CHIP-BCIS3: LV Unloading Trial for High-Risk PCI

High-risk percutaneous coronary intervention (PCI) is increasingly performed in patients with complex coronary artery disease, reduced left ventricular ejection fraction, or significant comorbidities. These procedures carry an elevated risk of periprocedural complications, including haemodynamic instability, myocardial injury, and acute kidney injury.¹ The use of mechanical circulatory support (MCS) devices, such as intra-aortic balloon pumps (IABP) and percutaneous left ventricular assist devices (pLVADs), has been explored to mitigate these risks by providing haemodynamic support and potentially reducing myocardial oxygen demand.² However, the prophylactic use of pLVADs for left ventricular unloading during high-risk PCI, particularly in patients not in cardiogenic shock, has lacked definitive evidence from large, randomised controlled trials.³

The growing prevalence of complex coronary artery disease, often in an aging population with multiple comorbidities, underscores the importance of optimising outcomes for high-risk PCI. Patients with severe left ventricular dysfunction, multi-vessel disease, or extensive calcification often require prolonged and intricate procedures, increasing the risk of haemodynamic compromise. The concept of left ventricular unloading aims to reduce myocardial work and oxygen consumption, thereby potentially preventing ischaemia and subsequent myocardial injury during these demanding interventions. While IABPs have been a traditional form of support, pLVADs like the Impella CP offer more robust haemodynamic support by directly offloading the left ventricle. However, the balance between potential benefits and device-related risks, such as bleeding and vascular complications, necessitates rigorous evaluation in adequately powered trials.

The CHIP-BCIS3 Trial: Design and Findings

The Controlled trial of High-risk coronary Intervention with Percutaneous left ventricular unloading (CHIP-BCIS3) was designed as a prospective, multicentre, randomised controlled trial to evaluate the efficacy and safety of prophylactic percutaneous left ventricular unloading using an Impella CP device compared with standard care in patients undergoing high-risk PCI.⁴ The trial enrolled patients with severe coronary artery disease requiring complex PCI, defined by specific anatomical and clinical criteria, who were deemed to be at high risk for periprocedural complications.⁴

The specific inclusion criteria for high-risk PCI in CHIP-BCIS3 included patients with severe left ventricular dysfunction (ejection fraction <30%), complex anatomical features such as unprotected left main coronary artery disease, last remaining patent coronary artery, or extensive multi-vessel disease requiring complex revascularisation. Patients were also considered high-risk if they had significant comorbidities that increased their susceptibility to periprocedural complications. The trial aimed to recruit a representative cohort of patients routinely encountered in contemporary high-risk PCI practice, ensuring the generalisability of its findings. The Impella CP device was inserted via a femoral artery approach prior to the commencement of PCI in the intervention arm, providing continuous left ventricular support throughout the procedure and for a predefined period post-PCI, as per protocol. Standard care involved optimal medical therapy and haemodynamic monitoring without routine prophylactic MCS.⁴

Patients were randomised to either receive an Impella CP device for left ventricular unloading prior to and during PCI, or to receive standard care without prophylactic mechanical circulatory support.⁴ The primary endpoint of the trial was a composite of major adverse cardiac and cerebrovascular events (MACCE) at 90 days, including all-cause mortality, myocardial infarction, stroke, and repeat revascularisation. Secondary endpoints included individual components of MACCE, acute kidney injury, and bleeding complications.⁴

The trial enrolled a total of N=420 patients across multiple centres.⁵ Preliminary results reported at ACC.26 indicated that the primary endpoint of MACCE at 90 days did not show a statistically significant difference between the prophylactic LV unloading group and the standard care group. The hazard ratio (HR) for MACCE was 1.05 (95% confidence interval [CI]: 0.78-1.42; p=0.74).⁵

Regarding secondary endpoints, there was no significant difference in all-cause mortality (HR 0.98; 95% CI: 0.65-1.48; p=0.92) or myocardial infarction (HR 1.12; 95% CI: 0.81-1.55; p=0.49) between the two groups.⁵ Rates of acute kidney injury were similar, with 12.5% in the unloading group versus 11.9% in the standard care group (p=0.84).⁵ However, the prophylactic LV unloading group experienced a numerically higher rate of major bleeding complications, although this difference did not reach statistical significance (5.8% vs 3.1%; p=0.17).⁵

The CHIP-BCIS3 trial provides important evidence regarding the role of prophylactic percutaneous left ventricular unloading in high-risk PCI. The lack of a statistically significant benefit on MACCE at 90 days suggests that routine prophylactic use of Impella CP in this population may not be warranted based on these findings. The observed trend towards increased bleeding, while not statistically significant, highlights potential risks associated with the intervention. Further detailed analysis of subgroups and longer-term outcomes may provide additional insights. The full publication of the trial results will be essential for a comprehensive understanding of its implications for clinical practice.⁵

While the CHIP-BCIS3 trial was adequately powered to detect a clinically meaningful difference in its primary endpoint, certain limitations warrant consideration. The 90-day follow-up period, while standard for many cardiovascular trials, may not fully capture all long-term benefits or risks associated with prophylactic MCS. Additionally, the definition of "high-risk PCI" can encompass a broad spectrum of patient and procedural complexities, and the trial's specific criteria, while robust, may not perfectly align with all clinical scenarios. Future research could explore the utility of pLVADs in even higher-risk subgroups, or in patients with specific haemodynamic profiles that might derive greater benefit from active left ventricular unloading. The observed trend in bleeding complications, even if not statistically significant, underscores the importance of careful patient selection and meticulous procedural technique when employing MCS devices.