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Mapping and localizing presystolic Purkinje potentials are crucial for determining the optimal ablation site for fascicular premature ventricular contractions (PVCs). Here we present a case of PVCs originating from the distal left anterior fascicle (LAF). Activation mapping using a multipolar catheter with small electrodes demonstrated early presystolic Purkinje potentials during the PVCs. A moderately good pace-map match was also obtained near the successful ablation site. This case demonstrates the activation pattern of PVCs originating from the distal LAF and the usefulness of multipolar catheters with small electrodes for the mapping of fascicular PVCs.

A 38-year-old woman with a structurally normal heart was referred for catheter ablation due to symptomatic, monomorphic, high burden (12%) premature ventricular complexes (PVC) refractory to medical therapy. The PVC's ECG morphology suggested an origin in the proximal left anterior fascicle (LAF). During procedure PVCs were mechanically suppressed. Consequently, selection of the ablation target site was based on pace-mapping. This case illustrates how ablation from the right coronary cusp (RCC) for PVC arising from the proximal LAF could be accurately guided by pace-mapping. At this location, pacing can result in both a selective and a non-selective capture of the proximal LAF.

Left bundle branch pacing (LBBP) is emerging as an alternative to His bundle pacing that overcomes the latter's limitations. Several studies have reported on the safety, efficacy, and electrophysiological properties of LBBP, while postoperative success rates range from 80.5% to 94%. The left posterior fascicle is composed of broad bands of fibers coursing inferiorly and posteriorly toward the papillary muscle, while the anterior fascicle is a thin, tendon-like structure. We report a case of a 70-year-old man in whom left posterior fascicular pacing was done after LBBP failed. We were able to demonstrate all the features of left posterior fascicular capture, including fascicular potential and a left anterior hemiblock pattern, using surface 12-lead electrocardiography. Left posterior fascicular pacing could be an alternative technique when attempts to deploy LBBP fail.

A 16-year-old female patient was hospitalized due to narrow QRS tachycardia suggestive of fascicular ventricular tachycardia. Initially, the differential diagnosis with supraventricular tachycardia can be challenging. The tachyarrhythmia is well controlled with medication, but electrophysiological study and ablation may be necessary in patients who remain symptomatic.

A 32‐year‐old male received catheter ablation of frequent ventricular extrasystoles (VEs). His electrocardiogram showed monomorphic VEs with an inferior axis and early precordial transitional zone. During electrophysiological testing, a 10‐pole catheter positioned in the left ventricular outflow tract recorded sharp pre‐potentials just before the ventricular activation during VEs as well as sinus beats. Three‐dimensional mapping was performed by annotating the sharp pre‐potentials to reveal that the earliest activation site was deemed to be close to the left anterior fascicle. A cryoablation catheter was introduced into the left ventricle and freezing for 240 seconds successfully eliminated the clinical VEs without any complications., A 32‐year‐old male received catheter ablation of frequent ventricular extrasystoles (VEs). During the electrophysiological study, a 10‐pole catheter positioned in the left ventricular outflow tract recorded sharp pre‐potentials just before the ventricular activation during the VEs as well as sinus beats. A cryoablation catheter was introduced into the left ventricle and freezing for 240 seconds on the blue tag successfully eliminated the clinical VEs without any complications.

A 33-year-old man had verapamil-sensitive ventricular tachycardia (VT) with a right bundle branch block (RBBB) and right axis deviation. Programmed stimulation from the para-Hisian region induced ventricular tachycardias (VT1 or VT2). VT1 was entrained during pacing from the para-Hisian region. A single para-Hisian stimulation antidromically captured the proximal portion of the left anterior fascicle (LAF), but the cycle length of VT2 remained unchanged. This observation indicated that the upper limb of the LAF was a bystander of the reentry circuit. We have clarified this mechanism with applying a single premature stimulation from the para-Hisian region.

A 17‐year‐old woman presented with frequent palpitations and shortness of breath and was diagnosed with drug‐refractory ventricular parasystole. We predicted that the parasystole originated from the left anterior fascicle (LAF). Detailed activation maps of both conduction systems, including the LAF, during sinus rhythm and ventricular parasystole were obtained using a parallel mapping system. We confirmed the earliest fascicular potential of the parasystole and performed catheter ablation with no complications. This novel mapping algorithm for simultaneous acquisition of multiple maps aided effective treatment of ventricular parasystole originating from the LAF., Ventricular parasystole originating from the left anterior fascicle can be effectively eliminated by using this novel mapping algorithm of parallel mapping and LAT hybrid mapping. Parallel mapping makes it possible to obtain both activation maps during ventricular parasystole and sinus rhythm simultaneously, decreasing the procedure time while also increasing efficacy. LAT hybrid mapping also makes it possible for precise positioning during parasystole ablation.

Belhassen ventricular tachycardia (BVT), also known as verapamil-sensitive ventricular tachycardia, is an infrequent finding that can be fatal unless recognized early and treated in a prompt manner. Most patients have insignificant presentation suggestive of the disease, but on electrocardiography (EKG), BVT is characterized by a complete right branch block (RBB) and a right axis deviation (RAD). In this case report, we describe an unusual case of a 35-year-old male patient who presented to the emergency department (ED) complaining of acute palpitations of two-hour duration; subsequent diagnostic testing revealed BVT in the patient.

The history dependence of force is an intrinsic property of muscle whereby a muscle actively shortened or lengthened to an isometric steady-state produces less (residual force depression; rFD) or more force (residual force enhancement; rFE), respectively, than a purely isometric contraction at the same muscle length and level of activation. Previous studies on the modifiability of the history dependence of force have been inconclusive, and none have attempted to modify rFD and rFE through isometric resistance training biased to short versus long muscle-tendon unit (MTU) lengths. We tested maximal voluntary rFD and rFE in 7 males and 6 females before and after 8 weeks of maximal isometric dorsiflexion training 3 days/week. Participants trained one leg at 0° of plantar flexion (short-MTU training) and one at 40° of plantar flexion (long-MTU training). Ultrasonography of the tibialis anterior assessed resting muscle architecture. Tibialis anterior fascicle length decreased by ~3% following short-MTU training (P = 0.03) and increased by ~4% following long-MTU training (P = 0.01). rFD did not change following training at either MTU length (absolute rFD: P = 0.53; percent rFD: P = 0.51), nor did rFE (absolute rFE: P = 0.78; percent rFE: P = 0.80), with no relationships between the change in fascicle length and the change in percent rFD (R2 = 0.01, P = 0.62) nor rFE (R2 = 0.001, P = 0.88). Our data indicate that voluntary rFD and rFE were not modified by isometric training and not related to the fascicle length adaptations we observed.

Background: Premature ventricular complex (PVC) with narrow QRS duration originating from proximal left anterior fascicle (LAF) is challenging for ablation. This study was performed to evaluate the safety and feasibility of ablation from right coronary cusp (RCC) for proximal LAF-PVC and to investigate this PVC’s characteristics. Methods: Mapping at RCC and left ventricle and ECG analysis were performed in 20 patients with LAF-PVC. Results: The earliest activation site (EAS), with Purkinje potential during both PVC and sinus rhythm, was localized at proximal LAF in 8 patients (proximal group) and at nonproximal LAF in 12 patients (nonproximal group). The Purkinje potential preceding PVC-QRS at the EAS in proximal group (32.6±2.5 ms) was significantly earlier than that in nonproximal group (28.3±4.5 ms, P =0.025). Similar difference in the Purkinje potentials preceding sinus rhythm QRS at the EAS was also observed between proximal and nonproximal groups (35.1±4.7 versus 25.2±5.0 ms, P P =0.002, and 3.9±0.8 versus 15.7±7.8 mm, P 5 , and V 6 ; lower R wave in leads I, aVR, aVL, V 1 , V 2 , and V 4 ; and smaller q wave in leads III and aVF. The QRS duration difference (PVC-QRS and sinus rhythm QRS) Conclusions: PVCs originating from proximal LAF, with unique electrocardiographic characteristics, could be eliminated safely from RCC.

We thank Yamada et al1 for their interest in our recent article. We wish to address the points raised by their letter. First, Yamada et al raise concerns about the location of the left anterior fascicle as depicted in Figures 1, 3, and 5. It should be pointed out that Figures 1 and 5 represent purely schematic depictions of the fascicular, papillary, and annular anatomy. To compress 3-dimensional anatomy into a 2-dimensional figure, we arbitrarily placed the left anterior fascicle along the septal aspect of the annular ring. Although the left anterior fascicle courses anteriorly and laterally after branching from the left bundle, we intentionally elected not to mark …