Review of the RIVAL trial

Radial vs femoral access for coronary angiography

THE LANCET 2011;377:1409-1420

Background: When patients undergo coronary angiography, a hollow tube called a sheath is inserted into an artery. The primary function for the sheath is to provide a stable entry point into the artery, allowing for the safe navigation of instruments to the coronary arteries. Traditionally these sheaths were inserted into the femoral artery. One of the common complications associated with this approach is bleeding which is associated with worse outcomes. An alternative approach is inserting the sheath into the radial artery which is more superficial and more readily compressible compared to the femoral artery.

Small randomized trials suggested that a radial artery access is associated with less bleeding with possible reduction in death and myocardial infarctions but also a signal of increased percutaneous coronary intervention (PCI) failure.

The RIVAL trial sought to assess if radial artery access is superior to femoral artery access in patients with acute coronary syndrome (ACS) undergoing coronary angiography.

Patients: Patients had acute coronary syndrome and an invasive strategy was planned. Dual circulation of the hand, as assessed by an Allen’s test, had to be intact.

Patients were excluded if they had cardiogenic shock, severe peripheral vascular disease precluding a femoral approach, active bleeding or high bleeding risk, or prior coronary artery bypass grafting (CABG) with the use of more than one internal mammary artery graft.

Baseline characteristics: The trial randomized 7,021 patients in 32 countries – 3,507 randomized to radial access and 3,514 to femoral access.

The average age of patients was 62 years and 73% were men. Approximately 60% had hypertension, 21% had diabetes, 18% had prior myocardial infarction, 2% had prior CABG, 2% had peripheral vascular disease, and 31% were current smokers.

The diagnosis at admission was unstable angina in 45% of the patients, NSTEMI in 27% and STEMI in 28%.

The use of antiplatelet and anti-thrombotic drugs was not significantly different between both groups.

Procedures: The RIVAL trial initially enrolled patients within the CURRENT-OASIS 7 trial which was a trial of antiplatelets therapy in ACS. After the conclusion of the CURRENT-OASIS 7 trial, RIVAL enrolled additional patients.

Patients were assigned in a 1:1 ratio to undergo femoral or radial artery access. The use of anti-thrombotic regimen at the time of PCI as well as femoral artery closure devices was at the discretion of the treating physician.

Endpoints: The primary outcome was a composite of all-cause death, myocardial infarction, stroke, or non-CABG related major bleeding, within 30 days. Secondary outcomes included the components of the primary outcome as well as major vascular access site complications and PCI procedural success.

The components of the primary outcome were adjudicated by a central committee blinded to the treatment assignment. Major vascular access site complications and PCI procedural success were reported by the investigators.

Analysis was performed based on the intention-to-treat principle. Due to low event rate, the sample size was increased from 4,000 to 7,000. This new sample size would provide 80% power to detect 25% relative risk reduction in the primary endpoint assuming 6% event rate in the femoral access arm.

The study had six prespecified subgroup analysis: Age (< 75 vs older), sex, body mass index, STEMI vs no STEMI, operator’s annual radial PCI volume and center’s median operator's radial PCI volume.

Results: Among the 7,021 randomized patients, 99.8% underwent coronary angiography. The rate of crossover was 7.6% in the radial group and 2.0% in the femoral group. Most of the crossover in the radial group was due to failure of the coronary angiogram using the radial approach. There was no significant difference in the number of PCI catheters used between both groups. Fluoroscopy time was higher in the radial group (7.8 minutes vs 6.5 minutes; p< 0.001).

The primary composite outcome at 30-days was not significantly different between both groups (3.7% with radial vs 4.0% with femoral, HR: 0.92, 95% CI: 0.72 – 1.71; p= 0.50). All of the components of the primary outcome were not significantly different between both groups: 1.3% vs 1.5% for death, 1.7% vs 1.9% for myocardial infarction, 0.6% vs 0.4% for stroke, and 0.7% vs 0.9% for non-CABG related major bleeding.

PCI procedural success was 95% in both groups. Major vascular complications were lower using the radial approach (1.4% vs 3.7%; p< 0.001). Major vascular complications were defined as pseudoaneurysms needing closure, large hematoma, arteriovenous fistula, or an ischemic limb needing surgery.

There were no significant subgroup interactions based on age, sex, body mass index or operator’s radial PCI volume. There was significant interaction based on STEMI vs no STEMI (p for interaction= 0.025) and center’s radial PCI volume (p for interaction 0.021), such as patients with STEMI and patients in centers with the highest tertile for PCI volume had reduction in the primary outcome with radial access.

Significantly more patients in the radial group said to prefer radial approach if they need a future coronary angiography (90.2% vs 50.7%; p< 0.001).

Conclusion: In patients with acute coronary syndrome undergoing coronary angiography, a radial approach compared to femoral approach, did not improve the primary composite outcome of all-cause death, myocardial infarction, stroke, or non-CABG related major bleeding, at 30 days. A radial approach reduced major vascular complications with a number needed to treat of approximately 43 patients. A radial artery approach was more commonly preferred by patients for future coronary angiography.

One of the limitations of this trial is that the outcome of major vascular complications is subject to bias as it was reported by the investigators rather than centrally adjudicated.

Given that this trial compares two approaches with similar costs, the observed reduction in vascular complications justifies an increased adoption of the radial approach. The safety of the radial approach has likely improved over the years as centers and operators have gained more experience. Moreover, patients have shown a clear preference for the radial approach, which is an important win as well.