Facilitated Planning of Intracoronary Stenting Using a 3-D Vessel Reconstruction Program

Case Study A physically active 57-year-old man presented to his primary cardiologist with complaints of substernal chest pain occurring at rest. Subsequent angiography revealed a high degree of narrowing in the proximal left anterior descending, and narrowing in the mid-portion of a tortuous right coronary artery. He underwent placement of a paclitaxel-eluting stent in the proximal left anterior descending. This was followed by episodes of recurrent chest pain. Repeat angiography revealed sluggish flow in the LAD distribution. The lumen of the stent was patent. Subsequently, his angina resolved. Four months later, however, he presented with recurrent exertional angina. Angiography again revealed a patent lumen of the left anterior descending (Figure 1) and an eccentric area of narrowing in the mid-portion of the right coronary artery (Figures 2a, 2b). The decision was made to undertake stenting of the mid-RCA. Because of the tortuous nature of the vessel, including the diseased segment, three-dimensional reconstruction using the IC3D system (Siemens Medical Solutions, Malvern, PA) was performed (Figure 3). This revealed a cross-sectional diameter narrowing of 68%, lesion length of 23.7 mm, and reference diameter of 3.73 mm proximally and 3.48 mm distally. Subsequently, a 28 mm paclitaxel-eluting stent was placed across the lesion and expanded to 4.0 mm diameter. The final angiographic result is shown in Figure 4. The patient has remained asymptomatic and physically active six months later. Discussion As the practice of intra-coronary stenting has evolved and as drug-eluting stents have become available, it has become clear that when placing the stent, it is necessary to cover not only most severe portion of the coronary narrowing, but to place the stent margins firmly within a cuff of healthy-appearing tissue. The generally accepted dictum is that the stent margin should be several millimeters longer than the diseased area on either side of the lesion. This practice is in contra-distinction to the previous practice of spot stenting (placing the shortest stent possible) that was adopted in the era of bare metal stenting. As drug-eluting stents in the current generation are considerably more bulky and less maneuverable than bare metal stents, the interventional operator pays a price for selecting a longer stent. Placement of a drug-eluting stent is particularly difficult in tortuous or rigid vessels, and those in which guiding catheter support may be less than optimal. It is always possible to use sequential short stents. However, at the current pricing levels of drug-eluting stents, such an approach is impractical. Although payment to healthcare institutions for placement of drug-eluting stents is higher than that for bare metal stents, use of multiple drug-eluting stents obviates the advantage of this increase in payment. Therefore, the availability of a readily utilized computer program to measure lesion length accurately would be desirable. One such program is the 3D IC, adopted from Paieon Medical. This program has the advantage of reconstructing vascular anatomy in three-dimensional space based on between two to three coronary angiography views. Data from the angiograms is integrated by the program. Using the centerline method, three-dimensional reconstruction is performed. The program operator can then designate a region of interest in the vessel, and by setting a cursor, designate its length. The vessel reference diameter is measured, and the degree of narrowing is calculated. This three-dimensional structure allows easy measurement of reference vessel size, lesion diameter, and most important, lesion length. Additionally, the reconstruction can be rotated in virtual space (Figures 5-7), allowing the operator to observe the selected segment from a variety of different angles, some of which may not be obtainable by the x-ray gantry. This feature also facilitates guidewire placement in some cases, since the reconstructed image facilitates appreciation of angles that might otherwise be overlooked. The system also has the advantage of being user-friendly. Even moderately experienced individuals can perform vascular reconstructions in a period of one to two minutes. In its current iteration, the reconstruction is visible on the angiographic viewing monitor, allowing the operator to select a stent size with relative ease. It is anticipated that, particularly in complex cases such as that shown, this approach will facilitate the placement of appropriately sized drug-eluting stents.

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