Ablation perioperative dabigatran in use envisioning in Japan: The ABRIDGE-J Study Design

BACKGROUND

Catheter ablation has become a standard treatment strategy for drug-resistant symptomatic non-valvular atrial fibrillation (NVAF). Periprocedural administration of uninterrupted warfarin could reduce the risk of thromboembolic complications. However, only a few retrospective studies have reported on the efficacy and safety of periprocedural dabigatran use.

METHOD

ABRIDGE is a prospective, randomized, parallel-group, controlled study that aims to evaluate the efficacy and safety of dabigatran compared with warfarin during the perioperative period of catheter ablation. Patients with drug-resistant paroxysmal NVAF from multiple Japanese ablation centers will be randomized using a 1:1 matrix. The main outcome measures include the incidence of embolism during the perioperative period and presence or absence of an intracardiac thrombus just before ablation. The secondary outcome measures include the incidence of all types of bleeding during the perioperative period, incidence of bleeding or thromboembolic events during the perioperative period and within 6 months after the procedure, duration of hospitalization, vascular death, all-cause mortality, net clinical benefit, and all adverse events.

CONCLUSION

In this study, we aim to evaluate the efficacy and safety of dabigatran compared with warfarin during the perioperative period in candidates for catheter ablation of NVAF. Moreover, we hope to obtain objective data that may guide the selection and usage of anticoagulants during catheter ablation.

Verapamil-Sensitive Upper Septal Idiopathic Left Ventricular Tachycardia: Prevalence, Mechanism, and Electrophysiological Characteristics

OBJECTIVES

This study sought to demonstrate the prevalence, mechanism, and electrocardiographic and electrophysiological characteristics of upper septal idiopathic left fascicular ventricular tachycardia (US-ILVT).

BACKGROUND

ILVT is classified into left anterior and posterior types with no clear data about US-ILVT.

METHODS

Among 193 ILVT patients, we identified 12 patients (6.2%; age 41 ± 22 years, 7 men) with US-ILVT.

RESULTS

Of 12 patients with US-ILVT, 6 patients (50%) had previous history of radiofrequency catheter ablation for common ILVT. Sustained VT (cycle length: 349 ± 53 ms) was seen in all patients with a QRS interval slightly wider (104 ± 18 ms) than that during sinus rhythm (90 ± 19 ms). The VT exhibited an identical QRS configuration as sinus rhythm in 6 (50%) and incomplete right bundle branch block configuration in another 6. His-ventricular interval during VT was always shorter than that during sinus rhythm (27 ± 5 ms vs. 47 ± 10 ms). Purkinje potentials were activated in a reverse direction to that of common ILVT; namely, the diastolic potential (P₁) was activated retrogradely but the pre-systolic potential (P₂) was activated antegradely. At the left upper-middle ventricular septum, P₁ potential was recorded during VT, preceding the QRS by 54 ± 20 ms. Radiofrequency catheter ablation at that site eliminated the VT with no recurrence during a 58 ± 35 months of follow-up.

CONCLUSIONS

US-ILVT is an identifiable VT that shares common criteria with ILVT and has a narrow QRS interval. Some US-ILVT cases appeared after common ILVT ablation. It is a reverse type of common ILVT (orthodromic form) with baseline morphological abnormalities that might provide a potential substrate for such VT.

Genetic defects in a His-Purkinje system transcription factor, IRX3, cause lethal cardiac arrhythmias

AIM

Ventricular fibrillation (VF), the main cause of sudden cardiac death (SCD), occurs most frequently in the acute phase of myocardial infarction: a certain fraction of VF, however, develops in an apparently healthy heart, referred as idiopathic VF. The contribution of perturbation in the fast conduction system in the ventricle, the His-Purkinje system, for idiopathic VF has been implicated, but the underlying mechanism remains unknown. Irx3/IRX3 encodes a transcription factor specifically expressed in the His-Purkinje system in the heart. Genetic deletion of Irx3 provides a mouse model of ventricular fast conduction disturbance without anatomical or contraction abnormalities. The aim of this study was to examine the link between perturbed His-Purkinje system and idiopathic VF in Irx3-null mice, and to search for IRX3 genetic defects in idiopathic VF patients in human.

METHODS AND RESULTS

Telemetry electrocardiogram recording showed that Irx3-deleted mice developed frequent ventricular tachyarrhythmias mostly at night. Ventricular tachyarrhythmias were enhanced by exercise and sympathetic nerve activation. In human, the sequence analysis of IRX3 exons in 130 probands of idiopathic VF without SCN5A mutations revealed two novel IRX3 mutations, 1262G>C (R421P) and 1453C>A (P485T). Ventricular fibrillation associated with physical activities in both probands with IRX3 mutations. In HL-1 cells and neonatal mouse ventricular myocytes, IRX3 transfection up-regulated SCN5A and connexin-40 mRNA, which was attenuated by IRX3 mutations.

CONCLUSION

IRX3 genetic defects and resultant functional perturbation in the His-Purkinje system are novel genetic risk factors of idiopathic VF, and would improve risk stratification and preventive therapy for SCD in otherwise healthy hearts.

Seasonal, weekly, and circadian distribution of ventricular fibrillation in patients with J-wave syndrome from the J-PREVENT registry

BACKGROUND

Ventricular fibrillation (VF) in Brugada syndrome (BrS) is known to occur more frequently during nighttime and from spring to early summer. In this study, we investigated whether early repolarization syndrome (ERS) has the same seasonal, weekly, and circadian distribution of VF events as BrS using data from the "J-wave associated with prior cardiac event" (J-PREVENT) registry.

METHODS

The study included 90 consecutive patients with BrS and 31 patients with ERS during a mean follow-up of 49±37 months. Follow-up data from implantable cardioverter-defibrillators were evaluated in all cases.

RESULTS

In patients with ERS, the circadian distribution of VF episodes differed among the four 6-h periods, with a significant peak from midnight to 6:00 am (p<0.01) similar to that observed in BrS patients. However, VF occurred more frequently on weekends in patients with ERS, whereas on weekdays in patients with BrS (p<0.01). The months of peak VF occurrence also differed between the groups, with the frequency of VF episodes at peak between December and March in ERS patients and between March and June in BrS patients. In ERS patients, VF events had an inverse correlation with air temperature (r=-0.726, p<0.01).

CONCLUSIONS

ERS and BrS patients show similar nighttime increases in the occurrence of VF, but different seasonal and weekly distributions, suggesting a pathophysiological difference between the two syndromes.

Difference in the Clinical Characteristics of Ventricular Fibrillation Occurrence in the Early Phase of an Acute Myocardial Infarction Between Patients With and Without J Waves

INTRODUCTION

We recently showed that the presence of J waves increases the risk of ventricular fibrillation (VF) occurrence in the early phase of an acute myocardial infarction (AMI). This study aimed to evaluate the clinical characteristics of VF occurrences in the early phase of an AMI between patients with and without J waves.

METHODS AND RESULTS

This retrospective, observational study included 281 consecutive patients with an AMI (69 ± 12 years; 207 men) in whom 12-lead ECGs before AMI onset could be evaluated. The patients were classified based on a VF occurrence <48 hours after AMI onset and the presence of J waves. J waves were electrocardiographically defined as an elevation of the terminal portion of the QRS complex of >0.1 mV from baseline in at least 2 contiguous inferior or lateral leads. VF occurred in 24 patients, and J waves were present in 37. VF occurrence was more prevalent in the patients with than without J waves (27% vs. 6%; P < 0.001). Among the 244 patients without J waves, peak creatine kinase level (P < 0.01), number of diseased coronary arteries (P < 0.01), and male sex (P < 0.05) were higher in the patients with than without VF occurrence. However, among the 37 patients with J waves, there was no significant difference in these variables. There was no association between the location of J waves and the infarct area.

CONCLUSIONS

In patients with AMI, those with J waves were more likely to develop VF and less likely to have high-risk clinical characteristics than those without J waves.

Epicardial Catheter Ablation of Ventricular Tachycardia in No Entry Left Ventricle

Background—

In patients with mechanical aortic and mitral valves and left ventricular tachycardia, catheter ablation may be prevented by limited access to the left ventricle.

Methods and Results—

In our series of 6 patients, 2 patients underwent direct surgical ablation and 4 underwent epicardial catheter ablation via a pericardial window. All patients had abnormal low voltage areas with fractionated or delayed isolated potentials on the apical epicardium. Most of the ventricular tachycardias were targeted by pace mapping. Sites with a good pace match or abnormal electrograms were ablated using an irrigated radiofrequency ablation catheter. A microscopic pathological evaluation of the resected tissue from 2 of the open-heart ablation patients revealed dense fibrosis on the epicardium compared with the endocardium, supporting the feasibility of an epicardial ablation for the ventricular tachycardia.

Conclusions—

Epicardial catheter ablation of ventricular tachycardia is a potentially useful therapy in patients who have mechanical aortic and mitral valves.

Role of electrophysiological studies in predicting risk of ventricular arrhythmia in early repolarization syndrome

BACKGROUND

The early repolarization (ER) pattern is associated with an increased risk of arrhythmogenic sudden death. However, strategies for risk stratification of patients with the ER pattern are not fully defined.

OBJECTIVES

This study sought to determine the role of electrophysiology studies (EPS) in risk stratification of patients with ER syndrome.

METHODS

In a multicenter study, 81 patients with ER syndrome (age 36 ± 13 years, 60 males) and aborted sudden death due to ventricular fibrillation (VF) were included. EPS were performed following the index VF episode using a standard protocol. Inducibility was defined by the provocation of sustained VF. Patients were followed up by serial implantable cardioverter-defibrillator interrogations.

RESULTS

Despite a recent history of aborted sudden death, VF was inducible in only 18 of 81 (22%) patients. During follow-up of 7.0 ± 4.9 years, 6 of 18 (33%) patients with inducible VF during EPS experienced VF recurrences, whereas 21 of 63 (33%) patients who were noninducible experienced recurrent VF (p = 0.93). VF storm occurred in 3 patients from the inducible VF group and in 4 patients in the noninducible group. VF inducibility was not associated with maximum J-wave amplitude (VF inducible vs. VF noninducible; 0.23 ± 0.11 mV vs. 0.21 ± 0.11 mV; p = 0.42) or J-wave distribution (inferior, odds ratio [OR]: 0.96 [95% confidence interval (CI): 0.33 to 2.81]; p = 0.95; lateral, OR: 1.57 [95% CI: 0.35 to 7.04]; p = 0.56; inferior and lateral, OR: 0.83 [95% CI: 0.27 to 2.55]; p = 0.74), which have previously been demonstrated to predict outcome in patients with an ER pattern.

CONCLUSIONS

Our findings indicate that current programmed stimulation protocols do not enhance risk stratification in ER syndrome.

Novel mutation in the α-myosin heavy chain gene is associated with sick sinus syndrome

BACKGROUND

Recent genome-wide association studies have demonstrated an association between MYH6, the gene encoding α-myosin heavy chain (α-MHC), and sinus node function in the general population. Moreover, a rare MYH6 variant, R721W, predisposing susceptibility to sick sinus syndrome has been identified. However, the existence of disease-causing MYH6 mutations for familial sick sinus syndrome and their underlying mechanisms remain unknown.

METHODS AND RESULTS

We screened 9 genotype-negative probands with sick sinus syndrome families for mutations in MYH6 and identified an in-frame 3-bp deletion predicted to delete one residue (delE933) at the highly conserved coiled-coil structure within the binding motif to myosin-binding protein C in one patient. Co-immunoprecipitation analysis revealed enhanced binding of delE933 α-MHC to myosin-binding protein C. Irregular fluorescent speckles retained in the cytoplasm with substantially disrupted sarcomere striation were observed in neonatal rat cardiomyocytes transfected with α-MHC mutants carrying delE933 or R721W. In addition to the sarcomere impairments, delE933 α-MHC exhibited electrophysiological abnormalities both in vitro and in vivo. The atrial cardiomyocyte cell line HL-1 stably expressing delE933 α-MHC showed a significantly slower conduction velocity on multielectrode array than those of wild-type α-MHC or control plasmid transfected cells. Furthermore, targeted morpholino knockdown of MYH6 in zebrafish significantly reduced the heart rate, which was rescued by coexpressed wild-type human α-MHC but not by delE933 α-MHC.

CONCLUSIONS

The novel MYH6 mutation delE933 causes both structural damage of the sarcomere and functional impairments on atrial action propagation. This report reinforces the relevance of MYH6 for sinus node function and identifies a novel pathophysiology underlying familial sick sinus syndrome.

Anemia and reduced kidney function as risk factors for new onset of atrial fibrillation (from the Ibaraki prefectural health study)

Chronic kidney disease (CKD) is a potential independent risk factor for atrial fibrillation (AF). It remains unclear whether anemia is synergistically associated with increased risk of AF onset in subjects with CKD. We evaluated the association of kidney function, hemoglobin (Hb), and their combination with new-onset AF in a population-based cohort study. We conducted a 15-year prospective cohort study of 132,250 Japanese subjects aged 40 to 79 years who participated in annual health checkups from 1993. Kaplan-Meier survival analysis was used to compare freedom from new-onset AF between groups classified by estimated glomerular filtration rate grade, Hb grade, and their combination. Cox proportional hazard model analysis was used to estimate hazard ratios (HRs) for new-onset AF. During a 13.8-year mean follow-up period, 1,232 (0.93%) subjects with new-onset AF were identified. Lower estimated glomerular filtration rate and lower Hb grades were significantly associated with a higher incidence of new-onset AF. Multivariate HRs and 95% confidence intervals (CIs) of new-onset AF were 1.38 (1.21 to 1.56) for mild CKD group, 2.56 (2.09 to 3.13) for CKD group, and 1.50 (1.24 to 1.83) for anemia group. Borderline Hb level was not significantly associated with increased risk for new-onset AF (HR 1.07, CI 0.91 to 1.25, p = 0.4284). In the model with interaction term between CKD and anemia, the risk was significantly higher (p = 0.0343 for the interaction) than that predicted by each factor independently. In conclusion, decreased kidney function and lower Hb level are associated with increased risk for new-onset AF, especially when both are present.

The QRS morphology pattern in V5R is a novel and simple parameter for differentiating the origin of idiopathic outflow tract ventricular arrhythmias

AIMS

There are many reports on the ECG characteristics of idiopathic outflow tract ventricular arrhythmias (OT-VAs) to predict their origin. However, differentiating near regions using 12-lead ECGs is still complicated. The synthesized 18-lead ECG derived from the 12-lead ECG can provide virtual waveforms of the right-sided chest leads (V3R, V4R, and V5R) and back leads (V7, V8, and V9). The aim of this study was to develop a simple and useful parameter for differentiating OT-VA origins using the 18-lead ECG.

METHODS AND RESULTS

We studied 28 and 73 patients with idiopathic VAs in a pacemapping study and validation cohort, respectively. In the pacemapping study, several sites out of five different sites were paced in each patient: the anterior and posterior right ventricular OT (RVOT-ant and RVOT-post), right and left coronary cusps (RCC and LCC), and junction of both cusps (RLJ). The 18-lead ECGs during pacemapping among the five sites were compared for establishing a simple parameter to predict VA origins. A novel parameter using 18-lead ECGs was tested prospectively in 73 patients. In the pacemapping study, the dominant QRS morphology pattern in the synthesized V5R significantly differed among those sites (RVOT-ant:Rs, RVOT-post:rS, RCC:QS, RLJ:qR, and LCC:R). The patients in the validation cohort were divided into five groups depending on those QRS morphology patterns during VAs in the synthesized V5R. Each V5R QRS morphology pattern could predict a precise origin of the OT-VAs with an overall accuracy of 75%.

CONCLUSION

The QRS morphology pattern in V5R was a simple and useful parameter for differentiating detailed OT-VA origins.

Trigger elimination of polymorphic ventricular tachycardia and ventricular fibrillation by catheter ablation: trigger and substrate modification

Ventricular fibrillation (VF) is a malignant arrhythmia, usually initiated by a ventricular premature contraction (VPC) during the vulnerable period of cardiac repolarization. Ablation therapy for VF has been described and increasingly reported. Targets for VF triggers are VPCs preceded by Purkinje potentials or from the right ventricular outflow tract (RVOT) in structurally normal hearts, and VPC triggers preceded by Purkinje potentials in ischemic cardiomyopathy. During the session, mapping should be focused on the earliest activation and determining the earliest potential is the key to a successful ablation. However, suppression of VF can be achieved by not only the elimination of triggering VPCs, but also by substrate modification of possible reentry circuits in the Purkinje network, or between the PA and RVOT. The most important issue before the ablation session is the recording of the 12-lead ECG of the triggering event, which can prove invaluable in regionalizing the origin of the triggering VPC for more detailed mapping. In cases where the VPC is not spontaneous or inducible, ablation may be performed by pace mapping. Further studies are needed to evaluate the precise mechanisms of this arrhythmia.

Left septal atrial tachycardia after open-heart surgery: relevance to surgical approach, anatomical and electrophysiological characteristics associated with catheter ablation, and procedural outcomes

BACKGROUND

Septal atrial tachycardia (AT) can occur in patients without structural heart disease and in patients with previous catheter ablation of atrial fibrillation. We aimed to assess septal AT that occurs after open-heart surgery.

METHODS AND RESULTS

This study comprised 20 consecutive patients undergoing catheter ablation of macroreentrant AT after open-heart surgery. Relevance to surgical approach, mechanisms, anatomic and electrophysiological characteristics, and outcomes were assessed. Septal AT was identified in 7 patients who had all undergone mitral valve surgery. All septal ATs were localized in the left atrial septum, whereas 10 of 13 nonseptal ATs originated from the right atrium. Patients with left septal AT had a thicker fossa ovalis (median, 4.0; 25th-75th percentile, 3.6-4.2 versus 2.3; 1.6-2.6 mm; P=0.006) and broader area of low voltage (<0.3 mV) in the septum than patients with nonseptal AT (82; 76-89 versus 31; 28%-36%; P=0.02). Repeated gradual prolongations of the tachycardia cycle length without change of the septal circuit were observed in all patients with septal AT (70; 63-100 versus 15; 10-40 ms; P=0.0008). Although ablation terminated all ATs, recurrence of targeted ATs was more frequent in patients with left septal AT during 30-month follow-up (71 versus 0%; P=0.001).

CONCLUSIONS

Left septal AT after open-heart surgery was characterized by a thicker septum, more scar burden in the septum, and repeated prolongations of the tachycardia cycle length during ablation. Such an arrhythmogenic substrate may interfere with transmural lesion formation by ablation and may account for higher likelihood of recurrence of left septal AT.

Mapping and ablating ventricular premature contractions that trigger ventricular fibrillation: trigger elimination and substrate modification

Ventricular fibrillation (VF) is a malignant arrhythmia, usually initiated by a ventricular premature contraction (VPC) during the vulnerable period of cardiac repolarization. Ablation therapy for VF has been described and increasingly reported. Targets for VF triggers are VPC preceded Purkinje potentials or the right ventricular outflow tract (RVOT) in structurally normal hearts, and VPC triggers preceded by Purkinje potentials in ischemic cardiomyopathy. The most important issue before the ablation session is the recording of the 12-lead electrocardiogram (ECG) of the triggering event, which can prove invaluable in regionalizing the origin of the triggering VPC for more detailed mapping. In cases where the VPC is not spontaneous or inducible, ablation may be performed by pacemapping. During the session, mapping should be focused on the earliest activation and determining the earliest potential is the key to a successful ablation. However, a modification of the Purkinje network might be applied when the earliest site cannot be determined or is located close to the His-bundle. Furthermore, the electrical isolation of the pulmonary artery (PA) can suppress RVOT type polymorphic ventricular tachycardia in some patients with rapid triggers from the PA. Suppression of VF can be achieved by not only the elimination of triggering VPCs, but also by substrate modification of possible reentry circuits in the Purkinje network, or between the PA and RVOT. Further studies are needed to evaluate the precise mechanisms of this arrhythmia.

Clinical and procedural predictors of early complications of ablation for atrial fibrillation: analysis of the national registry data

BACKGROUND

The risk assessment of the complication from atrial fibrillation (AF) ablation is important and needs to be updated.

OBJECTIVE

The purpose of this study was to investigate the clinical and procedural factors associated with AF ablation-related early complications.

METHODS

The Japanese Heart Rhythm Society invited electrophysiology centers in Japan to register data regarding all AF ablation procedures performed in September 2011, March 2012, and September 2012. Of the 46 putative predictors assessed in the univariate analysis, significant variables (P < .1) were entered into a stepwise logistic regression model for multivariate analysis.

RESULTS

Data for 3373 cases were submitted by 165 centers, with 158 early complications reported in 151 patients (4.5%). We identified 13 significant variables in the univariate analysis. Multivariate analysis revealed that 8 (62%) of them were independent predictors of early complications. Female sex (odds ratio and 95% confidence interval 1.6; 1.13-2.27), hypertrophic cardiomyopathy (2.2; 1.08-4.5), valvular heart disease (2.53; 1.28-5.05), deep sedation during the procedure (1.53; 1.09-2.12), and complex fractionated atrial electrocardiogram ablation (1.88; 1.23-2.87) increased early complications. Preprocedural transesophageal echocardiography (0.63; 0.43-0.92), irrigated-tip catheter use (0.46; 0.3-0.69), and periprocedural novel oral anticoagulant use (0.55; 0.32-0.97) decreased them.

CONCLUSION

The risk of early complications is increased by female sex, hypertrophic cardiomyopathy, valvular heart disease, deep sedation, and complex fractionated atrial electrocardiogram ablation. It is decreased by preprocedural transesophageal echocardiography, periprocedural novel oral anticoagulant, and irrigated-tip catheter use.

Direct comparison of optical lattice clocks with an intercontinental baseline of 9000 km

We have demonstrated a direct frequency comparison between two ⁸⁷Sr lattice clocks operated in intercontinentally separated laboratories in real time. Two-way satellite time and frequency transfer technique, based on the carrier-phase, was employed for a direct comparison, with a baseline of 9000 km between Japan and Germany. A frequency comparison was achieved for 83,640 s, resulting in a fractional difference of (1.1±1.6)×10⁻¹⁵, where the statistical part is the largest contributor to the uncertainty. This measurement directly confirms the agreement of the two optical frequency standards on an intercontinental scale.

Nationwide survey of catheter ablation for atrial fibrillation: The Japanese catheter ablation registry of atrial fibrillation (J-CARAF)-A report on periprocedural oral anticoagulants

BACKGROUND

Catheter ablation has become an established therapy for the treatment of atrial fibrillation (AF). To obtain a perspective on the current status of this therapy in Japan, the Japanese Heart Rhythm Society (JHRS) conducted a nationwide survey, the Japanese Catheter Ablation Registry of Atrial Fibrillation (J-CARAF). In this study, we focused on whether periprocedural use of novel oral anticoagulants (NOACs) was related with excessive thromboembolic or bleeding complications.

METHODS

Using an online questionnaire, JHRS requested electrophysiology centers in Japan to register the data of patients who underwent AF ablations in September 2011, March 2012, and September 2012. We compared the clinical profiles and ablation data, including the incidence of complications among patients in whom warfarin, a NOAC or neither was used as a periprocedural anticoagulant.

RESULTS

A total of 179 centers submitted data relating to 3373 patients (62.2±10.6 years). Paroxysmal atrial fibrillation (PAF) was observed in 64.4% of patients. Warfarin, as a periprocedural oral anticoagulant, was used by 53.6% (1808/3373) of patients. A NOAC was given to 541 subjects (dabigatran: 504 [16.1%], rivaroxaban: 37 [1.1%]). In the remaining 1024 patients (30.4%), no periprocedural oral anticoagulants (OACs) were used. The proportion of PAF in warfarin-treated patients (61.1%) was significantly lower than that in NOAC-treated patients (70.1%, p<0.01) or in patients not treated with an OAC (67.4%, p<0.01). Patients treated with uninterrupted warfarin therapy were associated with significantly higher CHA2DS2-VASc scores. A total of 158 complications occurred in 151 subjects (4.5%). The incidence of complications in NOAC-treated patients (14/541 [2.6%]) was lower than that in patients receiving uninterrupted warfarin therapy (4.8%, p<0.05). The incidence of pericardial effusion in NOAC-treated patients (0.7%) was lower than in warfarin-treated patients (2.6%, p<0.05). The difference in the periprocedural anticoagulant strategy was not related to the frequency of other bleeding events. Cerebral infarction occurred in one patient from each patient group.

CONCLUSIONS

Our results suggest that NOACs are safe for use as substitutes for warfarin without causing excessive increases in the rates of thromboembolic or bleeding complications.

Systematic treatment approach to ventricular tachycardia in cardiac sarcoidosis

BACKGROUND

Fatal arrhythmia is commonly observed in cardiac sarcoidosis, but clinical effects of a systematic treatment approach are still uncertain. This study sought to describe both clinical and electrophysiological characteristics and outcomes of systematic treatment approach to ventricular tachycardia (VT) associated with cardiac sarcoidosis.

METHODS AND RESULTS

We enrolled 37 consecutive patients (11 men; age, 56±11 years) with a diagnosis of sustained VT associated with cardiac sarcoidosis. Clinical effects of a systematic treatment approach including medical therapy (both steroid and antiarrhythmic agents), in association with radiofrequency catheter ablation, were evaluated. All patients received antiarrhythmic agents, and 34 received steroid therapy. During a 39-month follow-up, 23 (62%) patients were free from any VT episodes with medical therapy. Multivariable Cox regression analyses revealed that the absence of gallium-67 myocardial uptake was an independent predictor for VT recurrence (hazard ratio, 7.51; 95% confidence interval, 1.65-34.26; P<0.01). Fourteen patients who experienced VT recurrences even while on drug therapy underwent radiofrequency catheter ablation. Electrophysiological study revealed that the mechanisms of VTs could be classified into 2 subgroups: Purkinje-related or scar-related VT. The QRS duration of VT was narrower in Purkinje-related than in scar-related VTs (157±23 versus 183±22 ms; P<0.05). After a 33-month follow-up subsequent to the radiofrequency catheter ablation, 6 of 14 patients experienced VT recurrence. The number of VTs sustained during electrophysiological study was higher in the patients with VT recurrence than in those without (3.7±1.4 versus 1.9±0.8; P<0.01).

CONCLUSIONS

A systematic treatment approach to cardiac sarcoidosis with VT successfully suppressed VT recurrences in the majority of patients studied.

Sodium channelopathy underlying familial sick sinus syndrome with early onset and predominantly male characteristics

BACKGROUND

Sick sinus syndrome (SSS) is a common arrhythmia often associated with aging or organic heart diseases but may also occur in a familial form with a variable mode of inheritance. Despite the identification of causative genes, including cardiac Na channel (SCN5A), the pathogenesis and molecular epidemiology of familial SSS remain undetermined primarily because of its rarity.

METHODS AND RESULTS

We genetically screened 48 members of 15 SSS families for mutations in several candidate genes and determined the functional properties of mutant Na channels using whole-cell patch clamping. We identified 6 SCN5A mutations including a compound heterozygous mutation. Heterologously expressed mutant Na channels showed loss-of-function properties of reduced or no Na current density in conjunction with gating modulations. Among 19 family members with SCN5A mutations, QT prolongation and Brugada syndrome were associated in 4 and 2 individuals, respectively. Age of onset in probands carrying SCN5A mutations was significantly less (mean±SE, 12.4±4.6 years; n=5) than in SCN5A-negative probands (47.0±4.6 years; n=10; P<0.001) or nonfamilial SSS (74.3±0.4 years; n=538; P<0.001). Meta-analysis of SSS probands carrying SCN5A mutations (n=29) indicated profound male predominance (79.3%) resembling Brugada syndrome but with a considerably earlier age of onset (20.9±3.4 years).

CONCLUSIONS

The notable pathophysiological overlap between familial SSS and Na channelopathy indicates that familial SSS with SCN5A mutations may represent a subset of cardiac Na channelopathy with strong male predominance and early clinical manifestations.