Development of ventricular fibrillations with different characteristics in the local electrocardiogram: large and small amplitude of activation, and its implication for implantable cardioverter defibrillator treatment.

An implantable cardioverter defibrillator (ICD) was implanted in 2 patients with ventricular tachyarrhythmia related to old myocardial infarction, and defibrillation tests were attempted at the time of ICD implantation and at 2 or 4 weeks after the operation. Ventricular fibrillation (VF) was induced by T-wave shocks, but the amplitude of the ventricular electrogram was different in each VF. In most of the VFs with large ventricular electrograms, the local activity was appropriately detected. However, many undersensed beats were observed in other VFs that had fine ventricular electrograms and a longer time was needed before delivering the shock. The amplitude of the ventricular electrogram might be small in some cases of VF and this might result in undersensing and/or unsuccessful defibrillation. Close attention must be paid to the amplitude of ventricular activation in each VF to avoid possible difficulty in ICD therapy.

Both low and high energy cardioversion induced accelerated ventricular tachycardia in a patient treated with an implantable cardioverter defibrillator.

A 72-year old male with an old myocardial infarction who had drug-refractory ventricular tachyarrhythmias received an implantable cardioverter-defibrillator (ICD). The patient did not take his prescribed beta-blocking agent for two days, following which he experienced six discrete shocks for spontaneous VT while riding his bicycle. Both 5J and 30J cardioversions were ineffective at terminating the VT and accelerated VT developed following the shocks. After admission, an electrophysiological study was performed while he was taking the beta-blocking agent, both low and high energy cardioversions reproducibly terminated the clinical VT without showing any accelerated rhythm. These findings suggest that the increase in sympathetic discharge may enhance the proarrhythmic potential of ICDs.

Intracoronary acetylcholine-induced prolongation of monophasic action potential in long QT syndrome.

Two patients with long QT syndrome, who had episodes of syncope, underwent recordings of the monophasic action potential (MAP) from the right ventricle. Intracoronary administration of acetylcholine (ACh) induced prolongation of MAP duration and caused Torsade de Pointes (Tdp) in both patients. In one patient, intravenous atropine administration did not induce any change in MAP duration. In the other patient, ACh was administered after atropine. According to the results of the present study, abnormal regulation of the muscarinic receptor-mediated K-channel may be involved in the mechanism causing prolongation of MAP duration caused by ACh administration.

Repetitive ventricular responses induced by radiofrequency ablation for idiopathic ventricular tachycardia originating from the outflow tract of the right ventricle.

In 23 consecutive patients, radiofrequency (RF) ablation was used as treatment for idiopathic ventricular tachycardia (VT) originating from the outflow tract of the right ventricle. In this study, we focused on the repetitive ventricular response (> 5 consecutive QRS beats during RF application). The incidence and clinical implications of the repetitive ventricular response were examined through the results of endocardial mapping and RF ablation. VT origin was mapped as the earliest activation site during VT, and it was determined within 0.5 x 0.5 cm (narrow site) in 13 patients and wider than 0.5 x 0.5 cm (wide origin) in the other 10 patients. The repetitive ventricular response was induced during application of RF current in 14 of 23 patients (61%), and it was more frequently observed in VT from a wide origin (100%) than in the VT from a narrow site (31%). The QRS morphology of the repetitive ventricular response was identical to that of clinical VT. As RF application was continued and/or repeated, the RR interval of the repetitive ventricular response was gradually prolonged, the number of consecutive QRS complexes was decreased, and clinical VT was finally eliminated. The overall success rate of RF ablation was 96% (22/23 patients), and no complications were observed. In conclusion, a repetitive ventricular response was frequently observed in idiopathic right VT. The changing pattern of repetitive ventricular response, slowly and/or disappearing was consistent with successful RF ablation.

Internal thoracic artery malperfusion syndrome after bilateral internal thoracic artery grafting: report of a case.

A 58-year-old man with postinfarction unstable angina was referred to the Department of Cardiovascular Surgery at the Saiseikai Kitakami Hospital for urgent coronary revascularization. The bilateral internal thoracic arteries (ITAs) were subsequently utilized to revascularize the myocardium. The left anterior descending artery (LAD) was revascularized with the in situ right ITA and the obtuse marginal artery was revascularized with the in situ left ITA. Although he was successfully weaned from cardiopulmonary bypass, he collapsed hemodynamically 15 min later. Thus, he underwent supplementary vein bypass grafting to the distal LAD and the diagonal artery. Postoperatively, his course was uneventful, apart from the perioperative infarction, and a coronary arteriogram demonstrated patent bilateral ITAs and vein graft. This case report emphasizes the importance of early recognition of this rare syndrome and advocates surgical treatment consisting of supplementary vein grafting.

Relation between bradycardia dependent long QT syndrome and QT prolongation by disopyramide in humans.

BACKGROUND: Recent molecular biological investigations have identified abnormal genes in familial forms of long QT syndrome, but in bradycardia dependent acquired long QT syndrome, no such genetic abnormality has yet been identified. OBJECTIVE: To investigate the relation between the responses of QT interval to pacing change and to disopyramide. METHODS: This study included 13 patients with bradyarrhythmia who had undergone pacemaker implantation. The patients were divided into two groups: group I (n = 8), patients with QT prolongation (QT interval > or = 500 ms) during bradycardia; group II (n = 5), patients without QT prolongation (QT interval < 500 ms) during bradycardia. The responses of QT interval caused by the change of pacing rate were determined and compared with the changes of the QT interval after disopyramide administration. RESULTS: The QT interval in group I was significantly longer than that in group II when the pacing rate was decreased from 110 to 50 beats/min: mean (SD) 451 (16) v 416 (17) ms at 90 beats/min (p = 0.0033), and 490 (19) v 432 (18) ms at 70 beats/min (p = 0.0002), respectively. The QT interval was prolonged significantly by disopyramide in both groups, but the change was more pronounced in group I than in group II: 78 (33) v 35 (10) ms (p < 0.05). CONCLUSIONS: This study suggests that the patients showing bradycardia dependent QT prolongation are also more markedly affected by disopyramide and that abnormal potassium channel may be the underlying mechanism.

Action of antiarrhythmic agents on the area of slow conduction in ventricular tachycardia.

The most common mechanism of monomorphic sustained ventricular tachycardia (VT) is reentry with an excitable gap, but the electrophysiological properties and response to antiarrhythmic agents in the area of slow conduction are not yet fully known. The conduction time through the area of slow conduction may show a frequency-dependent delay in some VT but in others, constant conduction time was observed as the paced cycle length was decreased while VT was entrained. VT with a so-called decremental property could be terminated more often with rapid pacing with less risk of acceleration of the VT rate. When the excitable gap was estimated by the width of the zone of entrainment: defined as the difference between the cycle length of VT and the longest VT-interrupting paced cycle length during transient entrainment, there was no difference in the width of the zone of entrainment between the responders (VT induction was prevented with drugs) and the non-responders (VT remained inducible). The cycle length of VT was not a predictor of drug-efficacy. However, when the drug-effect was assessed at the intermediate doses, VT of those with a significantly narrowed width of the zone of entrainment were subsequently suppressed when the same drug was added. In conclusion, the electrophysiological properties of the area is diverse and it might affect pacing-induced terminability. Whether an antiarrhythmic agent is able to prevent VT-induction or not can not be predicted from the basal electrophysiologic parameters, but a significant narrowing of the width of the zone of entrainment, and hence the excitable gap, can be a hallmark for drug-efficacy.

Long-term results of radiofrequency catheter ablation in non-ischemic sustained ventricular tachycardia with underlying heart disease. Nonuniform arrhythmogenic substrate and mode of ablation.

This study examined 12 VTs in 8 patients who underwent radiofrequency (RF) catheter ablation for ventricular tachycardia (VT) associated with non-ischemic underlying heart diseases, and who were followed-up for more than 24 months after ablation. The site of VT origin was determined to be within a narrow site (within 1.0 x 1.0 cm) in 5 VTs (4 patients), but VT originated from a wide origin (more than 1.0 x 1.0 cm) in the other 5 VTs (3 patients). The remaining patient had two macroreentrant VTs revolving around an anatomical obstacle in both the clockwise and counterclockwise directions. Two of 5 VTs originating from a narrow site were successfully ablated by 2-3 RF applications. In VT associated with a wide origin, two perpendicular linear RF lesions with 6.0 +/- 1.8 RF applications were required to ablate the VT. Eight of the 12 VTs (66.7%) were finally ablated by RF current (30-50 watts), and they did not recur during the follow-up period of 31.2 +/- 6.5 months. An excellent long-term outcome is expected, even in VT associated with non-ischemic underlying heart disease, if VT is successfully treated by RF ablation.

Spatial orientation of the reentrant circuit of idiopathic left ventricular tachycardia.

In 6 patients with idiopathic left ventricular VT, the spatial orientation of the reentrant circuit was estimated from the results of transient entrainment of VT with rapid pacing at different sites. The entrance to the area of slow conduction was located toward the outflow tract, whereas the exist was located at the apicoposterior area of the left interventricular septum.

Effect of (+/-)-2-[p-(2-thenoyl)phenyl] propionic acid (suprofen) on experimental allergic reactions.

The effects of (+/-)-2-[p-(2-thenoyl)phenyl] propionic acid (suprofen), a new anti-inflammatory agent, on experimental allergic reaction and antibody formation were examined. The action was compared with those of ketoprofen, ibuprofen, indomethacin, tranilast, chlorpheniramine, prednisolone and/or cyclophosphamide. Suprofen inhibited homologous PCA in rats, immunological histamine release from rat peritoneal mast cells and guinea pig lung tissues, Forssman cutaneous vasculitis (FCV) and the Arthus reaction in guinea pigs. The potency for inhibition of the PCA reaction was similar to that of ketoprofen and more potent than ibuprofen and trailast. As for the release of anaphylactic mediators, suprofen was less potent than tranilast in terms of histamine release, but not the release of the slow reacting substance of anaphylaxis (SRS-A). Suprofen inhibited FCA more potently than other nonsteroidal anti-inflammatory drugs (NSAID). The inhibition of the Arthus reaction by suprofen was similar to those of other NSAID and prednisolone. Suprofen hardly affected delayed hypersensitivity in guinea pigs and antibody (IgM or IgE) formation in mice or rats.