MATRIX Score Predicts PCI Patients at High Risk for Transradial Failure

The MATRIX score, an eight-item checklist that includes readily available patient characteristics and also factors in operator expertise, helps predict which ACS patients will require crossover from the radial to femoral artery during PCI, according to a new study.

The risk-prediction tool, one that takes into account the patient’s age, height, smoking status, history of renal failure, prior CABG, Killip class, whether it’s a STEMI presentation, and the operator’s radial expertise, was derived from the largest randomized trial comparing outcomes between the two vascular-access sites and showed good discrimination in foreseeing which patients would ultimately cross over from radial to femoral access.  

“The [MATRIX] score is very easy to calculate and to use,” said lead investigator Felice Gragnano, MD (University of Campania “Luigi Vanvitelli,” Caserta, Italy). “It can provide important additional information with respect to the patient that we’re treating, . . . it takes no more than 10 or 15 seconds to calculate, and it can inform us of the risk of performing a procedure. Why shouldn’t we use it? I think it really should be routinely used before starting [radial PCI].”

If a patient is at high risk for crossover, Gragnano said operators might use ultrasound to guide radial artery cannulation to prevent issues in arterial puncture or sheath insertion. Additionally, teams could prepare for alternative vascular access, just in case, by doing a detailed examination of the femoral arteries. Cath lab teams could also have procedural materials available to help with vascular navigation and transradial problems, such as hydrophilic sheaths or dedicated radial shapes. Lastly, inexperienced transradial operators might hand off a patient to a more-skilled radialist if the patient is deemed very high risk for crossover.

To TCTMD, Gragnano said that European and US guidelines and professional societies recommend radial access as the default approach for angiography/PCI, with multiple studies showing that it is associated with better clinical outcomes, quality of life, and lower costs. However, radial crossover isn’t uncommon, he said, noting that it occurs in roughly 5% to 10% of cases, sometimes higher depending on the skills of the operator.  

“In the majority of centers, all operators will try to go radial by default,” said Gragnano. “The guidelines all recommend radial access, but they don’t really say, ‘OK, but sometimes you might have some difficulties.’ They neglect the possibility that you can incur some problems with radial access, and it’s not something that’s really rare.”

The paper was published August 11, 2021, in EuroIntervention.  

MATRIX Risk Score

Although there are two other risk scores that predict crossover from radial to femoral access, including WRIST-CASE, both were developed from a single high-volume center, making the generalizability of these scores uncertain, according to the researchers.

To develop a more generalizable risk prediction tool, they turned to the MATRIX trial, a randomized study of 8,404 patients undergoing either radial or femoral access for PCI of ACS. Of those assigned to transradial PCI, 183 (4.4%) crossed over to femoral access because the operator either had issues with the puncture or sheath insertion or was unable to complete angiography or PCI (mostly because of vessel tortuosity of vasospasm).

From the derivation cohort of 4,197 patients randomized to radial access, they identified eight independent predictors of crossover and these were used to develop the MATRIX score. Scores, ranging from 0 to 100, are calculated using a nomogram. In the study, 1,279 patients had a MATRIX score ≥ 41 and these patients had a more than threefold higher risk of radial crossover compared with those with a lower score (OR 3.67; 95% CI 2.71-4.97). The results were similar when the right or left radial artery was used for access.

Why shouldn’t we use it? I think it really should be routinely used before starting the procedure. Felice Gragnano

For the MATRIX score, the c-index was 0.71 for radial crossover and there was good agreement between the predicted and actual risks. To validate it, the group used data from the RIVAL and RIFLE-STEACS trials of radial versus femoral access, in which the c-index values for radial crossover were 0.64 and 0.66, respectively. Here again, there was a consistent agreement between the predicted and observed risks of radial crossover. In both RIVAL and RIFLE-STEACS, a MATRIX score ≥ 41 was associated with a higher risk of radial crossover (OR 1.71; 95 CI 1.32-2.20 and OR 2.70; 95% CI 1.45-5.01, respectively).

Needs Validation in a Real-world Population

Prior to the publication of the MATRIX score, it was believed that women might be at higher risk for crossover, said Gragnano, but female sex was not a significant predictor of radial failure in MATRIX and didn’t factor into the risk score. Other well-known risk factors for radial crossover—advanced age, previous CABG, and previous renal failure—were linked to radial failure, however. Like other studies, their model also showed that operator expertise with transradial PCI was associated with a lower risk of crossover.

Gragnano said the new eight-item risk score can be calculated by any member of the cath-lab team. While the tool is quite “actionable” for operators, he believes it is also important for informing patients of the risks and benefits of procedures so that they can provide consent.

“We know patients often ask to proceed with the radial artery because they know, often through the media, that it’s better and more comfortable,” he said. “In cases of NSTEMI, where you’re not really rushing and have 24 hours to proceed with PCI, then you can discuss more clearly with the patient the risks of performing PCI with the radial artery. In some cases, you might also consider the use of femoral artery if the risk of crossover is very high.”

Now, the new risk prediction tool needs to be validated in a real-world patient population. Additionally, the group would like to test the performance of the score in patients with chronic coronary syndrome undergoing PCI. The MATRIX risk calculator is available online here, and the team is currently working on the development of a downloadable app.