Toshihiro Honda

Significance of Late Diastolic Potential Preceding Purkinje Potential in Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia

BACKGROUND Verapamil-sensitive idiopathic left ventricular tachycardia (VT) is due to reentry with an excitable gap. A late diastolic potential (LDP) is recorded during endocardial mapping of this VT, but its relation to the reentry circuit and significance in radiofrequency (RF) ablation remain to be elucidated. METHODS AND RESULTS Sixteen consecutive patients with this specific VT were studied (12 men and 4 women; mean age, 32 years). In all patients, sustained VT was induced and during left ventricular endocardial mapping, LDP preceding Purkinje potential (PP) was recorded at the basal (11 patients), middle (3 patients), or apical septum (2 patients). The area with LDP recording was confined to a small region (0.5 to 1.0 cm2) in each patient and was included in the area where PP was recorded (2 to 3 cm2). The relative activation times of LDP, PP, and local ventricular potential (V) at the LDP recording site to the onset of QRS complex were -50.4+/-18.9, -15.2+/-9.6, and 3.0+/-13.3 ms, respectively. The earliest ventricular activation site during VT was identified at the posteroapical septum and was more apical in the septum than the region with LDP in every patient. In 9 patients, VT entrainment was done by pacing from the right ventricular outflow tract while recording LDP. During entrainment, LDP was orthodromically captured, and as the pacing rate was increased, the LDP-to-PP interval was prolonged, whereas stimulus-to-LDP and PP-to-V interval were constant. In 3 patients, the pressure applied to the catheter tip at the LDP region resulted in conduction block between LDP and PP and in VT termination. RF energy application at the LDP recording site successfully eliminated VT. CONCLUSIONS LDP was suggested to represent the excitation at the entrance to the specialized area with a conduction delay in response to the increase in the rate within the critical slow conduction zone participating in the reentry circuit of this VT. LDP can be a useful marker for successful RF ablation for this VT.

Effects of verapamil and lidocaine on two components of the re-entry circuit of verapamil-sensitive idiopathic left ventricular tachycardia

OBJECTIVES We characterized pharmacologically the slow conduction zone of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) with regard to the late diastolic potential (LDP). BACKGROUND We showed that the slow conduction zone of ILVT could be divided into two components by LDP; that is, the distal component with a tachycardia-dependent conduction delay property and the proximal one without it. METHODS Electrophysiologic studies were performed in eight consecutive patients. The LDP was recorded during left ventricular (LV) mapping during ILVT. Entrainment was performed from the right ventricular outflow tract while recording LDP. The effects of lidocaine (1 mg/kg body weight) and verapamil (0.5 or 1.0 mg) were examined during entrainment. RESULTS The LDPs preceding the Purkinje potential (PP) were serially recorded from the upper third to the middle of the LV septum along the narrow longitudinal line. The ventricular tachycardia (VT) cycle length increased after lidocaine (p < 0.05), and further after verapamil (p < 0.05). The increments in the VT cycle length after administration of the drugs strongly correlated with those in LDP-PP (r > 0.9 for both drugs). The interval from the ventricular potential to LDP was unchanged after administration of the drugs. In one patient, verapamil terminated VT by local conduction block between LDP and PP. The LDP-PP measured during entrainment increased after lidocaine, and further after verapamil, whereas the interval from the stimulus to LDP remained unchanged. CONCLUSIONS The component distal to LDP is mainly calcium channel-dependent and partly depressed sodium channel-dependent. The proximal component is considered to be sodium channel-dependent (normal).

ATRIAL ECTOPY ORIGINATING FROM THE POSTEROINFERIOR ATRIUM DURING RADIOFREQUENCY CATHETER ABLATION OF ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA

Atrial ectopy sometimes appears during RF ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia (AVNRT). However, its origin, characteristics, and significance are still unclear. To examine these issues, we analyzed 67 consecutive patients with AVNRT (60 with slow‐fast AVNRT and 7 with fast‐slow AVNRT), which was successfully eliminated by RF ablation to the sites with a slow potential in 63 patients and with the earliest activations of retrograde slow pathway conduction in 4 patients. During successful RF ablation, junctional ectopy with the activation sequence showing H‐A‐V at the His‐bundle region appeared in 52 patients (group A) and atrial ectopy with negative P waves in the inferior leads preceding the QRS and the activation sequence showing A‐H‐V at the His‐bundle region appeared in 15 patients (group B). Atrial ectopy was associated with (10 patients) or without junctional ectopy (5 patients). Before BF ablation, retrograde slow pathway conduction induced during ventricular burst and/or extrastimulus pacing was more frequently demonstrated in group B than in group A (9/15 [60%] vs 1/52 [2%], P < 0.001). Successful ablation site in group A was distributed between the His‐bundle region and coronary sinus ostium, while that in group B was confined mostly to the site anterior to the coronary sinus ostium. In group B, atrial ectopy also appeared in 21 % of the unsuccessful RF ablations. In conclusion, atrial ectopy is relatively common during slow pathway ablation and observed in 8% of RF applications overall and 22% of RF applications that successfully eliminated inducible AVNRT. Atrial ectopy appears to be closely related to successful slow pathway ablation among patients with manifest retrograde slow pathway function.

An autopsy case of the rupture of a giant aneurysm in a saphenous vein graft: 18 years after CABG

The saphenous vein is a widely used blood vessel for arterial bypass procedures. Failures of saphenous vein aortocoronary bypass grafts are predominantly the result of subsequent vein graft atherosclerotic disease. Rarely saphenous vein grafts undergo aneurysmal degeneration. This report describes a case of a ruptured aneurysm in a saphenous vein graft that occurred in an 82-year-old female who underwent a coronary artery bypass operation 18 years previously. We could not resuscitate her, but describe the autopsy findings in detail.

Superior Rhythm Discrimination With the SmartShock Technology Algorithm ― Results of the Implantable Defibrillator With Enhanced Features and Settings for Reduction of Inaccurate Detection (DEFENSE) Trial ―

BACKGROUND Shocks delivered by implanted anti-tachyarrhythmia devices, even when appropriate, lower the quality of life and survival. The new SmartShock Technology®(SST) discrimination algorithm was developed to prevent the delivery of inappropriate shock. This prospective, multicenter, observational study compared the rate of inaccurate detection of ventricular tachyarrhythmia using the SST vs. a conventional discrimination algorithm.Methods and Results:Recipients of implantable cardioverter defibrillators (ICD) or cardiac resynchronization therapy defibrillators (CRT-D) equipped with the SST algorithm were enrolled and followed up every 6 months. The tachycardia detection rate was set at ≥150 beats/min with the SST algorithm. The primary endpoint was the time to first inaccurate detection of ventricular tachycardia (VT) with conventional vs. the SST discrimination algorithm, up to 2 years of follow-up. Between March 2012 and September 2013, 185 patients (mean age, 64.0±14.9 years; men, 74%; secondary prevention indication, 49.5%) were enrolled at 14 Japanese medical centers. Inaccurate detection was observed in 32 patients (17.6%) with the conventional, vs. in 19 patients (10.4%) with the SST algorithm. SST significantly lowered the rate of inaccurate detection by dual chamber devices (HR, 0.50; 95% CI: 0.263-0.950; P=0.034). CONCLUSIONS Compared with previous algorithms, the SST discrimination algorithm significantly lowered the rate of inaccurate detection of VT in recipients of dual-chamber ICD or CRT-D.

Smoking history and underlying lung disease are associated with poor outcome in patients developing interstitial pneumonia during low-dose amiodarone therapy

Amiodarone is a useful antiarrhythmic drug, especially in patients with serious heart diseases, but amiodarone‐induced interstitial pneumonia (AMD‐IP) is sometimes lethal.

Thoracoscopic phrenic nerve patch insulation to avoid phrenic nerve stimulation with cardiac resynchronization therapy

A 76‐year‐old female was implanted with a cardiac resynchronization therapy (CRT) device, with the left ventricular lead implanted through a transvenous approach. One day after implantation, diaphragmatic stimulation was observed when the patient was in the seated position, which could not be resolved by device reprogramming. We performed thoracoscopic phrenic nerve insulation using a Gore‐Tex patch. The left phrenic nerve was carefully detached from the pericardial adipose tissue, and a Gore‐Tex patch was inserted between the phrenic nerve and pericardium using a thoracoscopic technique. This approach represents a potential option for the management of uncontrollable phrenic nerve stimulation during CRT.

Atrial tachycardia caused by a superior vena cava fibrillation with conduction block

Here, we report a case of a 62‐year‐old man with a history of incessant atrial tachycardia (AT) for several years. An electrophysiological study revealed rapid and irregular activity in the superior vena cava (SVC), but the surface 12‐lead electrocardiogram (ECG) exhibited a relatively regular AT (atrial cycle length=240 ms). CARTO mapping of the right atrium (RA) demonstrated that the earliest atrial activation occurred at the posterior septum of the upper RA (the SVC–RA junction). Intravenous administration of 20 mg adenosine triphosphate (ATP) led to an acceleration of the SVC–RA conduction up to 1:1 conduction, and the atrial cycle length decreased, consequently converting the AT to transient atrial fibrillation (AF). Application of single radiofrequency energy at the earliest atrial activation site during tachycardia terminated the AT and achieved isolation of the SVC from the RA, despite the continued presence of fibrillation in the SVC. We speculated that SVC fibrillation with spontaneous conduction block at the SVC–RA junction was the cause of this AT.

Electromagnetic Interference with Cardiac Implantable Devices by Household and Industrial Appliances

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: Irnichs 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 mT, 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.

Economical Evaluation of Remote Monitoring System in Patients with Cardiac Implantable Electronic Devices in Japan

Background: The number of implantation of cardiac implantable electric devices (CIEDs) is increasing steadily and rapidly, and as results, hospital workload is also increasing. Many studies showed that remote monitoring system (RMS) in patients with CIEDs is safe and effective for devices follow-up. While the introduction of RMS is expected to reduce the hospital workload, it was required more manpower, to analyze transmitted data. To evaluate the efficacy of RMS, we assessed economical benefit of RMS. Methods and Results: We assessed economical efficacy of RMS in patients with CIEDs by economical simulation model. Economical evaluation was based on the clinical data in Saiseikai Kumamoto Hospital from January 2007 to December 2010. To date, Carelink® (Medtronic), Merlin.net® (S.J.M.), and Biotronik Home Monitoring® (Biotronik) was available as RMS in Japan. We analyzed 1279 patients with pacemaker and 473 patients with ICD/CRT-D who were followed in our hospital. At 2010, 6% of patients in pacemaker, and 37.4% in ICD/CRT-D were introduced to RMS. This simulation model revealed that our hospital could never get economical benefit without reimbursement of RMS. However, when we could accept reimbursement of telemedicine without visiting hospital, the more numbers of RMS could lead the more benefits. Conclusions: If we want to encourage broad use of RMS, the imbursement of RMS was needed.