Radial Access in Primary PCI Offers Sustained Survival Benefit Even After Long Delays

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Radial access carries so great a survival benefit in primary percutaneous coronary intervention (PCI) that its advantage can only be offset when patients with ST-segment elevation myocardial infarction (STEMI) have substantial delays in reperfusion lasting more than 1 hour, reports a paper published online April 7, 2014, ahead of print in the American Heart Journal. The results challenge the idea that potential increases in door-to-balloon (D2B) time should deter use of the radial approach.

Robert W. Yeh, MD, MSc, of Massachusetts General Hospital (Boston, MA), and colleagues created a model to explore the interplay between access route, D2B time, and 30-day mortality. They pooled findings from RIVAL and RIFLE-STEACS, 2 large randomized trials that demonstrated a survival benefit with radial PCI among STEMI patients and estimated the relationship between reperfusion delays and mortality using data from the National Cardiovascular Data Registry.

The model’s base case assumed a crossover rate of 7.8% between access routes and a 50% reduction in mortality with radial. Delays longer than 1 hour would be required to equalize mortality rates between radial and femoral access, even in elderly patients. Radial access maintained its lead when the potential survival benefit was lessened to one-half and one-quarter of what was seen in RIVAL and RIFLE-STEACS (table 1).

Table 1. Delay Needed to Offset Advantage of Radial by Assumed Mortality Reduction

Because crossover between access routes is thought likely to be more common in real-world practice than in RIVAL and RIFLE-STEACS, the researchers calculated what would happen when crossover rates rose by 5% and 10% over the base-case rate of 7.8%. Results favoring radial were sustained (table 2).

Table 2. Delay Needed to Offset Advantage of Radial by Assumed Crossover Rate

Probabilistic sensitivity analyses demonstrated that the transradial approach would be better than the transfemoral approach 97% of the time assuming a 30-minute delay and 79.0% assuming a 60-minute delay.

Benefit Itself ‘Remains Controversial’

“These results may be surprising to many practitioners and reflect the large relative risk reduction seen with transradial PCI in the RIVAL STEMI substudy and RIFLE-STEACS trials,” Dr. Yeh and colleagues acknowledge. “Although these studies represent the best sources of data from which to estimate the treatment effect, it is important to note that these observed benefits were larger than anticipated, and in the case of one study, the one positive subgroup analysis of several performed.”

Study co-author Neil J. Wimmer, MD, MSc, of Brigham and Women’s Hospital (Boston, MA), told TCTMD in an email that the idea of a mortality reduction with radial “remains controversial.” In the same email, Dr. Yeh reported that most interventionalists believe existing trial data overstate the benefit of radial. This is why, he said, the research team did alternate calculations assuming differences that were far less dramatic than seen in RIVAL and RIFLE-STEACS.

Possible explanations as to why transradial might reduce mortality, the paper suggests, include reduced access-site bleeding, earlier ambulation, faster hospital discharge, and decreased renal failure.

D2B Not the Only Quality Metric

Dr. Wimmer said that the focus on reducing D2B times to recommended levels (≤ 60 minutes in Europe and ≤ 90 minutes in the United States) has been “incredibly successful” at improving patient care.

“However, public reporting and reimbursement implications of reporting D2B times pressure physicians to continue to try to reduce [delays] even if other interventions, in this case radial PCI, may be more beneficial,” he said, adding, “As with many conditions, the treatment of patients with STEMI may not be as simple as opening the culprit vessel as quickly as possible.  There are many factors to consider at once.”

In an editorial accompanying the paper, Samir B. Pancholy, MD, of The Commonwealth Medical Center (Scranton, PA), and Sunil V. Rao, MD, of Duke Clinical Research Institute (Durham, NC), agree that the current study “suggests that a shift in priorities may be [necessary] in order to achieve the best outcomes in STEMI.

“Rather than focus solely on a surrogate quality metric like D2B, a comprehensive approach aimed at restoring Thrombolysis In Myocardial Infarction 3 flow in the infarct artery, achieving optimal stent expansion, and preventing procedural complications like bleeding is likely a better goal,” they propose.

Yet, Drs. Pancholy and Rao urge, “enthusiasm for transradial PCI should be balanced against the other objectives of therapy. [The current] analysis represents a theoretical construct and should not be interpreted as an argument for using radial access at the expense of extreme prolongation of D2B, especially since D2B is a publicly reported hospital quality measure and the concept of ‘time is muscle’ has not been refuted.”

Interventionalists new to radial access must also recognize that STEMI patients are a uniquely challenging subset, they add.

“Importantly, operators should be experienced with elective transradial diagnostic and PCI cases so that they can obtain radial artery access, intubate the coronary arteries with a guiding catheter, wire the infarct artery, and achieve timely reperfusion in the STEMI setting,” the editorial authors note. “The [Society for Cardiovascular Angiography and Interventions] recommends that operators should not start performing transradial primary PCI until they have performed at least 100 elective PCI cases with a ‘radial first’ approach and their femoral crossover rate is < 4%.”

Small Delays ‘of Little Concern’

Ian C. Gilchrist, MD, of Hershey Medical Center (Hershey, PA), told TCTMD in an email, “This is a hypothetic model and whether the exact numbers would be true or not, I think the concept is the true value. That is, small differences between transradial or transfemoral procedures in D2B times are of little concern.” However, both RIVAL and RIFLE-STEACS were conducted in Europe, he said, where operators are more experienced with radial and as such may achieve better outcomes.

Dr. Gilchrist agreed that public reporting of D2B has driven “fear of delays” in the United States. “For those worried about transitioning to transradial, it has been used as a reason to stick with femoral. For those who believe radial is an evolutionary improvement in the field, small differences in time probably never really mattered,” he said.

Regardless of access route, operators must “be able to judge how well the procedure is progressing” and consider crossover when appropriate, Dr. Gilchrist said. “How long to wait is not necessarily set in stone, but switching from femoral to radial, or radial to femoral, may be necessary and should be done if the operator feels it in the best interest of the patient.”

In light of mounting evidence that radial access improves outcomes and is preferred by patients, this study will hopefully provide some reassurance, Dr. Yeh concluded. “STEMI patients are exactly the type of patients that benefit the most from a transradial approach, and we ought to be doing everything we can to optimize their outcomes.”

 

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Sources:
1. Wimmer NJ, Cohen DJ, Wasfy JH, et al. Delay in reperfusion with transradial percutaneous coronary intervention for ST-elevation myocardial infarction: might some delays be acceptable? Am Heart J. 2014;Epub ahead of print.

2. Pancholy SB, Rao SV. Improving outcomes in primary percutaneous coronary intervention: transradial is worth the time [editorial]. Am Heart J. 2014;Epub ahead of print.

 

 

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