Microcatheter

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 Interventional Management of Stroke (IMS I) Study was a multicenter, open-labeled, single-arm pilot study in which 80 patients (median NIHSS 18) were enrolled to receive IV rt-PA (0.6 mg/kg, 60 mg maximum, 15% of the dose as a bolus with the remainder administered over 30 minutes) within 3 hours of stroke onset (median time to initiation 140 minutes). " Additional rt-PA was subsequently administered via a microcatheter at the site of the thrombus in 62 of the 80 patients, up to a total dose of 22 mg over 2 hours of infusion or until complete recanalization. Primary comparisons were with similar subsets of the placebo and rt-PA-treated subjects from the NINDS rt-PA Stroke Trial. The 3-month mortality in IMS I subjects (16%) was numerically lower but not statistically different than the mortality of the placebo (24%) or rt-PA-treated subjects (21%) in the NINDS rt-PA Stroke Trial. The rate of symptomatic ICH (6.3%) in IMS I subjects was similar to that of the rt-PA-treated subjects (6.6%) but higher than the rate in the... 

The ongoing IMS III trial is a randomized, multicenter, phase III trial continuing the investigation into the efficacy of the combined IV and lA approach to treat acute stroke. Patients are being randomized to IV/IA therapy and IV rt-PA alone in a 2 1 ratio. In the group allocated to combination IV/IA therapy, the physician will select either the EKOS microcatheter or a standard microcatheter to infuse rt-PA, or select the Mechanical Embolus Removal in Cerebral Ischemia (MERCI) clot retrieval device. The primary outcome is the percentage of patients with an mRS score of 0-2 at 90 days. ... 

After a baseline angiogram confirms the presence and location of the vascular occlusion, a microcatheter is navigated over a microwire into the occluded vessel, traversing the thrombus. Once the microcatheter is positioned immediately distal to the clot, thrombolytic infusion begins the microcatheter is then pulled back through the clot while dmg is infused. Dose adjustments and total dose calculations are made depending on the clinical circumstances, pretreatment dose of rt-PA received, degree of recanalization, and relative size and function of the territory at risk. 

The neurointerventionalist should limit the number of microcatheter injections performed during the exam, as there is growing evidence that this may increase the chances of hemorrhagic transformation of the infarcted tissue. Direct injection of contrast into stagnant vessels, which contains injured glial cells and thus breakdown of the blood-brain barrier, allows for contrast extravasation. Contrast is readily visualized on the immediate post-thrombolysis CT as an area of high attenuation in the parenchyma. In some instances, MRI with susceptibility-weighted sequences may be useful to differentiate contrast extravasation from Such a distinction... 

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... 

Suction thrombectomy or thromboaspiration through either a microcatheter or a guiding catheter may be an option for fresh nonadhesive clot. As discussed above, aspiration devices have the advantage of causing less embolic events and vasospasm however, the more complex design of these devices makes them more difficult to navigate into the intracranial circulation. 

Khatri P, Broderick J, Khoury JC, Carrozzella J, Tomsick T, for the IMS-1 and 2 Investigators. Microcatheter contrast injections during intra-arterial thrombolysis increase intracranial hemorrhage risk. International Stroke Conference Kissimmee, Elorida 2006. 

Fig. 21.2. Two-microelectrode current-clamp technique used to observe, in single Ascaris body muscle cells in a body-flap preparation, the response to a controlled pulsed application of levamisole. One micropipette, to measure membrane potential, and another micropipette, to inject current, are inserted inside the area of the muscle cell known as the bag region. Levamisole is applied in a time- and pressure-controlled manner from a microcatheter placed over the bag region of the muscle. A second microcatheter is used to apply additional chemical agents (Martin, 1982).

Comparisons between the different intra-arterial thrombolysis trials and between intraarterial thrombolysis and intravenous thrombolysis is hampered by differences in methodology and type of thrombolytic therapy. In addition, within the intra-arterial thrombolysis trials, thrombolytic deUvery has varied between regional into a parent vessel of the thrombosed vessel, local into the affected artery and into the thrombus itself, or combinations of these methods. In addition, the infusion process has been variable, ranging from continuous to pulsed infusion. Some studies have allowed physical clot dispersion using the tip of the microcatheter while this was prohibited in others, for instance in the PROACT trials. 

Cauda equina syndrome has been reported after the use of microcatheters for continuous intrathecal anesthesia. The concern was sufficient reason for the FDA to withdraw microcatheters from the US market after 11 cases of cauda equina in 1992 (SEDA-21, 129) (206). It has now become obvious that a confounding factor was the use of hyperbaric solutions pooling around lumbosacral nerve roots, aggravated by the poor mechanics of microcatheters and the use of inappropriate amounts the authors of one study argued that the problem was not evident with the use of low concentrations of isobaric local anesthetics administered via microcatheters (207). 

A retrospective review of 603 continuous spinal anesthetics (127 had microcatheters) showed three patients with postoperative paresthesia, one of whom was from... 

Standi T, Eckert S, Schulte am Esch J. Microcatheter continuous spinal anaesthesia in the post-operative period a prospective study of its effectiveness and comphcations. Eur J Anaesthesiol 1995 12(3) 273-9. 

Standi TG, Horn E, Luckmann M, Burmeister M, Wilhelm S, Schulte am Esch J. Subarachnoid sufentanil for early postoperative pain management in orthopedic patients a placebo-controUed, double-bhnd study using spinal microcatheters. Anesthesiology 2001 94(2) 230-8. 

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... 

IMS 11 subjects treated with the EKOS catheter and IMS 1 subjects treated with the standard microcatheter demonstrated grade 2-3 recanalization rates at the specific site of arterial occlusion of 73% (24/33) in EKOS-treated subjects vs. 56% (33/59) in standard microcatheter-treated subjects (p=0.11) [57]. This device is being further investigated in the randomized IMS 111 trial. Likewise, enhanced fibrinolysis with intravenous rt-PA can be achieved with the use of continuous 2-MHz transcranial Doppler ultrasonography (CLOTBUST trial) [58]. 

Fig. 13.6 The Solitaire device (ev3 Neurovascular, Inc), (a) Baseline angiogram demonstrates complete occlusion of the right MCA black arrow) and ACA white arrow), (b) Native images demonstrate the Solitaire device distal white arrow) and proximal black arrow) markers as well as the microcatheter tip arrowhead), (c) Angiogram performed with the Solitaire device in place demonstrates immediate partial reperfusion black arrow), (d) Roadmap angiogram obtained during retrieval of the...

Dabus G, Nogueira RG. Empty microcatheter technique for the deployment of a self-expanding stent to treat refractory middle cerebral artery occlusion in the setting of severe proximal tortuosity. J Neuroimaging. 2009 19 164-168... 

Della Santa A, Mazzoldi A, de Rossi D (1996) Steerable microcatheters actuated by embedded conducting polymer structures. J Intell Mater Sys Stmct 7 292... 

Fig. 4.11. a Inconspicuous falciform artery (arrow) arising from a branch of the left hepatic artery, b Selective catheterisation of the left hepatic artery confirms the presence of a falciform artery which is subsequently entered with a microcatheter (c) in order to coil it, thus preventing nontarget radioembolization... 

The first method developed for resin microspheres was clinically derived with the added data of intraoperative activity calculations [24-26,38]. There are important details regarding the differences in these patients and those now treated worldwide with resin microspheres. First, patients were previously untreated by chemotherapy or early in a course of standard 5-fluorouracil and Leucovorin. Typical patients with breast, colorectal and primary cancers of the liver have often received multiagent chemotherapy reducing overall and liver-specific tolerance to additional anticancer therapies. Second, the volume treated included both lobes at the same time. This is not much different to current treatment approaches which try to treat all of the tumors in each lobe with placement of microcatheters in more than one position or at the bifurcation of the right and left hepatic arteries. However, if less than the whole liver is intended for treatment, this must be accounted for with a proportional reduction in the calculated activity planned for delivery. Third, concurrent infusion of the vasoactive agent angiotensin II shifted... 

AVM embolization is normally accomplished through transfemoral microcatheter delivery of the material under fluoroscopic guidance. The microcatheter tip is placed where the feeding artery branches off from healthy vasculature and... 

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