The association between late-phase early recurrence within the blanking period after atrial fibrillation catheter ablation and long-term recurrence: Insights from a large-scale multicenter study.

BACKGROUND: The relationship between the timing of the first early recurrence and late recurrence after a single catheter ablation procedure for atrial fibrillation is controversial. METHODS: The Efficacy of Short-Term Use of Antiarrhythmic Drugs After Catheter Ablation for Atrial Fibrillation trial followed 2038 patients who underwent radiofrequency catheter ablation for atrial fibrillation. RESULTS: Of the patients, 907 (45%) had early recurrences within 90 days after the initial ablation. We divided these patients into two groups according to the timing of the first early recurrence episode, namely the ER1 group (early recurrence during the early phase; 0-30 days, n = 814) and ER2 group (early recurrence during the late phase; 31-90 days, n = 93). Three years after ablation, patients with early recurrences had a significantly lower event-free rate from late recurrences after a 90-day blanking period than patients without early recurrences (36.2% and 74.2%, respectively; log-rank, P < 0.0001). Three years after ablation, the event-free rate was significantly higher in the ER1 than the ER2 group (38.3% and 17.1%, respectively; log-rank, P < 0.0001). Moreover, the event-free rate at 3 years in the ER2 group was extremely low (5.6%) in patient with non-paroxysmal atrial fibrillation. CONCLUSION: Early recurrences were strongly associated with late recurrences, especially in patients with the first recurrence episode at >1 month within the blanking period after a single ablation procedure. Therefore, these patients should undergo close observation during follow-up, when they had especially with non-paroxysmal atrial fibrillation.

Efficacy of Antiarrhythmic Drugs Short-Term Use After Catheter Ablation for Atrial Fibrillation (EAST-AF) trial.

AIMS: Substantial portion of early arrhythmia recurrence after catheter ablation for atrial fibrillation (AF) is considered to be due to irritability in left atrium (LA) from the ablation procedure. We sought to evaluate whether 90-day use of antiarrhythmic drug (AAD) following AF ablation could reduce the incidence of early arrhythmia recurrence and thereby promote reverse remodelling of LA, leading to improved long-term clinical outcomes. METHODS AND RESULTS: A total of 2038 patients who had undergone radiofrequency catheter ablation for paroxysmal, persistent, or long-lasting AF were randomly assigned to either 90-day use of Vaughan Williams class I or III AAD (1016 patients) or control (1022 patients) group. The primary endpoint was recurrent atrial tachyarrhythmias lasting for >30 s or those requiring repeat ablation, hospital admission, or usage of class I or III AAD at 1 year, following the treatment period of 90 days post ablation. Patients assigned to AAD were associated with significantly higher event-free rate from recurrent atrial tachyarrhythmias when compared with the control group during the treatment period of 90 days [59.0 and 52.1%, respectively; adjusted hazard ratio (HR) 0.84; 95% confidence interval (CI) 0.73-0.96; P = 0.01]. However, there was no significant difference in the 1-year event-free rates from the primary endpoint between the groups (69.5 and 67.8%, respectively; adjusted HR 0.93; 95% CI 0.79-1.09; P = 0.38). CONCLUSION: Short-term use of AAD for 90 days following AF ablation reduced the incidence of recurrent atrial tachyarrhythmias during the treatment period, but it did not lead to improved clinical outcomes at the later phase.

Adenosine triphosphate-guided pulmonary vein isolation for atrial fibrillation: the UNmasking Dormant Electrical Reconduction by Adenosine TriPhosphate (UNDER-ATP) trial.

AIMS: Most of recurrent atrial tachyarrhythmias after pulmonary vein isolation (PVI) for atrial fibrillation (AF) are due to reconnection of PVs. The aim of the present study was to evaluate whether elimination of adenosine triphosphate (ATP)-induced dormant PV conduction by additional energy applications during the first ablation procedure could reduce the incidence of recurrent atrial tachyarrhythmias. METHODS AND RESULTS: We randomly assigned 2113 patients with paroxysmal, persistent, or long-lasting AF to either ATP-guided PVI (1112 patients) or conventional PVI (1001 patients). The primary endpoint was recurrent atrial tachyarrhythmias lasting for >30 s or those requiring repeat ablation, hospital admission, or usage of Vaughan Williams class I or III antiarrhythmic drugs at 1 year with the blanking period of 90 days post ablation. Among patients assigned to ATP-guided PVI, 0.4 mg/kg body weight of ATP provoked dormant PV conduction in 307 patients (27.6%). Additional radiofrequency energy applications successfully eliminated dormant conduction in 302 patients (98.4%). At 1 year, 68.7% of patients in the ATP-guided PVI group and 67.1% of patients in the conventional PVI group were free from the primary endpoint, with no significant difference (adjusted hazard ratio [HR] 0.89; 95% confidence interval [CI] 0.74-1.09; P = 0.25). The results were consistent across all the prespecified subgroups. Also, there was no significant difference in the 1-year event-free rates from repeat ablation for any atrial tachyarrhythmia between the groups (adjusted HR 0.83; 95% CI 0.65-1.08; P = 0.16). CONCLUSION: In the catheter ablation for AF, we found no significant reduction in the 1-year incidence of recurrent atrial tachyarrhythmias by ATP-guided PVI compared with conventional PVI.

Late re-conduction sites in the second session after pulmonary vein isolation using adenosine provocation for atrial fibrillation.

AIMS: Intravenous adenosine triphosphate (ATP) administration could reveal dormant conduction (DC) gaps on the ablation line of a pulmonary vein isolation (PVI). We compared the ATP-provoked DC sites in the initial PVI with the PV re-conduction sites in the second session in patients with paroxysmal atrial fibrillation (AF). METHODS AND RESULTS: We conducted a multicenter, observational study from a prospective registry undergoing AF ablation. A total of 110 consecutive drug-refractory paroxysmal AF patients were enroled in this study. Dormant conduction was detected by an ATP provocation of up to 40 mg during a continuous isoproterenol infusion (0.5-2 µg/min). The DC sites at each of the right and left PVs were precisely determined by using double spiral catheters under the guidance of a three-dimensional constructed anatomical mapping system. In the initial session, DC was observed in 35 patients (31.8%, 1.3 gaps/patient), and the sites of the DC were commonly observed in the carina region (43.5%). Atrial fibrillation recurrence was confirmed in 33 patients (30.0%) during follow-up (27.1 months), and a second session was performed in 24 of 33 patients (70.6%). In the second session, the re-conduction sites were also commonly observed in the carina region (59.5%). CONCLUSION: The carina region was still a dominant re-conduction site even after the elimination of any ATP-provoked DC in the index procedure.

Latent genetic backgrounds and molecular pathogenesis in drug-induced long-QT syndrome.

BACKGROUND: Drugs with I(Kr)-blocking action cause secondary long-QT syndrome. Several cases have been associated with mutations of genes coding cardiac ion channels, but their frequency among patients affected by drug-induced long-QT syndrome (dLQTS) and the resultant molecular effects remain unknown. METHODS AND RESULTS: Genetic testing was carried out for long-QT syndrome-related genes in 20 subjects with dLQTS and 176 subjects with congenital long-QT syndrome (cLQTS); electrophysiological characteristics of dLQTS-associated mutations were analyzed using a heterologous expression system with Chinese hamster ovary cells together with a computer simulation model. The positive mutation rate in dLQTS was similar to cLQTS (dLQTS versus cLQTS, 8 of 20 [40%] versus 91 of 176 [52%] subjects, P=0.32). The incidence of mutations was higher in patients with torsades de pointes induced by nonantiarrhythmic drugs than by antiarrhythmic drugs (antiarrhythmic versus others, 3 of 14 [21%] versus 5 of 6 [83%] subjects, P<0.05). When reconstituted in Chinese hamster ovary cells, KCNQ1 and KCNH2 mutant channels showed complex gating defects without dominant negative effects or a relatively mild decreased current density. Drug sensitivity for mutant channels was similar to that of the wild-type channel. With the Luo-Rudy simulation model of action potentials, action potential durations of most mutant channels were between those of wild-type and cLQTS. CONCLUSIONS: dLQTS had a similar positive mutation rate compared with cLQTS, whereas the functional changes of these mutations identified in dLQTS were mild. When I(Kr)-blocking agents produce excessive QT prolongation (dLQTS), the underlying genetic background of the dLQTS subject should also be taken into consideration, as would be the case with cLQTS; dLQTS can be regarded as a latent form of long-QT syndrome.

A novel KCNH2 mutation as a modifier for short QT interval.

In a 34-year-old man showing short QT interval (QTc 329 ms), we identified a novel C-terminal KCNH2 mutation, R1135H. Using a heterologous expression system with CHO cells, the mutant channels were found to display a significantly slow deactivation, which resulted in a gain-of-function for reconstituted 'I(Kr)' channels. This mutation could modify clinical phenotypes for this patient.

Dynamic change in ST-segment and spontaneous occurrence of ventricular fibrillation in Brugada syndrome with a novel nonsense mutation in the SCN5A gene during long-term follow-up.

A 67-year-old male underwent genetic testing under the diagnosis of Brugada syndrome because of recurrent ventricular fibrillation with coincident ST-segment elevation in either right precordial, inferior leads or both since the age of 55 years. Screening of gene mutations using denaturing high-performance liquid chromatography (DHPLC) and direct sequencing identified a novel nonsense mutation (R179X) of SCN5A in a heterozygous manner. The functional assay for the identified mutation, using a whole-cell patch clamp in the heterologous expression system, revealed that the nonsense mutation, located in the second transmembrane segment of the first domain (DI-S2) of the alpha-subunit, failed to synthesize the complete structure of the cardiac sodium channel, thus causing the non-functional channel. Coding effects by the gene mutation was altered during the 12-year follow-up, which might affect the clinical features of the patient through the ion channel density in the ventricle, dynamics of repolarization abnormality and conduction disturbance.

Identification of local myocardial repolarization time by bipolar electrode potential.

PURPOSE: The aim of this study was to investigate whether bipolar electrode potentials (BEPs) reflect local myocardial repolarization dynamics, using computer simulation. METHODS: Simulated action potential and BEP mapping of myocardial tissue during fibrillation was performed. The BEP was modified to make all the fluctuations have the same polarity. Then, the modified BEP (mBEP) was transformed to "dynamic relative amplitude" (DRA) designed to make all the fluctuations have the similar amplitude. RESULTS: The repolarization end point corresponded to the end of the repolarization-related small fluctuation that clearly appeared in the DRA of mBEP. Using the DRA of mBEP, we could reproduce the repolarization dynamics in the myocardial tissue during fibrillation. CONCLUSIONS: The BEP may facilitate identifying the repolarization time. Furthermore, BEP mapping has the possibility that it would be available for evaluating repolarization behavior in myocardial tissue even during fibrillation. The accuracy of activation-recovery interval was also reconfirmed.

A paradoxical effect of lidocaine for the N406S mutation of SCN5A associated with Brugada syndrome.

BACKGROUND: Accelerated intermediate inactivation, which is caused by mutations in the cardiac voltage-gated sodium channel alpha-subunit gene (SCN5A), is one of the molecular mechanisms underlying Brugada syndrome. The N406S mutation associated with Brugada syndrome results in the accelerated intermediate inactivation, in addition to unique pharmacological characteristics. METHODS: Functional sodium channels were expressed transiently in HEK293 cells by transfecting equally the alpha- and beta-subunit plasmids (1 microg/ml) and the sodium current were measured in whole-cell mode of patch-clamp recording. RESULTS: Since the N406S mutant channel has a greatly reduced use-dependent block of lidocaine, we took the advantage of the mutant channel to examine the effect of lidocaine on intermediate inactivation using wild-type (WT) and N406S mutant channels recombinantly expressed in HEK293 cells. Lidocaine (100 microM) slowed the recovery from the fast inactivation similarly for WT and N406S. On the other hand, whereas lidocaine slowed the recovery from the intermediate inactivation for WT, lidocaine accelerated the recovery for N406S. Activity-dependent loss of channel availability by repetitive 500-ms pulses was more strongly enhanced and accelerated by lidocaine for WT, but lidocaine exerted little effect on the N406S channel. CONCLUSION: We demonstrate that lidocaine may suppress Brugada syndrome associated with the N406S mutation by preventing the sodium channel from accumulating in the intermediate inactivation state.

Gender and age effects on ventricular repolarization abnormality in Japanese general carriers of a G643S common single nucleotide polymorphism for the KCNQ1 gene.

BACKGROUND: The KCNQ1 single nucleotide polymorphism (SNP), G643S, is known to be associated with secondary long QT syndrome (LQTS) and to cause a mild reduction in KCNQ1 current. However, the precise incidence and its association with QT intervals remain unknown in the greater cohort of the population in Japan. METHODS AND RESULTS: The genotype was screened at codon 643 of KCNQ1 in 992 residents of a farming community. Eighty-eight individuals (female/male =52/36, 8.9%) were found to have a heterozygous G643S SNP. Matching both gender and age, we randomly selected 243 control (G643G) cases and compared the electrocardiogram parameters in both groups; QT, QTf (QT corrected by Fridericia's formula) intervals, the peak and the end of the T wave (Tpe) interval, and the Tpe/QT ratio. The latter 2 reflect the transmural dispersion of ventricular repolarization (TDR). In G643S carriers, both Tpe and Tpe/QT were significantly longer than in non-carriers, without significant QT prolongation. Both genders showed a tendency for an increase in QTf with aging. In females, both Tpe and Tpe/QT showed a similar significant increase with age, which was not observed in males. CONCLUSIONS: In elderly females, G643S might be an independent risk factor for secondary LQTS by causing a greater TDR.

Refractory gradient is responsible for the increase in ventricular vulnerability under sodium channel blockade.

BACKGROUND: Previous studies have shown that sodium channel (I(Na)) blockade increases ventricular vulnerability; however, there were differences in the degree of the increase. Because the vulnerable window (VW) is altered by the type of preshock refractory gradient (RG), the hypothesis was that the differences in the arrhythmogenesis of I(Na) blockade result from the different types of preshock RG employed. METHODS AND RESULTS: Simulations of regio(Na)l electric shock following constant pacing stimuli in 2-dimensional bidomain myocardial sheets under I(Na) blockade were conducted using 3 types of preshock RG: longitudinally tilted (LRG), transversely tilted (TRG), and non-tilted RG (NRG). The increase in the degree of I(Na) blockade almost linearly decreased the conduction velocity. The action potential duration in the LRG and TRG cases was non-linearly shortened with the increase in INa blockade because of electrotonic influences, whereas in the case of NRG it was slightly prolonged. In both LRG and TRG cases, the VW for reentry induction by electric shock was considerably widened by the INa blockade; however, this was not the case for NRG in which the VW was rather narrowed by the INa blockade. CONCLUSION: The type of preshock RG alters the degree of the increase in ventricular vulnerability under INa blockade.

Vortex cordis as a mechanism of postshock activation: arrhythmia induction study using a bidomain model.

INTRODUCTION: The ventricular apex has a helical arrangement of myocardial fibers called the "vortex cordis." Experimental studies have demonstrated that the first postshock activation originates from the ventricular apex, regardless of the electrical shock outcome; however, the related underlying mechanism is unclear. We hypothesized that the vortex cordis contributes to the initiation of postshock activation. To clarify this issue, we numerically studied the transmembrane potential distribution produced by various electrical shocks. METHODS AND RESULTS: Using an active membrane model, we simulated a two-dimensional bidomain myocardial tissue incorporating a typical fiber orientation of the vortex cordis. Monophasic or biphasic shock was delivered via two line electrodes located at opposite tissue borders. Transmembrane potential distribution during the monophasic shock at the center of the vortex cordis showed a gradient high enough to initiate postshock activation. The postshock activation from the center of the vortex cordis was not suppressed, regardless of the initiation of spiral wave reentry. Spiral wave reentry was induced by the monophasic shock when the center area of the vortex cordis was partially excited by the nonuniform virtual electrode polarization. Postshock activation following the biphasic shock also originated from the center of the vortex cordis, but it tended to be suppressed due to the narrower excitable gap around the center of the vortex cordis. The electroporation effect, which was maximal at the center of the vortex cordis, is another possible mechanism of postshock activation. CONCLUSION: Our simulations suggest that the vortex cordis may cause postshock activation.

Afterdepolarizations promote the transition from ventricular tachycardia to fibrillation in a three-dimensional model of cardiac tissue.

Recent experimental results regarding the action potential duration restitution curve have explained the transition from ventricular tachycardia (VT) to fibrillation (VF) in terms of spiral wave (SW) meandering and breakup. However, it remains unclear whether VF always has a steep restitution curve. The present study was designed to test the hypothesis that afterdepolarizations occur at excitable gaps during VF and affect the SW dynamics, even if the restitution curve is gentle. Homogeneous and isotropic 3-dimensional tissue was simulated with a LRd model. Because of the gentle restitution curve, it was not expected that SW instabilities would occur in this condition. In the tissue, a stationary SW reentry was initially observed; however, afterdepolarizations erupted from the excitable gap near the SW tip, and the SW then meandered widely. Following that, afterdepolarizations erupted far from the SW tip, resulting in SW breakup. In this manner, the wave dynamics degenerated into a chaotic state within a few seconds. Furthermore, not only triggered activity but also subthreshold afterdepolarizations were found to cause SW instabilities. These results suggest that afterdepolarizations may play an important role in the transition to VF and that the mechanism is independent of restitution properties.

Differences in sympathetic and vagal effects on paroxysmal atrial fibrillation: a simulation study.

The incidence of paroxysmal atrial fibrillation (AF) is affected by circadian variations in the vago-sympathetic balance. It is well known that both sympathetic and vagal effects increase the onset of paroxysmal AF, due to the shortened action potential duration. However, the reason why the vagally-mediated paroxysmal AF is maintained more than the adrenergically-mediated paroxysmal AF has remained unclear. In order to clarify this, we performed the following computer simulations. First, we constructed a homogeneous two-dimensional myocardial sheet (4.5 x 2.25 cm), using a bidomain ion channel model. The sympathetic and vagal effects were achieved by modifications of the ion channel conductance (Sympathetic effect: increased gSI and increased gK. Vagal effect: increased gK and increased gK1 with or without the dispersion of refractoriness). We found that the sympathetic effect shortened the action potential duration and flattened the restitution slope; therefore, this effect promoted spiral wave induction and restrained the spiral wave breakup. On the other hand, we found that the vagal effect also shortened the action potential duration and flattened the restitution slope; however, this effect promoted spiral wave breakup, due to the increase in both the IK1 and the dispersion of refractoriness. Overall, the differences between the sympathetic and vagal effects on the tendency toward spiral wave break-up may explain the reason why adrenergically-mediated paroxysmal AF terminates spontaneously and vagally-mediated paroxysmal AF tends to be maintained. In conclusion, our results may be helpful in understanding the difference in the action of sympathetic and vagal effects on paroxysmal AF.