RIVAL: Major benefits with radial PCI in STEMI vs NSTEMI

October 26, 2012

Hamilton, ON - Further analysis of the RIVAL trial has confirmed that the radial approach to PCI when performed by experienced operators shows major benefits over femoral for STEMI patients[1].

Publication of the current RIVAL analysis focusing on STEMI vs non-STEMI patients, published online in the Journal of the American College of Cardiology on October 24, 2012, coincides with presentation of another study ( STEMI-RADIAL ) at TCT 2012 showing similar results.

The RIVAL trial, however, is larger, with a total of 7000 ACS patients (5000 non-STEMI and 2000 STEMI). The main results, presented at last year's American College of Cardiology meeting, showed no difference in the primary end point of death, MI, stroke, or major bleeding at 30 days between patients assigned to the radial or femoral approach to PCI. But transradial access did result in a large reduction in the risk of vascular-access complications.

The current analysis, however, showed some important differences between the STEMI and non-STEMI populations in the trial.

In STEMI patients, radial access reduced the primary end point compared with femoral access. In addition, the key secondary end point of death/MI/stroke was also reduced with radial access in STEMI patients, as was all-cause mortality.

RIVAL: Radial vs femoral access PCI in STEMI patients

Outcome Radial (%) Femoral (%) HR p
Death, MI, stroke, or non-CABG major bleeding 3.1 5.2 0.60 0.026
Death/MI/stroke 2.4 4.6 0.59 0.031
All-cause mortality 1.3 3.2 0.39 0.006

 In contrast, there were no differences in major outcomes with the two approaches in the non-STEMI patients.

Lead investigator of the current RIVAL analysis, Dr Shamir Mehta (McMaster University, Hamilton, ON), told heartwire that the benefits seen were largely driven by a reduction in mortality, which was probably due to a reduced bleeding rate. "Bleeding was a very powerful predictor of mortality in this trial. A patient who bled had a clearly higher risk of death than a patient who didn't bleed," he noted.

He suggested three reasons for the better mortality results with the radial approach in STEMI patients:

  • Mortality is the most common event in STEMI patients, while nonfatal events are more common in non-STEMI patients. So a reduction in mortality is more likely to be seen in STEMI than non-STEMI patients.

  • STEMI patients are at a higher risk of bleeding, so the link between bleeding and mortality is more obvious in this population.

  • STEMI patients have a much higher rate of PCI (over 90%) than non-STEMI, and PCI increases the rate of bleeding.

While the rate of major bleeding using the definition specified for the RIVAL trial was not different in either STEMI or non-STEMI groups with radial access, Mehta pointed out that they used a very conservative definition of bleeding (the OASIS definition), which did not include major vascular access-site complications, with the result that major bleeding was very low (less than 1%) in the study. However, substantially lower rates of major vascular access-site complications and ACUITY-defined bleeding were seen with radial access in both the STEMI and non-STEMI cohorts. "In retrospect, the OASIS definition of bleeding was probably too conservative for this trial," he commented to heart wire .

Only for experienced operators

Mehta also stressed that the STEMI patients had more experienced operators in terms of the radial technique than the non-STEMI patients (400 cases/year vs 326 cases/year), so the results were applicable only to experienced operators.

"STEMI patients, especially those undergoing primary PCI, are not the population in which to learn the radial technique. This is an emergency situation, and radial PCI should be attempted in these patients only by experienced operators," Mehta emphasized. "The radial approach should be learned in stable patients first, graduating to non-STEMI ACS, then to STEMI."

He reminded that it is already well-known that radial access has many practical advantages in stable patients. "The patients tend to be more comfortable, become ambulatory sooner, and can often be discharged more quickly. The RIVAL trial was trying to get beyond these practicalities and look at hard outcomes in a higher-risk population."

Mehta noted that the US has the lowest rate of radial-access PCI worldwide, but even there it is increasing dramatically. "The world is changing, and new fellows are now being trained in both techniques."

But he believes there will always be a place for the femoral approach, too. "There are some situations where radial just cannot be done because of the patient's anatomy or poor circulation in the radial artery, so it is important that interventionalists can do both techniques," he said.

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