Temporary MCS is summarized in Table 2, and options include the following:

The IABP consists of an expandable balloon mounted on a vascular 7F to 8F catheter and is most commonly introduced via the femoral artery and positioned in the descending thoracic aorta distal to the left subclavian artery. Depending on factors such as the balloon size (which varies according to the patient’s height), positioning, and vascular compliance, the cardiac output provided is up to 1 L/min via the femoral approach. However, it may also be surgically placed via an axillary artery conduit if needed due to patient anatomy, which allows greater augmentation of cardiac output and mobility of the patient—this approach has gained favor to support patients with end-stage heart failure who are awaiting a durable LV assist device or heart transplant. The IABP is timed to inflate and deflate synchronously with the cardiac cycle, increasing the diastolic blood pressure and reducing the systolic blood pressure to improve coronary perfusion and cardiac output [5]. More specifically, the IABP acts passively by inflating during diastole and then deflating prior to systole. When inflated, there is an increase in aortic pressure (referred to as “augmented diastolic pressure”) that results in greater coronary blood flow. Then when the balloon deflates just prior to the onset of systole, there is an abrupt lowering of aortic pressure that results in a reduction in work for the LV during systole [20]. However, the IABP might cause a drop in mean arterial pressure, requiring the addition of vasopressor agents. Thus, IABP can be used to augment coronary and systemic perfusion but it may not provide enough support as a standalone MCS device. Some registry studies have reported no short- or long-term improvement in cardiac output or hemodynamic parameters with IABP use [8, 21]. Contraindications to IABP include moderate to severe aortic regurgitation, uncontrolled sepsis, uncontrolled bleeding diathesis, aortic aneurysm, aortic dissection, and severe peripheral artery disease [22].

In the large randomized multicenter IABP-SHOCK II trial, which randomized 600 patients with AMI-CS and early revascularization to IABP or medical therapy, IABP was not associated with any short-term mortality benefit [23]. Furthermore, the 1-year and 6-year data demonstrated no benefit of IABP on long-term outcomes (Fig. 1) [21, 22].

IABP SHOCK Trial II results. Screening, randomization, management strategy, and follow-up at 30 days, 1 year, and 6 years. AMI acute myocardial infarction, CI confidence interval, CS cardiogenic shock, IABP intra-aortic balloon pump, RR relative risk. Permission was obtained to adapt this figure from references 20, 21, and 22

Currently available pVADs include the TandemHeart® (Cardiac Assist, Inc, Pittsburgh, PA) and the micro-axial Impella® (Abiomed Europe, Aachen, Germany). With the aid of fluoroscopic guidance, a transseptal puncture is required between the right and left atria via the femoral vein for placement of TandemHeart®. TandemHeart® bypasses the LV by taking arterialized blood from the left atrium from a catheter that crosses the atrial septum and circulated through an external centrifugal pump, and diverts it to the lower abdominal aorta or iliac arteries via a femoral artery cannula (15–17 Fr) with retrograde perfusion of the abdominal and thoracic aorta allowing for blood flow rates of up to 4 L/min [5].

Contraindications for pVADs include significant peripheral artery disease, moderate-to-severe aortic valve insufficiency, mechanical tricuspid or pulmonary valve, severe tricuspid valve stenosis, severe pulmonary valve stenosis or insufficiency, thrombosis in the vena cava or right atrium or ventricle, and superior vena cava or internal jugular vein stenosis or occlusion [24]. Patients with a TandemHeart are more likely to experience vascular complications such as significant bleeding. This may be linked to the requirement for transseptal puncture, having two sites for percutaneous vascular access, the large sheath needed for insertion, and the necessity for anticoagulation to mitigate thromboembolism risk [25].

A small study of 42 patients that compared TandemHeart® to IABP in patients with CS found that patients randomized to TandemHeart® had a significantly improved cardiac index and pulmonary capillary wedge pressure, with no change in clinical outcomes, but with a higher frequency of complication including severe bleeding (n = 19 vs. n = 8, p = 0.002) and limb ischemia (n = 7 vs. n = 0, p = 0.009) with TandemHeart® support [26].

Currently, three classes of Impella® LVAD support are available in the US: 2.5, cardiac power (CP), and 5.5. These three classes differ in the peak flows offered for cardiac output, as 2.5 provides flows up to 2.5 L/min, CP provides flows up to 4.3 L/min, and 5.5 provides flows up to 6 L/min. The Impella 2.5® is now rarely used given the availability of the Impella CP® and 5.5 that offer higher flow rates. The Impella Expandable Cardiac Power® (ECP) is a smaller version of the Impella CP® that provides up to 5.5 L/min support, but is not approved by the US Food and Drug Administration for clinical use. It has a 21 Fr pump which is compressible to 9 Fr that is designed to be implanted and removed using small bore access and closure techniques. It is delivered wirelessly across the aortic valve into the LV [27]. The Impella® devices support hemodynamics by increasing cardiac output and unloading the heart, reducing LV end-diastolic pressure, thereby improving coronary flow and myocardial perfusion, and decreasing myocardial oxygen demand. To avoid malfunction and device-related complications, it is critical that the Impella® device be placed in the proper position and monitored with ultrasound. Importantly, the inlet area of the catheter should be well below the aortic outflow tract (approximately 3.5 cm in adults), free of the papillary muscle and mitral valve apparatus, in a free-floating position. In addition, adequate right ventricular function and filling pressures are necessary to avoid device suctioning [20]. Improper rotation of the device has been linked to poorer outcomes. Both the Impella®support devices  depend on adequate right ventricular function to maintain sufficient LV preload and require stable oxygenation for optimal performance. Contraindications include the presence of left ventricular thrombus and mechanical aortic valves [8]. It is important to note that for axillary devices, insertion of a perfusion catheter distally can help to mitigate distal limb complications. More specifically, this is done using ultrasound-guided antegrade access with a 5- or 6-F braided sheath [28].

Data comparing different types of percutaneous MCS devices for CS are sparse. A meta-analysis from 2009 combined data from three randomized trials (two involving TandemHeart® and one with Impella 2.5®, each compared to IABP). Patients receiving percutaneous MCS exhibited higher cardiac indices, elevated mean arterial pressures, lower pulmonary capillary wedge pressures, and a higher incidence of bleeding complications, but no significant difference in mortality rates between MCS devices versus IABP [29]. Two small studies with < 50 patients with CS showed that Impella 2.5® improved cardiac index compared to IABP, but there were no differences in mortality at 1 or 6 months [30, 31]. The Impella®-EUROSHOCK, a European registry comprised of 120 patients enrolled between 2005 and 2010 who had Impella 2.5® for CS, showed that the device improved hemodynamics compared to no MCS support in this high-risk cohort [32]. The available data suggest Impella® devices offer reasonable balance between greater hemodynamic support and ease of use; however, randomized data comparing various types of MCS in CS are limited.

For patients whose hemodynamics remain stable or improve, assessing readiness to wean from MCS should be pursued. The wean allows for evaluation of whether the heart can provide the necessary cardiac output to match demand. If hemodynamic, metabolic, and end-organ perfusion instability or ventricular dysfunction ensues during the wean, device settings should resume at the prior level of support before a further weaning attempt. If stability is maintained at the lowest device support, explantation of the device can be considered. However, if a patient’s clinical condition deteriorates (e.g., low cardiac indices or requirement of multiple vasoactive medications), the use of higher forms of support such as Impella 5.5® or VA-ECMO should be considered [16]. The Danish Cardiogenic Shock Trial (DanGerShock) was a multicenter study of 355 patients with CS following STEMI that were randomized to receive conventional circulatory support with Impella CP® with standard of care or standard of care alone. The study demonstrated a significant reduction in mortality with the routine use of MCS in patients with CS following STEMI [33]. Further details are discussed in a later section.

A first-in-human feasibility study with a small peripheral LVAD known as the Magenta Elevate demonstrated initial safety and feasibility of this device in 14 patients undergoing high-risk PCI. This self-expanding, catheter-mounted pump is inserted through a 10-F femoral catheter and can provide 5.4 L/min flow [34].

VA-ECMO provides both cardiovascular and pulmonary support in acute cardiorespiratory failure and has also been used to assist cardiopulmonary resuscitation in cardiac arrest [9]. For CS, VA-ECMO is most commonly used, since isolated right ventricular failure (for which veno-venous [VV]-ECMO could be considered) due to AMI is rare. VA-ECMO supports both ventricles and lung function, while VV-ECMO supports lung function and the right ventricle only.

In VA-ECMO, blood is removed from the right atrium (V), then circulated through a heat exchanger and membrane oxygenator (ECMO), before returning oxygenated blood to the femoral artery (A). This greatly enhances the flow of oxygenated blood to the body’s extremities. Peripheral VA-ECMO can be initiated percutaneously using ultrasound guidance, typically via the femoral vein and artery. Alternatively, it can be established through surgical means. With VA-ECMO, deoxygenated (venous) blood is withdrawn from either a peripheral (e.g., femoral) or central (e.g., superior vena cava) vein, oxygenated in an external circuit, and returned through an arterial cannula. With peripheral V-A ECMO, to avoid leg ischemia due to a large bore arterial catheter in the femoral artery, an antegrade perfusion catheter is advised [20]. Absolute contraindications to VA-ECMO include limited life expectancy (< 1 year); irreversible neurologic injury; severe peripheral arterial disease or other limitation to vascular access with large bore catheters; respiratory failure for > 1 week requiring very high levels of inhaled oxygen or high-pressure ventilation; advanced liver disease; and severe coagulopathy, contraindication to systemic anticoagulation, or refusal to receive blood products. Relative contraindications to VA-ECMO include advanced age, cognitive impairment, severe non-cardiac comorbid conditions, poor adherence to treatment, and insufficient social support [24].

A meta-analysis of five randomized trials in 567 patients with CS complicating AMI compared early, routine VA-ECMO with optimal medical therapy. There was no significant difference in 30-day mortality between treatments (OR for VA-ECMO vs. optimal medical therapy 0.93, 95% CI 0.66–1.29). However, VA-ECMO was associated with significantly higher complication rates, including major bleeding (OR 2.44 [1.55, 3.84]) and peripheral ischemic vascular complications (OR 3.53 [1.70, 7.34]) [33].