Microcatheter system

FDA testing and previous studies have verified that 150-250 cP is an ideal range for decreased sodium alginate injection resistance in many standard over-the-wire microcatheter systems and increased calcium alginate stability in gel form (Becker et al, 2005 2007). As for newer flow-directed microcatheter systems, an injectable biomaterial requires a lower alginate viscosity range (1-150 cP) to accommodate the microcather s minimal inner diameter. 

Since the introduction of the microcatheter systems, ischemic complications or infarction are rarely... 

Takahashi K, Yamada T et al. (2001) Selective balloon-occluded retrograde sclerosis of gastric varices using a coaxial microcatheter system. AJR Am J Roentgenol 177 1091-1093... 

Tanaka N, Yamakado K, Murashima S, Takeda K, Matsu-mura K.NakagawaT et al. (1997) Superselective bronchial artery embolization for hemoptysis with a coaxial microcatheter system. J Vase Interv Radiol 8(1 Pt l) 65-70... 

Following the initial anatomic survey, superselective right or left hepatic artery catheterization is then performed. While this is often possible with standard 4- to 5-F diagnostic angiographic catheters, coaxial microcatheter systems for all chemoembolization procedure are preferred. Microcatheter systems are easier to negotiate through tortuous hepatic arterial anatomy and probably reduce catheter-related spasm, thrombosis, and dissection. When tumor occupies more than 50% of the liver, or when the portal vein is occluded, microcatheter systems facilitate further... 

Figure 6.4 Prototype model of a microcatheter system with active guide wire using IPMC (ICPF) actuator (Reprinted with permission from Guo, S., Fukuda, T., Kosuge, K. et al. Micro catheter system with active guide wire-structure, experimental results and characteristic evaluation of active guide wire catheter using ICPF actuator. Proceedings of the IEEE 5th International Symposium on Micro Machine and Human Science, 191-8. Copyright (2004) IEEE).

The celiac trunk and hepatic artery are usually catheterized by 4-F or 5-F catheters (cobra or sidewinder configuration), while the tumor-bearing target vessels should be approached by 2.7- to 3-F coaxial micro-catheters. The advantages of a microcatheter system are the increased injection resistance, which reduces the risk of microsphere reflux, and the smaller likelihood of vascular spasms. 

Local intra-arterial thrombolysis (lAT) has several theoretical advantages over IV thrombolysis. For instance, by using coaxial microcatheter techniques, the occluded intracranial vessel is directly accessible and the fibrinolytic agent can be infused directly into the thrombus. This permits a smaller dose of fibrinolytic agent to reach a higher local concentration than that reached by systemic infusion, and ideally it allows for more complete recanalization with lower total doses of thrombolytic. With the smaller dose, complications from systemic fibrinolytic effects, including ICH, can theoretically be reduced. 

The Concentric Retriever (Concentric Medical Inc., Mountain View, CA), a flexible, nitinol wire with helical tapering coil loops (X5 and X6) that is used in conjunction with a balloon guide catheter (8 or 9 French) and a microcatheter, is the only device currently approved by the FDA for the endovascular treatment of stroke patients (Fig. 4.3). The second-generation devices (L5 and L6) differ from the X devices by the inclusion of a system of arcading filaments attached to a nontapering... 

Interest in thrombolytic therapy for acute ischemic stroke re-emerged with reports of successful thrombolysis for arterial thrombosis in the peripheral vascular system. Local lA infusion was found to have higher rates of recanalization compared with systemic IV delivery of thrombolytics without increased levels of hemorrhagic complications IV use of UK and SK was found to provide clinical benefit in patients with pulmonary embolism [5, 6]. In the early 1980s, lA infusion of UK or SK for acute MI was shown to be highly effective [5, 6]. At the same time, technical advances in endovascnlar microcatheter and microguidewire design made access to the intracranial vessels safer... 

Fig. 3.9a-d. A standard 7-F gonadal guide catheter for occlusion of the left spermatic or ovarian vein (Cordis Inc., Miami, FL) is demonstrated in (a) and in (b) the 7/5 pulmonary guiding catheter and inner catheter for occlusion of pulmonary arteriovenous malformations is shown. Once the ovarian or internal spermatic vein are catheterized, any standard 100-cm 5-F endhole multipurpose catheter is advanced over a Bentson wire deep into the spermatic or ovarian vein where sclerosants and coils are usually placed. A standard 6-F RDC (Cordis Inc., Miami, FL) guide catheter for visceral embolization is demonstrated with a coaxial 4-F catheter in (c) and in (d), a triaxial system is demonstrated with an inner 0.021 lumen microcatheter... 

Properties of the microcatheters and micro-guidewires we use are listed in Table 5.4. Most companies offer adequate coaxial systems. We do not adhere to specific brands and have used all kinds of microcatheters and microguidewires over the years. 

For this reason, when an embolotherapy is planned we recommend immediate cessation of prostaglandin Ej agonist infusion. In case of arterial spasm at the ostium of the uterine artery, the use of a coaxial system with a microcatheter is then required. It is possible to successfully catheterize the distal part of the uterine artery in most cases. In these circumstances, the preferred embolic agent is the one that can be easily delivered through a microcatheter, such as PVA (Polyvinyl alcohol) or Embospheres. We prefer to use particles with larger diameters, such as Embospheres 700-900 mg. Even if these particles are used for the above-mentioned reasons, additional Gelfoam embolization of internal iliac arteries is performed because of the extensive collateral pathways of the female pelvis. 

Eor the local administration of medicines in the inner ear and the cochlea highly sophisticated systems are used, like microcatheters, osmotic and peristaltic pumps. Current research on repairing patients hearing includes gene therapy, administration of neutrophins and stem cells [11, 12]. 

The more peripheral the embolization is to the tumor, the less the opportunity for collateral circulation and the greater likelihood of tumor necrosis. While tumor necrosis is a desired effect, necrosis of adjacent non-targeted tissue is not. Microcatheter coaxial systems allow subselective or superselective embolizations to access tumor vessels and avoid non-targeted embolization. Peripheral embolization produces small vessel occlusion without sacrificing the main arteries, allowing future re-embolization when necessary. 

Technical Considerations Catheterization of the bronchial arteries is best approached from the femoral artery. Since most patients with lung cancer are older and the aorta is tortuous and atherosclerotic, a 5-F catheter with good torque control in a shepherd s crook (reverse curve) or forward seeking configuration is recommended. A finely tapered tip catheter for access which would allow a 3-F microcatheter coaxial system is optimal to bypass the spinal artery. The use of nonionic contrast media should minimize pain and the risk of contrast media-induced complications. The digital subtraction technique is of value for the identification of the anterior spinal artery with small branches to the spinal cord. 

Catheter based diagnosis and therapy have become increasingly popular. Conventional catheters cannot move actively and the operations require certain human skill. If the direction of the tip of microcatheter and guide wires can be controlled outside the body, it would be very useful to use eatheter based diagnosis and therapy. Sueh eatheters are called active catheters . In order to develop active catheters, several miero-aetuators were applied to the active mieroeatheter system. The IPMC actuator is soft and driven by low voltage. And it is easy to miniaturize. Henee, the IPMC actuator was applied to the aetive microcatheter for aneurysm surgery in the brain. 

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