Atypical Fast-Slow Atrioventricular Nodal Reentrant Tachycardia Incorporating a "Superior" Slow Pathway: A Distinct Supraventricular Tachyarrhythmia.

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.

Electroanatomically estimated length of slow pathway in atrioventricular nodal reentrant tachycardia.

The length of the slow pathway (SP-L) in atrioventricular (AV) nodal reentrant tachycardia (NRT) has never been measured clinically. We studied the relationship among (a) SP-L, i.e., the distance between the most proximal His bundle (H) recording and the most posterior site of radiofrequency (RF) delivery associated with a junctional rhythm, (b) the length of Koch's triangle (Koch-L), (c) the conduction time over the slow pathway (SP-T), measured by the AH interval during AVNRT at baseline, and (d) the distance between H and the site of successful ablation (SucABL-L) in 26 women and 20 men (mean age 64.6 ± 11.6 years), using a stepwise approach and an electroanatomic mapping system (EAMS). SP-L (15.0 ± 5.8 mm) was correlated with Koch-L (18.6 ± 5.6 mm; R 2 = 0.1665, P < 0.005), SP-T (415 ± 100 ms; R 2 = 0.3425, P = 0.036), and SucABL-L (11.6 ± 4.7 mm; R 2 = 0.5243, P < 0.0001). The site of successful ablation was located within 10 mm of the posterior end of the SP in 38 patients (82.6 %). EAMS-guided RF ablation, using a stepwise approach, revealed individual variations in SP-L related to the size of Koch's triangle and AH interval during AVNRT. Since the site of successful ablation was also correlated with SP-L and was usually located near the posterior end of the SP, ablating anteriorly, away from the posterior end, is not a prerequisite for the success of ablation procedures.

Pseudo-postpacing interval of diastolic potential after entrainment pacing of remote bystander pathway in reentrant ventricular tachycardia.

After entrainment pacing, the postpacing interval of a diastolic potential may be misinterpreted if the distal tip of the ablation catheter captures a remote bystander pathway adjacent to the critical isthmus of a complex reentrant circuit in a structurally diseased heart. We discuss this possible pitfall of entrainment mapping of reentrant ventricular tachycardia, observed after a healed myocardial infarction.

Successful ablation of atypical atrioventricular nodal reentrant tachycardia from a noncoronary sinus of Valsalva.

An 81-year-old man with long RP narrow QRS tachycardia underwent catheter ablation. Ventricular pacing reset the atrial cycle over a retrograde slow pathway, followed by termination of the tachycardia without atrial capture, confirming the diagnosis of fast-slow atrioventricular nodal reentrant tachycardia (AVNRT). The earliest atrial activation during tachycardia was found in the noncoronary sinus of Valsalva, where the first delivery of radiofrequency energy terminated and eliminated the inducibility of the tachycardia, by retrograde conduction block over the slow pathway. This is the first report of a fast-slow AVNRT, with successful ablation of the slow pathway from a noncoronary sinus of Valsalva.

Compound and digenic heterozygosity in desmosome genes as a cause of arrhythmogenic right ventricular cardiomyopathy in Japanese patients.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a hereditary disorder mostly caused by desmosome gene mutations. Recent comprehensive desmosome mutation analyses of Caucasian ARVC patients have revealed the presence of not only a single heterozygous mutation, but also compound and digenic heterozygosity. However, the genetic basis of Japanese ARVC remains poorly elucidated. METHODS AND RESULTS: The subjects were 7 definite and 1 possible ARVC probands (6 males, 16-76 years of age), and their family members. Genetic screening for major ARVC-causing genes (junction plakoglobin, desmoplakin, plakophilin-2 (PKP2), desmoglein-2 (DSG2), and desmocollin-2) was performed. We identified 3 cases of compound heterozygosities (Case 1: DSG2 S194L and DSG2 R292C; Case 2: PKP2 2489+1G>A and PKP2 D812N; Case 3: PKP2 M565R and PKP2 D812N) and 1 of digenic heterozygosity (Case 4: PKP2 1728_1729insGATG and DSG2 R292C) among the definite ARVC patients. All family members we investigated have remained asymptomatic. They carried, if any, only a single variant, indicating that the probands carry in trans compound heterozygosity. These results suggest that each of these variants alone may not be sufficient and second variants may be required to manifest overt ARVC in Japanese patients. CONCLUSIONS: Our comprehensive genetic analysis of desmosome genes identified 3 cases of compound heterozygosities in trans and 1 of digenic heterozygosity among 7 definite Japanese ARVC patients, providing novel insights into the genetic basis of Japanese ARVC.

Detection of diastolic potentials around the mitral annulus of structurally normal human hearts.

To examine the electrophysiologic characteristics of the subvalvular mitral region, we retrospectively searched for the presence of subvalvular diastolic potentials (DP) in 91 patients (mean age, 46.9 ± 16.6 years) who underwent catheter ablation of left-sided accessory pathways (AP). We detected low-amplitude (0.19 ± 0.09 mV) DP in 14 patients (15.4%), including 8 with overt preexcitation and 6 patients with concealed AP. The mean interval between ventricular electrogram and DP was 383 ± 46 ms (range, 306-475). DP were detected in 4 of 20 patients with antero-lateral, 3 of 38 with lateral, 4 of 12 with postero-lateral, 2 of 14 with posterior, and 3 of 10 patients with postero-septal AP. In 6 of 14 patients, DP were detected before ablation. In 4 of 8 patients with overt preexcitation, DP were consistently recorded after elimination of the delta wave, suggesting that they were not associated with AP conduction. In 6 of 11 patients, DP were observed during both sinus rhythm and ventricular pacing, suggesting that they were not artifacts. The electrophysiologic characteristics of clinically relevant DP around the mitral annulus suggest that, in normal human hearts, an anatomical substrate may be present around the mitral annulus.

Discrimination between His-bundle and the right bundle branch during electrophysiologic studies.

BACKGROUND: The purpose of this study was to identify the His-bundle (HB) versus right bundle branch (RBB) during electrophysiologic studies, using the V3 phenomenon, and to compare the timing of HB versus RBB potentials of sinus cycles (His-ventricular [H-V] interval). METHODS: The study enrolled 16 patients without structural heart disease, who underwent electrophysiologic studies during which the H-V interval was within normal limits and the V3 phenomenon was induced during recordings of the HB and the RBB potentials by a multi-electrode catheter. The recording site of the earliest HB potential just before the V3 phenomenon was defined as the branching portion of His bundle (HBBP), the site immediately proximal to the HBBP as the HB, and the site immediately distal to the HBBP as the RBB. RESULTS: The HBBP was identified in all patients. In all cases but one patient, the H-V interval measured at the HB adjacent to the HBBP was > or =35 ms. However, in 12 patients, the H-V interval measured at the RBB adjacent to the HBBP was also > or =35 ms. CONCLUSIONS: The electrophysiologic identification of HB versus RBB by simultaneous recordings of HB and RBB potentials during induction of the V3 phenomenon was feasible. When the discrimination between HB and RBB was based on the measurement of the H-V interval, the proximal portion of the RBB was frequently misidentified as the HB.

Detection of sequential activation of left atrium and coronary sinus musculature in the general population.

BACKGROUND: The direction of impulse propagation across the coronary sinus (CS) musculature (CSM) is an important piece of the mechanistic puzzle underlying atrial tachyarrhythmias. We hypothesized that in the general population, the sequence of left atrial (LA) to CSM electrograms recorded in the CS reflects the direction of impulse propagation over the CSM. METHODS: We studied 19 patients with atrioventricular (AV) reentrant tachycardia (RT) utilizing a left-sided accessory pathway (AP) and 21 patients with typical counterclockwise atrial flutter (AFL). Conduction through the CSM during AVRT and AFL is from the left atrial (LA) to the right atrial (RA) and from the RA to LA direction, respectively. CS recordings of retrograde conduction over the AP and of AFL were analyzed in search of far-field, LA potentials. RESULTS: Among 19 patients with AP, LA potentials were visible in 7 (37%), all in an LA → CSM activation sequence, while among the 21 patients with AFL, LA potentials were visible in 14 (67%), all in a CSM-LA activation sequence (P<0.0001). The prevalence of LA potentials was similar between both study groups (P=0.1119), and the overall prevalence was 53%. CONCLUSIONS: Far-field LA potentials are often recorded in the CS during sequential LA and CSM activation in the general population. The timing of LA potentials in CS recordings reflected the direction of conduction across the CSM.

Measurement of the ventriculoatrial interval from the coronary sinus during para-Hisian pacing may fail to distinguish ventriculoatrial nodal conduction from conduction over a septal accessory pathway.

BACKGROUND: Para-Hisian pacing (PHP) helps differentiate retrograde conduction over an accessory pathway (AP) from retrograde conduction over the atrioventricular (AV) node. This study examined a potential limitation of this technique, focusing on the measurement of the ventriculoatrial (V-A) interval from the coronary sinus (CS) during PHP. METHODS: Our subjects were 9 patients undergoing electrophysiological studies before successful catheter ablation of a posteroseptal AP. During PHP, retrograde conduction occurred over an AP when the pacing stimulus to atrium (S-A) interval recorded near the AP remained unchanged whether the His bundle (HB) was captured or not (pattern 1), or when a loss of HB capture was associated with an increase in the S-A interval and no change in the V-A interval near the AP (pattern 2). RESULTS: Patterns 1 and 2 were observed in 5 (56%) and 2 (22%) patients, respectively. However, in the remaining 2 patients (22%), loss of HB capture during PHP was associated with an increase in the S-A interval (as in pattern 2), whereas the V-A interval near the AP could not be measured because no ventricular electrogram was visible on the CS recording (pattern 3); therefore, the presence of AP could not be confirmed by PHP. In patterns 2 and 3, the atrial activation sequence remained unchanged whether the HB was captured or not. CONCLUSIONS: PHP may not be able to discriminate between a retrograde septal AP and AV nodal conduction in patients whose proximal CS recording shows no visible ventricular electrogram.

Enhanced fast-inactivated state stability of cardiac sodium channels by a novel voltage sensor SCN5A mutation, R1632C, as a cause of atypical Brugada syndrome.

BACKGROUND: Mutations in SCN5A, which encodes the cardiac voltage-gated sodium channels, can be associated with multiple electrophysiological phenotypes. A novel SCN5A R1632C mutation, located in the domain IV-segment 4 voltage sensor, was identified in a young male patient who had a syncopal episode during exercise and presented with atrial tachycardia, sinus node dysfunction, and Brugada syndrome. OBJECTIVE: We sought to elucidate the functional consequences of the R1632C mutation. METHODS: The wild-type (WT) or R1632C SCN5A mutation was coexpressed with ß1 subunit in tsA201 cells, and whole-cell sodium currents (INa) were recorded using patch-clamp methods. RESULTS: INa density, measured at -20 mV from a holding potential of -120 mV, for R1632C was significantly lower than that for WT (R1632C: -433 ± 52 pA/pF, n = 14; WT: -672 ± 90 pA/pF, n = 15; P < .05); however, no significant changes were observed in the steady-state activation and fast inactivation rate. The steady-state inactivation curve for R1632C was remarkably shifted to hyperpolarizing potentials compared with that for WT (R1632C: V1/2 = -110.7 ± 0.8 mV, n = 16; WT: V1/2 = -85.9 ± 2.5 mV, n = 17; P < .01). The steady-state fast inactivation curve for R1632C was also shifted to the same degree. Recovery from fast inactivation after a 20-ms depolarizing pulse for R1632C was remarkably delayed compared with that for WT (R1632C: τ = 246.7 ± 14.3 ms, n = 8; WT: τ = 3.7 ± 0.3 ms, n = 8; P < .01). Repetitive depolarizing pulses at various cycle lengths greatly attenuated INa for R1632C than that for WT. CONCLUSION: R1632C showed a loss of function of INa by an enhanced fast-inactivated state stability because of a pronounced impairment of recovery from fast inactivation, which may explain the phenotypic manifestation observed in our patient.