Mitsuhiro Okamoto

Antiarrhythmic Efficacy of Dipyridamole in Treatment of Reperfusion Arrhythmias Evidence for cAMP-Mediated Triggered Activity as a Mechanism Responsible for Reperfusion Arrhythmias

BACKGROUND Intracellular calcium overload is believed to play an important role in development of reperfusion arrhythmias. Dipyridamole, an inhibitor of cellular uptake of adenosine, may prevent or terminate reperfusion arrhythmias by reducing intracellular calcium overload. METHODS AND RESULTS First, we tested for a preventive effect of dipyridamole. Sixty-one patients who underwent primary PTCA for treatment of acute anterior wall myocardial infarction were enrolled in this prospective study. Patients were divided into dipyridamole (DP) and nondipyridamole (non-DP) groups. The 2 groups had similar baseline characteristics. In the DP group, dipyridamole 0.5 mg/kg was infused intravenously for 3 minutes immediately before reperfusion during primary PTCA. Arrhythmias after reperfusion were analyzed from continuous ECG recordings. None of the patients in the DP group (n=23) had accelerated idioventricular rhythms (AIVR) or ventricular tachycardia (VT). In contrast, 7 (18.4%) had AIVR and 3 (7.9%) had VT in the non-DP group (n=38; P<0.01). Second, we tested for a termination effect of dipyridamole. Dipyridamole 0.5 mg/kg was infused intravenously while continuous ECG recordings were obtained in 9 patients who had either sustained AIVR (n=7) or sustained VT (n=2) after reperfusion of occluded coronary artery. Arrhythmias were terminated in all patients. CONCLUSIONS These results indicate that administration of dipyridamole can prevent and terminate reperfusion arrhythmias such as AIVR and VT. cAMP-mediated triggered activity may, at least in part, be responsible for reperfusion-induced AIVR and VT.

Usefulness of Electron Beam Tomography in the Prone Position for Detecting Atrial Thrombi in Chronic Atrial Fibrillation

Objective We compared the usefulness of electron beam tomography (EBT) in the prone position relative to that in the supine position for detecting atrial thrombi. Methods We studied 96 patients with chronic atrial fibrillation, of whom 71 were scanned in the supine position and 25 were scanned in the prone position. Electron beam tomography was performed twice after contrast medium injection to obtain early- and late-phase images. Results Filling defects were detected in 13 patients in the supine position by EBT. Transesophageal echocardiography (TEE) revealed a thrombus in the region of the filling defect in 9 patients. In 4 patients, filling defects in the left atrial appendage were not confirmed as thrombi by TEE. Filling defects were detected in 4 patients in the prone position, all of which were confirmed as thrombi by TEE. Conclusion Electron beam tomography in the prone position is an effective technique for reducing false-positive results in the detection of atrial thrombi.

Computerized Three-Dimensional Potential Mapping with a Multielectrode Basket Catheter Can be Useful for Pulmonary Vein Electrical Disconnection ∗

Introduction: Pulmonary vein (PV) isolation (PVI) has been recently proposed as an effective technique to cure atrial fibrillation (AF).Aims of the Study: The aim of this study was to investigate the efficacy of a novel technique utilizing a computerized three-dimensional mapping system (QMS2TM) with a multielectrode basket catheter (MBC) for PVI and to reveal the relation between the style of breakthrough and the network of the PV musculature.Methods: Sixty-five consecutive patients with frequent AF attacks underwent PV mapping with a 31-mm MBC, and a three-dimensional color animation of the potential map was constructed by the QMS2TM. The animation color schema was arranged to minimize the low-amplitude left atrial (LA) potentials and emphasize the high-amplitude PV potentials (PVPs). The longitudinal PVP map enabled us to recognize the true breakthroughs and reveal the network of the PV musculature.Results: A total of 205 PVs (65 left superior PVs, 65 right superior PVs, 57 left inferior PVs and 18 right inferior PVs) were mapped and successful PVI was achieved in all PVs, except one that had no PVPs, with a mean radiofrequency duration of 7 ± 5 minutes per PV. In about 90% of the PVs, a final radiofrequency application eliminated all the distal PVPs simultaneously because the PVI was performed at the appropriate LA-PV junction. A single segmental breakthrough was detected in 17 PVs, single broad breakthrough in 83 PVs, multiple separate breakthroughs with a distal connection between the PV musculatures extending from each separate breakthrough in 88 PVs and multiple separate breakthroughs without that connection in 16 PVs. During the follow-up period, fifty-one (78%) patients were free of symptomatic AF without any antiarrhythmic drugs after multiple procedures (thirty-three (51%) of those patients after the first procedure) and no PV stenosis was found.Conclusions: Computerized three-dimensional potential mapping can be useful for PVI because it can not only identify the true breakthrough, but can also confirm the elimination of the breakthroughs by the change in the activation sequence through the network of the PV musculature.