Effect of gradual rise in plasma calcium concentration on the impairment of atrioventricular nodal conduction due to verapamil

The possible reversal by calcium of the inhibitory action of verapamil on the atrioventricular (AV) node was investigated in anesthetized, atropinized dogs, with cardiac pacing. The His bundle potentials were recorded by endocavitory electrode and the AV node effective refractory period measured by the extrastimulus method. Calcium infusion was effective against the impairment of AV nodal conduction induced by verapamil, provided it remained moderate: the gradual rise in the plasma calcium concentration counteracted the effects of an infusion of verapamil on conduction time and effective refractory period in the AV node, as long as it did not exceed 5 mmol/L. However, beyond this level, calcium appeared less and less capable of reversing the effects of verapamil. Thus, the protective action of calcium had a bell-shaped dose-response curve, with the optimum at 5 mmol/L. This biphasic influence is consistent with the opposite opinions previously given concerning the antagonism between calcium and calcium blockers, depending on whether hypercalcemia brought into play was mild or major. In any case, the prominent role played by calcium in the slow inward current in the AV node accounts for the antagonism, observed in vivo, between calcium and verapamil. The pacemaker activity of the sinoatrial (SA) node was less influenced by both calcium blocker and calcium.     

Drug driving from a user's perspective

The bulk of research into drug driving in Australia has been undertaken from a road safety orientation where drug driving is viewed within the broader context of road safety and driver behaviour. Such a specific focus precludes the broader behavioural, contextual and cultural issues associated with substance use. This study aimed to address this issue by focusing on drug driving behaviour within the context of illicit substance use. A series of focused interviews were conducted with 211 illicit drug users from urban and regional centres. A consistent theme identified in the interviews was that drug driving was not necessarily viewed as risky behaviour but rather as an outcome of illicit substance use. Further, some interviewees saw their drug use as enhancing their driving skills and frequently the motor vehicle was viewed as a safe place to use. Overall there was agreement among interviewees that the likelihood of being apprehended for drug driving by police was minimal; this perception was reinforced by past experience. The lack of concern for detection of drug driving behaviour suggests that research should continue into the development and implementation of enforcement programs and roadside detection.     

The role of still-frame parametric imaging in magnetic resonance assessment of left ventricular wall motion by non-cardiologists.

BACKGROUND: Cardiac magnetic resonance (MR) images are often reviewed by non-cardiologists who are not trained in the interpretation of regional left ventricular (LV) function. We hypothesized that the use of still-frame parametric MR images of wall motion could aid in the assessment of regional LV function. METHODS: Dynamic, electrocardiogram-gated, steady-state free precession (FIESTA) short-axis images were obtained in 6 to 10 slices in 18 consecutive patients. Each loop was used to automatically generate a still-frame image, in which each pixel is assigned a value equal to the amplitude of cyclic variation in local intensity, resulting in higher intensity in pixels that change between blood and tissue during the cardiac cycle. The dynamic images were reviewed by an expert cardiologist who provided gold standard grades for regional wall motion and by four radiologists. Then the radiologists reviewed and graded the same MR images in combination with parametric images. Grades assigned to each segment in the two sessions were compared with the gold standard. RESULTS: According to expert interpretation, 6 patients had normal wall motion, and 12 had wall motion abnormalities. Parametric images showed a bright band in the area spanned by endocardial motion, with reduced brightness and thickness in areas of hypokinesis. The agreement between the radiologists' grades and the gold standard significantly improved by adding parametric images (from 77% to 81%), which also resulted in reduced interobserver variability (from 52% to 33%). CONCLUSIONS: Still-frame parametric images aid in the assessment of regional wall motion by non-cardiologists who are required to interpret cardiac images.     

急性冠状动脉综合征患者介入术前后血小板活化及血管内皮功能的变化

目的观察急性冠状动脉综合征患者介入治疗后血小板活化指标CD62p、CD63及糖蛋白Ⅱb/Ⅲa受体复合物及内皮功能的改变。方法60例急性冠状动脉综合征患者在冠状动脉介入术前和术后即刻以及次日采用流式细胞仪检测血小板活化指标CD62p、CD63及糖蛋白Ⅱb/Ⅲa受体复合物;双抗体夹心固相酶联免疫吸附试验测定血浆假血友病因子的表达水平;放射免疫测定法测定血浆内皮素1表达水平;酶法测定血浆一氧化氮的含量;彩色多谱勒超声诊断仪测量内皮依赖性血管舒张功能。选择健康体检者和稳定型心绞痛患者各30例作对照,观察急性冠状动脉综合征患者冠状动脉介入前后指标的变化并与对照组比较。结果与健康对照组和稳定型心绞痛组比,急性冠状动脉综合征组CD62p、CD63及糖蛋白Ⅱb/Ⅲa受体复合物明显增高(P<0.05或0.01);急性冠状动脉综合征患者介入术后即刻CD62p、CD63和糖蛋白Ⅱb/Ⅲa受体复合物与术前相比明显增高(P<0.01),但术后24h较术前无明显变化(P>0.05)。与健康对照组和稳定型心绞痛组比,急性冠状动脉综合征组假血友病因子、内皮素1的表达水平明显增高(P<0.01),内皮依赖性血管舒张功能和一氧化氮降低(P<0.05或<0.01);急性冠状动脉综合征患者介入术后即刻血浆假血友病因子和内皮素1水平升高(P<0.05或P<0.01),内皮依赖性血管舒张功能和一氧化氮水平降低(P<0.05),且介入术后24h假血友病因子水平也较术前升高(P<0.05),内皮依赖性血管舒张功能降低(P<0.05),但内皮素1和一氧化氮水平与术前差异无显著性(P>0.05)。结论血小板活化和内皮功能的损伤在急性冠状动脉综合征发生和发展过程中起重要的作用,冠状动脉介入术后血管内皮受到一定损伤,血小板有一定程度的激活。     

Endovascular treatment (EVT) of acute traumatic lesions of the descending thoracic aorta--7 years' experience.

OBJECTIVES: To present a single centers' 7-year experience in the endovascular treatment of acute traumatic lesions of the descending thoracic aorta (ATL of the DTA). MATERIALS & METHODS: Between March 1999 and December 2006, 34 consecutive acute traumatic lesions of the descending aorta (23 men, mean age 44 years) were treated endovascularly. Stentgrafts used were TAG Excluder, Zenith TX2 and Talent. In 23 patients the Left Subclavian Artery (LSA) was covered. Mean procedural duration was 20 to 75 minutes. RESULTS: Exclusion of the rupture site was achieved in all cases with no conversion to open surgery. Overall 30-day mortality was 8.8%. Two patients died on post operative day (pod) 1 and one on pod 22 from cranial injuries. No death or neurological deficit related to the endovascular treatment was reported. Four type I endoleaks required treatment either by balloon reexpansion (n=2) or by additional stentgraft implantation (n=2). In two patients the stentgraft collapsed totally several days postoperatively. Two patients required secondary surgical procedures (iliac access complication and revascularisation of the left subclavian artery n=1). The average follow-up was 43.8 months (1-93 months). No stentgraft related abnormality has been subsequently documented. CONCLUSIONS: The endovascular treatment of ATL of the DTA may offer the best means of therapy in a polytrauma patient.