Mode of initiation and ablation of ventricular fibrillation storms in patients with ischemic cardiomyopathy

OBJECTIVES: We report on the initiation of ventricular fibrillation (VF) storm in patients with ischemic cardiomyopathy (ICM) and the results of targeted ablation to treat VF storm. BACKGROUND: Monomorphic premature ventricular contractions (PVCs) have been shown to initiate VF in patients without structural heart disease. METHODS: A total of 29 patients with ICM and documented VF initiation were identified. In 21 patients, VF storm was controlled with antiarrhythmic drugs and/or treatment of heart failure. Eight patients with VF (mean 52 +/- 25 episodes) refractory to medical management required ablation. All patients underwent three-dimensional electroanatomical mapping using CARTO (Biosense-Webster Inc., Diamond Bar, California), and PVCs were mapped when present. Scarred areas were identified using voltage mapping. RESULTS: Monomorphic PVCs initiated VF in all 29 identified patients. Five of eight patients requiring ablation had frequent PVCs that allowed PVC mapping. The earliest activation site was consistently located in the scar border zone. The PVCs were always preceded by a Purkinje-like potential (PLP). Ablation was successfully performed at these sites. In three patients, infrequent PVCs prevented mapping, but PLPs were recorded around the scar border. Ablation targeting these potentials along the scar border was successfully performed. During follow-up (10 +/- 6 months), one patient had a single VF episode and another developed sustained, monomorphic ventricular tachycardia. There was no recurrence of VF storm. CONCLUSIONS: Ventricular fibrillation in ICM is triggered by monomorphic PVCs originating from the scar border zone with preceding PLPs; targeting these PVCs may prevent VF recurrence. In the absence of PVCs, both substrate mapping and ablation appear to be equally effective.     

A survey of hepatitis B surface antigen-positive blood donors: degree of understanding and action taken after notification

All blood donors in the United States are tested for hepatitis B surface antigen (HBsAg) upon donation; if the test result is positive, the primary method of notification is by letter. To assess the effectiveness of this notification methods in stimulating HBsAg-positive donors to seek medical care and take preventive measures, 54 donors who tested HBsAg-positive on donation at the American Red Cross Blood Services. Atlanta Region, from January 1987 to July 1989 were interviewed. Thirty-nine donors (72%) had sought medical care after notification; the only motivating factor was that the letter told the donor to consult with his or her physician. Compared with donors who did not seek medical care, donors who did so were more likely to understand that the blood test was abnormal or that they were infected, and they were more likely to understand how hepatitis B virus is transmitted and that a vaccine is available. The differences were not significant, however. Of those donors who sought medical care, less than half received appropriate recommendations for protection of contacts, and of those who did, only one-third received prophylaxis. In-person and telephone interviews with donors, revision of the notification letter, and hepatitis B education programs targeted at medical care providers are suggested.     

Circumferential ultrasound ablation for pulmonary vein isolation: analysis of acute and chronic failures

INTRODUCTION: In patients undergoing circumferential isolation of the pulmonary veins with an ultrasound ablation system, we analyzed the temperatures achieved while delivering circumferential ostial lesions in the pulmonary veins. We also reviewed the angiograms obtained during the procedure and identified anatomic variants that could be responsible for ineffective lesion formation. METHODS AND RESULTS: During the early clinical use in 33 patients, a total of 85 veins were ablated. A mean of 16.9 +/- 12.3 ablations were delivered per patient, and a mean of 6.7 ablations per vein were applied. Entry block was assessed by placing a deflectable octapolar or a circular catheter in the vein. The following anatomic characteristics and technical limitations were identified as possible reasons for ineffective energy delivery: (1) funnel-shaped ostium; (2) ostial diameter larger than the balloon diameter; (3) inability to deliver the catheter to the right inferior or other vein ostia; (4) ostial instability; (5) early branching of the vein; and (6) eccentric position of the ultrasound transducer in the vein. In patients with recurrence of atrial fibrillation, 40% of the ostial lesions reached a temperature >60 degrees C. However, in patients cured by the ablation, 64% of the ostial lesions reached a temperature >60 degrees C (P < 0.06). At least 12 of the 20 chronic recurrences could have been related to technical limitations of the first system. Duration of atrial fibrillation and eccentric deployment of the ultrasound transducer were more frequent in patients with recurrence of arrhythmias at follow-up. CONCLUSION: Ostial anatomy of the veins may affect delivery of ultrasound energy to achieve circumferential lesions. Energy delivery at the ostium with a temperature > 60 degrees C may be important to maximize success. Reconfiguration of the system to overcome the shortcomings identified in the initial experience could increase its performance.     

铅对肾上腺皮质细胞线粒体的氧化损伤

目的】 研究铅对肾上腺皮质细胞氧化应激和线粒体功能的 影响,为了解其肾上腺皮质毒作用机制提供依据。【方法】 原代分离培养豚鼠肾上腺皮质 细胞,以0、6.25、12.5、25、50、100 μmol/L醋酸铅(PbAc)处理细胞,观察PbAc诱导肾 上腺皮质细胞活性氧(ROS)产生和线粒体损伤作用。ROS检测采用荧光分光光度法,线粒体膜 电位(MMP)和细胞存活状态采用Rh123和PI双标记、流式细胞术检测,细胞ATP水平采用化学 发光法测定。【结果】 PbAc染毒后肾上腺皮质细胞ROS形成水平随剂量增加而增加,具有剂 量效应关系[y=4.16+10.21×1g(x+1),P<0.01,R2=0.64 1］;线 粒体膜电位呈剂量依赖性降低,Rh123的平均荧光强度(MFI)在6.25～100 μmol/L各剂量组 依次为1.01,0.94,0.96,0.95和0.91,与对照组(1.35)比较具有显著性差异(P<0 .01);染毒后细胞死亡率轻度增加,与对照组(1.02%)比较,50 μmol/L和100 μmol/L的 PbAc组分别为3.16%和3.40%,差异具有显著性(P<0.05);ATP水平降低与PbAc剂量之 间存在剂量效应关系[y=212965.7-51592.5×1g(x+1),P<0.01,R2= 0.568］,剂量和时间对ATP水平的影响呈协同抑制作用(P<0.01)。【结论】 线粒体 氧化应激介导肾上腺皮质细胞毒性可能是PbAc毒作用机制之一,线粒体损伤是铅致肾上腺皮 质毒作用的早期细胞和分子事件。