Vessel tortuosity

The Penumbra stroke system (Penumbra Inc., Alameda, CA) originally included two different revascularization options (1) thrombus debuUdng and aspiration with a reperfusion catheter that aspirates the clot while a separator device fragments it and prevents obstruction of the catheter and (2) direct thrombus extraction with a ring retriever while a balloon guide catheter is used to temporarily arrest flow. This system was initially tested in a pilot trial in Europe where 23 subjects at six international centers were emoUed with 21 vessel occlusions (7 ICA 5 MCA 9 Basilar) treated in 20 patients (mean NIHSS 21 8) up to 8 h after symptom onset. Three emolled subjects were not treated due to vessel tortuosity, resulting in an access rate of 87% (20 of 23). Recanalization prior to lA lysis... 

One of the ongoing needs is to continue to improve the ability of microcatheters to track out into very small peripheral branches. Since vessel tortuosity and spasm are the main causes of technical failure, improving catheter characteristics should improve... 

Fetal growth, congenital malformations Extent of plaque, blood vessel tortuosity... 

Progestogens, alone or together with estrogen, cause an increase in the width and tortuosity of peripheral blood vessels in the oral mucosa, which become more susceptible to local irritants and show increased permeability (204). 

Greater than 120° angulation of the proximal neck Critical inferior mesenteric artery Significant iliac occlusive disease Tortuosity of iliac vessels... 

Figure 28-2 Diffuse episcleritis demonstrating vessel injection, tortuosity, and saccular dilatations (arrows).

Hepatorenal syndrome is characterized by pronounced vasoconstriction of the renal cortex with tortuosity and narrowing of the interlobular and arcuate arteries. The blood supply to the renal cortex may be almost totally interrupted and, at the same time, the blood flow is diverted into areas containing cortical vessels... 

In one prospective study in 17 patients with hemoljdic anemia (aged 5-25 years) lens opacities were found in 41%, changes in the retinal pigment epithelium in 35%, tortuosity of retinal vessels in 24%, dilatation and sheathing of retinal vessels in 18%, defects in color vision in 29%, and abnormal dark adaptation in 18% (56). In many other studies much lower frequencies were found. Perhaps retinal injury is related to the depletion of metals such as zinc, copper, and/or iron (57). On the other hand, ocular and auditory disturbances are not infrequent in patients with thalassemia, iron storage diseases (58,59), or uremia (45), and may be coincidental in patients receiving deferoxamine (60). 

Although the architecture of tumor blood vessels has been studied using a number of techniques, one of the most fascinating involves the use of acrylic resin casts. This is exemplified by the work of Skinner et al (1), who studied a series of chemically induced tumors in rats. A resin solution was injected intraarterially into the anesthetized rat, the animal was killed, and the blood vessels to the tissue, were clamped while the resin set. Tissue was digested with alkali and the cast coated with gold and examined by electron microscopy. Whereas normal colon mucosa showed a consistent regular pattern, tissue from tumors showed considerable disorganization with marked dilation and tortuosity of capillaries. For small tumors it was possible to discern areas in the tumor that... 

Arterial vasospasm is the most common complication associated with passage of the guidewire and catheter into the uterine artery. Because of its diameter and tortuosity, the uterine artery is prone to spasm. In theory, embolization of an artery in spasm may not result in a lasting occlusion since relaxation of the vessel can increase luminal diameter enough to allow flow around the embolization particles [2], This may lead to a false angiographic end-point with secondary redistribution of the embolization particles [2, 10]. The systematic use of microcatheters and microguidewires has been shown to minimize the occurrence of spasm and medications such nitroglycerin or papaverine maybe effective to treat spasm [2]. 

Perforation and dissection of the uterine artery are less common causes of failure [6]. These complications can occur with the use of hydrophilic guidewires associated to the arterial tortuosity (Fig. 10.5.1). Vasospasm occurring primarily in patients undergoing hormone therapy is an important cause of vessel damage. Careful catheterization, use of a microcatheter and experience of operator performing the procedure are all important factors in reducing this type of failure. In cases where... 

Proximal Embolization In the absence of active contrast extravasation, the splenic artery is proximally embolized. We typically utilize either a 5F Cobra catheter or a 5F Omni-2 catheter to catheterize the celiac axis. Depending on the tortuosity of the vessel, we then either use the Cobra catheter or a microcatheter with a 0.021 inner luminal diameter for more selective catheterization. Once the catheter is in place, just distal to the dorsal pancreatic artery, coils are deposited. The size of the coils chosen depends on the size of the vessel. 

Diagnostic procedures are performed with 4 to 5 French diagnostic catheters single (Berenstein) or double curve (Sidewinder) depending on the tortuosity of the vessels. These catheters are used in combination with guidewires (0.035 ) (Fig. 18.6). 

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