Modified Catheter for Percutaneous Transluminal Treatment of Arteriosclerotic Obstructions

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Experience with transluminal dilatation of superficial femoral artery stenoses resulted in modification of the original outer catheter because of the following problem. The patient in Figure 1, A and B had generalized arteriosclerosis and one severely stenotic segment in the superficial femoral artery at the adductor hiatus. Although containing some atheromatous plaques, the popliteal artery was patent. Transluminal dilatation was carried out by the method of Dotter and Judkins (1–3). No difficulty was encountered in dilating the stenotic segment with the wire guide or with the small catheter. After the stenosis was traversed by the larger catheter, arteriography showed that the previously stenotic segment was now wide open. A stenosis had developed in the originally patent popliteal artery (Fig. 1, C), however, and atheromatous material had apparently been deposited in the lumen of the popliteal artery. I postulated that the difficulty arose from a “snow-plow” effect due to a small ridge which formed around the second catheter when it was passed over the first. A roentgenogram (Fig. 2, A) of the original catheters shows this sharp ridge formed by the junction of the leading edge of the outer catheter and the outside surface of the inner catheter. In a tight stenosis first traversed by the tapered inner catheter, the ridge of the outer catheter can push atheromatous material ahead of it rather than compress it to the sides of the lumen as was originally intended (Fig. 3, A). This thesis is supported by the appearance of the vessel wall at the original superficial femoral artery stenosis following dilatation. The step-like configuration suggests a gouging out of an atheromatous plaque (Fig. 1, C, arrow). The manufacturer2 modified the larger catheter so that the tip was molded to the diameter of the wire guide. Figure 2, B demonstrates the relationship of the modified outer catheter to the inner catheter and guide. The outer catheter has a smooth transition from the wire guide to its greatest diameter. The smooth change in diameter allows the tip of the catheter to occupy the space previously dilated by the smaller catheter. The proximal gradually widening larger tube then compresses the atheromatous material against the vessel wall (Fig. 3, B). With this arrangement the larger catheter cannot be passed over the smaller tubing. Therefore, after dilatation has been accomplished with the smaller catheter, it is removed and the larger catheter is inserted over the wire guide. This is no different from exchanging catheters in any vascular diagnostic catheter procedure. If more stiffness is required, the smaller catheter can be reintroduced inside the larger catheter. If this is not sufficient, a long metal cannula provided by the manufacturer can be passed over the wire guide inside the smaller catheter to increase stiffness in penetrating the stenosis.