An important substudy investigated the clinical outcome in patients assigned to emergency revascularization in the SHOCK trial undergoing PCI compared with CABG [16]. Out of 128 patients undergoing emergency revascularization 81 underwent PCI (63.3%), and 47 underwent CABG (36.7%). Patients undergoing CABG were at higher risk at baseline with a greater extent of coronary artery disease and a greater prevalence of diabetes mellitus. In the CABG group, 87.2% of patients were considered completely revascularized whereas only 23.1% of patients in the PCI group were considered completely revascularized. Despite the higher baseline risk profile of patients undergoing CABG one‐year survival was similar in both treatment arms, suggesting a potential benefit of complete revascularization. This hypothesis was tested in the CULPRIT‐SHOCK trial which randomized 706 CS patients with multivessel disease to PCI of the culprit lesion only or immediate multivessel PCI [4]. At 30–days there were higher rates of death or renal‐replacement therapy in the multivessel PCI group compared with the culprit‐lesion‐only PCI group (55.4% vs 45.9%, p = 0.01). At one‐year follow‐up, mortality was similar in both groups (50.0% culprit‐only vs. 56.9% multivessel PCI, p = ns) [17]. This led the European Society of Cardiology to include a Class III recommendation (harm) for routine revascularization of non‐IRA lesions in MI complicated by CS [18].
Left‐ventricular assist devices and the intra‐aortic balloon pump
Mechanical support devices aim to overcome the inability of the heart to pump adequate amounts of blood by supporting the circulation and increasing cardiac output. Moreover, support devices aim to unload the damaged left ventricle by afterload (pressure unloading) or pre‐load reduction (volume unloading). Currently available devices include the intra‐aortic balloon pump (IABP), the Impella axial flow pump, the TandemHeart device, and extra‐corporeal membrane oxygenation (ECMO) [19]. These devices are discussed in further detail in chapter 69 (percutaneous ventricular assist devices).
IABP
IABP In one small study that randomized 40 patients in cardiogenic shock to optimal medical therapy alone or to optimal medical therapy and an IABP, no significant differences were observed in hemodynamic parameters such as cardiac output and systemic vascular resistance between both groups [20]. The 600‐patient IABP SHOCK II trial randomized patients with cardiogenic shock complicating myocardial infarction to treatment with an IABP or no IABP. Early revascularization and optimal medical therapy were provided in both study arms. The use of the IABP did not reduce 30‐day or 1‐year mortality [11, 21]. Moreover, there were no differences in time to hemodynamic stabilization, the length of intensive care unit stay, serum lactate levels, dose and duration of catecholamine administration, and renal function [21]. ESC guidelines therefore recommend against routine use of IABP in patients with CS due to ACS [18].
Impella
Currently, available evidence on the use of the Impella device in cardiogenic shock is limited to observational studies and one small randomized trial [22–24]. In the ISAR‐SHOCK (efficacy study of LV assist device to treat patients with cardiogenic shock) trials, 26 patients with advanced/established cardiogenic shock were randomized to IABP or Impella [22]. In this small study the cardiac index after 30 minutes of support was significantly higher in the Impella group compared with the IABP group (delta 0.49±0.46 l/min/m2 vs 0.11±0.31 l/min/m2, p = 0.02). Overall, 30‐day mortality was similar in both groups. Recent retrospective database studies using the American College of Cardiology’s National Cardiovascular Data Registry [25] and the Premier Healthcare Database [26] reported an association between higher mortality and use of Impella during PCI for CS as compared to either IABP or no Impella use. Given the retrospective nature of these data it is not possible to distinguish whether Impella is a marker for unknown confounders (sicker patients) or Impella leads to worse outcomes in CS. Randomized data is currently scarce, the 48‐patient IMPRESS‐in‐Severe‐SHOCK trial randomized intubated and ventilated patients with CS to Impella CP or IABP [27]. This underpowered study failed to show a benefit in terms of 30‐day mortality with Impella. The ongoing Danish‐German Cardiogenic Shock Trial (DanGer) is investigating whether mechanical support with Impella can improve survival in CS patients [28].
Tandemheart
In 2 small randomized clinical trials enrolling about 40 patients each, the Tandemheart was associated with significant improvements in hemodynamic parameters when compared with the IABP [29, 30]. However, without direct left ventricular unloading the Tandemheart increases left ventricular afterload which partially offsets the potential cardiac workload benefits. Other concerns with the TandemHeart are the complications (bleeding and limb ischaemia) and the complex trans‐septal insertion procedure, which have limited its uptake in clinical practice.
ECMO
The use of ECMO for cardiogenic shock has evolved significant during the past decade. Compared with other support devices, ECMO is able to provide higher blood flow rates, oxygenation and ability to support both the left‐ as well as the right ventricle. Important advances include a compact ECMO device (Cardiohelp®, Maquet, Rastatt, Germany) allowing for out‐of‐hospital or bedside ECMO insertion. French physicians have pioneered pre‐hospital extracorporeal cardiopulmonary resuscitation with encouraging survival rates (ECPR) [31]. Several randomized controlled trials investigating ECMO in cardiogenic shock are currently ongoing including the ECMO‐CS (Extra Corporeal Membrane Oxygenation in the Therapy of Cardiogenic Shock) [32], ANCHOR (assessment of ECMO in Acute Myocardial Infarction Cardiogenic Shock, NCT 04184635), ECLS‐SHOCK (Extracorporeal Life Support in Cardiogenic Shock, NCT 03637205) and EURO‐SHOCK (Testing the Value of Novel Strategy and its Cost Efficacy in Order to Improve the Poor Outcomes in Cardiogenic Shock, CT 03813134) trials.
Guideline recommendations for the IABP and left ventricular assist devices
The 2018 ESC/EACTS guidelines for myocardial revascularization no longer recommend the use of IABP in patients with cardiogenic shock (class III recommendation, level of evidence A) [33]. These guidelines state a class IIb, level of evidence C recommendation for the use of left ventricular assist devices “short‐term mechanical circulatory support in ACS patients with cardiogenic shock may be considered”. The 2013 ACC/AHA guidelines state a class IIa level of evidence B recommendation for the use of the IABP “The use of intra‐aortic balloon pump (IABP) counterpulsation can be useful for patients with cardiogenic shock after STEMI who do not quickly stabilize with pharmacological therapy” [14]. The ACC/AHA recommendation for left ventricular assist devices is class IIb, level of evidence C “Alternative LV assist devices for circulatory support may be considered in patients with refractory cardiogenic shock”.
Vasopressors and inotropes
Rapid treatment of hypoperfusion and hypotension is essential when dealing with cardiogenic shock. Inotropes can be used to increase cardiac output and vasopressors to increase blood pressure. However, inotropes and vasopressors increase myocardial oxygen consumption and current guidelines suggest their use should be assessed on an individual basis [14]. Sympathomimetic agents are most commonly used in the setting of cardiogenic shock, but phosphodiesterase inhibitors and calcium sensitizers are also sometimes used.
Sympathomimetic agents
Norephinephrine has a high affinity for the alpha‐adrenergic receptor and has minor beta‐agonistic effects. Therefore, norepinephrine is a potent vasopressor with limited inotropic effects. Dopamine has a variety of effects depending on