Masateru Takigawa

Arrhythmogenic response to isoproterenol testing vs. exercise testing in arrhythmogenic right ventricular cardiomyopathy patients

AimsnTo compare the arrhythmic response to isoproterenol and exercise testing in newly diagnosed arrhythmogenic right ventricular cardiomyopathy (ARVC) patients.nnnMethods and resultsnWe studied isoproterenol [continuous infusion (45u2009µg/min) for 3u2009min] and exercise testing (workload increased by 30u2009W every 3u2009min) performed in consecutive newly diagnosed ARVC patients. Both tests were evaluated with regard to the incidence of (i) polymorphic premature ventricular contractions (PVCs) and couplet(s) or (ii) sustained or non-sustained ventricular tachycardia (VT) with left bundle branch block [excluding right ventricular outflow tract VT]; and compared to a control group referred for the evaluation of PVCs without structural heart disease. Thirty-seven ARVC patients (63.5% male, age 38u2009±u200916u2009years) were included. The maximal sinus rhythm heart rate achieved during isoproterenol testing was significantly lower compared to exercise testing (149u2009±u200917 bpm vs. 166u2009±u200919 bpm, Pu2009<u20090.0001). However, the incidence of polymorphic ventricular arrhythmias was much higher during isoproterenol testing compared to exercise testing [33/37 (89.2%) vs. 16/37 (43.2%), Pu2009<u20090.0001]. Interestingly, isoproterenol testing was arrhythmogenic in all 15 patients in whom baseline PVCs were reduced or suppressed during exercise testing. During both isoproterenol and exercise testing, control group presented a low incidence of ventricular arrhythmias compared to ARVC patients (8.1% vs. 89.2%, Pu2009<u20090.0001 and 2.7% vs. 43.2%, Pu2009<u20090.0001, respectively).nnnConclusionsnThe incidence of polymorphic ventricular arrhythmias is significantly higher during isoproterenol compared to exercise testing in newly diagnosed ARVC patients, suggesting its potential utility for the diagnosis.

Revisiting anatomic macroreentrant tachycardia after atrial fibrillation ablation using ultrahigh-resolution mapping: Implications for ablation

BACKGROUNDnAnatomic macroreentrant atrial tachycardias (MATs) are conventionally reported to depend on the cavotricuspid isthmus, the mitral isthmus, or the left atrial roof, and are commonly seen following catheter ablation for atrial fibrillation.nnnOBJECTIVESnTo define the precise circuits of anatomic MAT with ultrahigh-resolution mapping.nnnMETHODSnIn 57 patients (mean age, 62 years; 10 female) who developed ≥1 anatomic MAT, we analyzed 88 MAT circuits including 16 peritricuspid, 42 perimitral, and 30 roof-dependent circuits, using high-density mapping and entrainment.nnnRESULTSnOf 16 peritricuspid atrial tachycardias (ATs), 8 (50.0%) showed a circuit not limited to the tricuspid annulus. However, cavotricuspid isthmus ablation terminated the tachycardia in all patients. Similarly, 26 of 42 perimitral ATs (61.9%) showed a circuit not limited to the mitral annulus, and a low-voltage zone <0.1 mV around the mitral annulus was associated with nontypical perimitral ATs (P < .0001). The practical isthmus was not in the mitral isthmus in 13 of these 26 perimitral ATs (50%). Finally, 22 of 30 roof-dependent ATs (73.3%) had a circuit not rotating around both pairs of pulmonary veins. Brief assessment of the activation direction on the posterior wall in relation to that on the septal, anterior, and lateral wall helped deduce the circuit of roof-dependent AT in 27 of 30 (90.0%). Practical isthmus was not in the roof in 8 of 22 (36.4%). Practical isthmuses mapped with the system were significantly shorter than the usual anatomic isthmuses (16.1 ± 8.2 mm vs 33.7 ± 10.4 mm) (P < .0001).nnnCONCLUSIONSnHigh-density mapping successfully identified the precise circuits and the practical isthmus of anatomic MATs in patients with prior atrial fibrillation ablation.

Long-Term Outcome of Substrate Modification in Ablation of Post–Myocardial Infarction Ventricular Tachycardia

Background: Long-term results of substrate modification for ablation of ventricular tachycardia (VT) have not been reported. We report long-term outcomes of substrate elimination targeting local abnormal ventricular activities (LAVA) for post–myocardial infarction VT. Methods and Results: One hundred fifty-nine consecutive patients undergoing first ablation were included (65±11 years, 92% implantable cardioverter defibrillators, 54% storms, and 73% appropriate shocks). LAVA were identified in 92% and VT was inducible in 73%. Complete LAVA elimination and noninducibility after ablation were achieved in 64% and 85%. During a median follow-up of 47 months (interquartile range, 34–82), single-procedure ventricular arrhythmia (VA)–free survival was 55% (10% storms and 19% shocks). The VA-free survival was 73%, 68%, 61%, 55%, and 49% after 1, 2, 3, 4, and 5 years, respectively. Complete LAVA elimination was associated with improved outcomes: VA-free survival of 82% at 1 year and 61% at 5 years. In the subgroup treated with multielectrode mapping and real-time image integration, VA-free survival was 86% and 65% at 1 year and 4 years, respectively. Including repeat procedures in 18% of pts (1.3±0.6 ablations/pt) outcomes improved to 69% VA-free survival (2% storms and 9% shocks) during median 46-month follow-up. Overall survival was 91% at 1 year and 77% at 5 years of follow-up. Conclusions: In this monocentric study, substrate modification targeting LAVA for post–myocardial infarction VT resulted in a substantial reduction of VT storm and implantable cardioverter defibrillator shocks and up to 49% of patients free from arrhythmia at 5 years after a single procedure. Complete LAVA elimination, multielectrode mapping, and real-time integration were associated with improved VA-free survival.

High-density characterization of a localized reentry circuit occurred after AF ablation

We present the case of a localized reentry circuit that developed 24 h after radiofrequency ablation of atrial fibrillation (AF). The circuit was of interest because it overlapped with sites of previous defragmentation during AF. The circuit presented a small funnel that measured only 1.4 mm at its narrowest segment. Fractionated signals, which codify for slow conduction zones, corresponded to the isthmus site. Ablation at this site interrupted the atrial tachycardia.

Detailed comparison between wall thickness and voltages in chronic myocardial infarction: TAKIGAWA et al.

The relationship between the local electrograms (EGMs) and wall thickness (WT) heterogeneity within infarct scars has not been thoroughly described. The relationship between WT and voltages and substrates for ventricular tachycardia (VT) was examined.

Targeted ablation of specific electrogram patterns in low voltage areas after pulmonary vein antral isolation in persistent atrial fibrillation: Termination to an organized rhythm reduces atrial fibrillation recurrence: EFREMIDIS et al.

Ablation strategies have been developed to improve outcomes in patients with persistent atrial fibrillation (PsAF). However, the impact of atrial fibrillation (AF) termination on late AF recurrence is not well known. The aim of our study was to evaluate the impact of AF termination to atrial tachycardia (AT) or sinus rhythm (SR) during catheter ablation on late AF recurrence after the 3‐month blanking period.

Importance of bipolar electrode orientation on local electrogram properties

BACKGROUNDnThe direct effect of bipolar orientation on electrograms (EGMs) remains unknown.nnnOBJECTIVEnThe purpose of this study was to examine the variation of EGMs with diagonally orthogonal bipoles.nnnMETHODSnThe HD-32 Grid catheter (Abbott, Minneapolis, MN) can assess the effect of bipolar orientation while keeping the interelectrode distance and center unchanged. Seven sheep with anterior myocardial infarction were analyzed using diagonally orthogonal electrode pairs across splines by comparing local EGMs from each pair of opposing electrodes {eg. A1-B3 (southeast direction [SE]) vs A3-B1 (northeast direction [NE])}.nnnRESULTSnA total of 4084 EGMs (1 in each direction) were analyzed for 2042 sites (544 in the infarcted area, 488 in the border area, and 1010 in the normal area). The higher and lower voltages measured using each pair of opposing electrodes significantly differed (1.10 mV [0.43-2.56 mV] vs 0.69 mV [0.28-1.58 mV]; P < .0001), and the median variation was 0.28 mV (0.11-0.80 mV) (31.7% [16.0%-48.9%]). The voltage variation was maximized to 48.7% (37.7%-61.6%) (P < .0001) on sites where the activation wavefront was perpendicular to the one bipolar direction and parallel to the other. A total of 594 of 719 (82.6%) sites with the voltage <0.5 mV and 539 of 699 (77.1%) sites with the voltage >1.5 mV in NE stayed in the same voltage range as those in SE. However, only 348 of 624 (55.8%) sites with the voltage 0.5-1.5 mV in NE stayed in the same range as those in SE. Local ventricular abnormal activities (LAVAs) were detected in 592 of 2042 (29.0%) sites in total, frequently distributed in the border area. A total of 177 (29.9%) LAVAs were missed in one direction and 180 (30.4%) in the other. When 415 (70.1%) LAVAs detected in NE are defined as the reference, 235 of 415 (56.6%) matched with those detected in SE.nnnCONCLUSIONnThe bipolar voltage and distribution of LAVAs may differ significantly between diagonally orthogonal bipolar pairs at any given site.

Comprehensive Multicenter Study of the Common Isthmus in Post–Atrial Fibrillation Ablation Multiple-Loop Atrial Tachycardia

Background: Characteristics of multiple-loop atrial tachycardia (AT) circuits have never precisely examined. Methods: In 193 consecutive post–atrial fibrillation ablation patients with AT, 44 multiple-loop ATs including 42 dual-loop AT and 2 triple-loop AT in 41 (21.2%) were diagnosed with the high-resolution mapping system and analyzed off-line. Results: In dual-loop ATs, 3 types were identified: type M, a combination of 2 anatomic macroreentrant ATs (AMATs) in 19 (43.2%); type MN, with 1 AMAT and 1 non-AMAT in 12 (27.3%); and type N with 2 non-AMATs in 11 (25.0%). The remaining 2 triple-loop ATs (4.5%) were a combination of perimitral-, roof-dependent-, and non-AMAT. At least 1 AMAT was included in 33 (75.0%), and 1 non-AMAT in 25 (56.8%). Of the ATs with at least 1 non-AMAT circuit, a pulmonary vein formed part of the circuit in 16/25 (64.0%). The length of the common isthmus was 3.6±1.4 cm in type M, 1.6±0.7 cm in type MN, and 1.1±0.7 cm in type N (P<0.0001). The area of the common isthmus was 12.92±7.68, 2.46±1.53, and 0.90±0.81 cm2, in Type M, MN, and N (P<0.0001). The narrowest width of the common isthmus was 1.8±0.7 cm, 1.1±0.3 cm, and 0.7±0.3 cm in type M, MN, and N (P<0.0001), respectively. The electrograms in the common isthmus showed longer duration and lower voltage in type N, type MN, and type M (duration: 106±25 ms, 87±27 ms, and 69±27 ms; P=0.006; and voltage: 0.06±0.02 mV, 0.22±0.21 mV, and 0.57±0.50 mV; P<0.0001), respectively. Conclusions: Multiple-loop ATs are complex, frequently including anatomic circuits. They have specific characteristics determined by the combination of AMAT and non-AMAT.

The electrical circuit of a hemodynamically unstable and recurrent ventricular tachycardia diagnosed in 35 s with the Rhythmia mapping system

Herein, we report a 47‐year‐old woman with ischemic cardiomyopathy who underwent ablation therapy due to an electrical storm without any triggers. The voltage mapping in sinus rhythm with the Rhythmia system and Orion catheter displayed several LAVAs in and around the anteroapical scar area. Although the patient did not tolerate the induced clinical ventricular tachycardia, which was reproductively induced, 35‐second‐mapping in the scar zone with the Orion catheter demonstrated the VT circuit with the critical isthmus. This report shows the possibility of the new ultra‐high density mapping system in a specific ischemic VT patient.

Dual-loop circuit of ventricular tachycardia in repaired tetralogy of Fallot patient

A 22-year-old man who had had a surgical repair of tetralogy of Fallot (TOF) with a patch closure of the ventricular septal defect (VSD) and reconstruction of the right ventricular outflow tract (RVOT) with a patch at the age of 3 was referred for ventricular tachycardia (VT) risk assessment prior to pulmonary valve (PV) replacement. Voltage mapping during sinus rhythm with the Orion catheter and Rhythmia system (Boston Scientific, Marlborough, MA, USA) showed three potential isthmuses as shown in Figure 1A; isthmus-1, between PV and the VSD patch [length: 12.4 mm, width: 19.2 mm, and conduction velocity (CV): 0.21 m/s], isthmus-2, between the PV and RVOT patch (length: 16.3 mm, width: 13.5 mm, and CV: 0.34 m/s), and isthmus-3 between the RVOT patch and the tricuspid annulus (length: 39.4 mm, width: 51.4 mm, and CV: 0.80 m/s). Ventricular tachycardia [cycle length (CL)1⁄4 230 ms] was easily induced by programmed pacing (Figure 1B). The activation map in VT with 18 519 points (Figure 1C) suggested that isthmuses 1 and 2 were used simultaneously for a dual-loop VT, which was confirmed by entrainment mapping (Figure 1D and E). Ablation at isthmus-1 resulted in a 10-ms increase of the CL without a remarkable alteration in surface ECG morphology. Then, we could not continue to ablate the isthmus-2 due to hemodynamically compromise. The patient was cardioverted and complete block of the isthmuses 1 and 2 was created in sinus rhythm. Afterwards, no VT was inducible. Zeppenfeld et al. reported that after surgical repair of TOF, the four types of potential isthmus between (i) the tricuspid annulus and scar/ patch in the right anterior ventricular outflow, (ii) the pulmonary annulus and right ventricular free wall scar/patch, (iii) the pulmonary annulus and septal scar/patch, and (iv) the septal scar/patch and tricuspid annulus. In the present case, two isthmuses ([2] and [3]) were simultaneously included in the circuit of the VT. The right ventricle between tricuspid annulus and RVOT patch, which was also described as a potential isthmus ([1]) in the report, was commonly included in the both circuits. However, it was too long to be the practical isthmus in this case. Kapel et al. examined 74 repaired TOF patients and succeeded in mapping 37 VTs in 24 patients. Although four patients among them had two VTrelated anatomical isthmuses, each isthmus supported a different VT re-entry. They described that CV <0.5 m/s was associated with induced VTs. In the present study, the isthmuses 1 and 2 met this criterion. However, anatomical isthmus dimensions and conduction velocity may not be directly comparable to that in the previous study, as we performed an ultra-high density mapping with a multipolar catheter with smaller bipolar spacing and used a dense scar threshold of 0.2 mV, based on our previous experience with this mapping system in the right ventricle. Here, high-resolution mapping and entrainment demonstrated that two isthmuses were simultaneously used as a VT circuit. This is the first report that demonstrates a dual-loop VT circuit in repaired TOF.