Yoshiaki Yamaguchi

Vagal activity modulates spontaneous augmentation of J-wave elevation in patients with idiopathic ventricular fibrillation

BACKGROUND Although J-wave elevation in the inferolateral leads could be related to idiopathic ventricular fibrillation (IVF), little is known about the pathophysiologic characteristics of J-wave elevation in patients with IVF. OBJECTIVE This study aimed to determine the relationship between augmentation of J-wave elevation and changes in RR interval or autonomic nervous activities in patients with IVF. METHODS Eight patients with IVF and 22 controls with J-wave elevation (≥0.1 mV) in lead V5 were studied. The J-wave amplitude was automatically measured in lead CM5 of a digital Holter electrocardiogram, and the J-RR relationship was determined. Based on the analysis of heart rate variability, the relationship between the J-wave amplitude and the natural logarithm of high-frequency (HF) components (J-ln HF relationship) or the ratio of low frequency (LF) components to HF components (J-LF/HF relationship) was also determined. RESULTS The J-RR slope (mm/s) was greater in patients with IVF than in controls (3.5 ± 0.7 vs 2.4 ± 0.8; P <.01), as was J-wave amplitude (mm) at an RR interval of 1.2 seconds (2.8 ± 0.9 vs 2.0 ± 0.6; P <.05). The J-wave amplitude was correlated positively with ln HF and negatively with LF/HF, and the slopes of both J-ln HF and J-LF/HF regression lines were greater in patients with IVF than in controls. During an entire 24-hour period, there was no difference between the 2 groups in either HF or LF/HF. Nine of the total 11 episodes (82%) of spontaneous ventricular fibrillation occurred between 18:00 and 6:00. CONCLUSIONS In patients with IVF as compared with control subjects, J-wave elevation was more strongly augmented during bradycardia and was associated with an increase in vagal activity. This could be related to the occurrence of ventricular fibrillation predominantly at night in patients with IVF.

Tranilast Prevents Atrial Remodeling and Development of Atrial Fibrillation in a Canine Model of Atrial Tachycardia and Left Ventricular Dysfunction

OBJECTIVES This study sought to assess the effects of tranilast on atrial remodeling in a canine atrial fibrillation (AF) model. BACKGROUND Tranilast inhibits transforming growth factor (TGF)-β1 and prevents fibrosis in many pathophysiological settings. However, the effects of tranilast on atrial remodeling remain unclear. METHODS Beagles were subjected to atrial tachypacing (400 beats/min) for 4 weeks while treated with placebo (control dogs, n = 8) or tranilast (tranilast dogs, n = 10). Sham dogs (n = 6) did not receive atrial tachypacing. Atrioventricular conduction was preserved. Ventricular dysfunction developed in the control and tranilast dogs due to rapid ventricular responses. RESULTS Atrial fibrillation duration (211 ± 57 s) increased, and AF cycle length and atrial effective refractory period shortened in controls, but these changes were suppressed in tranilast dogs (AF duration, 18 ± 10 s, p < 0.01 vs. control). The L-type calcium channel α1c (Cav1.2) micro ribonucleic acid expression decreased in control dogs (sham 1.38 ± 0.24 vs. control 0.65 ± 0.12, p < 0.01), but not in tranilast dogs (0.97 ± 0.14, p = not significant vs. sham). Prominent atrial fibrosis (fibrous tissue area, sham 0.8 ± 0.1 vs. control 9.3 ± 1.3%, p < 0.01) and increased expression of tissue inhibitor of metalloproteinase protein 1 were observed in control dogs but not in tranilast dogs (fibrous tissue area, 1.4 ± 0.2%, p < 0.01 vs. control). The TGF-β1 (sham 1.00 ± 0.07 vs. control 3.06 ± 0.87, p < 0.05) and Rac1 proteins were overexpressed in control dogs, but their overexpression was inhibited in tranilast dogs (TGF-β1, 1.28 ± 0.20, p < 0.05 vs. control). CONCLUSIONS Tranilast prevented atrial remodeling and suppressed AF development in a canine model. Its inhibition of TGF-β1 and Rac1 overexpression may contribute to its antiremodeling effects.

Silent Cerebral Ischemic Lesions After Catheter Ablation of Atrial Fibrillation in Patients on 5 Types of Periprocedural Oral Anticoagulation - Predictors of Diffusion-Weighted Imaging-Positive Lesions and Follow-up Magnetic Resonance Imaging.

BACKGROUND The aim of this study was to identify the predictors of silent cerebral ischemic lesions (SCIL) after catheter ablation of atrial fibrillation (AF) and to determine whether SCIL develop into cerebral infarcts in patients with 5 types of oral anticoagulants (OAC). METHODSANDRESULTS We retrospectively studied 286 consecutive patients (median, 67 years; 208 male; paroxysmal/persistent/long-standing persistent AF [LSP-AF], 147/90/49) who received periprocedural OAC and underwent MRI after the procedure. Warfarin (n=46) was continued, while dabigatran (n=47), rivaroxaban (n=89), apixaban (n=87), and edoxaban (n=17) were discontinued on the day of the procedure. I.v. heparin was infused to maintain an activated clotting time of 300-350 s during the procedure. Fifty-eight SCIL in 40 patients (14.0%) were identified on diffusion-weighted MRI. On multivariate logistic analysis, LSP-AF and dabigatran use were significant positive predictors of SCIL (OR, 2.912 and 2.287; P=0.006 and 0.042, respectively). Among 34 patients with 49 SCIL undergoing follow-up MRI, 45 (91.8%) of the lesions disappeared and 4 lesions developed into chronic cerebral infarcts. The SCIL with development into infarcts had a larger lesion diameter than those without (median, 6.55 mm vs. 4.2 mm; P=0.002). CONCLUSIONS LSP-AF and dabigatran use were independent risk factors for post-ablation SCIL in patients with uninterrupted warfarin and interrupted non-vitamin K antagonist OAC, but the majority of SCIL disappeared.

Early repolarization in Wolff-Parkinson-White syndrome: prevalence and clinical significance.

AIMS Idiopathic ventricular fibrillation (IVF) with early repolarization (ER) has recently been reported; however, ER is a common finding in healthy subjects and is also found sporadically in patients with Wolff-Parkinson-White (WPW) syndrome. The present study was designed to evaluate the prevalence and clinical significance of ER in patients with WPW syndrome. METHODS AND RESULTS One hundred and eleven patients with WPW syndrome were studied retrospectively. Early repolarization was defined as QRS slurring or notching with J-point elevation ≥ 1 mm. The prevalence of ER was determined before and after successful catheter ablation. Before ablation, ER was found in 35 of 75 patients with a left free wall, 6 of 23 with a right free wall, and 7 of 13 with a septal accessory pathway (48 of 111, 43% as a whole). Early repolarization was always observed in leads with positive deflection of the initial part of the delta wave. After successful ablation of accessory pathways, ER was preserved in 28 (25%), disappeared in 20 (18%), and newly developed in 8 (7%) patients. In the remaining 55 (50%) patients, ER was not observed either before or after ablation. In patients with persistent ER, the amplitude and width of ER were significantly decreased 3-7 days after the ablation (1.7 ± 0.7 vs. 1.4 ± 0.6 mm, P < 0.005 and 42 ± 11 vs. 34 ± 9 ms, P < 0.001, respectively). CONCLUSION In patients with WPW syndrome, ER could be partly related to early depolarization through the accessory pathway. However, persistent ER and new ER appearing after the ablation were frequently found. Therefore, in these patients, mechanisms other than early depolarization may be involved in the genesis of ER.

Postmortem genetic analysis of sudden unexplained death syndrome under 50 years of age: A next-generation sequencing study

BACKGROUND Recent studies on the genetic analysis of victims of sudden unexplained death syndrome (SUDS) have shown diagnostic potential. Previously, such analyses mainly targeted the major channelopathy-associated genes. OBJECTIVE The purpose of this study was to evaluate the utility of next-generation sequencing (NGS) in the postmortem diagnosis of SUDS. METHODS Our data are derived from 25 cases of SUDS (21 men and 4 women; age 19-50 years). A total of 70 genes were examined by NGS, and the pathogenicity of any detected rare variants with minor allele frequencies of <0.5% was evaluated using a widely used database and eight in silico algorithms. RESULTS Five known and 15 potentially pathogenic variants with a high in silico score were identified in 14 cases. In all, 6 channelopathy-related variants were identified in 5 cases, including 2 cases with history of arrhythmia; 11 cases had cardiomyopathy- or cardiac transcription factor-related variants. Three cases with desmosomal gene- or other cardiomyopathy-related variants showed possibly related pathologic changes. Three cases with RYR2 or TBX5 variants showed possible pathogenic fibrosis of the cardiac conduction system. Only 12 variants showed moderate or strong possible pathogenicity in SUDS cases compared with qualifying controls. CONCLUSION Hereditary heart diseases other than channelopathy may also be a significant cause of SUDS, even if clinical and pathologic findings do not show advanced disease. A combination of gene analysis using NGS and some predictive methods for detecting variants and careful pathologic evaluation may provide a reliable diagnosis of hereditary heart disease for potential SUDS cases.

The efficacy of ablation based on the combined use of the dominant frequency and complex fractionated atrial electrograms for non-paroxysmal atrial fibrillation.

BACKGROUND This study aimed to evaluate an approach for an endpoint of non-inducibility using a combined high-dominant frequency (DF) and continuous complex fractionated atrial electrogram (CFAE) ablation following circumferential pulmonary vein isolation (PVI) in a sequential fashion, including linear ablation as compared to PVI alone. METHODS AND RESULTS A total of 84 non-paroxysmal patients with atrial fibrillation (AF) were investigated retrospectively. The AF patients were divided into two groups: patients with PVI following a combined high-DF and continuous CFAE ablation with linear ablation (substrate modification group, n=59) and those with PVI alone (n=25). DF sites of ≥8Hz and then continuous CFAE sites defined by fractionation intervals of ≤50ms were modified after PVI. The ablation endpoint was non-inducibility. Atrial tachyarrhythmias (ATs) could not be induced in 54 of 59 (92%) patients after a sequential ablation, and in 18 of 25 (64%) with PVI alone. The ATs freedom without antiarrhythmic drugs in the substrate modification group was significantly greater than that in those with PVI alone after 1 procedure during 12 months of follow-up (78.6% vs. 53.8%, log-rank test p=0.039). CONCLUSION This sequential approach using a substrate based ablation was associated with a better clinical long-term outcome as compared to PVI alone.

Electrophysiological and anatomical differences of the slow pathway between the fast-slow form and slow-slow form of atrioventricular nodal reentrant tachycardia.

AIMS This study aimed to clarify whether electrophysiological and anatomical properties of the slow pathway (SP) could be different between the fast-slow form (F/S) and the slow-slow form (S/S) atrioventricular nodal reentrant tachycardia (AVNRT). METHODS AND RESULTS Nine patients with F/S and 15 patients with S/S of atypical AVNRT were studied. The patients with S/S were divided into two groups; those with the anterograde SP being eliminated (S/S aSP-E) or preserved (S/S aSP-P) during catheter ablation. HA (CS-His) was determined as the difference of the shortest HA interval between the His bundle region and the coronary sinus (CS) region. The ratio of the amplitudes of atrial and ventricular potential (A/V ratio) of the successful ablation site of the SP was also evaluated. Effective refractory period of the retrograde SP was shorter and HA intervals during both tachycardia and ventricular pacing were longer in F/S than in S/S. HA (CS-His) did not differ between F/S and S/S (-4.3 ± 20.2 vs.-4.4 ± 18.4 ms, NS). The A/V ratio was significantly greater in the S/S aSP-P group compared with the both groups of F/S and S/S aSP-E (0.83 ± 0.29 vs. 0.38 ± 0.09 and 0.26 ± 0.15 ms, P < 0.01). CONCLUSION Properties of the retrograde SP differ between F/S and S/S of AVNRT. Fast-slow form may utilize the same pathway for the retrograde conduction as the anterograde SP in S/S.

Abnormal repolarization dynamics in a patient with KCNE1(G38S) who presented with torsades de pointes.

Risk of G38S, major KCNE1 polymorphism [KCNE1(G38S)], for long QT syndrome (LQTS) remains unclear. A 72-year-old woman was admitted with recurrent torsades de pointes (TdP). She had remarkable QT prolongation (corrected QT interval 568 ms) under conditions of hypokalemia and hypomagnesemia. After correction of this electrolytic imbalance, TdP was suppressed and metoprolol was started. The QT-RR slope in 24-hour Holter electrocardiogram was steep and this enhanced bradycardia-dependent QT prolongation was similar to that in LQTS. She carried KCNE1(G38S). Patients with KCNE1(G38S) could have similar potential risk of ventricular arrhythmia as with LQTS. Analysis of QT-RR relationship could also evaluate the latent arrhythmogenicity of KCNE1(G38S).

SCN5A(K817E), a novel Brugada syndrome-associated mutation that alters the activation gating of NaV1.5 channel.

BACKGROUND Brugada syndrome (BrS) is an inherited lethal arrhythmic disorder characterized by syncope and sudden cardiac death from ventricular tachyarrhythmias. Here we identified a novel K817E mutation of SCN5A gene in a man with type 1 BrS electrocardiogram pattern using next-generation sequencing targeted for 73 cardiac disorder-related genes. SCN5A encodes the α-subunit of NaV1.5 voltage-gated Na(+) channel, and some of its mutations are linked to BrS. The proband had no mutation in any of the other arrhythmia-related genes sequenced. OBJECTIVE We investigated whether the K817E mutation causes a functional change of NaV1.5 channel responsible for the BrS phenotype. METHODS We compared the electrophysiological properties of the whole-cell currents mediated by wild-type and mutant channels heterologously expressed in human embryonic kidney 293 cells by using a voltage-clamp technique. RESULTS The K817E mutation reduced the Na(+) current density by 39.0%-91.4% at membrane potentials from -55 to -5 mV. This reduction resulted from a ~24-mV positive shift in the voltage dependence of activation. The mutation also decelerated recovery from both fast and intermediate inactivation, whereas it had little effect on the cell surface expression, single-channel conductance, voltage-dependence of fast inactivation, entry into intermediate inactivation, use-dependent loss of channel availability, or closed-state inactivation. CONCLUSION The K817E mutation of SCN5A gene leads to loss of function of NaV1.5 channel and may underlie the BrS phenotype of the proband.

Recurrent syncope in two patients with a sigmoid-shaped interventricular septum and no left ventricular hypertrophy.

Sigmoid‐shaped interventricular septum (SIS) is not uncommon in elderly patients and is considered a normal part of the aging process. However, several patients have been reported to have clinical symptoms due to the narrowing of the left ventricular outflow tract (LVOT). Two patients with SIS presented with recurrent episodes of syncope after drinking or taking sublingual nitroglycerin (NG). In both patients, a head‐up tilt test involving provocation with alcohol, NG, or isoproterenol induced the vasovagal reflex along with an increase in the pressure gradient between the apex and LVOT. The patients experienced no further episodes of syncope after initiating bisoprolol treatment. In patients with SIS, induction of the vasovagal reflex via an increase in left ventricular (LV) pressure due to LVOT obstruction concomitant with increased LV construction is a potentially important cause of syncope, which may be effectively prevented by beta‐blockers.