that of DP (P < 0.05). Positive and negative predictive values were 94% and 100%, respectively, for V-H-A and 71% and 74%, respectively, for DP. CONCLUSIONS: The appearance of V-H-A during ventricular extrastimulation is a simple criterion for differentiating atypical AVNRT masquerading AVRT from AVRT utilizing a posterior paraseptal accessory pathway.

Mechanism of ST elevation and ventricular arrhythmias in an experimental Brugada syndrome model.

BACKGROUND: Although phase 2 reentry is said to be responsible for initiation of ventricular tachycardia (VT) in Brugada syndrome, information about the activation sequence during VT is limited. METHODS AND RESULTS: We developed an experimental Brugada syndrome model using a canine isolated right ventricular preparation cross-circulated with arterial blood of a supporter dog and examined the VT mechanism. Two plaque electrodes (35x30 mm) containing 96 bipolar electrodes were attached to the endocardium and epicardium. Saddleback and coved types of ST elevation in transmural ECG were induced by pilsicainide, a pure sodium channel blocker, and pinacidil, a KATP channel opener. Eighteen polymorphic VT episodes were recorded in 9 of the 12 preparations associated with ST elevation. Fourteen episodes spontaneously developed in 5 preparations after an extrasystole during basic drive pacing. Analysis of local recovery times revealed increased dispersion especially in epicardium, and the extrasystole originated from a site with a short recovery time, suggesting that phase 2 reentry was its mechanism. The other 4 VTs in 4 preparations were induced by premature stimulation. Analysis of the activation sequences during VT revealed reentry between epicardium and endocardium or reentry around an arc of a functional block confined to epicardium or endocardium with bystander activation of the other. CONCLUSIONS: Electrical heterogeneity in the recovery phase was induced in this experimental Brugada syndrome model, which can be a substrate for the development of phase 2 reentry and the subsequent reentry around an arc of the functional block, resulting in sustained VT.

[Relationship between duration of arrhythmia and subsequent preventive effect of disopyramide after cardioversion in patients with symptomatic paroxysmal and persistent atrial fibrillation].

OBJECTIVES: The relationship between the duration of arrhythmia and the subsequent long-term efficacy of disopyramide in preventing atrial fibrillation was investigated in patients with symptomatic paroxysmal and persistent atrial fibrillation. METHODS: A total of 60 patients (39 men, 21 women, mean age 65 +/- 11 years) were given disopyramide (300 mg/day) after electrical and pharmacological cardioversion based on American Heart Association Task Force on Practice Guidelines. The patients were divided into two types based on the duration of atrial fibrillation: conversion within 48 hr (group A, n = 35) and more than 48 hr (group B, n = 25) after the episode. Mean follow-up period was 47.1 +/- 28.7 months. RESULTS: Patient characteristics showed no statistically significant difference between groups A and B. The actuarial rates of maintenance of sinus rhythm at 1, 3, 6, 12, 18 and 24 months were 88.6%, 77.1%, 57.1%, 48.6%, 42.9% and 37.1%, respectively, in group A, and 72.0%, 44.0%, 28.0%, 16.0%, 12.0% and 8.0%, respectively, in group B. There was a significant difference in the rate at 24 months between groups A and B (p < 0.05). The periods for maintenance of sinus rhythm in groups A and B were 20.9 +/- 3.9 and 6.7 +/- 2.1 months, respectively, with a significant difference between groups A and B (p < 0.01). CONCLUSIONS: The efficacy of disopyramide in preventing the recurrence of atrial fibrillation varies with the duration of the previous episode. These results demonstrate that it is important to convert to normal sinus rhythm earlier to prevent the recurrence of atrial fibrillation in the long term.

Impaired longitudinal conduction in crista terminalis is necessary for sustenance of experimental atrial flutter.

Sustained atrial flutter (AFL) can be induced by creating a lesion between the vena cava in dogs. In previous studies on this model, the crista terminalis (CT) was often injured, and thus, role of CT in sustained reentry was not well understood. We hypothesized that impaired longitudinal conduction in CT is necessary for sustained AFL. In 16 anesthetized, open-chest dogs, linear radiofrequency ablation of the intercaval region was performed without interrupting CT. Intra-atrial conduction times (IAT) along CT were measured using a plaque electrode (25x35 mm) containing 30 bipolar electrodes before and after additional ablation of CT (group A, n=10) or the pectinate muscle (PM) region (group B, n=6). In group A, IAT along CT was 27 +/- 5 ms at baseline and was increased to 43 +/- 3 ms after ablation of CT (P<0.001). In group B, IAT along CT was 28 +/- 4 ms at baseline and 27 +/- 3 ms after ablation of PM (P=NS). Sustained AFL lasting >20 minutes was induced in 10/10 dogs in group A only after additional ablation of CT, and in 0/6 dogs in group B (P<0.001). The cycle lengths of AFL after ablation of the intercaval region and additional ablation of CT were 119 +/- 14 and 140 +/- 14 ms, respectively (P<0.01). There was a significant positive correlation between the cycle length of AFL and IAT along CT (r2=0.63, P<0.001). These results indicate that longitudinal conduction property in CT and not in PM strongly affects sustenance of AFL in this model.

[Comparison of the efficacies of disopyramide, cibenzoline and aprindine for the termination of paroxysmal and persistent atrial fibrillation in elderly and non-elderly patients].

OBJECTIVES: The relationship between the efficacy of the anticholinergic action of disopyramide, cibenzoline and aprindine and age was examined in patients with paroxysmal and persistent atrial fibrillation. METHODS: This prospective, randomized study included 278 patients (200 men, 78 women, mean age 61 +/- 11 years) divided into two groups; the non-elderly group (age below 60 years) and the elderly group (age over 60 years). Successful termination was defined as conversion of sinus rhythm within 30 min of intravenous administration of 50 mg disopyramide (n = 91), 70 mg cibenzoline (n = 93) or 100 mg aprindine (n = 94) in this prospective and randomized study. RESULTS: No statistically significant difference was found in patient characteristics between the three agents. 1) The rate of conversion to sinus rhythm after disopyramide administration in the non-elderly group(37.8%) was significantly higher than that in the elderly group (17.4%, p = 0.0361). 2) The rate of conversion to sinus rhythm after cibenzoline administration in the non-elderly group (62.2%) tended to be greater than that in the elderly group (43.8%, p = 0.0972). 3) The rate of conversion to sinus rhythm after aprindine administration in the non-elderly group (25.6%) was not significantly higher than that in the elderly group (18.2%, p = 0.4474). CONCLUSIONS: The anticholinergic action of antiarrhythmic agents has an effect on successful termination in non-elderly patients with paroxysmal and persistent atrial fibrillation.