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A risk score predicts the likelihood of successful radial access for percutaneous coronary intervention (PCI), according to a single-center study.

With a C statistic of 0.868 (95% CI 0.866-0.869), the WRIST-CASE scale incorporates nine risk factors in determining if radial access might fail in ST-segment elevation myocardial infarction (STEMI) patients: weight, radial proficiency, intra-aortic balloon pump, shock, tube, creatinine, age, prior stent, and elevated blood pressure, , of Quebec Heart-Lung Institute in Canada, and colleagues reported online in Heart.

Mortality at 1 year was less common in those whose PCI was performed with radial access (6% versus 42% for transfemoral strategy versus 14% for radial-to-transfemoral crossover, P<0.0001). Major vascular complications occurred less frequently for them as well (0.1% versus 6.5% versus 2.3%, respectively, P<0.0001).

"Our results strongly show that outcomes of patients undergoing primary PCI after failed [transradial access] are worse," Bertrand and colleagues wrote.

They suggested that "all efforts should be put in place to maximise the use of [transradial access] in such patients. The use of ultrasound-guided puncture may potentially help operators gain radial access in case of haemodynamic compromise. Conversely, if [transradial access] remains impossible in such circumstances, particular attention should be paid to technical aspects in obtaining the safest possible femoral puncture (sheath sizes and femoral puncture technique), as well as pharmacological therapies and haemostasis management."

, of Pennsylvania State University in Hershey, and , of Keele University in Stoke on Trent, England, agreed.

"Avoidance of the transfemoral route results in minimisation of adverse outcomes in the setting of primary PCI and even the best can become better," they wrote in an accompanying editorial. "Given the hazard of the femoral approach, initial failure at one radial should prompt exploration of other alternatives such as the contralateral radial artery and in the situation of shock the use of adjunctive technology such as ultrasound to maintain access in the upper extremity may minimise access-related problems."

Even so, Bertrand's group noted, the "choice of [transradial access] must also be balanced against the individual's risk of failure, as well as the imperative of timely reperfusion in STEMI."

The study included 2,020 consecutive STEMI patients at a high-volume radial access center from 2006 to 2011.

There was a 92% success rate with transradial PCI among patients. Few of them -- at just 2.2% -- started with radial access but had to switch to a femoral one after procedural failure, most commonly due to inadequate radial arterial puncture (64%) followed by difficulty passing guidewires and guiding catheters (27%).

Another 5.5% started off with the transfemoral approach due to clinical reasons such as cardiogenic shock, resuscitated sudden cardiac death, and operator preference.

Bertrand and colleagues noted that their observational study was limited by potential residual confounders and that their WRIST-CASE score requires more external validation.

Gilchrist and Mamas also questioned whether the scale can be generalized to other centers, particularly those with less radial experience, writing: "The applicability of the 'risk score' for failure developed from this centre's experience to other institutions is unclear, particularly its applicability to cases undertaken in the non-primary PCI setting, where the clinical demographics of the patients will be very different. Not many centres have the radial pedigree of this institution and its predictive accuracy is untested in an external validation cohort."

In addition, "the history of the prior catheterisations and the techniques used to preserve radial artery function are not available," the editorialists noted.

"Institutionalised protocols to maximise radial artery patency rates at each catheterisation episode of care will maximise long-term viability of this access and serve to minimise risk for conversion to femoral," they suggested. "The future maintenance of radial patency should be considered an important part of all radial procedures."