Response to Letter Regarding Article, “Drug-Eluting Stents in Animals and Patients: Where Do We Stand Today?”
In their letter regarding my editorial1, Drs Virmani, Wilson, and Finn highlight the parallels between inflammation in pig coronary arteries treated with sirolimus-eluting stents and human coronary arteries in which thrombosis has occurred in relation to the same stent platform. Clearly, inflammation may occur in some human arteries treated with sirolimus-eluting stents. In cases where inflammation is severe, perhaps due to a rare hypersensitivity reaction, the treated arterial segment may be susceptible to thrombosis. These observations, although interesting, raise 2 important questions. First, how often does such extensive inflammation occur in humans? Second, if present, how often does coronary inflammation lead to thrombotic sequelae?
As Virmani et al comment, “the animal data…may be predictive of a local hypersensitivity reaction in humans, although its prevalence may be much lower than in pigs.” The actual frequency of drug-eluting, stent-based inflammation in humans is uncertain, and our ability to identify coronary inflammation (or other features that may predispose to stent thrombosis) remains inadequate. Molecular imaging techniques, coupled with advanced anatomic imaging modalities such as intravascular ultrasound, optical coherence tomography, or angioscopy, may help us to identify the prevalence and culpability of such factors.
At present, clinical decisions about which stents to use, in which patients, and for which lesions must depend on the growing body of data from clinical trials. On balance, drug-eluting stents continue to emerge as superior to bare metal stents largely due to a reduction in the need for repeat revascularization procedures and their associated risks.
No matter how rare it may be, we must always consider the profound risk associated with stent thrombosis. Understanding the basic mechanisms of vessel healing after drug-eluting stent implantation in animal models can provide an understanding of potential problems, and this insight must be reconciled with the actual outcomes that we observe when stents are used in humans. Only through the continued combined examination of the pathophysiology of experimental introduction of endoluminal devices into coronary arteries, and the real-world results of human experience, can we learn how to make the best decisions for our patients.