3-fold and early develop of stent thrombosis among African American than Whites after inplantation of a drug-eluting stent (DES) than whites, Why? Professional Medicine

3-fold and early develop of stent thrombosis among African American than Whites after inplantation of a drug-eluting stent (DES) than whites, Why?

September 4, 2010, 8:35 am

In recent retrospective analysis by led investigator, Dr Sara D Collins from Washington Hospital Center, Washington, DC, 1594 black patients compared with 5642 nonblack patients underwent drug-eluting stent (DES) implantation.

65.7% were men (age range; 52-78) and average age was 65 years. The median household income was significantly lower in blacks than in whites ($144 197 vs $60 838). In addition, blacks were younger and were more likely to have history of hypertension, diabetes mellitus, chronic renal insufficiency, and congestive heart failure.

Although blacks were more likely to be taking clopidogrel at the time of stent thrombosis, however, the differences to nonblack were not significant statistically (87.5% vs 77.8%).

Overall, from the study results, the researchers found that after 30 days, nearly three times in blacks more likely to develop stent thrombosis than nonblacks after inplantation of a drug-eluting stent (DES).

In multivariate analysis, black race emerged as an independent predictor of early stent thrombosis at 30 days and persisted as an independent predictor of late stent thrombosis beyond 30 days.

Published in August 30, 2010 in Circulation, the senior author of the study, Dr Ron Waksman from Washington Hospital Center, Washington, DC, said that they have to understand exactly why this is happening cause there is popular answer that said this was an issue of compliance (such as black patients are sicker and some other confounders).

However, he added, with this study, they found that it was not a compliance issue, but it is real deal.

Due to why stent thrombosis most occur in blacks, their hypothesis that this population may have a genetic polymorphism that make them less responsive to clopidogrel.

However, he said that those hypothesis just speculation and the study not include any genomica data.

In the meantime, he said that physicians and patients need to be aware that this is happening, and it’s not necessarily a compliance issue. This may be a consideration to take into account in the decision to place a drug-eluting stent. For what are the other options for these patients?, he said that if it is a question of a polymorphism, that may address the issue, but they don’t know for sure at the moment. That was the purpose in publishing this study, to increase awareness and to continue to search for an answer.

Commenting with this findings, although Dr Mauro Moscucci from University of Miami Miller School of Medicine, FL, agreed that genetics probably has a role in the disparity, however, other factors also may play the role.

He said that he disagree that the authors necessarily ruled out all other possibilities, including compliance with clopodpogrel. A more valid way of assessing compliance would be to use the medication-possession ratio [MPR] (defined as the sum of days’ supply of medication divided by 365 to measure adherence).

Moscucci said that if the patients is supposed to be on the medication for one year, the total numbers of prescription multiplied by the numbers of days should be 365 days, so the MPR should be 1. If it is less than 1, it means that there have been some gaps in taking the medication. Some recent registry analyses that have been presented on an abstract level have shown that there are, in fact, differences in the MPR across different ethnic groups.

Also, he added that socioeconomic factors may still have been of some importance. He said, the study looked at median income, which is certainly a way to look at socioeconomic status, but he thinks it would have been worthwhile to know more. According to Moscucci, studies looking at subacute stent thrombosis have shown that being on minimum wage or being unemployed is also associated with an increased risk.

Nevertheless, he noted that there does seem to be some underlying genetic differences in the way blacks and whites metabolize clopidogrel. He said that as the authors of the study nicely state in their discussion, there has been a lot of interest in different genes that code enzymes that metabolize clopidogrel. There has been a lot of interest in the CYP2C19 gene and reduced-function alleles. There are some data to suggest that African Americans and Asians tend to have a higher frequency of reduced-function alleles compared with whites.

He said that it is likely that the health disparities are due to a combination of factors. According to Moscucci, some are ocioeconomic, some are probably genetic, and it is going to be our role now to start digging more into those factors, trying to identify what we can correct. If it is genetic, we can address it perhaps with genetic testing to identify low responders and then use different medications to reduce the risk of subacute stent thrombosis. But the socioeconomic factors would be difficult to address, especially now in the current economic situation.

Agreed with Moscucci, Dr Oscar C Marroquin from University of Pittsburgh Medical Center, PA, said the fact that the study was retrospective is an important limitation. According to Marroquin, given this, confounding variables not included in their adjusted model could account for the observed findings.

He is also feel that the role that socioeconomic status might have played in the outcome cannot be completely discounted. Finally, the study reports on outcomes in patients receiving so-called “first-generation” DES. According to Marroquin, Whether these observations can be extrapolated to patients who receive newer-generation DES is unknown.

Despite these limitations, Marroquin feels that the study observations are important. He said that they should be viewed as hypothesis-generating, rather than conclusive. As the study authors suggest, further study of race genetics/pharmacogenomics and their impact on responsiveness to dual antiplatelet therapy to potentially explain these findings is warranted.

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