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“Res ipsa loquitur.” (The thing speaks for itself.)— Source unknown
“Primum non nocere.” (First, do no harm.)— Attributed to Hippocrates
These quotations aptly describe the stages that the drug-eluting stent (DES) has moved through in the last few years. In this progression, the next stage we should look for is “Caveat emptor,” or “Let the buyer beware.”
After the results of intervention with a DES were first published, the DES was deemed superior to the bare-metal stent (BMS) because of the striking reduction of repeat intervention associated with its use. Unfortunately, this conclusion—formed on the basis of short-term data—did not acknowledge the risk of such long-term sequelae as stent thrombosis, a problem that still has not been sufficiently remedied.
Some few readers might remember that surgeons were sentenced to wait 5 to 10 years after the introduction of coronary artery bypass surgery for confirmation that the highly invasive procedure (which they knew was beneficial) saved lives. To change clinical practice, evidence was required. In contrast, the change in clinical practice after the introduction of the DES required only 9 months. No long-term follow-up was thought necessary. No comparison was made to coronary bypass surgery or medical therapy. As a result, the evidence was completely inadequate and the calculus for deciding which patient would benefit from revascularization—and with what method—became entirely non-empirical.
When compared with the BMS, the DES is without question an advance; it reduces the risk of reintervention or even a return trip to the cath lab. However, long-term follow-up in patients with drug-eluting stents has revealed that a price is involved. To avoid restenosis, patients who receive such stents are required to receive long-term antiplatelet therapy, which cannot be interrupted for an extended period and which does not confer the same protection against restenosis that surgery does. Therefore, choosing a DES just to avoid reintervention can be particularly risky for patients who have diverticular bleeding or kidney failure, or for those who are elderly or prone to falling.
The results of the Rapamycin-Eluting Stent Evaluated at Rotterdam Cardiology Hospital (RESEARCH) registry study by Shen and colleagues1 suggested that after placement of a DES, the risk of stent thrombosis is constant and does not appear to change with time. Although patients with a BMS appear to have the same overall risk of thrombosis as do patients with a DES, the risk is greatest in the first few months after placement of a BMS, whereas the period of risk may last years after the placement of a DES. Al-Dehneh and colleagues,2 in this issue of the THI Journal (see page 343), report that after antithrombotic drug withdrawal, a patient with a DES may develop thrombosis up to 4.5 years after stent placement. However, this observation was made in a patient who had discontinued a regimen of aspirin and clopidogrel, an action that is common in reports of late stent thrombosis. Even patients with bare-metal stents have been reported to have late stent thrombosis after the withdrawal of both antiplatelet agents. However, late stent thrombosis is reported much more often after DES placement than after BMS placement.
Stent thrombosis is far more devastating than restenosis because generally it presents in a not-so-subtle way as myocardial infarction. Therefore, we must address ourselves to the question, “In patients who need revascularization therapy, who should receive a DES rather than a BMS?” For example, in my patient with high-risk unstable angina who has pain at rest and an elevated troponin level, I find a discrete lesion less than 10 mm long in the mid-portion of the right coronary artery with a reference vessel diameter of 2.5 mm. Does the calculus suggest a BMS or a DES for this patient? In addition to lesion characteristics and clinical setting, we must now consider the presence of the following: diverticulosis, a history of peptic ulcer disease, a history of intracerebral bleeding, diabetic retinopathy, retroperitoneal bleeding, a history of medical noncompliance, and even the patient's age.
The prospect of late stent thrombosis renders the decision for revascularization more challenging. With surgery, there is a threshold (consisting of physiologic and anatomic indicators) at which survival benefit is indicated: left main disease >50%, 3-vessel disease, or 2-vessel disease that includes the proximal LAD and either depressed left ventricular ejection fraction or high-risk treadmill findings. Recently, percutaneous therapy has found a place as a treatment for patients who have high-risk unstable angina or unacceptable symptom control with no likelihood of improved survival should they undergo coronary bypass surgery. The choice of percutaneous therapy is then based solely upon the perceived severity and anatomy of the underlying lesion. With the advent of routine DES use and the recognition of very late risks of thrombosis in a small number of patients, a new point of decision has been reached: can or will patients tolerate long-term dual antiplatelet therapy, or will they likely have periods of withdrawal from all antiplatelet therapy?
Unfortunately, the DES has altered our calculus in a way that we cannot yet determine. The use of the DES carries a risk of late stent thrombosis that alters recommendations of medical therapy and follow-up. We cannot compare DES therapy with medical therapy because we cannot estimate the effect of medical therapy (which involves the use of long-term, dual antiplatelet drugs) on the efficacy of non-DES therapy, whether surgical or medical. To determine the proper place and use of the DES, we need controlled, long-term studies that examine all 3 forms of therapy (DES, surgical, and medical) in coronary disease, unstable angina, non-ST-segment-elevation myocardial infarction, and ST-segment-elevation myocardial infarction.
Coronary stents have proved to be invaluable for patients who require revascularization to improve their probability of survival but who do not have the anatomic indications for surgical revascularization. With the inclusion of coronary stents in the algorithm for revascularization techniques, we must now establish a calculus for stent choice that takes into account both the risk of repeat intervention and the risk of long-term, uninterrupted antiplatelet therapy.
Address for reprints: James M. Wilson, MD, 6624 Fannin St., Suite 2480, Houston, TX 77030