Researchers Discount Finding of Lower Non-Access Site Bleeding with Transradial PCI

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Percutaneous coronary intervention (PCI) via the transradial route lowers both access-site and non-access site bleeding compared with transfemoral PCI. But the non-access site findings may be due to residual confounding, according to a large, Massachusetts-based study appearing online August 14, 2013, ahead of print in the Journal of the American College of Cardiology.

Researchers led by Robert W. Yeh, MD, MSc, of Massachusetts General Hospital (Boston, MA), looked at 17,509 patients who underwent PCI at 5 Massachusetts hospitals from 2008 to 2011. Nearly one-fifth (17.8%) of procedures were transradial.

Overall, 240 patients (1.4%) had either access site or non-access site bleeding. After using propensity scoring to account for differences in baseline characteristics, 3 different statistical methods were used to assess the odds of both types of bleeding with transradial vs. transfemoral PCI, with a fourth comparison culled from the randomized RIFLE STEACS trial.

Each of the 3 statistical methods showed reductions in both access site and non access site bleeding with transradial PCI (table 1).

Table 1. Bleeding Outcomes with Transradial vs. Transfemoral PCI

 

In the randomized RIFLE STEACS trial, access site bleeding was lower with transradial PCI (OR 0.34; 95% CI 0.16-0.68), but non-access site bleeding was unaffected by access route (OR 0.96; 95% CI 0.53-1.74).

The researchers note that they “identified a relationship between transradial PCI and non-access site bleeding that was not identified in [randomized clinical trials] and that is most likely due to the inability of our methods to fully adjust for unmeasured patient differences.”

Furthermore, the meta-analysis was designed so that non-access site bleeding was a so-called falsification endpoint, or a claim that researchers believe is highly unlikely to be causally related to the intervention under study, “similar to a ‘negative’ control experiment in a laboratory.”

Therefore, the finding of a relationship between transradial PCI and reduced non-access site bleeding signifies, in fact, that the association is due to residual confounding “because transradial PCI would not be expected to differentially influence bleeding apart from at the arterial access site,” they explain.

Two Plus 2 Is 4

Sunil V. Rao, MD, of Duke University Medical Center (Durham, NC), agreed with the overall message of the study that transradial PCI most likely does not reduce non-access site bleeding. “The actual underlying scientific question is not all that shocking,” he told TCTMD in a telephone interview. “I’m not even sure you need a study to show that. It’s like 2 plus 2 is 4.”

He added that the most important lessons from the study are primarily for the research community. “Whenever you have new methods, and these are certainly new to cardiology literature, it’s important for clinical researchers to be aware of them because we’re always trying to come up with new ways to overcome confounding,” Dr. Rao said. “Basically what they’re trying to do with all these techniques is to simulate randomization. Unfortunately, there’s no substitute for randomization.”

The “falsification endpoint” approach is certainly not foolproof, he stressed. “All of this assumes we are acutely aware of all the mechanisms that are in play, but we’ve proven over and over again that we’re not as smart as we think we are,” Dr. Rao said.

Still, the study gives important guidance for future research efforts. “Traditionally, I would have expected to see something like this in a very methodology oriented journal, but these are important lessons for even knuckle-dragging interventionalists to understand,” Dr. Rao said, noting, “I’m not sure there’s anything new here except to emphasize that bleeding avoidance strategies involve not just an access-site strategy or pharmacological strategy in isolation but really a combination of approaches, particularly in patients at highest risk.” 

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Source:
Wimmer NJ, Resnic FS, Mauri L, et al. Comparison of transradial versus transfemoral percutaneous coronary intervention in routine practice: Evidence for the importance of “falsification hypotheses” in observational studies of comparative effectiveness. J Am Coll Cardiol. 2013;Epub ahead of print.

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