Background It is not known if the most delayed late potentials are functionally most specific for scar-related ventricular tachycardia (VT) circuits. Methods and Results Isochronal late activation maps (ILAM) were constructed to display ventricular activation during sinus rhythm over eight isochrones. Analysis was performed at successful VT termination sites and prospectively tested. 33 patients with 47 scar-related VTs where a critical site was demonstrated by termination of VT during ablation were retrospectively analyzed. In those that underwent mapping of multiple surfaces, 90% of critical sites were on the surface that contained the latest late potential. However, only 11% of critical sites were localized to the latest isochrone (87.5–100%) of ventricular activation. The median percentage of latest activation at critical sites was 78% at a distance from the latest isochrone of 18 mm. Sites critical to reentry were harbored in regions with slow conduction velocity, where 3 isochrones were present within a 1 cm radius. 10 consecutive patients underwent ablation prospectively guided by ILAM, targeting concentric isochrones outside of the latest isochrone. Elimination of the targeted VT was achieved in 90%. Termination of VT was achieved in 6 patients at a mean ventricular activation percentage of 78%, with only 1 requiring ablation in the latest isochrone. Conclusions Late potentials identified in the latest isochrone of activation during sinus rhythm are infrequently correlated with successful ablation sites for VT. The targeting of slow conduction regions propagating into the latest zone of activation may be a novel and promising strategy for substrate modification.

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Background— The existence of an atypical fast-slow (F/S) atrioventricular nodal reentrant tachycardia (AVNRT) including a superior (sup) pathway with slow conductive properties and an atrial exit near the His bundle has not been confirmed. Methods and Results— We studied 6 women and 2 men (age, 74±7 years) with sup-F/S-AVNRT who underwent successful radiofrequency ablation near the His bundle. Programmed ventricular stimulation induced retrograde conduction over a superior SP with an earliest atrial activation near the His bundle, a mean shortest spike-atrial interval of 378±119 milliseconds, and decremental properties in all patients. sup-F/S-AVNRT was characterized by a long-RP interval; a retrograde atrial activation sequence during tachycardia identical to that over a sup-SP during ventricular pacing; ventriculoatrial dissociation during ventricular overdrive pacing of the tachycardia in 5 patients or atrioventricular block occurring during tachycardia in 3 patients, excluding atrioventricular reentrant tachycardia; termination of the tachycardia by ATP; and a V-A-V activation sequence immediately after ventricular induction or entrainment of the tachycardia, including dual atrial responses in 2 patients. Elimination or modification of retrograde conduction over the sup-SP by ablation near the right perinodal region or from the noncoronary cusp of Valsalva eliminated and confirmed the diagnosis of AVNRT in 4 patients each. Conclusions— sup-F/S-AVNRT is a distinct supraventricular tachycardia, incorporating an SP located above the Koch triangle as the retrograde limb, that can be eliminated by radiofrequency ablation.

Cardiac sympathetic denervation (CSD) is reported to reduce the burden of ventricular tachyarrhythmias [ventricular tachycardia (VT)/ventricular fibrillation (VF)] in cardiomyopathy patients, but the mechanisms behind this benefit are unknown. In addition, the relative contribution to cardiac innervation of the middle cervical ganglion (MCG), which may contain cardiac neurons and is not removed during this procedure, is unclear. The purpose of this study was to compare sympathetic innervation of the heart via the MCG vs. stellate ganglia, assess effects of bilateral CSD on cardiac function and VT/VF, and determine changes in cardiac sympathetic innervation after CSD to elucidate mechanisms of benefit in 6 normal and 18 infarcted pigs. Electrophysiological and hemodynamic parameters were evaluated at baseline, during bilateral stellate stimulation, and during bilateral MCG stimulation in 6 normal and 12 infarcted animals. Bilateral CSD (removal of bilateral stellates and T ganglia) was then performed and MCG stimulation repeated. In addition, in 18 infarcted animals VT/VF inducibility was assessed before and after CSD. In infarcted hearts, MCG stimulation resulted in greater chronotropic and inotropic response than stellate ganglion stimulation. Bilateral CSD acutely reduced VT/VF inducibility by 50% in infarcted hearts and prolonged global activation recovery interval. CSD mitigated effects of MCG stimulation on dispersion of repolarization and T-peak to T-end interval in infarcted hearts, without causing hemodynamic compromise. These data demonstrate that the MCG provides significant cardiac sympathetic innervation before CSD and adequate sympathetic innervation after CSD, maintaining hemodynamic stability. Bilateral CSD reduces VT/VF inducibility by improving electrical stability in infarcted hearts in the setting of sympathetic activation. Sympathetic activation in myocardial infarction leads to arrhythmias and worsens heart failure. Bilateral cardiac sympathetic denervation reduces ventricular tachycardia/ventricular fibrillation inducibility and mitigates effects of sympathetic activation on dispersion of repolarization and T-peak to T-end interval in infarcted hearts. Hemodynamic stability is maintained, as innervation via the middle cervical ganglion is not interrupted.

Background Variability in premature ventricular contraction (PVC) coupling interval (CI) increases the risk of cardiomyopathy and sudden death. The autonomic nervous system regulates cardiac electrical and mechanical indices, and its dysregulation plays an important role in cardiac disease pathogenesis. The impact of PVCs on the intrinsic cardiac nervous system (ICNS), a neural network on the heart, remains unknown. The objective was to determine the effect of PVCs and CI on ICNS function in generating cardiac neuronal and electrical instability using a novel cardio-neural mapping approach. Methods and Results In a porcine model (n=8) neuronal activity was recorded from a ventricular ganglion using a microelectrode array, and cardiac electrophysiological mapping was performed. Neurons were functionally classified based on their response to afferent and efferent cardiovascular stimuli, with neurons that responded to both defined as convergent (local reflex processors). Dynamic changes in neuronal activity were then evaluated in response to right ventricular outflow tract PVCs with fixed short, fixed long, and variable CI. PVC delivery elicited a greater neuronal response than all other stimuli (P<0.001). Compared to fixed short and long CI, PVCs with variable CI had a greater impact on neuronal response (P<0.05 versus short CI), particularly on convergent neurons (P<0.05), as well as neurons receiving sympathetic (P<0.05) and parasympathetic input (P<0.05). The greatest cardiac electrical instability was also observed following variable (short) CI PVCs. Conclusions Variable CI PVCs affect critical populations of ICNS neurons and alter cardiac repolarization. These changes may be critical for arrhythmogenesis and remodeling leading to cardiomyopathy.

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We recently observed a case of BrS characterized by prominent J waves in the inferolateral leads of the 12-lead ECG and electrical storms (ESs). 7 Case-control studies have described a close association between J waves, a sign of early repolarization (ER), and idiopathic VF. [8][9][10] The presence of J waves in patients presenting with BrS may also be a predictor of poor prognosis. 6,[11][12][13] The purpose of this multicenter study was to evaluate the characteristics of patients with BrS and ES, with a special attention to the presence of J waves. Methods Study PopulationWe retrospectively identified 22 men at 8 Japanese medical institutions, who presented with BrS and ES, defined as ≥3 episodes of VF/d. BrS was diagnosed according to the following currently accepted criteria 2,6,[11][12][13][14] : (1 Original ArticleBackground-Electrical storms (ESs) in patients with Brugada syndrome (BrS) are rare though potentially lethal. Methods and Results-We studied 22 men with BrS and ES, defined as ≥3 episodes/d of ventricular fibrillation (VF) and compared their characteristics with those of 110 age-matched, control men with BrS without ES. BrS was diagnosed by a spontaneous or drug-induced type 1 pattern on the ECG in the absence of structural heart disease. Early repolarization (ER) was diagnosed by J waves, ie, >0.1 mV notches or slurs of the terminal portion of the QRS complex. The BrS ECG pattern was provoked with pilsicainide. A spontaneous type I ECG pattern, J waves, and horizontal/descending ST elevation were found, respectively, in 77%, 36%, and 88% of patients with ES, versus 28% (P<0.0001), 9% (P=0.003), and 60% (P=0.06) of controls. The J-wave amplitude was significantly higher in patients with than without ES (P=0.03). VF occurred during undisturbed sinus rhythm in 14 of 19 patients (74%), and ES were controlled by isoproterenol administration. All patients with ES received an implantable cardioverter defibrillator and over a 6.0±5.4 years followup, the prognosis of patients with ES was significantly worse than that of patients without ES. Bepridil was effective in preventing VF in 6 patients. Conclusions-A high prevalence of ER was found in a subgroup of patients with BrS associated with ES. ES appeared to be suppressed by isoproterenol or quinidine, whereas bepridil and quinidine were effective in the long-term prevention of VF in the highest-risk patients. (Circ Arrhythm Electrophysiol. 2014;7:1122-1128.)

SummaryMutations in SCN5A are linked to Brugada syndrome in approximately 20% of all cases (BrS1). Several dozen distinct SCN5A mutations in BrS1 have been associated with the increased risk of cardiac arrhythmias. However, the genotype-phenotype relationship remains elusive. The current study analyzed the SCN5A gene to elucidate the potential variability of clinical features in Japanese BrS1 subjects. Subjects of the present study included 30 probands (25 male subjects, 45 ± 15 years of age) with Brugada-pattern ECG. Seven patients had been resuscitated from cardiopulmonary arrest (CPA group). Another 10 patients had a history of syncope (Sy group), and 13 more remain asymptomatic (Asy group). We identified 8 different SCN5A mutations, including 6 novel mutations (CPA group: 1/7, Sy group: 3/10, Asy group: 4/13). An A735E mutation (located at segment (S)1 in domain (D)2) was identified in the CPA group. A novel splice acceptor site mutation (c.393-1c>t), which may produce a prematurely truncated protein, was identified in the Sy group. An E1784K mutation (C-terminus) and a novel mutation V1951M (C-terminus) were also identified in the Sy group. Four novel missense mutations, A586T (D1-D2 linker), R689H (D1-D2 linker), S1553R (S1-S2 in D4), and Q1706H (S5-Pore in D4) were identified in the Asy group. These data may help us understand the genetic heterogeneity of BrS1, which is more prevalent in Japanese than in whites and other ethnic groups. (Int Heart J 2011; 52: 27-31) Key words: Brugada syndrome, SCN5A, Mutation T he Brugada syndrome (BrS), characterized by ST-segment elevations in the right precordial ECG leads without structural heart disease, is a hereditable disease associated with an increased risk of sudden death due to polymorphic ventricular tachycardia or ventricular fibrillation (VF).1) Genetic analyses of BrS revealed that BrS is genetically heterogeneous, and is linked to at least 7 different genes. [2][3][4][5][6][7][8] Mutations in SCN5A, which encodes the pore-forming subunit of the cardiac voltage-gated sodium channel, have been associated with the major form of BrS (BrS1) in approximately 20% of cases. [9][10][11] The clinical severity of BrS may vary with the responsible genes and/or mutation sites, although the genotypephenotype relationship remains poorly characterized. The presence of SCN5A mutations is not related to the severity of the disease.9,10,12) However, Meregalli, et al have recently reported that the type of SCN5A mutation in BrS1 in European countries may determine the clinical severity.13) Because the clinical features of BrS vary among different ethnicities, 14,15) it is of great value to investigate the genotype-phenotype relationship of BrS in Asians in whom the ratio of BrS patients is relatively high compared to subjects from different ethnic backgrounds.In the present study, we analyzed the SCN5A gene to elucidate the potential variability of clinical features of BrS1 subjects recruited from Gunma University Hospital. Consequently, we identified 8 SCN5A mutations, incl...