Comparison of Hemodynamic Support by Impella vs. Peripheral Extra-Corporeal Membrane Oxygenation: A Porcine Model of Acute Myocardial Infarction

Systemic Hemodynamics, Cardiac Mechanics, and Signaling Pathways Induced by Extracorporeal Membrane Oxygenation in a Cardiogenic Shock Model

Peripheral venoarterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly being used in patients suffering from refractory cardiogenic shock (CS). Although considered life-saving, peripheral VA-ECMO may also be responsible for intracardiac hemodynamic changes, including left ventricular overload and dysfunction. Venoarterial extracorporeal membrane oxygenation may also increase myocardial wall stress and stroke work, possibly affecting the cellular cardioprotective and apoptosis signaling pathways, and thus the infarct size. To test this hypothesis, we investigated the effects of increasing the peripheral VA-ECMO blood flow (25-100% of the baseline cardiac output) on systemic and cardiac hemodynamics in a closed-chest CS model. Upon completion of the experiment, the hearts were removed for assessment of infarct size, histology, apoptosis measurements, and phosphorylation statuses of p38 and protein Kinase B (Akt), and extracellular signal-regulated kinase mitogen-activated protein kinases (ERK-MAPK). Peripheral VA-ECMO restored systemic perfusion but induced a significant and blood flow-dependent increase in left ventricular preload and afterload. Venoarterial extracorporeal membrane oxygenation did not affect infarct size but significantly decreased p38-MAPK phosphorylation and cardiac myocyte apoptosis in the border zone.

Complications and Outcomes of Impella Treatment in Cardiogenic Shock Patients With and Without Acute Myocardial Infarction

Background In patients with cardiogenic shock (CS), acute myocardial infarction (AMI) is the most common cause, and a percutaneous microaxial ventricular assist device (Impella, Abiomed, Danvers, MA) is a choice for temporary mechanical circulatory support. However, data are limited on complications and outcomes of Impella treatment in patients with CS with and without AMI. Methods and Results Using nationwide prospective registry data in Japan, we included a total of 2047 patients with CS in whom the Impella devices were successfully placed between February 2020 and December 2021. Patients were divided into 2 groups according to the primary indication for the Impella use: AMI versus non-AMI. The primary end point was a composite of in-hospital all-cause death and major complications. Of the 2047 patients, the Impella was indicated for AMI in 1337 (65.3%). In the group without AMI, myocarditis was the leading cause of CS. Patients with AMI-CS were older and more likely to have cardiovascular risk factors than those with non-AMI-CS. The rates of in-hospital mortality (46.0% versus 43.9%, P=0.38) and major complications (35.2% versus 34.7%, P=0.85) were similar between the 2 groups. Overall, multivariable analysis identified older age, higher body mass index, previous transient ischemic attack or stroke, out-of-hospital cardiac arrest, and the Impella 5.0 as factors significantly associated with the primary end point. Conclusions The use of Impella in patients with and without AMI was related to similar clinical outcomes with high mortality and complication rates. Further studies are needed to identify patients who may benefit from the Impella devices in CS. Registration URL: https://www.umin.ac.jp/english. Identifier: UMIN000033603.

IABP versus Impella Support in Cardiogenic Shock: “In Silico” Study

Cardiogenic shock (CS) is part of a clinical syndrome consisting of acute left ventricular failure causing severe hypotension leading to inadequate organ and tissue perfusion. The most commonly used devices to support patients affected by CS are Intra-Aortic Balloon Pump (IABP), Impella 2.5 pump and Extracorporeal Membrane Oxygenation. The aim of this study is the comparison between Impella and IABP using CARDIOSIM© software simulator of the cardiovascular system. The results of the simulations included baseline conditions from a virtual patient in CS followed by IABP assistance in synchronised mode with different driving and vacuum pressures. Subsequently, the same baseline conditions were supported by the Impella 2.5 with different rotational speeds. The percentage variation with respect to baseline conditions was calculated for haemodynamic and energetic variables during IABP and Impella assistance. The Impella pump driven with a rotational speed of 50,000 rpm increased the total flow by 4.36% with a reduction in left ventricular end-diastolic volume (LVEDV) by ≅15% to ≅30%. A reduction in left ventricular end systolic volume (LVESV) by ≅10% to ≅18% (≅12% to ≅33%) was observed with IABP (Impella) assistance. The simulation outcome suggests that assistance with the Impella device leads to higher reduction in LVESV, LVEDV, left ventricular external work and left atrial pressure-volume loop area compared to IABP support.

Venoarterial extracorporeal membrane oxygenation improves survival in a rat model of acute myocardial infarction

BACKGROUND

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) has been widely used in high-risk acute myocardial infarction (AMI) patients with promising outcomes. However, the underlying molecular mechanisms remain unknown and a VA-ECMO animal model has not yet been established. The purpose of this study was to establish a VA-ECMO model in AMI rats and evaluate long-term cardiac function.

METHODS

We first established AMI in 20 Sprague-Dawley (SD) rats by ligating the left anterior descending coronary artery, while five rats underwent a thoracotomy to form the sham group. VA-ECMO was established after 30mins of AMI in 10 rats through the right jugular vein for venous drainage and right femoral artery for arterial infusion. Arterial blood pressure was monitored using a catheter in the left femoral artery, blood gas parameters were measured using a blood gas analyzer, while myocardial enzymes were detected using an ELISA Kit. Cardiac function was assessed through echocardiography on day 15. Masson staining and Western Blot were used for evaluating myocardial fibrosis, while histological injury was evaluated using hematoxylin and eosin staining.

RESULTS

VA-ECMO support stabilized blood pressure, decreased the levels of myocardial enzymes including cTnI, cTnT, CK-MB, and was associated with a higher survival rate. In the long term, the VA-ECMO group showed improved cardiac function, significantly increased EF and FS but significantly decreased EDV and ESV compared to the AMI group. Furthermore, VA-ECMO significantly alleviated pathological damage and myocardial fibrosis.

CONCLUSION

We established an economical, reliable, and reproducible VA-ECMO animal model in AMI rats, and demonstrated that VA-ECMO support prevents deteriorated cardiac function.

Mock circulatory loop applications for testing cardiovascular assist devices and in vitro studies

The mock circulatory loop (MCL) is an in vitro experimental system that can provide continuous pulsatile flows and simulate different physiological or pathological parameters of the human circulation system. It is of great significance for testing cardiovascular assist device (CAD), which is a type of clinical instrument used to treat cardiovascular disease and alleviate the dilemma of insufficient donor hearts. The MCL installed with different types of CADs can simulate specific conditions of clinical surgery for evaluating the effectiveness and reliability of those CADs under the repeated performance tests and reliability tests. Also, patient-specific cardiovascular models can be employed in the circulation of MCL for targeted pathological study associated with hemodynamics. Therefore, The MCL system has various combinations of different functional units according to its richful applications, which are comprehensively reviewed in the current work. Four types of CADs including prosthetic heart valve (PHV), ventricular assist device (VAD), total artificial heart (TAH) and intra-aortic balloon pump (IABP) applied in MCL experiments are documented and compared in detail. Moreover, MCLs with more complicated structures for achieving advanced functions are further introduced, such as MCL for the pediatric application, MCL with anatomical phantoms and MCL synchronizing multiple circulation systems. By reviewing the constructions and functions of available MCLs, the features of MCLs for different applications are summarized, and directions of developing the MCLs are suggested.

Effectiveness and Safety of a Prolonged Hemodynamic Support by the IVAC2L System in Healthy and Cardiogenic Shock Pigs

Background

Mechanical circulatory supports are used in case of cardiogenic shock (CS) refractory to conventional therapy. Several devices can be employed, but are limited by their availability, benefit risk-ratio, and/or cost.

Aims

To investigate the feasibility, safety, and effectiveness of a long-term support by a new available device (IVAC2L) in pigs.

Methods

Experiments were carried out in male pigs, divided into healthy (n = 6) or ischemic CS (n = 4) groups for a median support time of 34 and 12 h, respectively. IVAC2L was implanted under fluoroscopic and TTE guidance under general anesthesia. CS was induced by surgical ligation of the left anterior descending artery. An ipsilateral lower limb reperfusion was created with the Solopath® system. Reperfusion was started after 1 h of support in healthy pigs and upon IVAC2L insertion in CS pigs. Hemodynamic and biological parameters were monitored before and during the whole period of support in each group.

Results

Occurrence of an ipsilateral lower limb ischemia was systematic in healthy and CS pigs in a few minutes after IVAC2L implantation, and could be reversed by the arterial reperfusion, as demonstrated by distal transcutaneous pressure in oxygen (TcPO₂) and lactate normalization. IVAC2L support decreased pulmonary capillary wedge pressure (PCWP) (15.3 ± 0.3 vs. 7.5 ± 0.9 mmHg, p < 0.001), increased systolic blood pressure (SBP) (70 ± 4.5 vs. 101.3 ± 3.1 mmHg, p < 0.01), and cardiac output (CO) (4.0 ± 0.3 vs. 5.2 ± 0.6 l/min, p < 0.05) in CS pigs; at CS onset and after 12 h of support, without effects on heart rate or pulmonary artery pressure (PAP). Non-sustained ventricular arrhythmias were frequent at implantation (50%). A non-significant hemolysis was observed under support in CS pigs. Bleedings were frequent at the insertion and/or operating sites (30%).

Conclusion

Long-term support by IVAC2L is feasible and associated with a significant hemodynamic improvement in a porcine model. These preclinical data open the door for a study of IVAC2L in human ischemic CS, keeping in mind the need for systematic reperfusion of the lower limb and the associated risk of bleeding.

Overview of Veno-Arterial Extracorporeal Membrane Oxygenation (VA-ECMO) Support for the Management of Cardiogenic Shock

Cardiogenic shock accounts for ~100,000 annual hospital admissions in the United States. Despite improvements in medical management strategies, in-hospital mortality remains unacceptably high. Multiple mechanical circulatory support devices have been developed with the aim to provide hemodynamic support and to improve outcomes in this population. Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is the most advanced temporary life support system that is unique in that it provides immediate and complete hemodynamic support as well as concomitant gas exchange. In this review, we discuss the fundamental concepts and hemodynamic aspects of VA-ECMO support in patients with cardiogenic shock of various etiologies. In addition, we review the common indications, contraindications and complications associated with VA-ECMO use.