Electrophysiological Effects of MS-551 in Humans: A Class III Antiarrhythmic Agent

To investigate the clinical effects of MS-551, a Class III antiarrhythmic agent, 11 patients underwent electrophysiological study. MS-551 was given intravenously as an initial dose of 0.2 or 0.3 mg/kg for 5 minutes followed by the continuous infusion at 0.2 or 0.3 mg/kg for 30 minutes, respectively, in all patients. The rate corrected QT interval increased significantly from 3 minutes after the beginning of MS-551 infusion. The sinus heart rate decreased significantly by 8% at 10 minutes after the drug administration (P ± 0.025). Mean PR and QRS intervals, and blood pressure were not significantly affected by the drug. Mean PA, AH, and HV intervals during sinus rhythm were also not affected. The effective refractory periods (ERPs) of the atrium and ventricle were significantly prolonged by 13% from 202 ± 24 ms to 231 ± 26 ms (P ± 0.0005), and by 7% from 238 ± 11 ms to 257 ± 13 ms (P ± 0.002), respectively, by MS-551. The ERP of the atrioventricular node and sinoatrial nodal recovery time were not changed significantly by the drug. This is a report of the effects of MS-551 in humans. This agent could be useful for treatment of tachyarrhythmias by prolongation of ERPs of the atrium and ventricle without significant variations of blood pressure and intracardiac conduction times. It is noteworthy that MS-551 slightly but significantly decreased heart rate.     

Radiofrequency Catheter Ablation of Concealed Atrioventricular Accessory Pathways Using a "Simultaneous Pacing Method"

The retrograde atrial potential at a successful ablation site is usually obscured by the wide and large ventricular potential during atrioventricular reentrant tachycardia or ventricular pacing, which makes it difficult to determine the appropriate ablation site for concealed accessory pathway. A pacing maneuver named the “simultaneous pacing method” is proposed herein to differentiate the retrograde atrial potential from the ventricular potential for a successful ablation of the concealed accessory pathway. Catheter ablation was performed in 12 patients with a single left free-wall concealed accessory pathway. The atrial insertion site was determined by the simultaneous pacing method in six patients (group I) and by ventricular pacing in six patients (group II), In the simultaneous pacing method, electrograms recorded during ventricular pacing in the earliest retrograde atrial activation site are a fusion of the ventricular potential and the following retrograde atrial potential. When atrial and ventricular pacings are performed simultaneously (simultaneous pacing), the end portion of the electrograms recorded at the same site is solely the ventricular component, because atrial is activated earlier. The atrial potential can be confirmed during ventricular pacing in comparison with the electrograms during the “simultaneous pacing.” Radiofrequency catheter ablation was successful in eliminating conduction through the accessory pathway in all 12 patients. The radiofrequency applications in group I were significantly fewer than those in group II (1.7 ± 1.0 in group I, 5.3 ± 3.2 in group II, P < 0.05). The total procedure time in group I was significantly shorter than in group II (57.8± 15.7 vs 106.7 ± 41.6 mins in group II. respectively, P < 0.05). The fluoroscopy time in group I was significantly shorter than in group II (54.0 ± 7.9 vs 81.3± 26.3 mins, respectively, P < O.05). We were able to determine the atrial insertion site of accessory pathways by the simultaneous pacing method. The simultaneous pacing method was useful in eliminating concealed left free-wall accessory pathways.     

Role of vagotony in sinus node dysfunction in children with symptomatic congenital long QT syndrome

The present study examined chronotropic dysfunction and the role of vagotony in congenital long QT syndrome, sinus node function and the effects of parasympathetic blockade. Six patients with congenital long QT syndrome were studied. The four males and two females, aged 1–15 years, had episodes of syncope and malignant ventricular arrhythmias. Congenital long QT syndrome was defined as a corrected QT interval greater than 0.45 s, T wave alternans and the age at diagnosis. The sinus heart rate measured from a 24 h electrocardiograph was abnormally low (< 50 min) in three patients (1, 4 and 5 years old) and did not increase sufficiently with the administration of atropine in five of the six patients with congenital long QT syndrome. From intracardiac electrophysiological studies, the corrected sinus node recovery time was prolonged in three patients and the total sinoatrial conduction time was prolonged in two patients. In most patients who had an abnormally long sinoatrial conduction time and corrected sinus node recovery time, these values returned to normal following atropine administration. In one patient, the corrected sinus node recovery time was prolonged paradoxically by atropine. Sinus node dysfunction in congenital long QT syndrome was affected by vagotony associated with a right sympathetic nerve system abnormality.     

Ureteral obstruction due to retroperitoneal fibrosis secondary to a solitary internal iliac aneurysm

We report a case of ureteral obstruction due to retroperitoneal fibrosis secondary to a solitary left internal iliac aneurysm. It has been reported that as a cause of ureteral obstruction, an internal iliac aneurysm without aortic and/or common iliac aneurysms is very rare. In the present case, magnetic resonance imaging was a useful modality to diagnose retroperitoneal fibrosis secondary to an internal iliac aneurysm as a direct cause of ureteral obstruction.     

Mid-Diastolic Potential is Related to the Reentrant Circuit in a Patient with Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia

Mid-Diastolic Potential in Idiopathic VT. We report a case of verapamil-sensitive idiopathic ventricular tachycardia in which a mid-diastolic potential (MDP) 45 msec preceding the Purkinje potential ( P potential) was recorded. Pacing during the tachycardia caused concealed entrainment, and the stimulus–QRS interval was equal to the P potential–QRS interval. The interval between the last pacing stimulus and the next P potential (postpacing interval) was longer than the ventricular tachycardia cycle length, but the MDP was orthodromically activated. These findings suggest that the MDP was on the reentrant circuit and the P potential was not on the reentrant circuit, but a bystander.     

Polysomnography and body temperature changes by phototherapy in a delayed sleep phase syndrome case

Abstract We examined polysomnography (PSG) and body temperature in a patient with delayed sleep phase syndrome who responded to phototherapy. The patient was a 31-year-old woman whose condition had slightly improved by a vitamin B₁₂ administration. Phototherapy was administered to her in combination with the vitamin B₁₂ medication, and this combined treatment successfully advanced her delayed sleep phase. On PSG, the regimen showed shortened sleep latency, decreased total sleep time and stages 1 and 2 sleep, and increased slow wave sleep. Phototherapy also improved temporal distribution of delta half-waves (0.5-2.0 Hz, 31 µV) as well as phase relationship between sleep and body temperature.     

Effects of ultraviolet B irradiation on cell–cell interaction; implication of morphological changes and actin filaments in irradiated cells

We studied the effects of ultraviolet B (UV-B) irradiation on cell–cell interactions using mouse lymphoma RMA cells and T cell hybridoma HTB-176.10 cells. RMA cells act as stimulators by presenting H-2K^b surface antigens to HTB-176.10 cells, inducing IL-2 production in HTB-176.10 cells. Irradiating RMA cells with 1000 J/m² UV-B suppressed cell cluster formation between RMA and HTB-176.10 cells and reduced the level of IL-2 production in HTB-176.10 cells, although H-2K^b surface antigens of RMA cells were still expressed. Electron microscopic observations of irradiated RMA cells revealed that UV-B irradiation damaged cell structures, resulting in the disappearance of microvilli on the cell surface, destruction of mitochondria, vacuolation of cytoplasm and swelling of the perinuclear cisterna space. We found that these alterations were accompanied by polymerization of filamentous actin quantified by flow cytometry after NBD-phallacidin staining. Our results suggest that a target of UV-B-induced alterations is actin filaments, which support the cell morphology as the cytoskeleton, and that modification of filamentous actin inhibits interaction between RMA and HTB-176.10 cells. This underlying mechanism may account for the impaired interaction between antigen-presenting cells and T cells after transfusion with UV-B-irradiated allogeneic blood components.     

Acute Effects of Different Atrial Pacing Sites in Patients with Atrial Fibrillation: Comparison of Single Site and Biatrial Pacing

It has been reported that a trial single site or biatrial pacing can suppress the occurrence of AF. However, its mechanism remains unclear. The study population included 32 patients with AF (n = 20: AF group), or without paroxysmal AF (n = 12: control group). The mechanism and efficacy of atrial pacing were investigated by electrophysiological studies to determine which was more effective for suppressing AF induction; single site pacing of the right atrial appendage (RAA) or distal coronary sinus (CS-d), or biatrial (simultaneous BAA and CS-d) pacing. In the AF group, AF inducibility was significantly higher with BAA extrastimulus during RAA (12/20; P < 0.0001) or biatrial paced drive (7/20; P < 0.01) than during CS-d paced drive (0/20). In the control group, AF was not induced at any site paced. In the AF group, the conduction delay and other parameters of atrial vulnerability significantly improved during CS-d paced drive. The atrial recovery time (ART) at RAA and CS-d was measured during each basic pacing mode. ART was defined as the sum of the activation time and refractory period, and the difference between ARTs at RAA and CS-d was calculated as the ART difference (ARTD). The ARTD was significantly longer during BAA pacing in the AF group than in control group (155.0 +/- 32.8 vs 128.8 +/- 32.9 ms, P < 0.05). In the AFgroup, ARTDs during biatrial (52.0 +/- 24.2 ms) and CS-d pacing (51.7 +/- 26.0 ms) were significantly shorter than ARTD during RAA pacing. The CS-d paced drive was more effective for suppressing AF induction than biatrial or RAA paced drive by alleviating conduction delay. CS-d and biatrial pacing significantly reduced ARTD compared with RAA pacing.