Unprotected left main PCI remains rare in US

Despite recent clinical trial evidence suggesting the outcomes of unprotected left main PCI rival those of coronary artery bypass grafting (CABG), very few unprotected left main PCIs are performed in everyday clinical practice in the United States.

The infrequency of this procedure may be “judicious,” according to the authors of a new study in JAMA Cardiology, considering they found the risk of in-hospital death, MI, stroke or emergent CABG was 46 percent higher in those undergoing unprotected left main (ULM) PCI compared to traditional PCI, even after covariate adjustment. Lead author Javier A. Valle, MD, and colleagues also noted the patients who received ULM PCI in routine practice were older and had a higher burden of comorbidities than those included in the clinical trials of the procedure for left main coronary artery stenosis.

The researchers used the NCDR CathPCI Registry, which encompasses more than 90 percent of PCI-capable hospitals in the U.S., to identify 3.34 million PCIs performed between April 2009 and July 2016. ULM PCIs accounted for only 1 percent of all PCIs, increasing modestly from 0.7 percent of procedures in the first year of the study to 1.3 percent of procedures in the final year.

Nine percent of ULM PCI patients required emergent CABG or experienced in-hospital death, MI or stroke, compared to 2.6 percent of patients receiving all other PCI. The elevation in major adverse cardiovascular events (MACE) with ULM PCI was evident for each component of that outcome and remained 46 percent higher after covariate adjustment.

“In contrast to clinical trials, the present analysis demonstrates significantly worse outcomes for a contemporary cohort undergoing ULM PCI in the United States as well as major differences in demographic, clinical and procedural characteristics,” wrote Valle, with the University of Colorado School of Medicine, and coauthors. “Much of this demonstrated difference in outcomes is likely attributable to patient and procedural factors, with age and burden of comorbidities greater among patients in the CathPCI Registry than those reported in clinical trials, and procedural distinctions, such as the use of intravascular imaging.”

Inexperience may play a role as well, the authors noted. The average operator performed just 0.5 ULM PCIs per year and the average facility conducted just 3.2 of these cases. However, there was evidence that increasing PCI experience at both the operator and facility level might improve outcomes.

ULM PCI patients treated by operators with the highest total PCI volume demonstrated 10 percent lower rates of in-hospital MACE versus those undergoing ULM PCI from an operator in the lowest tertile of volume. Similarly, individuals treated at the highest-volume centers experienced a 16 percent reduction in the odds of MACE compared to those treated at facilities which performed the fewest PCIs.

Valle et al. said about 6 percent of the 1 million patients who receive coronary angiography each year in the U.S. are estimated to have left main disease, making the annual number of patients undergoing ULM PCI in this registry “quite low in comparison to the extrapolated incidence of ULM stenoses” and indicating that other strategies are more common in managing this condition. They noted the demonstrated efficacy of CABG and the comfort level referring physicians have with that procedure could be one explanation for the relatively limited uptake of ULM PCI.

“It is also possible that clinicians see that real-world outcomes for patients undergoing ULM PCI—many of whom are older, frail and may be determined to be at prohibitive risk for surgery—compare unfavorably with patients undergoing both all other PCI as well as CABG, leaving practitioners hesitant to refer younger, healthier patients for ULM PCI and further propagating the demonstrated differences in case mix," they wrote.

This is a conundrum, they pointed out, because treating even more patients at the highest-volume centers may improve outcomes, but operators at other institutions might need to treat some of those lower-risk individuals with ULM PCI to achieve the necessary experience and comfort level with the technique.