Baseline Anemia Raises Risk for Stent Thrombosis After DES

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Severe anemia puts patients at increased risk for adverse outcomes, including stent thrombosis, following drug-eluting stent (DES) implantation. In an analysis published online March 27, 2012, ahead of print in Circulation: Cardiovascular Interventions, researchers say it is unclear whether widespread DES use is justified in this population and suggest that bare-metal stents (BMS) should be chosen instead.

Stephan Windecker, MD, of Bern University Hospital (Bern, Switzerland), and colleagues analyzed data from 6,528 consecutive patients who underwent PCI with early and new-generation DES between April 2002 and March 2009.

Patients were grouped according to the World Health Organization definition for no/mild anemia (n = 5,965) or severe anemia (n = 347). Severe anemia, with a prevalence of 21.6% among the total population, was more common among the elderly, diabetics, and patients with chronic kidney disease.

Multiple Risks Emerge

At 4 years, patients with severe anemia had higher rates of death, cardiac death, and MI compared with patients with no/mild anemia. The condition also was associated with increased risk of Academic Research Consortium-defined definite and definite/probable stent thrombosis (table 1).

Table 1. Major Adverse Events at 4 Years

The increased risk of death emerged in the first 6 months and continued to accrue during long-term follow-up. In a landmark analysis with a cutoff of 30 days after the procedure, there was no difference in mortality during the periprocedural period (severe vs. no/mild anemia: HR 1.51; 95% CI 0.68-3.33; P = 0.31), while an increased risk of death was observed between 31 days and 4 years for patients with severe anemia compared with no/mild anemia  (HR 1.97; 95% CI 1.41-2.73; P < 0.0001).

The relationship between severe anemia and death was unaffected by patient sex (P interaction = 0.857) or ACS presentation (P interaction = 0.613), although there was a trend toward a high mortality risk mortality in anemic patients less than 65 years old (P interaction = 0.066).

“Even though no difference in the prescription of dual antiplatelet therapy was noted at the time of hospital discharge, the increased risk of early [stent thrombosis] may have been related to premature discontinuation of antiplatelet agents—a strong predictor of [stent thrombosis] in the DES era,” the study authors write. “Alternatively, patients who had early [stent thrombosis] also had anemia of chronic disease associated with malignancies or autoimmune diseases, which may in turn be associated with prothrombotic activity.”

Due to the “alarmingly high rates of overall mortality and [stent thrombosis] among patients with severe anemia treated with DES,” the study authors say it is unclear whether the potential advantages of DES justify their use in this population.

“Caution requires that unless data from randomized trials indicate otherwise, bare-metal stents should be used instead,” they conclude.

Troubling Finding

According to Mauro Moscucci, MD, of the University of Miami Miller School of Medicine (Miami, FL), the mechanism behind the relationship between anemia and adverse outcomes in this population is unclear. “Anemia can have multiple causes, . . . and it is a marker of the severity of chronic inflammation,” he told TCTMD in a telephone interview.

Dr. Moscucci added that while the increased risks of death, cardiac death, and MI are not necessarily unexpected in anemic patients since they tend to be older and have more comorbidities, the increased frequency of stent thrombosis is troubling and deserves further study.

“They clearly showed that at baseline and at the end of the study the use of dual antiplatelet therapy was the same in both groups. However, it is important to realize that we don’t know what happened in between,” Dr. Moscucci said. “There may have been early discontinuation in the early stage after stent implantation, which perhaps can explain some of the differences. Some of this [discontinuation] may have been due to concern about the anemia status.”

But the study authors raise an important question of whether clinicians should routinely be thinking of BMS as the preferred revascularization option in these patients, he said. This line of thinking is becoming more common as part of the socioeconomic assessment of PCI patients, which attempts to account for who will comply with prolonged dual antiplatelet therapy.

“Anemia is one more issue that we may need to consider depending on our long-term concerns about the risk of stent thrombosis,” Dr. Moscucci concluded.

Study Details

Dual antiplatelet therapy (≥ 100 mg aspirin and 300-600 mg clopidogrel) was given before or at the time of the procedure. At discharge, aspirin was continued indefinitely and clopidogrel was prescribed for at least 12 months. Periprocedural use of glycoprotein IIb/IIIa inhibitors was left to the discretion of the operator.

Anemia was defined as a hemoglobin concentration of less than 120 g/L for women and less than 130 g/L for men. Patients below the 25th percentile, calculated separately for men and women, were categorized as having severe anemia.

 

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Source:
Pilgrim T, Vetterli F, Kalesan B, et al. The impact of anemia on long-term clinical outcome in patients undergoing revascularization with the unrestricted use of drug-eluting stents. Circ Cardiovasc Interv. 2012;Epub ahead of print.

 

 

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• Anemia Inhibits Platelet Response to Clopidogrel in PCI Patients
• Anemia Worsens Prognosis After Primary PCI—Especially for Men
• Thrombocytopenia in PCI Patients Signals Higher Complication Risk

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