The primary composite endpoint was reached by 68 patients (13.6 percent) in the radial arm and 105 patients (21 percent) in the femoral arm at 30 days, a relative risk reduction of 36 percent. The difference was driven primarily by a lower incidence of bleeding complications (7.8 percent vs. 12.2 percent, respectively; p=0.026) and cardiac death (5.2 percent vs. 9.2 percent, respectively; p=0.020) with the radial approach. The radial approach was also associated with a shorter hospital stay (five days vs. six days, p=0.03).

The second study, RIVAL, is the largest study to date to compare radial and femoral approaches. The multinational study enrolled a total of 7,021 patients with acute coronary syndrome (ACS): 1,958 with STEMI and 5,063 with non-ST-elevation ACS. The primary outcome was a composite of death, MI, stroke and non-CABG-related major bleeding at 30 days.

Overall, there was no significant difference in the incidence of the primary endpoint between radial and femoral approaches for the entire RIVAL cohort (3.7 percent vs. 4.0 percent, respectively; p=0.50). However, when stratified according to pre-specified STEMI/non-STEMI subgroups, the radial approach appeared to have significant advantages vs. the femoral approach for STEMI patients. The rate of the primary composite endpoint was lower (3.1 percent vs. 5.2 percent, respectively; p=0.026), as was the all-cause mortality rate (1.3 percent vs. 3.2 percent, respectively; p=0.006). No differences in outcomes were observed among non-STEMI patients. The incidence of non-CABG-related bleeding complications varied depending on the definitions used.

Lead author Shamir R. Mehta, MD, MSc, FACC, McMaster University and Population Health Research Institute, Hamilton, Ontario, Canada, concluded that the radial approach might be the preferred treatment strategy among patients with STEMI.

In an accompanying editorial, Olivier F. Bertrand, MD, PhD, Quebec Heart-Lung Institute, Quebec City, Quebec, Canada, and Tejas Patel, MD, FACC, Apex Heart Institute, Ahmedabad, Gujarat, India, addressed the question of whether the radial approach should become the standard for treating patients with STEMI and what potential mechanisms contribute to the benefits of the radial approach, especially the mortality benefit.

"There is firm and convincing evidence that the radial approach reduces vascular complications and access site-related bleeding, accelerates ambulation and is largely preferred by patients over the femoral approach," they wrote. They also noted that the radial approach's "impact on bleeding is highly dependent on the definitions used."

Reductions in bleeding complications would be a "simplistic" explanation for the mortality reductions, and while the radial approach reduces access-site bleeds, it is unclear how the approach affects other bleeding complications. Reductions in access-site bleeds alone are unlikely to result in a mortality reduction, the editorial authors said.

Although questions remain, they concluded, "The researchers discussed here and investigators throughout the world must be congratulated on providing this important clinical information to the cardiology community."