RIVAL Confounds Transradial PCI

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 - Cardiac Cath Lab
Lahey Clinic’s cardiac cath lab.

The randomized, controlled RIVAL trial, presented in April at ACC.11, was expected to show a bleeding reduction with using radial access for PCI in patients with acute coronary syndromes (ACS). While the trial did not achieve its anticipated primary endpoint, transradial PCI may continue to gain utilization momentum if physicians succeed in deciphering how the results could impact their practice.

Unraveling RIVAL

With the goal of assessing radial versus femoral access for PCI in ACS patients, the RIVAL investigators, led by Sanjit Jolly, MD, of McMaster University's Population Health Research Institute in Hamilton, Ontario, enrolled 7,021 patients from 158 hospitals in 32 countries and randomly assigned them to radial (3,507 patients) or femoral access (3,514).

For the primary outcome of death, MI, stroke or non-CABG major bleeding, the rates were 3.7 percent in the radial access arm compared with 4 percent in the femoral access arm.

"The RIVAL findings came as a surprise to many practitioners, when the primary endpoints were not met for the general study population," according to Christopher T. Pyne, MD, of the Lahey Clinic in Burlington, Mass. At the study's inception, the RIVAL investigators had a working hypothesis that the major bleeding rates in the femoral arm would be much higher than the ultimate outcomes. The big surprise of RIVAL was how well the operators performed the femoral cases, which is a positive thing for patients."

However, the findings showed a more than 60 percent reduction in major vascular complications in the transradial arm. At 30 days, 42 patients in the radial group had large hematomas compared with 106 in the femoral arm. Pseudoaneurysms needing closure also were lower in the radial group: seven versus 23 patients.

Jolly concludes the "major benefit of radial access is preventing vascular complications, which is an important issue for patients." RIVAL also revealed that patients prefer the radial approach, causing the investigators to speculate that the adoption rate will continue to rise.

"While we do not completely understand why the radial arm performed better with vascular complications, the results of RIVAL reveal a very positive trend for patients, as both procedures indicate low bleeding rates," says Pyne. "As physicians, we are more concerned with improving patient outcomes than politicizing techniques."

Bleeding risk

"There are multiple bleeding definitions from TIMI Major Bleeding, which is stringent, to the ACUITY definition, which is broader, but RIVAL used a definition that would capture serious and life-threatening bleeding from the OASIS trial," Jolly explains.

In the trial, access-site bleeding accounted for one-third of the overall bleeds in these ACS patients, and two-thirds of the bleeding occurred due to gastrointestinal bleeding and other sources.

Sunil V. Rao, MD, of Durham VA Medical Center in N.C., who worked on the consensus report of the Bleeding Academic Research Consortium (BARC), which is looking to standardize bleeding definitions, says the consortium may help clarify the plethora of definitions. However, he says that bleeds should not be qualified as major or minor because of their severity to the patient.

"If the ACUITY bleeding definition that focuses on bleeds beyond the access-site had been employed in RIVAL, the transradial approach may have shown a benefit," Rao says. He adds that proper pharmacoinvasive therapy remains "tremendously important," and a complementary technique of employing bivalirudin (Angiomax, The Medicines Company), in addition to the transradial approach may ultimately result in the best patient outcomes.

"We're becoming increasingly aware of the potential for non-access site bleeding," says Pyne. "We previously thought that wrist access prohibited bleeding, but now we are becoming more cognizant of patients at risk for bleeding regardless of access site."

Interestingly, only 3 percent of the RIVAL population received bivalirudin, leading many physicians to speculate that the bleeding rates could have been equivalent between the femoral and radial access arms with greater usage of bivalirudin.

"Bivalirudin has been shown to be safer than heparin plus glycoprotein IIb/IIa inhibitors, but the rate the IIb/IIa inhibitors was only 25 percent in the trial," Jolly notes. Currently, there has not been a head-to-head trial of bivalirudin compared with a low modern dose of heparin monotherapy or selective use of IIb/IIa inhibitors.