There is a strong and significant association between the degree of inhibition of neointimal formation with the use of DES and the clinical impact of using DES instead of BMS.

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Objectives: To evaluate the feasibility of percutaneous aortic valve replacement without cardiac arrest in animal experiments. Methods: A self expanding nitinol stent, containing pulmonary valves from pigs in its proximal part, was implanted in six pigs (94-118 kg) by means of a 25 French catheter through the left subclavian artery under guidance of fluoroscopy and transoesophageal echocardiography. During stent deployment the original aortic valve was pushed against the aortic wall by the self expanding force of the stent while the new valve was expanded. Results: It was possible to replace the aortic valve in the beating heart in four pigs (67%) with no complication or relevant drop in blood pressure. The procedure failed in two pigs (33%) due to dysfunction of the catheter device in one case and to problems with correct positioning in the left ventricular outflow tract in the other. After successful stent valve implantation, dopamine was infused in doses of 5 mg/kg/min, 10 mg/kg/min, and 15 mg/kg/min. Cardiac output increased from 4.4 to 8.8 l/min and the mean arterial pressure rose from 79 to 105 mm Hg. The maximum peak to peak pressure gradient across the valve carrying stent reached a maximum of 8 mm Hg under dopamine infusion. All pigs were killed six hours after transvascular aortic valve replacement. The chest was opened, and the left ventricle and the ascending aorta were carefully inspected. There were no signs of malfunction of the implant, of damage of the aortic vessel wall, or of obstruction of the coronary ostia. Conclusions: Percutaneous aortic valve replacement with a self expanding nitinol stent in the beating heart is possible. The device was safe under pharmacological stress test. After successful chronic animal experiments, this concept may become a feasible option for treating patients with relevant aortic valve disease but where open heart surgery would be risky. P atients with a stenosis of the aortic valve do not show any symptoms for several years. But when they become symptomatic, their prognosis is limited if the valve is not replaced.1 The prevalence of severe calcification of the aortic valve is 13% in patients 75 years and older. 2 The number of elderly patients with relevant co-morbidity and symptomatic aortic valve disease is increasing. These patients are often high risk candidates for open heart surgery with a heart-lung machine.3 Recently, a one month mortality rate of nearly 24% was reported among patients 90 years and older after open heart valve surgery. 4 Thus, there is need for a less invasive technique of aortic valve replacement. Several groups have been working on this field during the past decade. 5-8Bonhoeffer and colleagues 9 were the first to implant a valve percutaneously with a transvenous approach in a human. They sutured a bovine jugular vein valve within a balloon expandable stent for replacing the pulmonary valve. Cribier and colleagues 10 also used a biological valve mounted in a balloon expandable stent, which was implanted in a transseptal approach. These...

Both sirolimus (SES) and paclitaxel eluting stents (PES) have been shown to reduce significantly both the incidence of binary angiographic restenosis and the need for new revascularization procedures [1]. We read with great interest the paper by Sidhu et al., in which the better angiographic behaviour of SES in comparison with PES was not translated into significant differences in terms of clinical events [2]. As paclitaxel is cytotoxic, whereas sirolimus is cytostatic, the risk of stent thrombosis between the two types of drug-eluting stents could be different. In fact, in a recent work, a trend to an increased risk of stent thrombosis after PES implantation was found, whereas the risk of stent thrombosis was similar with SES and bare-metal stents [3].Stent thrombosis is an infrequent complication. Because of that, data from single trials are not sufficient to compare the incidence of stent thrombosis between two different types of stent. For the evaluation of such an infrequent entity, meta-analysis may increase increase power and precision and provides an overall estimate and range of effect. In order to help to clarify whether the risk of stent thrombosis is different between SES and PES, we have performed a meta-analysis from nine randomized trials that have compared SES and PES, including 5024 patients (2514 allocated to SES, 2510 allocated to PES). The trials included in the metaanalysis were: TAXI (n = 202), REALITY (n = 1353), SIRTAX (n = 1012), ISAR-DIABETES (n = 250), ISAR-DESIRE (n = 200), CORPAL (n = 652), ISAR-SMART-3 (n = 360), BASKET (n = 545) and ISAR-TEST (n = 450) [4][5][6][7][8][9][10][11][12]. Follow-up ranged from 6 to 12 months. In most trials, the Cypher stent (Cordis Corp., Miami Lakes, FL, USA) and the Taxus stent (Boston Sci., Natick, MA, USA), with polymeric-release of sirolimus and paclitaxel, respectively, were randomly compared in patients with native de novo lesions. In the ISAR-DESIRE study, only patients with in-stent restenosis after bare-metal stent implantation were included. In the ISAR-TEST, the Yukon stent, with nonpolymeric release of sirolimus, was compared with the Taxus stent.The risk ratio for stent thrombosis and its 95% confidence interval (CI) was calculated comparing SES with PES rates using raw data for each study and for the pooled population. The Q-test for heterogeneity and the fixed-effect model were used.There was no heterogeneity among the trials [Q-test for heterogeneity: c 2 = 5.41, d.f. = 6 (P = 0.49); I 2 = 0%]. The overall risk of stent thrombosis in the overall population was 0.92% (n = 46 patients): 0.83% (21/ 2514) and 1.00% (25/2510) in patients allocated to SES and PES, respectively (risk ratio 1.17, 95% CI 0.67, 2.35; P = 0.57) (Figure 1).Sirolimus and paclitaxel have different mechanisms of action (sirolimus is cytostatic, whereas paclitaxel is cytotoxic). Moreover, both stent platform and polymer are different in Taxus and Cypher stents, and whereas Taxus releases paclitaxel from a polymer, the Yukon stent has a nonpolymeric release of sirol...

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