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Headline News:
November 20th, 2008
Sidebranchability and Bifurcation Stenting
- There are unresolved challenges facing bifurcation stenting. At present, drug eluting stents have not provided the answer.
While several drug eluting stent (DES) trials indicate lower bifurcation restenosis in the main branch, a renarrowing of the side branch often occurs leading to significant increases in peri-procedural myocardial infarctions up to 30 days.1 This can be observed if the side branch ostium is not supported by DES struts or if flow to the side branch is obstructed by the stent itself. The renarrowing may also be attributed to the polymer.2
In fact, a recently published study3 to evaluate a drug eluting stent implanted at bifurcation lesions concluded, "Restenosis at the side branch remains a problem to be solved, and additional efforts need to be addressed to reduce the risk of thrombosis." IVUS examinations were suggestive of incomplete coverage of the side branch ostium by the stent struts.
With ring and coil stent designs, cells can be opened wider than slotted tube stents, but coverage of the bifurcation, particularly at the ostium, is less. Easy side branch access is achieved at the expense of lesion coverage With closed cell slotted tube designs, side branch access is often difficult and the cell's size, once expanded, is more limited.
- The optimal stent design coupled with the most effective technique has remained elusive.
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1Data from the TAXUS V trial are instructive: in the multiple stent subgroup, 30 day MACE was significantly higher in the TAXUS arm as compared to the bare metal stent control (8.3% vs 3.3%, p=0.047), a difference mainly driven by a significant increase in peri-procedural MI. Prinicipal investigator, Dr. Gregg W. Stone of the Cardiovascular Research Foundation and Columbia University, said, "We did a very detailed, blinded angiographic study and the reason that happened was because there was transient decreased flow in the side branches."
| Side branch analysis in multiple stenting | Control (n=184) | TAXUS' (n=188) | P-value |
| Branch TIMI flow reduction (anytime) (%) | 28.6 | 41.9 | 0.016 |
| Any side branch narrowing >70% DS (%) | 30.6 | 42.6 | 0.033 |
2Dr. Stone said we can only speculate why this happens, but he suspects the difference is related to the polymer used on the DES (ACC, 2005).
3This study, entitled "Randomized Study to Evaluate Sirolimus Eluting Stents Implanted at Coronary Bifurcation Lesions" by Colombo et al. reported total in segment restenosis of either the side branch or the main branch or both was 25.7% (17 of 66 cases). 14 cases were of focal restenosis at the ostium of the side branch. In addition, there were three cases (3.5%) of thrombosis affecting the side branch in two of them and both branches in the other one. This could have been related to stent struts obstructing blood flow at the ostium.
