Shingen Owada

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.

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 (35×30 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.

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

Abstract 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.

High Correlation of Estimated Local Conduction Velocity with Natural Logarithm of Bipolar Electrogram Amplitude in the Reentry Circuit of Atrial Flutter

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.

Validation of Accuracy of Three‐Dimensional Left Atrial CartoSound™ and CT Image Integration: Influence of Respiratory Phase and Cardiac Cycle

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).

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.

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.

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.

Telediagnosis of heart failure with continuous intrathoracic impedance monitoring by Medtronic CareLink Network: Importance of the elevation pattern of OptiVol Fluid Index

The Medtronic implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy with defibrillator (CRT‐D) device is equipped with the OptiVol fluid status monitoring system, which continuously measures intrathoracic impedance and provides an early warning of thoracic fluid retention, which is indicative of decompensated heart failure (HF). The accuracy of the telediagnosis of HF with this system still remains to be elucidated.

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 (25 × 35 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. (PACE 2003; 26:2008–2015)