The Purkinje system has been found to be responsible for the mechanism of some ventricular tachyarrhythmias. These ventricular tachyarrhythmias can be called Purkinje-related arrhythmias, and are manifested as monomorphic ventricular tachycardia (VT) and polymorphic VT, including ventricular fibrillation (VF). In monomorphic VTs, 4 distinct tachycardias have been found to be related to the Purkinje system: (1) verapamil-sensitive left fascicular VT, (2) Purkinje fiber-mediated VT post infarction, (3) bundle branch reentry (BBR) and interfascicular reentry VTs, and (4) focal Purkinje VT. In polymorphic VT and VF, the Purkinje system may also play an important role. The Purkinje network plays a pivotal role in both the initiation and perpetuation of VF. A triggering ventricular premature beat could arise from either the right or left Purkinje system, and the catheter ablation of the trigger results in a very high cure rate for VF. In patients with an electrical storm, catheter ablation of the triggering VPBs from the Purkinje system should be used as an electrical bailout therapy.

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Torsades de pointes (TdP) is characterized not only by its electrocardiographic morphology but also by a tendency to spontaneously terminate. Although clinical and experimental studies suggested that TdP is triggered exclusively by early afterdepolarization, the reentrant mechanism seems to play a certain role in its maintenance. In this article, I review the studies that investigated the origin and activation sequences of the twisting QRS complexes of TdP, and discuss whether it is fortunate or unfortunate for us if TdP has something to do with reentry.

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Introduction: The aim of this study was to clarify the characteristics of lower loop reentry (LLR) in patients who underwent cardiac surgery.
Methods: Of 194 patients from 2000 to 2007 with negative flutter waves in the inferior leads (II, III, and aVf), 4 patients had LLR and reentrant circuits identified by a 3D activation sequence mapping system. We studied the characteristics of the surface electrocardiogram (ECG) patterns of those LLRs.
Results: All 4 patients had a history of an intracardiac operation. The 3D activation sequence mapping system during the LLR exhibited a clockwise (CW) wavefront around the inferior vena cava (IVC) from the caudal view. During the LLR, the right atrium (RA) free wall was activated in a caudal-cranial sequence and a collision of two activation wavefronts from the lower RA and upper RA occurred at the RA free wall.
Conclusions: The 3D activation mapping during the AT revealed an activation wavefront propagating around the IVC and the diagnosis of LLR. Detailed 3D electroanatomical mapping and pacing study are needed to identify the reentrant circuit of LLR in patients with previous intracardiac surgery.

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Modern cardiac implantable devices (CIDs) such as pacemakers (PMs), implantable cardioverter defibrillators (ICDs), and defibrillators for cardiac resynchronization therapy (CRT-Ds) are engineered to be resistant to electromagnetic interference (EMI). However, such interference is still a concern when patients are exposed to household and occupational appliances in daily life. The aim of this study was to evaluate the risk of EMI caused by several types of household and industrial appliances. EMI with 20 CIDs (12 PMs, 7 ICDs, 1 CRT-D) was tested for 16 household and 19 industrial appliances using three methods of measurement: Irnich’s human body model, an alternating electric field device, and an alternate-current and static-current magnetic field device. The thresholds for the risk of EMI were defined as an alternating electric field of 5000 V/m, an alternate-current magnetic field of 20 μT, and a static-current magnetic field of 10 G. In 35 tests, 15 of the 16 household appliances showed no EMI with any CIDs, but an induction oven showed a potential risk of EMI with 2 PMs. None of the 19 industrial appliances showed EMI with any CIDs, provided that an appropriate distance from the appliances was maintained. These findings should allow physicians to evaluate whether patients with a CID can safely return to their homes and workplaces.

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Introduction: Landiolol hydrochloride is an ultra-short-acting β-blocker that is administered intravenously and has many advantages in cardiac surgery. This study was performed to examine the safety and efficacy of low-dose landiolol continuous infusion in cardiac surgery.
Methods and Results: Nineteen patients who underwent either aortic valve replacement or coronary artery bypass surgery received low-dose continuous infusion of landiolol (2.8±0.75 μg/kg/min) from the time of skin incision until the second postoperative day. Nineteen patients who did not receive landiolol served as controls. Heart rate, arterial pressure, cardiac index, and stroke volume were measured and the occurrence of supraventricular tachyarrythmia was monitored for one week after surgery. Landiolol decreased the heart rate without causing hemodynamic deterioration. The incidence of supraventricular tachyarrythmia was 32% and 47% in the landiolol and control groups, respectively (P=0.50).
Conclusions: Landiolol is effective for decreasing heart rate while maintaining other hemodynamic parameters. Our data did not show a clear prophylactic effect of landiolol on postoperative supraventricular tachyarrythmia.

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The patient was a 43-year-old male whose chief complaint was syncope. Electrocardiography at the first visit revealed escaped rhythm (38 bpm). After hospitalization he developed reverse common atrial flutter (AFL) and underwent catheter ablation. After termination of atrial flutter by ablation, sinus arrest was noted, allowing a diagnosis of bradycardia-tachycardia syndrome, for which the patient underwent pacemaker implantation.
Twenty days after implantation, a marked elevation of atrial threshold was noted, despite absence of a change in lead resistance or position, and atrial capturing was not possible even at the maximum output (8 V/1.2 ms). The cause remained unknown and the patient was followed without active intervention. Atrial threshold normalized during the follow-up, but no change was noted in lead resistance or position even at the time of normalization.

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We experienced 2 cases in which oversensing of a particular noise after the implantation of an implantable cardiac device was observed in the acute phase. These were unusual cases in which the noise exhibited a low frequency pattern and appeared several hours after the implantation, but disappeared within 1 week. Here we present these cases and the details of an experiment investigating the origin of the noise and the methods for its prevention.
The noise in these cases led to pacing inhibition and could have induced an inappropriate shock due to oversensing, but its morphology and electromagnetic interference were atypical for a lead failure or myopotentials. The noise spontaneously disappeared from the analysis of the data stored in the device. In an experiment based on the Irnich model, in which it was assumed that blood invaded a damaged grommet, low frequency noise occurred which was similar to the noise in the two cases. We concluded that care must be exercised when handling grommets.

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We report a case of clonic-tonic seizures diagnosed using an implantable loop recorder, a device for detecting cardiac arrhythmias. A 65-year-old man was referred to our hospital for loss of consciousness with myotonic jerks during sleep. He had experienced several similar episodes. No family history of sudden death was evident, and no structural heart disease was present. Coronary angiography with intracoronary acetylcholine (ACh) showed neither organic stenosis nor vasospastic angina. Ventricular tachyarrhythmias were not induced by programmed electrical stimuli. Sleep electroencephalography, brain magnetic resonance imaging and magnetic resonance angiography revealed no specific findings. We implanted a loop recorder to monitor rhythm abnormalities. One month later, an attack occurred at night. His wife recognized the episode and activated the implantable loop recorder. No arrhythmia was recorded, but myopotentials characteristic of tonic-clonic seizures were detected.

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