Takafumi Iijima

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.

A novel KCNQ1 splicing mutation in patients with forme fruste LQT1 aggravated by hypokalemia

BACKGROUND Several KCNQ1 splicing mutations have been identified in patients with type-1 long QT syndrome (LQT1). It was suggested that the clinical severity may differ according to the aberrant splicing products. There may be precipitating factors that cause cardiac events in those with a mild clinical phenotype (forme fruste LQT1). METHODS AND RESULTS We analyzed the KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2 genes in 31 consecutive LQTS patients. A novel KCNQ1 1251+1G>A (IVS9+1G>A) mutation was identified in three probands and their two relatives. The QT interval in all of the five individuals with mutation was not much prolonged in the absence of precipitating factors (mean QTc was 461±30ms.). Two of the five individuals with mutation were symptomatic. One patient (a 38-year-old female) had experienced recurrent episodes of syncope due to ventricular tachyarrhythmias (VTAs) accompanied by QT prolongation (QTc: 750ms) when the serum potassium concentration ([K(+)]) was 2.7mEq/L. After correction of [K(+)], the QTc interval was shortened to 515ms, and the occurrence of VTAs ceased. Another patient (a 22-year-old female) was resuscitated from cardio-pulmonary arrest due to VTAs. Just after resuscitation, the QTc interval was 629ms, and [K(+)] was 2.9mEq/L. After correction of [K(+)], the QTc interval was dramatically shortened to 440ms. In order to identify abnormal splicing products of the responsible mutation, we analyzed the reverse transcription-polymerase chain reaction products from peripheral bloods of the mutation carrier, and identified exon 9-skipping (Δ9) and cryptic sequential exons 8 and 9-skipping (Δ8-9) products, as well as a no exon-skipping product. CONCLUSIONS We identified a novel KCNQ splicing mutation 1251+1G>A in forme fruste LQT1, which induces cryptic splicing. Two of the five individuals with mutation experienced VTAs in the setting of hypokalemia, emphasizing the need to increase awareness of the significance of hypokalemia in this subgroup of LQT1 patients.

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; R2 = 0.1665, P < 0.005), SP-T (415 ± 100 ms; R2 = 0.3425, P = 0.036), and SucABL-L (11.6 ± 4.7 mm; R2 = 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.

V‐A‐A‐V Activation Sequence at the Onset of a Long RP Tachycardia: What is the Mechanism?

A 52-year-old woman with a history of multiple episodes of paroxysmal supraventricular tachycardia underwent electrophysiologic studies and a catheter ablation procedure. The 12-lead electrocardiogram during tachycardia showed a long RP tachycardia with negative P waves in leads II, III, and aVF. At baseline, dual atrioventricular (AV) and ventriculoatrial (VA) nodal conduction was elicited by atrial and ventricular premature stimulation. During intravenous administration of isoproterenol, the earliest site of atrial activation during ventricular pacing was observed near the His bundle, and a previously recorded narrow QRS tachycardia was reproducibly induced by premature or rapid ventricular apical pacing, with an initial V-A-A-V activation sequence (Fig. 1). During tachycardia, the HA and AH intervals measured 71 and 342 milliseconds, respectively, and the earliest atrial activation was recorded at the ostium of the coronary sinus (CS). The earliest first “A” of the initial “V-A-A-V” activation sequence was recorded in the His bundle region, reflecting conduction over a fast pathway (FP), as was observed during ventricular pacing, while the second “A” was recorded near the CS ostium, as was observed during the tachycardia. The interval between the first and second “A” was often shorter than the subsequent tachycardia cycle length. Premature ventricular stimuli delivered during tachycardia while the His bundle was refractory did not reset the atrial cycle. From these observations, what is the mechanism of tachycardia?

Putative Mechanism of a Postpacing Interval Paradoxically Shorter Than the Tachycardia Cycle Length

A 79-year-old man without structural heart disease underwent electrophysiological studies and radiofrequency catheter ablation of drug-refractory paroxysmal atrial flutter (AFl). The 12-lead electrocardiogram showed negative flutter waves in leads II, III, aVF, and V5 and V6, and positive flutter waves in lead V1 and V2, consistent with typical counterclockwise AFl. A 7F InquiryTM eicosapolar electrode catheter (St. Jude Medical, AF Division, Minnetonka, MN, USA) with 2-mm interelectrode spacing was advanced into the coronary sinus (CS) from the right subclavian vein, with its middle electrodes (9–10) placed at the ostium and proximal electrodes (20–11) along the Eustachian ridge (ER). Counterclockwise AFl was confirmed by entrainment pacing at multiple sites along the tricuspid annulus. Double potentials were recorded along the ER during ongoing AFl, with the first potential (DP1) in a proximal-to-distal and the second (DP2) in a distal-to-proximal direction, with fusion of the 2 potentials at the CS ostium (Fig. 1A). Two different postpacing intervals were reproducibly observed after the cessation of entrainment pacing near the ER (Figs. 1B and C). In Figure 1B, the interval between the last pacing stimulus (S) and the first atrial electrogram is equal to, whereas in Figure 1C, the interval is shorter than, the tachycardia cycle length (TCL). What are the (a) mechanism and (b) implications of this observation?

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 β1 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.

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

Abstract 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.

Regular Atrial Tachyarrhythmia with Double Coronary Sinus Potentials: What Is the Diagnosis?

A 63-year-old woman underwent electrophysiologicalstudies and radiofrequency catheter ablation of a persistent,drug-refractoryatrialtachyarrhythmia(ATA).Shehadnohis-tory of left atrial (LA) surgery or catheter ablation. Positivewaves were present in leads II, III, aVF, and V1–V6 of the12-lead electrocardiogram, inconsistent with typical atrialflutter (AFL). A 7F Inquiry

Is the Targeted Accessory Pathway Alive or Dead

J Cardiovasc Electrophysiol, Vol. 22, pp. 478-480, April 2011.No disclosures.Addressforcorrespondence:YoshiakiKaneko,M.D.,Ph.D.,DepartmentofMedicine and Biological Science, Gunma University Graduate School ofMedicine, 3-39-22 Showa, Maebashi, Gunma 371-8511, Japan. Fax: +81-27-220-8158; E-mail:kanekoy@gunma-u.ac.jpdoi: 10.1111/j.1540-8167.2010.01935.x

Long RP′ Tachycardia with an Initial A‐A‐V Activation Sequence: What Is the Mechanism?

A 79-year-old man with a history of multiple episodes of paroxysmal supraventricular tachycardia underwent electrophysiologic studies and a catheter ablation procedure. The 12-lead electrocardiogram during tachycardia showed a long RP′ tachycardia with negative P waves in leads II, III, and aVF. No dual anterograde atrioventricular (AV) nodal conduction was elicited by atrial extrastimulation. A narrow QRS tachycardia documented previously was reproducibly induced by atrial extrastimulation (Fig. 1A). During tachycardia, the HA and AH intervals measured 136 and 252 ms, respectively, and the earliest atrial activation was recorded at the ostium of the coronary sinus. Atrial extrastimuli delivered during the tachycardia did not reset the atrial cycle. Atrial overdrive pacing induced a second tachycardia with a similar atrial activation sequence and cycle length, and 2:1AV conduction (Fig. 1B). Ventricular overdrive pacing was delivered at a slightly shorter cycle length than the tachycardia (Fig. 2). Based upon these observations, what is the mechanism of tachycardia?