Drug-Eluting Stent Solutions: Evaluating Endpoints in Drug-Eluting Stent (DES) Trials

Louis Cannon, MD, FACA, FACC, FAC
Louis Cannon, MD, FACA, FACC, FAC
When evaluating clinical trials of DES, which endpoints do you think are most important? Target lesion revascularization (TLR) is the first endpoint I look at when evaluating a clinical trial. There are two types of TLR: clinicall driven and angiographically driven TLR. Clinically driven TLR is defined as revascularization performed on a patient who returns with clinical symptoms such as unstable angina, that is, chest pain that increases in frequency, intensity or duration. Angiographically driven TLR is performed due to angiographic detection of significant restenosis in a patient who is clinically asymptomatic. For the most part, clinical trials mandate angiographic follow-up at approximately nine months. This means that even asymptomatic patients who are not experiencing any difficulty in going about normal, everyday activities are brought back to the cath lab to undergo a repeat angiogram. If the angiogram shows a borderline lesion in the 50-70% range, the interventional cardiologist may want to perform an intervention to open up the lesion or improve it a bit even though the lesion may not be clinically significant to the patient. In research studies, clinically driven TLR rates are usually much lower than angiographically driven TLR rates. This makes sense, because in real-world practice, patients typically come back to us only if they have problems; they are not required to return at nine months for an angiogram. As a clinician, I am most interested in clinically driven TLR. What other differences would you expect to see between clinically driven TLR and angiographically driven TLR? It is important to understand that some studies are designed differently. For example, if a study has a high angiographic follow-up rate, then you can expect the TLR rate for that study to be higher than the TLR rate in another study that does not have high follow-up rates, which is why it is very important to look at clinically driven TLR. Two studies, the TAXI Trial and the REALITY Trial, have recently shown that both the Taxus (Boston Scientific Corporation, Maple Grove, Minnesota) and the Cypher (Cordis Corporation, Miami, Florida) stents have similar rates of clinical revascularization in terms of clinically driven TLR. Is this consistent with what you have seen in your own practice? Yes, it is very consistent with what I have observed in my practice. I would estimate that approximately 5% of the patients I see have clinically driven TLR, which means that about 95% of patients who receive a DES are going to have a fantastic outcome. What can cath lab staff take away from this information? How will it benefit their patients? DES may allow interventional cardiologists to address patients and clinical situations that may not have been previously approachable through percutaneous intervention or bypass surgery. The low rate of clinically driven TLR is one factor that will encourage interventional cardiologists to tackle more complex lesions. Another factor involves the attributes of the stent delivery systems. Deliverability is key to accessing complex lesions, and although the Cypher and Taxus stents are both excellent products, the Taxus Express2 stent’s flexibility allows the stent to be delivered in certain difficult cases that years ago may not have been attempted percutaneously. The main benefit for patients is that a DES can help them return to their daily routines with a greatly reduced fear of recurring chest pain and subsequent trips to the catheterization laboratory. Sponsored by Boston Scientific