Using radial access site intervention reduces the risk of adverse outcomes in STEMI patients, but it offers no increased benefit to patients with non-ST segment elevation acute coronary syndrome (NSTEACS), according a RIVAL analysis published online Oct. 24 in the Journal of the American College of Cardiology.

The multinational RIVAL (RadIal Vs femorAL access for coronary intervention trial) study enrolled more than 7,000 patients with STEMI or NSTEACS and randomized them to intervention using either a radial or femoral artery approach. The goal was to compare bleeding and major cardiovascular events based on the two access sites.

RIVAL researchers previously reported no difference in the primary composite outcome of death, MI, stroke or non-CABG-related major bleeding. But they found a substantial reduction in major vascular access site complications with the radial approach.

Shamir R. Mehta, MD, of Hamilton Health Sciences in Hamilton, Canada, and colleagues noted that STEMI and NSTEACS patients differ, though. The former receive more potent antithrombotic therapies, are at higher risk of bleeding complications and undergo PCI more frequently. As a consequence, the treatment access site may affect these two patient groups differently, they proposed.

Using RIVAL data (1,958 STEMI and 5,063 NSTEACS patients), they compared the efficacy and bleeding outcomes by access site. They used the RIVAL primary outcome plus a secondary outcome of death, MI, stroke and mortality. Analyses were by intention to treat.

They wrote that patient and procedural characteristics were well matched between the two groups, and there were no significant differences in operator procedure volumes.

Mehta et al found that radial access reduced the rate of the primary outcome in STEMI patients compared with NSTEACS patients. STEMI patients in the radial access group had rates of 3.1 percent vs. 5.2 percent for STEMI patients in the femoral access group. NSTEACS patients, on the other hand, had rates of 3.8 percent for radial and 3.5 percent for femoral.

Radial access also reduced the rate of the secondary outcome in STEMI patients, at 2.7 percent vs. 4.6 percent for the femoral access group. Mortality was lower in the STEMI radial access group, at 1.3 percent vs. 3.2 percent for the STEMI femoral group. There were no differences in the secondary outcome between the NSTEACS groups.

“In patients with STEMI, radial artery access significantly reduced the primary outcome and the secondary outcome of death, MI, or stroke as well as all-cause mortality,” Mehta and colleagues wrote. “In patients presenting with NSTEACS, we found no significant differences in any of these outcomes.”

Operator experience in the radial approach was greater in the STEMI group compared with the NSTEACS group, at 400 cases vs. 326 cases. Among both STEMI and NSTEACS patients, the radial groups had fewer occurrences of ACUITY major bleeding and major vascular access site complications. The 30-day mortality rate among patients undergoing primary PCI was lower with radial access compared with femoral access, at 1.4 percent vs. 3.1 percent, respectively.

The authors offered several reasons for the radial access-related mortality findings. STEMI patients have a higher 30-day mortality risk compared with NSTEACS patients. If reducing bleeding-related complications improves mortality then that might be reflected in outcomes. STEMI patients are more likely to undergo PCI, which puts them at higher risk of access site complications. They also often receive more potent antiplatelet and antithrombotic therapies that affect bleeding risk and mortality.

The researchers cautioned that in RIVAL the primary outcome results had been neutral and those results may be the most reliable. They also cautioned that RIVAL-defined bleeding events were infrequent in the trial. “Although we demonstrated a much higher mortality rate in patients who experienced a major bleed compared with those who did not, the low frequency of events may have impeded our ability to determine whether a reduction in major bleeding could have affected longer-term mortality,” they wrote.

Based on their current findings, they determined that radial artery access reduced the primary outcome and mortality in STEMI patients but not NSTEACS patients.  “These data suggest that radial artery access might be the preferred option in patients with STEMI,” they concluded.