Transradial PCI Shows Consistent Benefit in All ACS Patients: MATRIX Access

PARIS, France—The treatment of patients with acute coronary syndrome with PCI via the radial artery results in a significant reduction in major bleeding and major cardiovascular events when compared with the transfemoral approach, with the benefit of transradial access extending to the STEMI and NSTE ACS subgroups alike, according to a new study.

The benefit of transradial PCI in both types of ACS patients became clearer once investigators tested for an interaction in a subgroup analysis of the MATRIX Access study presented this week at EuroPCR. 

Prior to testing for an interaction between subgroups, investigators initially observed that treatment with transradial PCI significantly reduced the rate of MACE, a combined endpoint of all-cause mortality, MI, and stroke, and the rate of net adverse clinical events (NACE), which included major bleeding, among unstable angina and NSTEMI patients. In contrast, treating STEMI patients with PCI via the radial artery was not associated with a significant reduction in the MACE and NACE rates.  

Lead MATRIX investigator Marco Valgimigli, MD (Erasmus Medical Center, Rotterdam, the Netherlands) stressed, however, that the “superiority” of reduced MACE and NACE rates among NSTE ACS patients, a benefit not seen in the STEMI patients, is not statistically meaningful and that the benefit of transradial PCI extends to all ACS patients. 

“You have to realize that 50% of patients, more or less, had STEMI and 50% had no STEMI,” said Valgimigli. “When looking at subgroup analyses, you’re losing statistical power. So you have to be careful in relying on superiority P values to make your conclusion. That’s why the interaction P value is so important here.”

Speaking with TCTMD, Bernardo Cortese, MD (Ospedale Fatebenefratelli, Milan, Italy), who presented the subgroup results, said the prespecified analysis was designed to determine if transradial access was associated with consistent clinical outcomes in different ACS patients. “When we designed the MATRIX trial in 2009, we decided to stratify the randomization based on the type of ACS,” said Cortese. “We wanted to know if the transradial approach was better than the transfemoral approach in ST-segment elevation MI patients.”

The MATRIX study, published in the Lancet in 2015, showed that radial-access PCI reduced the risk of death, MI, stroke, and major bleeding by 33% compared with transfemoral PCI. There was a 15% decrease in the risk of MACE (death, stroke, and MI) with the transradial approach, but the reduction did not meet the standard for statistical significance.   

Like the main trial results, investigators say there was no significant difference in clinical outcomes among STEMI and NSTE ACS patients, concluding that the transradial approach should be the default approach in all patients with acute coronary syndromes.   

To TCTMD, Cortese noted that the MATRIX subgroup analysis contained a bit of a statistical anomaly in that it showed the risk of major bleeding was significantly lower among STEMI patients treated with transradial PCI but not in the NTSE ACS patients. In contrast, all-cause mortality was significantly reduced among NSTE ACS patients treated via the radial artery but not among the STEMI patients. A reduction in mortality would be expected to track with a reduction in major bleeding, said Cortese. Again, though, the test for interaction was not statistically significant between the subgroups across all secondary endpoints. He added that a clinical trial showing a significant reduction in mortality with transradial PCI in the higher-risk STEMI patients would require at least 15,000 patients.

The bottom line is that the subgroup analysis mirrors the overall results of the MATRIX trial, with Cortese saying transradial PCI should be the default access strategy in all ACS patients, given the significant reduction in NACE and trend toward lower MACE.     

•  Cortese B. Radial vs femoral access in patients with ACS with or without ST-segment elevation (MATRIX-Access). Presented at: EuroPCR 2016. May 18, 2016. Paris, France.

Disclosures:

•  MATRIX Access was funded by Terumo Medical and The Medicines Company.
•  Cortese reports consulting for Aachen Resonance, Abbott Vascular, AstraZeneca, and Kardia and receiving institutional grant/research support from AB Medica and Movi. 

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