Randomized trials of patients in cardiogenic shock (CS) have been challenging to conduct. The DanGer Shock (Microaxial Flow Pump in Infarct-Related Cardiogenic Shock) trial was an important study in this space that was successfully concluded after 10 years because of slow recruitment.¹ The trial results demonstrated that routine implantation of a mechanical circulatory support (MCS) device (Impella CP® microaxial pump [ABIOMED, Danvers, Massachusetts]), in addition to standard care, was superior to standard care alone in reducing 6-month death among patients presenting with ST-segment elevation myocardial infarction (STEMI) and CS. The results also included a reduction in escalation to short-term or long-term MCS and transplantation.

It is important to note that augmented cardiac output with an intra-aortic balloon pump (IABP) is commonly <1 L. Impella CP provides support in the range of 3.5 L, which is considerably more than IABP's range of 1 L and less than extracorporeal membrane oxygenation (ECMO) systems' range of 5 L. Data from other trials exploring the routine use of ECMO and IABP have failed to show a survival benefit.^2-3 The increase in survival rates is commendable because the DanGer Shock trial is one of the only trials of CS whose findings translate into a survival benefit. The primary outcome (survival) comes at the expense of a higher rate of vascular injury and need for renal replacement therapy. Although this tradeoff appears to be a win for Impella CP, it is important to carefully understand the caveats and limitations. A higher rate of complications was registered in the Impella CP arm, namely bleeding, limb ischemia, need for renal replacement therapy, and sepsis, which translated into a longer hospital stay for those receiving MCS. As the trial investigators only reported 6-month outcomes, the longer-term morbidity and mortality rates will provide valuable insights once available. In addition, patients with cardiac arrest were excluded because, as investigators noted, neurologic recovery is not an endpoint with MCS and survivors are a variable population.

The results of subgroup analyses indicated that the benefit of the device was greater in those with multivessel disease and a systolic blood pressure lower than the median for this study (82 mm Hg). No interactions were detected with the Society of Cardiovascular Angiography and Interventions (SCAI) classification or lactate levels, although this trial was designed before these definitions were standardized and adopted widely.⁴ Finally, the timing of unloading remains unclear and operators will need to individualize the strategy as they await the results of the STEMI-DTU (Primary Unloading and Delayed Reperfusion in ST-Elevation Myocardial Infarction) trial.⁵ In the DanGer Shock trial, 57% of patients received MCS before revascularization and >80% were randomized in the catheterization laboratory. The decision was left to the participating operators, providing little guidance on timing in real-world scenarios.

Overall, this trial met its primary endpoint and its findings warrant a closer examination of the current guidelines and revision of shock pathways. However, the findings lend poor insight into escalation and de-escalation algorithms, combination therapies, and the management of those with cardiac arrest.

References

1. Møller JE, Engstrøm T, Jensen LO, et al.; DanGer Shock Investigators. Microaxial flow pump or standard care in infarct-related cardiogenic shock. N Engl J Med 2024;390:1382-93.
2. Thiele H, Zeymer U, Akin I, et al.; ECLS-SHOCK Investigators. Extracorporeal life support in infarct-related cardiogenic shock. N Engl J Med 2023;389:1286-97.
3. Saad M, Fuernau G, Desch S, et al. Prognostic impact of non-culprit chronic total occlusions in infarct-related cardiogenic shock: results of the randomised IABP-SHOCK II trial. EuroIntervention 2018;14:e306-e313.
4. Jentzer JC, Sanghavi D, Patel PC, et al. Prognostic performance of serial determination of the Society for Cardiovascular Angiography and Interventions shock classification in adults with critical illness. Shock 2024;61:246-52.
5. Kapur NK, Kim RJ, Moses JW, et al. Primary left ventricular unloading with delayed reperfusion in patients with anterior ST-elevation myocardial infarction: rationale and design of the STEMI-DTU randomized pivotal trial. Am Heart J 2022;254:122-32.