The science behind percutaneous hemodynamic support: A review and comparison of support strategies

Left ventricular unloading therapy using Impella 5.5 after emergency surgery for acute myocardial infarction mechanical complication: a case report

BACKGROUND

Following an acute myocardial infarction (AMI), surgery for left ventricular free wall rupture (LVFWR) and ventricular septal rupture (VSR) has a high in-hospital mortality rate, which has not improved significantly over time. Unloading the LV is critical to preventing excessive stress on the repair site and avoiding problems such as bleeding, leaks, patch dehiscence, and recurrence of LVFWR and VSR because the tissue is so fragile. We present two cases of patients who used Impella 5.5 for LV unloading following emergency surgery for AMI mechanical complications.

CASE PRESENTATION

A 76-year-old male STEMI patient underwent fibrinolysis of the distal right coronary artery. Three days later, he passed out and went into shock. Echocardiography revealed a cardiac tamponade. We found an oozing-type LVFWR on the posterolateral wall and treated it with a non-suture technique using TachoSil. Before the patient was taken off CPB, Impella 5.5 was inserted into the LV via a 10 mm synthetic graft connected to the right axillary artery. We kept the flow rate above 4.0 to 4.5 L/min until POD 3 to reduce LV wall tension while minimizing pulsatility. On POD 6, we weaned the patient from Impella 5.5. A postoperative cardiac CT scan showed no contrast leakage from the LV. However, a cerebral hemorrhage on POD 4 during heparin administration complicated his hospitalization. Case 2: A diagnosis of cardiogenic shock caused by STEMI occurred in an 84-year-old male patient, who underwent PCI of the LAD with IABP support. Three days after PCI, echocardiography revealed VSR, and the patient underwent emergency VSR repair with two separate patches and BioGlue applied to the suture line between them. Before weaning from CPB, we implanted Impella 5.5 in the LV and added venoarterial extracorporeal membrane oxygenation (VA-ECMO) support for right heart failure. The postoperative echocardiography revealed no residual shunt.

CONCLUSIONS

Patients undergoing emergency surgery for mechanical complications of AMI may find Impella 5.5 to be an effective tool for LV unloading. The use of VA-ECMO in conjunction with Impella may be an effective strategy for managing VSR associated with concurrent right-sided heart failure.

Alterations in Coronary Blood Flow and the Risk of Left Ventricular Distension in Venoarterial Extracorporeal Membrane Oxygenation

Previous theoretical studies have suggested that veno-arterial extracorporeal membrane oxygenation (VA-ECMO) ought to consistently result in markedly increased left ventricular (LV) intracavitary pressures and volumes because of increased LV afterload. However, this phenomenon of LV distension does not universally occur and occurs only in a minority of cases. We sought to explain this discrepancy by considering the potential implications of VA-ECMO support on coronary blood flow and consequently improved LV contractility (the "Gregg" effect), in addition to the effects of VA-ECMO support upon LV loading conditions, in a lumped parameter-based theoretical circulatory model. We found that LV systolic dysfunction resulted in reduced coronary blood flow; VA-ECMO support augmented coronary blood flow proportionally to the circuit flow rate. On VA-ECMO support, a weak or absent Gregg effect resulted in increased LV end-diastolic pressures and volumes and increased end-systolic volume with decreased LV ejection fraction (LVEF), consistent with LV distension. In contrast, a more robust Gregg effect resulted in unaffected and/or even reduced LV end-diastolic pressure and volume, end-systolic volume, and unaffected or even increased LVEF. Left ventricular contractility augmentation proportional to coronary blood flow increased by VA-ECMO support may be an important contributory mechanism underlying why LV distension is observed only in a minority of cases.

The Use of Cardioprotective Devices and Strategies in Patients Undergoing Percutaneous Procedures and Cardiac Surgery

In the United States, about one million people are seen to visit the operating theater for cardiac surgery annually. However, nearly half of these visits result in complications such as renal, neurological, and cardiac injury of varying degrees. Historically, many mechanisms and approaches have been explored in attempts to reduce injuries associated with cardiac surgery and percutaneous procedures. Devices such as cardioplegia, mechanical circulatory support, and other methods have shown promising results in managing and preventing life-threatening cardiac-surgery-related outcomes such as heart failure and cardiogenic shock. Comparably, cardioprotective devices such as TandemHeart, Impella family devices, and venoarterial extracorporeal membrane oxygenation (VA-ECMO) have also been proven to show significant cardioprotection through mechanical support. However, their use as interventional agents in the prevention of hemodynamic changes due to cardiac surgery or percutaneous interventions has been correlated with adverse effects. This can lead to a rebound increased risk of mortality in high-risk patients who undergo cardiac surgery. Further research is necessary to delineate and stratify patients into appropriate cardioprotective device groups. Furthermore, the use of one device over another in terms of efficacy remains controversial and further research is necessary to assess device potential in different settings. Clinical research is also needed regarding novel strategies and targets, such as transcutaneous vagus stimulation and supersaturated oxygen therapy, aimed at reducing mortality among high-risk cardiac surgery patients. This review explores the recent advances regarding the use of cardioprotective devices in patients undergoing percutaneous procedures and cardiac surgery.

Noninvasive neurological monitoring to enhance pLVAD-assisted ventricular tachycardia ablation - a Mini review

For critically ill patients, hemodynamic fluctuations can be life-threatening; this is particularly true for patients experiencing cardiac comorbidities. Patients may suffer from problems with heart contractility and rate, vascular tone, and intravascular volume, resulting in hemodynamic instability. Unsurprisingly, hemodynamic support provides a crucial and specific benefit during percutaneous ablation of ventricular tachycardia (VT). Mapping, understanding, and treating the arrhythmia during sustained VT without hemodynamic support is often infeasible due to patient hemodynamic collapse. Substrate mapping in sinus rhythm can be successful for VT ablation, but there are limitations to this approach. Patients with nonischemic cardiomyopathy may present for ablation without exhibiting useful endocardial and/or epicardial substrate-based ablation targets, either due to diffuse extent or a lack of identifiable substrate. This leaves activation mapping during ongoing VT as the only viable diagnostic strategy. By enhancing cardiac output, percutaneous left ventricular assist devices (pLVAD) may facilitate conditions for mapping that would otherwise be incompatible with survival. However, the optimal mean arterial pressure to maintain end-organ perfusion in presence of nonpulsatile flow remains unknown. Near infrared oxygenation monitoring during pLVAD support provides assessment of critical end-organ perfusion during VT, enabling successful mapping and ablation with the continual assurance of adequate brain oxygenation. This focused review provides practical use case scenarios for such an approach, which aims to allow mapping and ablation of ongoing VT while drastically reducing the risk of ischemic brain injury.

Clinical expert consensus document on the use of percutaneous left ventricular assist devices during complex high-risk PCI in India using a standardised algorithm

Over the past decade, percutaneous left ventricular assist devices (pLVAD), such as the Impella microaxial flow pump (Abiomed), have been increasingly used to provide haemodynamic support during complex and high-risk revascularisation procedures to reduce the risk of intraprocedural haemodynamic compromise and to facilitate complete and optimal revascularisation. A global consensus on patient selection for the use of pLVADs, however, is currently lacking. Access to these devices is different across the world, thus, individual health care environments need to create and refine patient selection paradigms to optimise the use of these devices. The Impella pLVAD has recently been introduced in India and is being used in several centres in the management of high-risk percutaneous coronary intervention (PCI) and cardiogenic shock. With this increasing utilisation, there is a need for a standardised evaluation protocol to guide Impella use that factors in the unique economic and infrastructural characteristics of India's health care system to ensure that the needs of patients are optimally managed. In this consensus document, we present an algorithm to guide Impella use in Indian patients: to establish a standardised patient selection and usage paradigm that will allow both optimal patient outcomes and ongoing data collection.

Echocardiography for extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) provides advanced cardiopulmonary life support for patients in cardiac and/or respiratory failure. Echocardiography provides essential diagnostic and anatomic information prior to ECMO initiation, allows for safe and efficient ECMO cannula positioning, guides optimization of flow, provides a modality for rapid troubleshooting and patient evaluation, and facilitates decision-making for eventual weaning of ECMO support. Currently, guidelines for echocardiographic assessment in this clinical context are lacking. In this review, we provide an overview of echocardiographic considerations for advanced imagers involved in the care of these complex patients. We focus predominately on new cannulas and complex cannulation techniques, including a special focus on double lumen cannulas and a section discussing indirect left ventricular venting. Echocardiography is tremendously valuable in providing optimal care in these challenging clinical situations. It is imperative for imaging physicians to understand the pertinent anatomic considerations, the often complicated physiological and hemodynamic context, and the limitations of the imaging modality.

Pulmonary artery catheterization in acute myocardial infarction complicated by cardiogenic shock: A review of contemporary literature

Acute myocardial infarction (AMI) with left ventricular (LV) dysfunction patients, the most common cause of cardiogenic shock (CS), have acutely deteriorating hemodynamic status. The frequent use of vasopressor and inotropic pharmacologic interventions along with mechanical circulatory support (MCS) in these patients necessitates invasive hemodynamic monitoring. After the pivotal Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness trial failed to show a significant improvement in clinical outcomes in shock patients managed with a pulmonary artery catheter (PAC), the use of PAC has become less popular in clinical practice. In this review, we summarize currently available literature to summarize the indications, clinical relevance, and recommendations for use of PAC in the setting of AMI-CS.

Intra-aortic balloon pump for acute-on-chronic heart failure complicated by cardiogenic shock

The Intra-aortic balloon pump (IABP) is widely implanted as temporary mechanical circulatory support for cardiogenic shock (CS). However, its use is declining following the results of the IABP-SHOCK II trial, which failed to show a clinical benefit of IABP in acute coronary syndrome (ACS) related CS. Acute-on-chronic heart failure has become an increasingly recognized, distinct etiology of CS (HF-CS). The pathophysiology of HF-CS differs from ACS-CS, as it typically represents the progression from a state of congestion (with relatively preserved cardiac output) to a low output state with hypoperfusion. The IABP is a "volume displacement pump" that promotes forward flow from a high-capacitance reservoir to low-capacitance vessels, improving peripheral perfusion and decreasing left ventricular afterload in the setting of high filling pressures. The IABP can improve ventricular-vascular coupling and, therefore, myocardial energetics. Additionally, many HF-CS patients are candidates for cardiac replacement therapies (left ventricular assist device or heart transplantation), and, therefore, may benefit from a "bridge" strategy that stabilizes the hemodynamics and end-organ function in preparation for more durable therapies. Notably, the new United Network for Organ Sharing donor heart allocation system has recently prioritized patients on IABP support. This review describes the role of IABP for the treatment of HF-CS. It also briefly discusses new strategies for vascular access as well as a fully implantable versions for a longer duration of support.

The role of mechanical support devices during percutaneous coronary intervention

The practice of interventional cardiology has changed dramatically over the last four decades since Andreas Gruentzig carried out the first balloon angioplasty. The obvious technological improvements in stent design and interventional techniques have facilitated the routine treatment of a higher risk cohort of patients, including those with complex coronary artery disease and poor left ventricular function, and more often in the setting of cardiogenic shock (CS) complicating acute myocardial infarction (AMI). The use of mechanical cardiac support (MCS) in these settings has been the subject of intense interest, particularly over the past decade . A number of commercially available devices now add to the interventional cardiologist’s armamentarium when faced with the critically unwell or high-risk patient in the cardiac catheter laboratory. The theoretical advantage of such devices in these settings is clear- an increase in cardiac output and hence mean arterial pressure, with variable effects on coronary blood flow. In doing so, they have the potential to prevent the downward cascade of ischaemia and hypoperfusion, but there is a paucity of evidence to support their routine use in any patient subset, even those presenting with cardiogenic shock. This review will discuss the use and haemodynamic effect of MCS devices during percutaneous coronary intervention (PCI), and also examine the clinical evidence for their use in patients with cardiogenic shock, and those undergoing ‘high risk’ PCI

Outcome of patients with non-ischaemic cardiogenic shock supported by percutaneous left ventricular assist device

Aims

Percutaneous left ventricular assist devices (pVADs) are used to haemodynamically stabilize patients with cardiogenic shock (CS) caused by acute myocardial infarction (AMI). One out of every two patients has a non‐ischaemic cause of CS, and these patients differ profoundly from patients with AMI‐related CS. We assessed the usefulness of pVAD support for patients with non‐ischaemic CS.

Methods and results

We analysed 106 patients with CS and Impella® support between 2015 and 2018. CS was non‐ischaemic in 36 patients and AMI‐related in 70 patients. Compared with the AMI group, those in the non‐ischaemic group were significantly younger [median age 62 (50.8, 70.8) years vs. 68 (58.0, 75.5) years, P = 0.007] and had more patients with severely reduced left ventricular function (94% vs. 79%, P = 0.035) and worse glomerular filtration rate [45 (27, 57) mL/min vs. 60 (44, 78) mL/min]. Propensity score matching yielded 31 patients with non‐ischaemic CS and 31 patients with AMI‐related CS, without a difference in baseline laboratory values or comorbidities. In both groups, pVAD support was performed along with haemodynamic stabilization, reduction of catecholamines and normalization of lactate levels. In 7 days, systolic blood pressure increased from 91 (80, 101) mmHg at baseline to 100 (100, 120) mmHg in the non‐ischaemic CS group (P = 0.001) and 89 (80, 100) mmHg at baseline to 112 (100, 128) mmHg in the AMI‐related CS group (P = 0.001). Moreover, in 7 days, the need of catecholamines (calculated as vasoactive‐inotropic score) decreased from 32.0 (11.1, 47.0) at baseline to 5.3 (0, 16.1) in the non‐ischaemic group (P = 0.001) and from 35.2 (18.11, 67.0) to zero (0, 0) in the AMI‐related CS group (P = 0.001). Lactate level decreased from 3.8 (2.8, 5.9) mmol/L at baseline to 1.0 (0.8, 2.1) mmol/L (P = 0.001) in the non‐ischaemic CS group and from 3.8 (2.6, 6.5) mmol/L to 1.2 (1.0, 2.0) mmol/L in the AMI‐related group (P = 0.001).

In the non‐ischaemic CS group, eight patients (25.8%) were upgraded to veno‐arterial extracorporeal membrane oxygenation (VA‐ECMO) or long‐term mechanical circulatory support. Two of these upgraded patients received heart transplantation. In the AMI group, eight patients (25.8%) were upgraded to VA‐ECMO or long‐term mechanical circulatory support. Ninety‐day survival did not significantly differ between the groups (non‐ischaemic CS group 48.4%, AMI‐related CS group 45.2%, P = 0.799).

Conclusions

pVAD support is useful for haemodynamic stabilization of patients with non‐ischaemic CS and is valuable as a bridge to patients' recovery or long‐term left ventricular support and heart transplantation.

Invasive left ventricle pressure-volume analysis: overview and practical clinical implications

Ventricular pressure–volume (PV) analysis is the reference method for the study of cardiac mechanics. Advances in calibration algorithms and measuring techniques brought new perspectives for its application in different research and clinical settings. Simultaneous PV measurement in the heart chambers offers unique insights into mechanical cardiac efficiency. Beat to beat invasive PV monitoring can be instrumental in the understanding and management of heart failure, valvular heart disease, and mechanical cardiac support. This review focuses on intra cardiac left ventricular PV analysis principles, interpretation of signals, and potential clinical applications.

Tipless transseptal cannula concept combines improved hemodynamic properties and risk-reduced placement: An in silico proof-of-concept

As a leading cause of death worldwide, heart failure is a serious medical condition in which many critically ill patients require temporary mechanical circulatory support (MCS) as a bridge-to-recovery or bridge-to-decision. In many cases, the TandemHeart system is used to unload the left heart by draining blood from the left atrium (LA) to the femoral artery via a transseptal multistage cannula. However, even though the correct positioning of the cannula is crucial for a safe treatment, the long cannula tip currently used in transseptal cannulas complicates positioning, making the cannula vulnerable to displacement during MCS. To overcome these limitations, we propose the development of a new tipless transseptal cannula with improved hemodynamic properties. We discuss the tipless cannula concept by comparing it to the common multistage cannula concept using computational fluid dynamics simulations and assess the flow field in the LA, the wall shear stresses (WSS), and the pressure loss. Across the two distinct time points of end-systole and end-diastole and two drainage flow rates of 3.5 and 5.0 L/min, we find a more homogeneous inlet flow pattern for the tipless cannula concept, accompanied by a remarkably reduced area of platelet-activating WSS (up to 10-times smaller area compared to the multistage cannula). Moreover, pressure loss is up to 14.5% lower in the tipless cannula concept, confirming overall improved hemodynamic properties of the tipless cannula concept. Finally, a diameter-dependent study reveals that lower WSS and pressure losses can be further reduced by large-lumen designs for any simulation setting. Overall, our results suggest that a tipless cannula concept remedies the crucial disadvantages of a long-tip multistage cannula by reducing the risk of misplacement, and it furthermore promotes optimized hemodynamics. With this successful proof-of-concept, we underscore the potential for and encourage the realization of further experimental investigations regarding the development of a tipless transseptal cannula for MCS.

Sufficient cardiac unloading by Impella 5.0 in left ventricular rupture following mitral valve replacement: a case report

A 72-year-old woman presented with exertional dyspnea. Echocardiography revealed severe mitral valve stenosis; therefore, mitral valve replacement was performed using a bioprosthetic valve. However, left ventricular wall rupture occurred following mitral valve replacement. Under re-cardiac arrest, we found a left ventricular tear under the posterior annulus of the mitral valve. We repaired the left ventricular muscle using a bovine pericardial patch and implanted a bioprosthetic valve again. Postoperatively, we implanted an Impella 5.0 heart pump through the right axillary artery to ensure left ventricular wall unloading. Systemic blood flow depended almost completely on mechanical circulatory assistance until postoperative day 3. After the fourth postoperative day, we started weaning the patient from Impella 5.0. Finally, it was completely discontinued on the sixth postoperative day. After that, the patient's condition was stable, and she was discharged 44 days postoperatively. Impella 5.0 is a potentially beneficial device for left ventricular unloading in patients with left ventricular wall rupture following mitral valve replacement.

Mechanical Circulatory Support in High-Risk Percutaneous Coronary Intervention

The use of mechanical circulatory devices to support high-risk elective percutaneous coronary intervention (PCI) has become more common as the group of patients considered inoperable or high risk for surgical revascularization has grown. Most of the data examining outcomes in high-risk PCI are observational and retrospective. Limited prospective randomized studies have been unable to show improved clinical outcomes with routine mechanical circulatory support (MCS) in patients with a high burden of coronary artery disease and reduced ejection fraction. The role for MCS in high-risk PCI continues to evolve as understanding of the appropriate groups for this therapy evolves.

The "TIDE"-Algorithm for the Weaning of Patients With Cardiogenic Shock and Temporarily Mechanical Left Ventricular Support With Impella Devices. A Cardiovascular Physiology-Based Approach

Objectives: Mechanical circulatory support (MCS) is often required to stabilize therapy-refractory cardiogenic shock patients. Left ventricular (LV) unloading by mechanical ventricular support (MVS) via percutaneous devices, such as with Impella® axial pumps, alone or in combination with extracorporeal life support (ECLS, ECMELLA approach), has emerged as a potential clinical breakthrough in the field. While the weaning from MCS is essentially based on the evaluation of circulatory stability of patients, weaning from MVS holds a higher complexity, being dependent on bi-ventricular function and its adaption to load. As a result of this, weaning from MVS is mostly performed in the absence of established algorithms. MVS via Impella is applied in several cardiogenic shock etiologies, such as acute myocardial infarction (support over days) or acute fulminant myocarditis (prolonged support over weeks, PROPELLA). The time point of weaning from Impella in these cohorts of patients remains unclear. We here propose a novel cardiovascular physiology-based weaning algorithm for MVS.

Methods: The proposed algorithm is based on the experience gathered at our center undergoing an Impella weaning between 2017 and 2020. Before undertaking a weaning process, patients must had been ECMO-free, afebrile, and euvolemic, with hemodynamic stability guaranteed in the absence of any inotropic support. The algorithm consists of 4 steps according to the acronym TIDE: (i) Transthoracic echocardiography under full Impella-unloading; (ii) Impella rate reduction in single 8–24 h-steps according to patients hemodynamics (blood pressure, heart rate, and ScVO₂), including a daily echocardiographic assessment at minimal flow (P2); (iii) Dobutamine stress-echocardiography; (iv) Right heart catheterization at rest and during Exercise-testing via handgrip. We here present clinical and hemodynamic data (including LV conductance data) from paradigmatic weaning protocols of awake patients admitted to our intensive care unit with cardiogenic shock. We discuss the clinical consequences of the TIDE algorithm, leading to either a bridge-to-recovery, or to a bridge-to-permanent LV assist device (LVAD) and/or transplantation. With this protocol we were able to wean 74.2% of the investigated patients successfully. 25.8% showed a permanent weaning failure and became LVAD candidates.

Conclusions: The proposed novel cardiovascular physiology-based weaning algorithm is based on the characterization of the extent and sustainment of LV unloading reached during hospitalization in patients with cardiogenic shock undergoing MVS with Impella in our center. Prospective studies are needed to validate the algorithm.

Myocardial ischemia and coronary disease in heart failure

Heart failure is a complex clinical syndrome and represents the final path of numerous heart diseases. Coronary artery disease is recognized as the primary risk factor for heart failure development, being the main etiological factor in more than 50% of heart failure patients in North America and Europe. Regardless of overt coronary artery disease, myocardial ischemia is a common finding in failing hearts, likely due to structural or functional coronary circulation alterations. Ischemia is a self-propagating process which irreversibly impairs the cardiac function and negatively impacts prognosis. Thus, a better and thorough understanding of myocardial ischemia pathophysiology in heart failure would likely lead to significantly improved outcomes in these patients. This review aims to describe the mechanisms of myocardial ischemia and coronary artery disease in heart failure, focusing on coronary circulation dysfunctions due to increased parietal stress or non-obstructive coronary disease, and discussing the association and management of coronary artery disease in patients with heart failure.

Percutaneous left ventricular assist support is associated with less pulmonary congestion and lower rate of pneumonia in patients with cardiogenic shock

Objectives

The aim of this study was to investigate the impact of acute left ventricular unloading by percutaneous left ventricular assist device on pulmonary congestion and pneumonia in patients with cardiogenic shock (CS).

Methods

In this retrospective study, we analysed patients with CS who received the Impella percutaneous left ventricular assist device (n=50) compared with those who received intra-aortic balloon pump (IABP) support (n=50). Pulmonary congestion was longitudinally assessed while on support by calculating characteristic findings on the chest X-ray using the Halperin score. The rate of pneumonia and early mortality were assessed as a secondary endpoint.

Results

The groups (Impella vs IABP) did not differ in terms of age, Sequential Organ Failure Assessment (SOFA) score, Acute Physiology, Chronic Health Evaluation (APACHE) II score or serum lactate levels. Pulmonary congestion decreased in patient treated with Impella at each time point postimplantation. No change in congestion status was observed in patients supported with IABP. Multivariate analysis indicated Impella support as an independent predictor for pulmonary decongestion (OR 4.06, 95% CI 1.15 to 14.35, p=0.030). The rate of early pneumonia was lower in the Impella group compared with the IABP group (54% vs 74%, p=0.037). Failure of pulmonary decongestion during mechanical circulatory support independently predicted early pneumonia (OR 0.28, 95% CI 0.12 to 0.70, p=0.006).

Conclusion

Pulmonary decongestion may facilitate treatment of pneumonia in patients with CS. Left ventricular unloading by Impella device might support pulmonary decongestion, although a larger prospective trial in this patient population is required.

PulseCath iVAC2L: next-generation pulsatile mechanical circulatory support

Contemporary state of the art percutaneous coronary intervention techniques offer treatment strategies and solutions to an increasing number of patients with heart failure and complex coronary artery disease. Percutaneous mechanical circulatory support is intended to alleviate the mechanical and energetic workload imposed to a failing ventricle by reducing left ventricle pressures and volumes and potentially also increasing coronary blood flow. The PulseCath iVAC2L is a transaortic left ventricular assist device that applies a pneumatic driving system to produce pulsatile forward flow. Herein, the essential aspects regarding iVAC2L are discussed with focus on its mechanisms of action and the available clinical experience.

Mechanical Circulatory Support for Acute Heart Failure Complicated by Cardiogenic Shock

Acute heart failure is a potentially life-threatening condition that can lead to cardiogenic shock, which is associated with hypotension and organ failure. Although there have been many studies on the treatment for cardiogenic shock, early mortality remains high at 40–50%. No new medicines for cardiogenic shock have been developed. Recently, there has been a gradual decline in the use of the intra-aortic balloon pump mainly due to a lack of adequate hemodynamic support. Extracorporeal membrane oxygenation and the percutaneous ventricular assist device have become more widely used in recent years. A thorough understanding of the mechanisms of such mechanical support devices and their hemodynamic effects, components of the devices, implantation technique, management, criteria for indications or contraindications of use, and clinical outcomes as well as multidisciplinary decision making may improve the outcomes in patients experiencing cardiogenic shock.

Utilization of Percutaneous Mechanical Circulatory Support Devices in Cardiogenic Shock Complicating Acute Myocardial Infarction and High-Risk Percutaneous Coronary Interventions

Given the tremendous progress in interventional cardiology over the last decade, a growing number of older patients, who have more comorbidities and more complex coronary artery disease, are being considered for technically challenging and high-risk percutaneous coronary interventions (PCI). The success of performing such complex PCI is increasingly dependent on the availability and improvement of mechanical circulatory support (MCS) devices, which aim to provide hemodynamic support and left ventricular (LV) unloading to enable safe and successful coronary revascularization. MCS as an adjunct to high-risk PCI may, therefore, be an important component for improvement in clinical outcomes. MCS devices in this setting can be used for two main clinical conditions: patients who present with cardiogenic shock complicating acute myocardial infarction (AMI) and those undergoing technically complex and high-risk PCI without having overt cardiogenic shock. The current article reviews the advancement in the use of various devices in both AMI complicated by cardiogenic shock and complex high-risk PCI, highlights the available hemodynamic and clinical data associated with the use of MCS devices, and presents suggestive management strategies focusing on appropriate patient selection and optimal timing and support to potentially increase the clinical benefit from utilizing these devices during PCI in this high-risk group of patients.

Effects of Impella on Coronary Perfusion in Patients With Critical Coronary Artery Stenosis

BACKGROUND

Mechanical circulatory support devices are used to maintain hemodynamic stability during high-risk percutaneous coronary interventions. Little is known on the effects of such devices on coronary hemodynamics in patients with significant coronary stenosis. We sought to investigate whether mechanical circulatory support in the form of Impella (Abiomed Inc, Danvers, MA) can improve coronary hemodynamics in the presence of a critical coronary stenosis.

METHODS AND RESULTS

We examined coronary perfusion pressures and coronary pressure distal to a critical stenosis using a coronary pressure wire in 11 patients (12 coronary lesions) undergoing high-risk percutaneous coronary interventions with the use of mechanical circulatory support. Systemic, ventricular, and coronary hemodynamics were obtained at both minimum and maximum support levels before high-risk percutaneous coronary interventions. All patients had obstructive lesions with angiographically estimated diameter stenosis between 70% and 99% and distal coronary artery pressure to aortic pressure ratios between 0.44 and 0.88. When compared with minimum support, maximum support resulted in a decrease in the left ventricular end-diastolic pressure (27.3±8.6 versus 21.5±5.2 mm Hg; P=0.002) and increases in the mean systemic blood pressure (77.6±13.5 versus 88.2±12.2 mm Hg; P<0.001) and mean distal coronary pressure (51.8±20.2 versus 60.8±18.1 mm Hg; P<0.001). Effective coronary perfusion pressure (mean aortic pressure-left ventricular end-diastolic pressure) significantly increased with maximum support (49.8±15.7 versus 67.2±13.6 mm Hg; P<0.001). Diastolic perfusion pressure (diastolic blood pressure-left ventricular end-diastolic pressure) also significantly increased with maximum support (32.9±13.4 versus 52.0±11.6 mm Hg; P<0.001).

CONCLUSIONS

Mechanical circulatory support with Impella can improve distal coronary pressure and coronary perfusion pressures in the presence of critical coronary stenosis.

Hemodynamic Effects of Mechanical Circulatory Support Devices in Ventricular Septal Defect

Background:

Ventricular septal defect (VSD) is a lethal complication of acute myocardial infarction (AMI) and is often associated with cardiogenic shock. The optimal form of percutaneous mechanical circulatory support (MCS) for AMI-VSD is unknown.

Methods and Results:

We used a previously validated cardiovascular model to simulate AMI-VSD with parameters adjusted to replicate average hemodynamics reported in the literature, including a pulmonary-to-systemic blood flow ratio of 3.0. We then predicted effects of different types of percutaneous MCS (including intra-aortic balloon pumping, Impella, TandemHeart, and extracorporeal membrane oxygenation) on pressures and flows throughout the cardiovascular system. The simulation replicated all major hemodynamic parameters reported in the literature with AMI-VSD. Inotropes and vasopressors worsened left-to-right shunting, whereas vasodilators decreased shunting at the expense of worsening hypotension. All MCS devices increased forward blood flow and arterial pressure but other effects varied among devices. Impella 5.0 provided the greatest degree of pulmonary capillary wedge pressure reductions and decreased left-to-right shunting. Extracorporeal membrane oxygenation worsened pulmonary capillary wedge pressure and shunting, which could be improved by adding Impella or passive left ventricular vent. Pulmonary-to-systemic blood flow ratio could not be reduced below 2.0, and pulmonary flows remained high with all forms of MCS.

Conclusions:

Although no form of percutaneous MCS normalized hemodynamics in AMI-VSD, pulmonary capillary wedge pressure and shunting were worsened by extracorporeal membrane oxygenation and improved by Impella. Accordingly, based on hemodynamics alone, Impella provides the optimal form of support in AMI-VSD. However, other factors, including team experience, device availability, potential for tissue ingestion, and clinical characteristics, need to be considered when choosing a percutaneous MCS device for AMI-VSD.

Beyond Reperfusion: Acute Ventricular Unloading and Cardioprotection During Myocardial Infarction

Heart failure is a major cause of morbidity and mortality around the world, and myocardial infarction is its leading cause. Myocardial infarction destroys viable myocardium, and this dead tissue is replaced by a non-contractile scar that results in impaired cardiac function and a significantly increased likelihood of the patient developing heart failure. Limiting infarct scar size has been the target of pre-clinical and clinical investigations for decades. However, beyond reperfusion, few therapies have translated into the clinic that limit its formation. New approaches are needed. This review will focus on new clinical and pre-clinical data demonstrating that acute ventricular unloading prior to reperfusion by means of percutaneous left ventricular support devices reduces ischemia-reperfusion injury and limits infarct scar size. Emphasis will be given to summarizing our current mechanistic understanding of this new therapeutic approach to treating myocardial infarction.

Percutaneous temporary circulatory support devices and their use as a bridge to decision during acute decompensation of advanced heart failure

Temporary mechanical cardiac support (TMCS) devices intend to restore systemic perfusion and prevent further end-organ damage in patients with refractory cardiogenic shock until the insult is addressed. TMCS has been associated with reductions in hospital costs and in-hospital mortality. We review the four primary TMCS modalities available: intra-aortic balloon pump, TandemHeart, veno-arterial extracorporeal membrane oxygenation, and Impella pump. All have their own implantation technique and hemodynamic profile, and their use may therefore be tailored to the specific patient's needs. The appropriate TMCS may thus help stabilize the patient, enabling the care team to make decisions about durable support or transplantation.

Speckle-Tracking Echocardiographic Strain Analysis Reliably Estimates Degree of Acute LV Unloading During Mechanical LV Support by Impella

Non-invasive means of evaluating appropriate cardiac unloading remain to be established. We hypothesized that myocardial deformation assessed by echocardiographic speckle-tracking strain analysis can reliably estimate the degree of left ventricular (LV) unloading under mechanical circulatory support. A total of 24 Yorkshire pigs underwent Impella-mediated acute LV unloading 1-2 weeks after myocardial infarction (MI). Echocardiographic and invasive pressure-volume measurements were used to evaluate the degree of LV unloading. Pressure-volume analysis before and after LV unloading exhibited a significant decrease in stroke work (3399 ± 1440 to 1244 ± 659 mmHg ml, p < 0.001), suggesting reduced external cardiac work. Both longitudinal strain (- 14.6 ± 4.1% to - 10.6 ± 2.3%, p < 0.001) and circumferential strain (- 18.7 ± 6.1% to - 9.3 ± 3.5%, p < 0.001) decreased after LV unloading, and there were linear relationships between stroke work and echocardiographic longitudinal (r = - 0.61, p < 0.001) as well as circumferential strains (r = - 0.75, p < 0.001). Echocardiographic LV strain analysis offers a non-invasive assessment of LV unloading in subacute MI.

When more is not better-appropriately excluding patients from mechanical circulatory support therapy

Mechanical circulatory support (MCS) devices are continually evolving and are providing greater hemodynamic support. This review was conducted to evaluate the prophylactic use of MCS in hemodynamically stable patients who were awaiting future coronary artery revascularization. A thorough review of published literature was conducted to evaluate for patients and clinical scenarios that are indicated for MCS, including hemodynamically stable and unstable patients awaiting revascularization. Although there have been several studies demonstrating the benefit of MCS use in hemodynamically unstable patients, there was limited trials in patients that were hemodynamically stable. The use of prophylactic MCS was limited to intra-aortic balloon pump (IABP) in "high risk" patients awaiting coronary artery bypass grafting (CABG). This review article was conducted to evaluate for possible prophylactic MCS in patients awaiting revascularization. In hemodynamically stable patients, literature is limited to the use of IABP for "high-risk" patients awaiting CABG. A thorough review of literature suggest that hemodynamically stable patients likely would not benefit from prophylactic placement MCS while awaiting revascularization although further clinical trials are needed to identify the ideal patients and clinical scenarios for the use of MCS.

'Combat' Approach to Cardiogenic Shock

The incidence of cardiogenic shock is rising, patient complexity is increasing and patient survival has plateaued. Mirroring organisational innovations of elite military units, our multidisciplinary medical specialists at the INOVA Heart and Vascular Institute aim to combine the adaptability, agility and cohesion of small teams across our large healthcare system. We advocate for widespread adoption of our 'combat' methodology focused on: increased disease awareness, early multidisciplinary shock team activation, group decision-making, rapid initiation of mechanical circulatory support (as appropriate), haemodynamic-guided management, strict protocol adherence, complete data capture and regular after action reviews, with a goal of ending preventable death from cardiogenic shock.

ECMO in cardiac arrest and cardiogenic shock

Cardiogenic shock is an acute emergency, which is classically managed by medical support with inotropes or vasopressors and frequently requires invasive ventilation. However, both catecholamines and ventilation are associated with a worse prognosis, and many patients deteriorate despite all efforts. Mechanical circulatory support is increasingly considered to allow for recovery or to bridge until making a decision or definite treatment. Of all devices, extracorporeal membrane oxygenation (ECMO) is the most widely used. Here we review features and strategical considerations for the use of ECMO in cardiogenic shock and cardiac arrest.

Mechanical Circulatory Support in Acute Decompensated Heart Failure and Shock

An array of interventional therapeutics is available in the modern era, with uses depending on acute or chronic situations. This article focuses on support in acute decompensated heart failure and cardiogenic shock, including intra-aortic balloon pumps, continuous aortic flow augmentation, and extra-corporeal membrane oxygenation.

Acute mechanical circulatory support for cardiogenic shock: the "door to support" time

Cardiogenic shock (CS) remains a major cause of in-hospital mortality in the setting of acute myocardial infarction. CS begins as a hemodynamic problem with impaired cardiac output leading to reduced systemic perfusion, increased residual volume within the left and right ventricles, and increased cardiac filling pressures. A critical step towards the development of future algorithms is a clear understanding of the treatment objectives for CS. In this review, we introduce the "door to support" time as an emerging target of therapy to improve outcomes associated with CS, define four key treatment objectives in the management of CS, discuss the importance of early hemodynamic assessment and appropriate selection of acute mechanical circulatory support (AMCS) devices for CS, and introduce a classification scheme that identifies subtypes of CS based on cardiac filling pressures.

The role of acute circulatory support in ST-segment elevation myocardial infarction complicated by cardiogenic shock

In the setting of ST-segment elevation myocardial infarction (STEMI) complicated by cardiogenic shock, three primary treatment objectives include providing circulatory support, ventricular unloading, and restoring myocardial perfusion. In addition to primary percutaneous coronary intervention, each of these three objectives can be achieved with appropriate use of an acute mechanical circulatory support (AMCS) pump. Over the past decade, utilization of percutaneously-delivered AMCS devices including the Impella axial-flow catheter, TandemHeart left atrial-to-femoral artery bypass system, and veno-arterial extracorporeal membrane oxygenation (VA-ECMO) has grown exponentially. In this review, we will discuss the hemodynamic impact of each AMCS device and clinical data surrounding their use in the setting of STEMI complicated by cardiogenic shock.

Comparative Hemodynamic Effects of Contemporary Percutaneous Mechanical Circulatory Support Devices in a Porcine Model of Acute Myocardial Infarction

OBJECTIVES

The aim of this study was to directly compare the hemodynamic effects of 2 contemporary percutaneous mechanical circulatory support devices in a porcine model of acute myocardial infarction.

BACKGROUND

Percutaneous support devices offer the ability to unload the ischemic left ventricle, but the comparative hemodynamic effects of contemporary platforms are unclear.

METHODS

Yorkshire swine (mean weight 76 ± 2 kg; n = 7) were instrumented with a left ventricular (LV) pressure-volume (PV) catheter and subjected to a 2-h coronary occlusion. Hemodynamic parameters and PV-derived indexes of LV performance were assessed 30 min after reperfusion and during LV support with Impella CP (ICP) and TandemHeart devices (in randomized order) at comparable flow rates.

RESULTS

Myocardial infarction produced a rightward shift of the PV loop and increased LV end-diastolic pressure (from 9 ± 2 mm Hg to 15 ± 2 mm Hg; p = 0.04). After reperfusion, both devices maintained aortic pressure, shifted the PV loop to the left, and decreased LV end-diastolic pressure (ICP vs. TandemHeart; 11 ± 1 mm Hg vs. 7 ± 4 mm Hg; p = 0.04). However, only TandemHeart elicited significant reductions in native LV stroke volume (from 75 ± 7 ml to 39 ± 7 ml; p < 0.01), dP/dt_max (from 988 ± 77 mm Hg/s to 626 ± 42 mm Hg/s; p < 0.01), stroke work (from 0.70 ± 0.03 J to 0.26 ± 0.05 J; p < 0.01), PV area (from 0.95 ± 0.11 J to 0.47 ± 0.10 J; p < 0.01), and pre-load-recruitable stroke work slope (from 41.7 ± 2.8 J/ml to 30.6 ± 3.9 J/ml; p = 0.05).

CONCLUSIONS

At comparable device flow rates, TandemHeart decreased LV pre-load, native LV stroke volume, and myocardial contractility to a greater degree than ICP. Reductions in load-independent indexes of LV performance indicate favorable effects on myocardial oxygen balance and support further study of TandemHeart in clinical scenarios requiring mechanical support in the setting of acute myocardial ischemia.