Advantage of Radial PCI Most Apparent at Extremes of BMI

Although the radial approach to PCI is associated with less major bleeding and need for transfusion than femoral access regardless of patients’ body mass index (BMI), it is particularly beneficial in those at the low or very high end of the spectrum. The findings, from a large statewide registry, were published online May 22, 2015, in Catheterization and Cardiovascular Interventions.

Jonathan R. McDonagh, MD, of the University of Michigan Medical Center (Ann Arbor, MI), and colleagues analyzed data from the Blue Cross Blue Shield of Michigan Cardiovascular Consortium registry on 96,381 patients who underwent PCI between 2010 and 2012. Patients were classified as being:

• Lean (BMI < 25 kg/m²)
• Overweight (BMI 25 kg/m² to < 30 kg/m²)
• Obese (BMI 30 kg/m² to 40 kg/m²)
• Morbidly obese (BMI ≥ 40 kg/m²)

Overall, femoral access was used in 89% of cases and radial in 11%. The prevalence of radial access rose from 2% to 21% over the 3-year study period.

Patients treated via femoral access were more likely to present with STEMI, be undergoing primary PCI, have preprocedural cardiac arrest or cardiogenic shock, require use of an intra-aortic balloon pump, have higher baseline creatinine level, and have a history of CABG. Radial-access patients had a higher mean BMI.

Bleeding, Transfusion Lower With Radial

Researchers performed a propensity-matched analysis of 9,996 pairs of femoral and radial access patients. Within this cohort, femoral cases were more likely to involve use of bivalirudin or low-molecular weight heparin and less likely to include unfractionated heparin or aspirin (all P < .001). Other characteristics were well balanced between the matched groups.

In the propensity-matched analysis, patients receiving femoral-access PCI were more likely to experience major bleeding and to require transfusion during hospitalization compared with the radial group. The benefit was greatest in patients classified as lean or morbidly obese (table 1).

A separate analysis of retroperitoneal bleeding found events were numerically lower with radial vs femoral access in all BMI categories, although the difference only reached statistical significance in the obese group, which had the highest absolute number of events (P < .001). Similarly, in-hospital mortality differed by access route only in the obese group, with a rate of 0.3% for radial vs 0.6% for femoral (OR 0.42; 95% CI 0.28-0.90).

Potential Greatest in Morbidly Obese, Lean Patients

“We propose that radial access for PCI be the preferred strategy with respect to the goal of reducing the complications of bleeding and transfusion across all BMI categories, recognizing the potential for greater effect in morbidly obese and lean patients,” the researchers conclude.

The “dramatic reduction” in retroperitoneal bleeding is particularly noteworthy, they say, as it is one of the most serious bleeding types and, while rare, is strongly tied to adverse outcomes.

“[Retroperitoneal] bleeding after cardiac catheterization and PCI may be owing to spontaneous bleeding associated with anticoagulant medications or, more commonly, owing to local vascular trauma,” the investigators note, citing risk factors, including glycoprotein IIb/IIIa inhibitor use, female sex, cardiogenic shock, and low body weight. “Our findings are consistent with the empirical notion that [transradial access] by virtue of avoiding vascular trauma to the iliac and femoral vessels is associated with a reduction in [retroperitoneal] bleeding.”

Reason for Mortality Difference Unclear

As for mortality, the researchers suggest that a lack of statistical power may account for the heterogeneity seen among BMI groups. However, they say that the issue “is worthy of exploration in further studies.”

Sunil V. Rao, MD, of Duke University Medical Center (Durham, NC), cautioned in an email with TCTMD that unmeasured confounding is always a possibility in an observational analysis. One explanation could be that “obese patients are at greater risk of retroperitoneal hematomas, which are associated with increased mortality,” he suggested, noting that radial access “eliminates” this bleeding type. He agreed that it could also simply relate to statistical power.

In a telephone interview with TCTMD, Dr. McDonagh said, “The mortality data in our paper are an interesting signal, but I don’t think you can draw [any other] conclusions than that.”

Interplay Between BMI, Risk Well Known

Overall, said Dr. Rao, the paper “demonstrates what we have seen in other studies—the effect of bleeding avoidance strategies is greatest in patients at highest risk for bleeding. Patients at the extremes of BMI are at increased risk for bleeding and vascular complications, so it stands to reason that radial has a greater absolute benefit in these groups.”

While the patterns have “been anecdotally known,” he added, “[t]his is a very nice study that proves what radialists have experienced in their clinical practice.”

Carl J. Lavie, MD, of Ochsner Medical Center (New Orleans, LA), a noninvasive cardiologist who wrote The Obesity Paradox, commented in an email to TCTMD: “I believe that most experts currently feel that the radial approach is better for almost all patients when performed in expert hands [by operators] who have experience in this approach and when radial is technically possible. These results support that the patients who get the most benefit… are those with the 2 extremes of BMI.”

Dr. McDonagh agreed that awareness of the interplay between BMI, access route, and bleeding is high. Few studies have addressed the issue, he noted, but “I think most interventionalists probably are familiar with the risks, especially with [regard to] obesity.”

Radial access is no harder in obese patients, Dr. McDonagh related. “Sometimes it’s a little easier, to be honest, because they often have bigger arms and bigger arteries to go along with [them].” Conversely, he noted, smaller patients can “have very small radial arteries and much tighter turn of the arch, which makes catheter maneuvers a little bit more difficult.”

Importantly, the “lean” category includes patients “who are probably frail. I think that’s why they are at increased risk of bleeding. They have more frail tissues that don’t tolerate our equipment as well,” he noted.

McDonagh JR, Seth M, LaLonde TA, et al. Radial PCI and the obesity paradox: insights from Blue Cross Blue Shield of Michigan Cardiovascular Consortium (BMC2). Catheter Cardiovasc Interv. 2015;Epub ahead of print.

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