**6.2. Impella devices**

The Impella device is a nonpulsatile, axial flow device that is implanted inside the LV percutaneously, commonly through the femoral artery for the 2.5 Impella or with surgical cutdown, commonly through the axillary artery for the 5.0 Impella. The Impella acts as a pump that propels blood from the LV into the ascending aorta (**Figure 6**) [43].

The Impella device has three versions; 2.5 Impella, which is a 12 Fr system that provides a maximal flow of 2.5 L/min, the 5.0 Impella which is a 21 Fr system and provides a maximal flow of 5 L/min, and the CP Impella, which is a 14 Fr system that provides between 3 and 4 L/ min of flow [43, 53].

L/min increase in the CO. IABP induces around 10% drop in SBP indicating proper systolic unloading, causes an increase in DBP which in turn improves the coronary perfusion and leads to a net increase in the mean arterial pressure (MAP). There is also an increase in the LV ejection fraction with IABP and a decrease in the LV end diastolic volume and pressure

Despite all the hemodynamic advantages with IABP, studies have failed to show any mortality benefit with its use. The SHOCK II trial, which compared IABP vs. medical stabilization, showed no difference in mortality along with other variables such as time to hemodynamic stabilization, length of ICU stay, the dose and duration of catecholamines, and changes in

Currently the main indication for IABP counterpulsation is CS refractory to pharmacotherapy; IABP is currently a class IIa indication for the treatment of CS complicating a STEMI in the American Heart Association/American College of Cardiology guidelines (AHA/ACC), while its routine use in CS is discouraged by the European Society of Cardiology [21, 49].

Other indications where IABP can help stabilize the patient include refractory heart failure, papillary muscle rupture or acute mitral regurgitation, ventricular septal rupture, refractory unstable angina, high-risk PCI or the inability to wean from cardiopulmonary bypass

The absolute contraindications to IABP are significant aortic regurgitation and aortic dissection. Other relative exclusion criteria include: significant peripheral arterial disease (PAD) that precludes placement, severe coagulopathy, active infection, and cancer with metastasis [44]. The complication rate with IABP is rather rare with thrombocytopenia and fever being the most common (about 50% and 40% of patients, respectively). Other major complications include: major limb ischemia (0.9% of patients); severe access site bleeding (0.8%); amputation (0.1%); balloon leak (1%); and IABP-related mortality (0.05%). The main risk factors associated with IABP complications are female gender, PAD, small body surface area (BSA) (BSA <

Due to the lack of data, the use of anticoagulation with IABP is variable among different centers. Most centers, like ours, use anticoagulation, but some will not, especially with 1:1

The Impella device is a nonpulsatile, axial flow device that is implanted inside the LV percutaneously, commonly through the femoral artery for the 2.5 Impella or with surgical cutdown, commonly through the axillary artery for the 5.0 Impella. The Impella acts as a pump that

The Impella device has three versions; 2.5 Impella, which is a 12 Fr system that provides a maximal flow of 2.5 L/min, the 5.0 Impella which is a 21 Fr system and provides a maximal flow of 5 L/min, and the CP Impella, which is a 14 Fr system that provides between 3 and 4 L/

[44–47].

152 Interventional Cardiology

renal function [6, 48].

[44, 49, 50].

1.65 m2

pumping [43].

**6.2. Impella devices**

min of flow [43, 53].

), and advanced age (>75 years) [51, 52].

propels blood from the LV into the ascending aorta (**Figure 6**) [43].

**Figure 6.** The Impella device with the pump inside the left ventricle and the outer catheter inside the aorta. Reproduced with permission from Abiomed.

The Impella unloads the LV, reduces the left ventricular end diastolic volume (LVEDV) and the LV wall tension and improves the systemic and coronary perfusion through an increase in the mean arterial pressure. The Impella device requires an adequate RV function (or an RV assist device) to maintain adequate LV preload, and unlike the IABP, the Impella devices can work properly through transient arrhythmias.

The main indications of the Impella devices are similar to those of the IABP counterpulsation with slight differences, for example, the Impella may worsen right-left shunting in patients with ventricular septal defect (VSD).

The main contraindications to Impella are mechanical aortic valve and LV thrombus. Other relative exclusion criteria are severe aortic regurgitation and severe PAD. The most common complications are those of vascular nature such as access site bleeding, retroperitoneal hematoma, limb ischemia and vascular injury. Hemolysis is also common with the Impella device due to the mechanical shear stress of the device on the red blood cells. In addition, anticoagulation is generally required during treatment with Impella [43, 53].

Compared to the IABP, Impella does provide greater hemodynamic support but it has not been shown to change the mortality [54]. In the largest most recent randomized controlled trial (the IMPRESS trial) comparing Impella to IABP in CS complicating AMI; 48 patients with severe CS complicating STEMI were randomized to the Impella device (24 patients) and to IABP (24 patients), the mortality at 30 days and at 6 months was similar between the two groups (50% in both groups at 6 months). Of note: those were extremely ill patients with 92% of the entire group having cardiac arrest prior to randomization, and half the mortality at 6 months was attributed to brain damage in both groups [55].

And although not commonly done, the successful use of Impella in combination with IABP has been reported [56].

A brief comparison between the Impella and the IABP is summarized in **Table 3**.

#### **6.3. Other percutaneous mechanical circulatory support devices**

The IABP and the Impella are not the only circulatory support devices used in CS, there are other—less commonly used—devices such as the Tandemheart, the extracorporeal membrane oxygenation (ECMO) and others.

The TandemHeart is left atrial to aorta support device that is inserted percutaneously and requires a transseptal puncture to access the left atrium. It bypasses the LV and pumps blood extracorporeally—from the left atrium into the iliofemoral arterial system (**Figure 7**) [43, 57].


**Table 3.** A brief comparison between intra-aortic balloon pump (IABP) and Impella.

hematoma, limb ischemia and vascular injury. Hemolysis is also common with the Impella device due to the mechanical shear stress of the device on the red blood cells. In addition,

Compared to the IABP, Impella does provide greater hemodynamic support but it has not been shown to change the mortality [54]. In the largest most recent randomized controlled trial (the IMPRESS trial) comparing Impella to IABP in CS complicating AMI; 48 patients with severe CS complicating STEMI were randomized to the Impella device (24 patients) and to IABP (24 patients), the mortality at 30 days and at 6 months was similar between the two groups (50% in both groups at 6 months). Of note: those were extremely ill patients with 92% of the entire group having cardiac arrest prior to randomization, and half the mortality at 6

And although not commonly done, the successful use of Impella in combination with IABP

The IABP and the Impella are not the only circulatory support devices used in CS, there are other—less commonly used—devices such as the Tandemheart, the extracorporeal membrane

The TandemHeart is left atrial to aorta support device that is inserted percutaneously and requires a transseptal puncture to access the left atrium. It bypasses the LV and pumps blood extracorporeally—from the left atrium into the iliofemoral arterial system (**Figure 7**) [43, 57].

**Impella IABP** ECG Unrelated to systole or diastole Inflates with diastole and deflates

CO Up to 5 L/min of CO Modest increase in CO (0.5–1 L

LVEDV Reduces LVEDV and LVEDP Reduces LVEDV and LVEDP

asystole and VF are poorly tolerated)

Absolute contraindications Mechanical AV, LV thrombus Severe AR, aortic dissection

Complications Similar complication profile of vascular injury and access site bleeding, with these complications being slightly higher with the Impella Mortality No difference in mortality between both devices in CS patients complicating AMI CO, cardiac output; LVEDV, left ventricular end diastolic volume; LV, left ventricle; AV, aortic valve; AR, aortic

Catheter size Between 12 and 21 Fr 7.5–8 Fr

**Table 3.** A brief comparison between intra-aortic balloon pump (IABP) and Impella.

Rhythm Does not require a stable rhythm (although

with systole

increase CO)

Requires a stable rhythm

A brief comparison between the Impella and the IABP is summarized in **Table 3**.

anticoagulation is generally required during treatment with Impella [43, 53].

months was attributed to brain damage in both groups [55].

**6.3. Other percutaneous mechanical circulatory support devices**

has been reported [56].

154 Interventional Cardiology

regurgitation.

oxygenation (ECMO) and others.

**Figure 7.** The TandemHeart. The left panel shows the entire system: there is a venous catheter and an arterial catheter, and the pump is situated extracorporeally. The right panel shows the transseptal puncture and how the venous catheter bypasses the left ventricle. Reproduced with permission from Tandemlife.

The TandemHeart device has two separate catheters, a 21 Fr venous catheter that goes transseptally and aspirates the LA blood and an arterial perfusion outflow cannula between 15 and 19 Fr. The TandemHeart pump can provide flow rates up to 4.5 L/min of assisted cardiac output [8, 43].

The TandemHeart has been studied in severe refractory CS patients not responding to vasopressors/inotropes in combination with IABP. The TandemHeart significantly improved the hemodynamics in this extremely ill population, along with PCWP, lactic acid levels and creatinine levels. This device can also be used as a bridge to a more definitive therapy such as left ventricular assist device (LVAD) or heart transplantation [28].

ECMO can provide a full pulmonary and/or cardiac support for those with failing hearts and/or lungs. The ECMO device can be either venoarterial (V-A ECMO) or venovenous (V-V ECMO); the V-A ECMO is ideal for those with CS and poor oxygenation while the V-V ECMO provides oxygenation only when the cardiac hemodynamics are stable. The venous catheter size is usually 20 Fr and the arterial catheter size is 17 Fr. ECMO can provide even more than 6 L/min of CO depending on catheter size and unlike other MCS devices, a trained perfusionist is required to manage the ECMO [43].

IABP, Impella, TandemHeart and ECMO can all be used in the setting of CS with slight differences in indications. They offer hemodynamic support, and it is recommended that one of these devices be inserted rapidly in CS if hemodynamic stability cannot be achieved with fluid resuscitation and/or pharmacotherapy. The experience with these devices in CS patients has been to start with an IABP along with vasopressors/inotropes, and if hemodynamic stability cannot be achieved, one may consider upgrading to one of the more powerful percutaneous MCS devices. Although these devices are FDA approved for the use of up to 6 h, they have been used successfully for days in patients with prolonged shock [43].

Our center's experience is to insert an IABP or an Impella—depending on operator's experience—rapidly in CS patients secondary to AMI prior to attempted revascularization. We recommend—as it is endorsed by the 2015 SCAI/ACC/HFSA/STS consensus document for the use of MCS devices—that one of these devices inserted rapidly if hemodynamic stability cannot be achieved rapidly with pharmacotherapy.

Other devices are being used such as the right ventricular assist devices (RVAD), which is used for the failing RV, and others. For further read on these devices and other MCS devices, refer to the 2015 SCAI/ACC/HFSA/STS expert consensus statement on the use of percutaneous MCS [43].
