EDITORIAL

Price of Protection — Microaxial Flow Pump in High-Risk PCI

Brahmajee K. Nallamothu, Brett L. Wanamaker

N Engl J Med 2026;394:1855-1856

DOI: 10.1056/NEJMe2602727

In the catheterization laboratory, the most consequential decisions are frequently not about whether to treat, but rather about how far to extend treatment. Nowhere is that tension more apparent than in high-risk percutaneous coronary intervention (PCI). In these cases, the margin between a good outcome and a catastrophic one is narrow, and the instinct to add protection with mechanical circulatory support can be powerful. Transient ischemia induced by balloon inflation or atherectomy can precipitate physiological collapse in patients with little reserve. Yet, to date, randomized trials have not supported routine use of mechanical circulatory support in cases other than cardiogenic shock.¹

In a trial report now published in the Journal, Perera and colleagues² describe the results of the Controlled Trial of High-Risk Coronary Intervention with Percutaneous Left Ventricular Unloading (CHIP-BCIS3). In this trial, the investigators tested whether routine use of the microaxial flow pump (Impella CP) in high-risk PCI improved outcomes, as compared with standard care. The latter was defined as no mechanical circulatory support, including the use of an intraaortic balloon pump or extracorporeal membrane oxygenation, except for emergency bailout.

The 300 patients who underwent randomization had complex coronary disease and a left ventricular ejection fraction of 35% or less. The primary analysis focused on a hierarchical composite outcome of death, stroke, spontaneous myocardial infarction, hospitalization for a cardiovascular cause, or periprocedural myocardial injury, with the results of all analyses reported as a win ratio.³ Several secondary analyses of individual outcomes were also performed to help with interpretability. Overall, the routine use of the microaxial flow pump did not improve outcomes, and secondary analyses even suggested a trend toward a higher risk of death among the pump recipients.

These findings are important for multiple reasons. The use of the microaxial flow pump for high-risk PCI has grown considerably despite a lack of randomized evidence showing benefit.⁴ The PROTECT II trial, which formed the basis for the expanded approval of this procedure to high-risk PCI, was stopped early for futility after showing no difference in 30-day clinical outcomes.⁵ The approval by the Food and Drug Administration relied on repeated analyses of trial and registry data that suggested the superiority of the microaxial flow pump over the intraaortic balloon pump in long-term follow-up.⁶ This approval and the commercial framing of these devices under the “Protected PCI” designation has reinforced a perception of procedural safety for the operator.⁷

This is not a trivial issue. The psychological effect of treating a patient whose condition deteriorates rapidly on the table can leave a lasting imprint that influences future approaches to similar cases. Expanded use of the Impella device has been particularly pronounced in the United States, with a much lower frequency of adoption by a factor of 40 in the United Kingdom and Canada.⁴ Although this between-country variation is the result of multiple factors, it is no doubt influenced by health system costs and reimbursement patterns.⁸

We think that hemodynamic support with the microaxial flow pump is useful in patients who are in a decompensated state. However, an understanding of when and in whom pump use is beneficial remains limited. As interventional cardiologists, we have seen some patients who appear to be highly dependent on mechanical support during procedures. Yet we have also observed many patients in whom the use of the device appeared in retrospect to be unnecessary. Discerning between these two cases remains clinically challenging. Beyond crude features, such as the ejection fraction and general aspects of coronary anatomy, the criteria for the selection of appropriate patients remain poorly defined despite years of use. Heterogeneity of risk within this high-risk group suggests that a meaningful proportion of patients who receive mechanical circulatory support may not require it — and more important, that the routine use of such devices may trend toward net harm. The use of a more nuanced evaluation of direct hemodynamic measures — such as elevated left-sided filling pressures and reduced cardiac output — may offer better selection criteria but requires further evaluation.

Additional observations from the trial merit attention. Unlike the PROTECT II trial, CHIP-BCIS3 showed similar degrees of revascularization across groups, although complete revascularization in the control group was often achieved through staged procedures. The microaxial flow pump is purported to protect the patient’s myocardium while allowing for complete revascularization during a single procedure. Yet markers of periprocedural myocardial injury were higher in the pump group. Whether staged intervention represents a more appropriate strategy than single-session complete revascularization with support in high-risk PCI is a question that the trial raises but cannot fully answer. Finally, vascular complications were fewer than anticipated, a result that possibly reflected careful procedural planning with imaging and concentration of enrollment at high-volume centers. Investigators minimized procedural complications associated with large-bore access in a way that may not be reproduced in other settings.

So how should interventional cardiologists respond to these findings? As a community, we have accepted an expanding use of mechanical circulatory support in high-risk PCI without consistent evidence that this approach improves survival or quality of life. Yet there are tangible consequences of that choice: large-bore access-site injuries, bleeding, limb ischemia, hemolysis, and acute kidney injury in patients already near the limits of physiological reserve. We tolerate these complications because of a presumption of benefit. Thus, these findings force the interventional cardiologist to occupy an uncomfortable position between two unsatisfying options — the potential burden of perceived undertreatment when a patient’s condition deteriorates or recognition that the act of doing more may itself constitute harm. Any honest appraisal must begin with that tension.

The CHIP-BCIS3 investigators provide sufficient data to encourage a more selective approach to the use of mechanical circulatory support in high-risk PCI, particularly in the absence of clear hemodynamic instability. We eagerly await results of the PROTECT IV trial (ClinicalTrials.gov number, NCT04763200), which will enroll more than 1200 patients and may finally provide the scale of evidence that the field requires. Until those data are available, this trial reminds us that the price of protection is not borne by those who prescribe it but by the patients who receive it. Whether the protection being offered is theirs, or ours, remains the central question yet to be answered.