Despite advancements in medical and intensive care management for cardiogenic shock, survival outcomes remain generally poor. With mortality rates ranging between 27% and 51%, this condition represents a significant therapeutic challenge for intensivists, cardiologists, and cardiovascular surgeons. Mechanical circulatory support (MCS) has undergone substantial progress in recent years, with continuous improvements in existing devices and the development of novel technologies. Within this context, temporary mechanical circulatory support (MCS) devices are frequently employed as a therapeutic bridge, either facilitating patient recovery or, in cases where myocardial deterioration is irreversible, transitioning toward durable ventricular assist devices (VAD) or heart transplantation (HT). Amongst the historically most used temporary MCS devices for these patients are intra-aortic balloon pumps (IABP) and extracorporeal membrane oxygenation (ECMO).
In recent years, a new category of devices has emerged, enabling minimally invasive temporary MCS, such as the Impella® family (Abiomed®). These ventricular assist devices offer temporary axial flow MCS and can be inserted with a minimally invasive or even fully percutaneous approach, as seen with the Impella CP® and 2.5® models. These devices withdraw blood from the left ventricle and eject it directly into the aorta. The future perspectives for these devices in cardiogenic shock are promising. The DANGER-SHOCK study, which exclusively focused on the Impella CP® model, was the first to demonstrate positive survival outcomes with mechanical circulatory support in cardiogenic shock. For a comprehensive review of this study, we refer you to another entry on this blog.
This article will specifically focus on the Impella 5.5® model, considered the “surgical” device in its family due to its implantation technique. The Impella 5.5® is a transvalvular axial flow left ventricular assist device that is surgically implanted via a graft, typically placed in the subclavian artery or, in certain cases, the ascending aorta. Approved by the FDA in 2019 for the treatment of cardiogenic shock, its use has become widespread in clinical practice due to its ability to stabilize hemodynamically unstable patients in a minimally invasive manner, providing complete left ventricular circulatory support.
The main limitation of the device lies in its size (21 Fr), requiring an axillary artery diameter of at least 6–6.5 mm. This necessitates a preoperative computed tomography scan to evaluate arterial access and dimensions. If the size of both subclavian arteries or other anatomical constraints contraindicate peripheral implantation, direct implantation into the ascending aorta via partial sternotomy remains an option. However, this approach compromises some of the advantages of the device due to its more invasive nature. Additionally, its use is contraindicated in cases of severe aortic stenosis, prior mechanical aortic valve prostheses, or moderate-to-severe aortic insufficiency. It is also discouraged in patients with intraventricular thrombus, ventricular septal defect, or severe hypertrophic cardiomyopathy, among other conditions.
Clinical Management Strategy
The clinical strategy involving the Impella 5.5® and the patients’ clinical evolution primarily depend on key factors such as the severity of cardiogenic shock, its etiology, and associated prognosis, among other aspects.
Regarding the first point, the initial question to address is how effective this device is in the most severe cases of cardiogenic shock, specifically INTERMACS 1 (Interagency Registry for Mechanically Assisted Circulatory Support) or postcardiotomy shock. Recent experiences published by high-volume centers like Cleveland Clinic (where up to 30% of their series includes INTERMACS 1 patients) or the series by Schumer et al. show that this strategy is feasible due to the significant circulatory support provided by the Impella 5.5®. However, most authors and centers still prefer ECMO support as the initial management in these patients. In such cases, ECMO therapy appears to offer initial advantages, particularly in the presence of biventricular failure, respiratory support requirements, or when an initial evaluation is needed after a cardiac arrest, for example.
Although it is possible, depending on the etiology, to maintain ECMO as a bridge to recovery or even as a direct bridge to durable ventricular assist devices (VAD) or heart transplantation (HT), when recovery is deemed unlikely or temporary contraindications exist for transitioning directly to advanced therapies, progression to other types of MCS should occur as early as possible. For this reason, after initial stabilization of the patient with ECMO support, many centers have adopted the “bridge-to-bridge” strategy using Impella® devices to avoid the inherent deleterious effects of ECMO. This transition should be performed as early as possible, once right ventricular dysfunction and/or respiratory support needs have been ruled out. Even in these patients, transitioning from ECMO to biventricular assist devices (BIVAD) by combining the Impella 5.5® with an Impella RP® or a Centrimag® (Thoratec Corporation®) using the ProtekDuo® cannula (LivaNova®) appears reasonable. The latter combination (Impella 5.5® + ProtekDuo®), which some authors refer to as a Hybrid BIVAD and is preferred in our center, offers significant advantages over “classic” BIVADs. Among its main benefits are the possibility of respiratory support (by incorporating an oxygenator into the Centrimag® circuit) and its low invasiveness (via percutaneous jugular-subclavian access).
Another distinct group of patients includes those on the HT waiting list or with previously undiagnosed cardiomyopathy admitted with heart failure decompensation requiring inotropic support without the possibility of weaning (INTERMACS 3). In these patients, the strategy varies depending on the center and, in some cases, the country’s organ distribution policy. In our context, given the greater availability of donors compared to other countries, a direct transition to HT using temporary VADs (status 0) seems reasonable. However, in other countries with limited organ availability, the most common strategy involves implanting durable VADs as a bridge to HT. Until the advent of the Impella 5.5®, the most frequently used temporary VAD in this scenario was the left Centrimag®. In recent years, however, most centers have shifted away from this device in favor of the Impella®. While it retains its indications in certain scenarios (this topic warrants another review), the implantation of a Centrimag® involves greater surgical aggressiveness as it requires central implantation via sternotomy.
Specific Considerations for Bridging to Durable VAD with Impella®
The mortality associated with a direct bridge from INTERMACS 1 patients on ECMO to durable VAD is typically high, ranging from 60% to 70% in the first year. In this context, a prior transition with Impella® support, removing the ECMO whenever possible, appears more reasonable. Maintaining patients on Impella® support for several days before durable VAD implantation not only stabilizes them but also improves their general condition in terms of mobility, nutritional status, and resolution of multiorgan dysfunction, while facilitating patient extubation. Additionally, this period allows for assessment of right ventricular function following durable VAD implantation and the exclusion of potential neurological injuries, particularly in patients who required ECMO during cardiac arrest or extreme hypotension scenarios.
However, direct implantation of a durable VAD without prior bridging with Impella 5.5®, in a carefully selected cohort of patients, may also offer certain advantages. It is important to note that “bridge-to-bridge” strategies are not without significant complications. Determining which patients could benefit from prior VAD bridging support is critical. This decision should be made by a multidisciplinary team and involve an individualized evaluation of each case.
Published experiences in the literature mainly come from small series with a limited number of cases. One of the first publications, involving the Impella 5.0® in the bridge-to-bridge strategy (ECMO-ECPELLA-Impella bridge to durable VAD), was by Bertoldi et al., who described their experience in 9 patients. All patients were successfully weaned from ECMO (mean duration of 22 hours with ECPELLA) and maintained on Impella® support until durable VAD implantation (mean duration of 17 days), achieving an overall survival rate of 100%. In the study by Ajello et al., involving 21 patients treated with Impella® (5.0 and CP) as a bridge to durable VAD, the outcomes were similarly excellent, with 100% survival at 30 days and a low rate of complications.
Our Experience
At our center, a total of 20 Impella 5.5® devices were implanted between January 2023 and October 2024. The distribution of etiologies was as follows: acute myocardial infarction (AMI) in 47% of cases, decompensated dilated cardiomyopathy (DCM) in 41%, and myocarditis in 12%. The majority were male patients (85%) with a mean age of 53 years. The mean support duration was 14 days (range: 2–55 days). Regarding surgical access, the left subclavian artery was used in 11 cases, the right in 8 cases, and central access via partial sternotomy in the ascending aorta was required in 1 case.
Out of the total series, durable VAD implantation was performed in 8 cases (40%) under INTERMACS 1 conditions (following prior ECMO support), while in the remaining 12 cases (60%), the Impella 5.5® was implanted directly in INTERMACS 2/3 patients. Among the INTERMACS 2/3 patients (7 DCM; 5 AMI), the initial strategies were: one case as a bridge to recovery, 10 cases as a bridge to HT, and one case as a bridge to destination therapy (HeartMate 3®, Abbott®). In the HT bridge subgroup, all patients reached heart transplantation after a mean support duration of 11 days (range: 5–17 days), with an overall hospital survival rate of 90% (one patient died post-transplantation). Among these 10 patients, biventricular support was required in 3 cases using a combination of Impella 5.5® and ProtekDuo®. The patient on destination therapy received a HeartMate 3® after 15 days of Impella® support and was subsequently discharged while awaiting HT. The patient in the recovery group died on the ninth day. The overall survival rate for this group was 83.3% (10/12).
The INTERMACS 1 group, as expected, had lower survival rates (50%). In all cases (4 AMI, 2 myocarditis, 2 DCM), patients were previously supported with ECMO. Although the initial strategy was to progressively de-escalate toward durable VAD and withdraw ECMO, this was achieved in only two patients. In two cases, escalation to BIVAD support (Impella® + ProtekDuo®) was necessary after ECMO withdrawal, but both patients died after 55 and 20 days of support due to respiratory-origin sepsis. Among the remaining patients, three of the four HT-bridge patients were ultimately transplanted (75% survival in the HT-bridge strategy for INTERMACS 1). One patient recovered ventricular function and was weaned off support, while another died.
Overall Results and Comparative Analysis
The overall survival rate in our series was 75% (15/20). When stratified by INTERMACS level, patients in INTERMACS 3 demonstrated a survival rate of 90.9%, while those in INTERMACS 1/2 had significantly lower survival rates at 44.4%. In the subgroup of patients in a heart transplantation (HT) bridge strategy (INTERMACS 1-3), the success of the Impella® strategy, defined as the proportion of patients who reached transplantation, was 92.8% (13/14). In this subgroup, the overall survival rate reached 85.7% (12/14).
Among our complications, the most notable were reintervention due to surgical access site bleeding in two cases, a cerebrovascular accident following HT, and one case requiring device repositioning due to displacement.
When comparing these results with other initial experiences or even with our own historical series using other VADs, significant conclusions can be drawn. First, when comparing our series with the first 200 Impella 5.5® implants performed in the United States, we observed outcomes comparable to ours. In the US series, 83% of patients were male (mean age 62 years), with an overall survival rate of 74% (148/200). Of the 148 patients, 63 underwent bridging to durable VAD or HT, and in 63 cases, ventricular function recovery allowed device removal. In that registry, a statistically significant difference was observed between survival rates in patients with isolated Impella® support versus those with ECPELLA, showing figures similar to ours (78.8% vs. 51.4%, p = .002).
Regarding our results compared to pre-Impella 5.5® strategies, Domínguez et al. published the outcomes of our series involving 60 patients transplanted under status 0 with VAD as a bridge to HT between 2015 and 2021. The devices implanted were 53 Centrimag® (8 BIVAD) and 7 Impella CP®. Notably, 20 cases had prior ECMO support (INTERMACS 1) and the device was used as a bridge-to-bridge. The outcomes, compared to our initial experience with Impella 5.5®, showed worse evolution and higher mortality across all subgroups. Among patients previously supported with ECMO followed by bridge-to-bridge VAD, only 5 out of 20 (25%) reached HT, compared to 75% with Impella 5.5®. On the other hand, among those directly supported with Centrimag® or Impella CP®, 31 out of 40 (77.5%) reached transplantation, with a 100% effectiveness rate in our current series with Impella 5.5®. The overall mortality following transplantation was 16.7%, while the overall mortality for the entire series reached 50%, compared to only 14.3% with Impella 5.5®. It is also noteworthy that for patients with isolated left Centrimag®, the approach involved a left thoracotomy and outflow anastomosis of the VAD to the subclavian artery, minimizing surgical aggressiveness.
Based on these findings, two conclusions can be drawn:
- The Impella 5.5® has established itself as an essential tool in managing patients with cardiogenic shock and advanced heart failure, particularly in scenarios transitioning to definitive therapies or as a bridge to recovery. Its minimally invasive nature and axillary implantation option offer significant advantages, such as greater patient mobility and optimization of metabolic parameters, even in cases of multiorgan failure, while awaiting recovery or final treatment decisions.
- Our initial experience, although limited, shows promising results comparable to those reported in larger series. This reinforces the utility of the Impella 5.5® in current strategies, such as bridge-to-bridge from ECMO or support in INTERMACS 3 patients, where we observed better outcomes compared to previous devices. These findings support the continued application of this device in the comprehensive management of complex cardiogenic shock patients.
REFERENCES:
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