The Hemopump in 1997: a clinical, political, and marketing evolution

Temporary Mechanical Circulatory Support after Cardiac Surgery

Postcardiotomy shock in the cardiac surgical patient is a highly morbid condition characterized by profound myocardial impairment and decreased systemic perfusion inadequate to meet end-organ metabolic demand. Postcardiotomy shock is associated with significant morbidity and mortality. Poor outcomes motivate the increased use of mechanical circulatory support (MCS) to restore perfusion in an effort to prevent multiorgan injury and improve patient survival. Despite growing acceptance and adoption of MCS for postcardiotomy shock, criteria for initiation, clinical management, and future areas of clinical investigation remain a topic of ongoing debate. This article seeks to (1) define critical cardiac dysfunction in the patient after cardiotomy, (2) provide an overview of commonly used MCS devices, and (3) summarize the relevant clinical experience for various MCS devices available in the literature, with additional recognition for the role of MCS as a part of a modified approach to the cardiac arrest algorithm in the cardiac surgical patient.

The Evolution of Durable, Implantable Axial-Flow Rotary Blood Pumps

Left ventricular assist devices (LVADs) are increasingly used to treat patients with end-stage heart failure. Implantable LVADs were initially developed in the 1960s and 1970s. Because of technological constraints, early LVADs had limited durability (eg, membrane or valve failure) and poor biocompatibility (eg, driveline infections and high rates of hemolysis caused by high shear rates). As the technology has improved over the past 50 years, contemporary rotary LVADs have become smaller, more durable, and less likely to result in infection. A better understanding of hemodynamics and end-organ perfusion also has driven research into the enhanced functionality of rotary LVADs. This paper reviews from a historical perspective some of the most influential axial-flow rotary blood pumps to date, from benchtop conception to clinical implementation. The history of mechanical circulatory support devices includes improvements related to the mechanical, anatomical, and physiologic aspects of these devices. In addition, areas for further improvement are discussed, as are important future directions-such as the development of miniature and partial-support LVADs, which are less invasive because of their compact size. The ongoing development and optimization of these pumps may increase long-term LVAD use and promote early intervention in the treatment of patients with heart failure.

Cardiogenic Shock and Temporary Mechanical Circulatory Support

Cardiogenic shock is a state of circulatory collapse due to low cardiac output resulting from heart failure. Heart failure in this setting may be due to left, right, or biventricular dysfunction. Acute myocardial infarctions remain the most common cause of cardiogenic shock, although in contemporary patient populations, the increasing prevalence of end-stage heart failure has resulted in a growing population of heart failure cardiogenic shock presentations. Clinicians practicing in the cardiac intensive care unit are challenged with these increasingly complex patients. Such patients often require hemodynamic support to improve end-organ perfusion and reduce mortality. Mechanical devices, collectively known as temporary mechanical circulatory support, provide clinicians with additional tools in our armamentarium to combat the increased mortality associated with cardiogenic shock. In this article, we provide an overview of cardiogenic shock and its phenotypic clinical presentations, in addition to providing a description of temporary mechanical circulatory support devices that are currently utilized in the management of cardiogenic shock.

Future Devices for Percutaneous Mechanical Circulatory Support

Percutaneous mechanical circulatory support options include intra-aortic balloon pump, transvalvular axial flow pumps, left atrial to femoral artery pumping, and oxygenated right atrium to femoral artery circuits. Percutaneous mechanical circulatory support devices providing greater support have not proven superiority over the intra-aortic balloon pump. Novel counterpulsation devices target durability and ambulatory capability and direct unloading of left ventricle (LV) and right ventricle. Device innovations in transvalvular axial pumping include miniaturization of partial-support devices and development of larger self-expanding devices for near-complete LV support. Aortic entrainment pumping is a novel mode of blood displacement with potential benefits beyond reduced LV afterload.

The Impella Device: Historical Background, Clinical Applications and Future Directions

The Impella device is a catheter-based miniaturized ventricular assist device. Using a retrograde femoral artery access, it is placed in the left ventricle across the aortic valve. The device pumps blood from left ventricle into ascending aorta and helps to maintain a systemic circulation at an upper rate between 2.5 and 5.0 L/min. This results in almost immediate and sustained unloading of the left ventricle, while increasing overall systemic cardiac output. The most common indications for using the Impella device are in the treatment of acute myocardial infarction complicated by cardiogenic shock and to facilitate high risk coronary angioplasty. Other indications include the treatment of cardiomyopathy with acute decompensation, postcardiotomy shock, and off-pump coronary bypass surgery. A growing body of observational and registry data suggest a potentially valuable role for the Impella system in reducing the mortality associated with cardiogenic shock. However, there are, as of yet, no randomized controlled trial data supporting this observation.

Temporary Mechanical Circulatory Support in Cardiac Critical Care: A State of the Art Review and Algorithm for Device Selection

With more than 60 years of continuous development and improvement, a variety of temporary mechanical circulatory support (MCS) devices and implantation strategies exist, each with unique advantages and disadvantages. A thorough understanding of each available device is essential for optimizing patient outcomes in a fiscally responsible manner. In this state of the art review we examine the entire range of commonly available peripheral and centrally cannulated temporary MCS devices, including intra-aortic balloon pumps, the Impella (Abiomed, Danvers, MA) family of microaxial pumps, the TandemHeart (CardiacAssist Inc, Pittsburg, PA) pump and percutaneous cannulas, centrally cannulated centrifugal pumps such as the CentriMag (Thoratec Corp, Pleasanton, CA/St Jude Medical, St Paul, MN/Abbott Laboratories, Abbott Park, IL) and Rotaflow (Maquet Holding BV & Co KG, Rastatt Germany), and extracorporeal membrane oxygenation. Several factors need detailed consideration when contemplating MCS in any given patient, mandating a balanced, algorithmic approach for these sick patients. In this review we describe our approach to MCS, and emphasize the need for multidisciplinary input to consider patient-related, logistical, and institutional factors. Evidence is summarized and referenced where available, but because of the lack of high-quality evidence, current best practice is described. Future directions for investigation are discussed, which will better define patient and device selection, and optimize MCS-specific patient care protocols.

Hemodynamic Support: Science and Evaluation of the Assisted Circulation with Percutaneous Assist Devices

Pathophysiologic mechanisms that lead to hemodynamic abnormalities in cardiogenic shock (including hypotension, hypoperfusion, and elevated venous pressures) are reviewed within the framework of pressure-volume analysis. This approach provides the foundation for understanding how different modes of circulatory support impact key these cardiovascular parameters in various clinical settings. Four fundamentally different modes of circulatory support are reviewed, including aortic counterpulsation, left atrial-to-arterial pumping, right atrial-to-arterial pumping, and left ventricular-to-aortic pumping. Each approach has a distinct hemodynamic fingerprint with regard to effects on the ventricular pressure-volume loop and key hemodynamic and metabolic parameters.

Small pumps for ventricular assistance: progress in mechanical circulatory support

Compared with earlier models, current pumps are much smaller, simpler, and more efficient, offering long-term or even permanent support. They fit a wider size range of patients and are less invasive to implant. Because they have few moving parts, they are less susceptible to infection and failure. Additionally, they offer much greater patient comfort, allowing a relatively normal lifestyle. This article focuses on the current state of continuous-flow pumps for both temporary and long-term use in treating acute and chronic heart failure.

Development of "plug and play" TransApical to aorta VAD

Our TransApical to Aorta pump, a simple and minimally invasive left ventricular (LV) assist device, has a flexible, thin-wall conduit connected by six struts to a motor with ball bearings and a turbine extending into the blood path. Pulsatile flow is inherent in the design as the native heart contraction preloads the turbine. In six healthy sheep, the LV apex was exposed by a fifth intercostal left thoracotomy. The pump was inserted from the cardiac apex through the LV cavity into the ascending aorta. Aortic and LV pressure waveforms, pump flow, motor current, and pressure were directly measured. All six cannula pumps were smoothly advanced on the first attempt. Pump implantation was <15 minutes (13.6 +/- 1.8 minutes). Blood flow was 2.8 l/min to 4.4 l/min against 86 +/- 8.9 mm Hg mean arterial blood pressure at maximum flow. LV systemic pressure decreased significantly from 102.5 +/- 5.55 mm Hg to 58.8 +/- 15.5 mm Hg at the fourth hour of pumping (p = 0.042), and diastolic LV pressure decreased from 8.4 +/- 3.7 to 6.1 +/- 2.3 mm Hg (p > 0.05). The pump operated with a current of 0.4 to 0.7 amps and rotation speed of 28,000 to 33,000 rpm. Plasma free hemoglobin was 4 +/- 1.41 mg/dl (range, 2 to 5 mg/dl) at termination. No thrombosis was observed at necropsy.A left ventricular assist device using the transapical to aorta approach is quick, reliable, minimally invasive, and achieves significant LV unloading with minimal blood trauma.

Therapeutic strategies for cardiogenic shock, 2006

Cardiogenic shock, a devastating consequence of acute myocardial infarction, is associated with extremely high mortality. Treatment strategies should focus on prompt reperfusion and hemodynamic support. The primary approach for therapy is emergent angiography and revascularization using percutaneous coronary intervention or coronary artery bypass surgery, with the assistance of intra-aortic balloon pump counterpulsation. Several adjunctive pharmacologic agents, particularly inotropic drugs and vasopressors, are also helpful for hemodynamic support. However, these agents have not been shown to provide a survival benefit, and their use is primarily based on clinical experience. Since our last publication, several important advances have been made in the understanding and treatment of cardiogenic shock. Recent evidence suggests that a systemic inflammatory response, including the upregulation of inducible nitric oxide synthase, complement activation, and an inflammatory cytokine cascade, play a role in the development of cardiogenic shock. Newer therapeutic strategies, including C5 inhibitors and nitric oxide synthase inhibitors, are being combined with traditional strategies, such as inotropic agents, vasopressors, and circulatory assist, to treat cardiogenic shock.

Mechanical Device–Based Methods of Managing and Treating Heart Failure

Despite advances in pharmacological treatments aimed at neurohormonal blockade for heart failure in the setting of left ventricular pump dysfunction, there is still a growing number of patients with advanced symptoms who suffer significant morbidity and mortality. Mechanical stresses and chronic neurohormonal activation conspire to propagate maladaptive ventricular remodeling responsible for the insidious nature of this disease. Recent studies suggest that further pharmacological neurohormonal blockade may not be safe or effective, which has driven development of devices for this patient population. Furthermore, such devices may target fundamental pathophysiological abnormalities that are largely hemodynamic and mechanical in nature that are not addressed by available pharmacological agents. The profound reverse remodeling routinely associated with left ventricular assist device use, reviewed in detail, further validates device-based approaches and should inspire research to find ways to make this recovery more complete and permanent. Accordingly, this review focuses on the multitude of mechanical device–based approaches currently being investigated to manage and treat this population. From devices for monitoring patient status to anticipate congestive heart failure exacerbations and preemptively adjust therapy to devices to support preterminal patients with end-stage disease, it is recognized that these device-based approaches will assume an increasingly important role in treating the growing number of patients with advanced heart failure.

Optimum control of the Hemopump as a left-ventricular assist device

A general framework for designing an optimum control strategy for the Hemopump is described. An objective function was defined that includes four membership functions, each constructed based on the desired values of one of the four members: stroke volume, mean left atrial pressure, aortic diastolic pressure and mean pump rotation speed. The Hemopump was allowed to operate either at a constant speed or at two different speeds during a cardiac cycle. The goal was to maximise the objective function by varying the magnitude and timing of the pump speed. Using a canine circulatory model, it was demonstrated that, in general, different cardiac conditions or different clinical objectives require different operation parameters. For example, when a left ventricle with minor ischaemia was simulated, and the main objective was to increase stoke volume, the objective function was maximised, from a value of 0.877 when the pump was off, to 0.946 when the pump was operated at speed 2 (18 500 revolutions min(-1)). On the other hand, for a severely ischaemic heart, the optimum pump speed became speed 3 (20 000 revolutions min(-1)), which maximized the objective function to 0.943 (from 0.707 when the pump was off). The results also suggest that it is more beneficial to operate the Hemopump at two different speeds during a cardiac cycle (a higher speed during systole and early diastole, and a lower speed during late diastole) than to maintain a constant speed throughout the cardiac cycle.

Successful high-risk coronary angioplasty in a patient with cardiogenic shock under circulatory assist with a 16F axial flow pump

We report the case of a 75-year-old patient who suffered from subacute myocardial infarction and severely impaired left ventricular ejection fraction (EF: 17%). Using a novel 16F left ventricular assist device we performed an angioplasty of the right coronary artery, and of the left anterior descending artery. As a result of the circulatory support the patient recovered from cardiogenic shock within 8 hr. At a pump speed of 45,000 rpm the axial flow pump generated flow rates up to 3.3 l/min. The 16F pump cannula was removed using local compression. The EF was 51% at 30-day follow-up examination.

Therapeutic Strategies for Cardiogenic Shock

Cardiogenic shock is a devastating consequence of acute myocardial infarction; it is associated with an extremely high mortality. Treatment strategies should be focused on prompt reperfusion, as well as hemodynamic support. The optimal approach for therapy is emergent angiography and revascularization using percutaneous coronary intervention or coronary artery bypass surgery, with the assistance of intra-aortic balloon pump counterpulsation. Several adjunctive pharmacologic agents, particularly inotropic drugs and vasopressors, are also helpful for hemodynamic support. However, these agents have not been shown to provide a survival benefit, and their use is primarily based on clinical experience.

Enhanced intra-aortic balloon pump: markedly improved systemic hemodynamics and cardiac function in canines with severe, acute left ventricular failure

Intra-aortic balloon pumps (IABPs) cannot sustain hemodynamics if the left heart is severely injured. An enhanced IABP was evaluated in 6 anesthetized dogs with acute stenosis of the left anterior descending coronary artery, regional left ventricular (LV) stunning, and global LV dysfunction. An IABP balloon was inserted into the descending aorta and an external chamber containing another IABP balloon was connected to the aorta through a catheter inserted into the left subclavian artery. This emulated the enhanced IABP with a conduit from its external chamber passing axially through an internal IABP balloon. Compared to IABP, enhanced IABP improved hemodynamics and LV function in all conditions. During severe LV dysfunction and circulatory failure, IABP failed to augment diastolic aortic pressure or improve coronary and carotid flows. Enhanced IABP augmented diastolic pressure from 32 +/- 3 mm Hg to 87 +/- 2 mm Hg and increased coronary and carotid flows. Enhanced IABP may be a lifesaving device for patients with severe LV failure.

Postoperative coronary revascularization on LVAD support for surgically inaccessible myocardial ischemia

The authors have used the concept of hybrid revascularization to salvage a patient in persistent cardiogenic shock after incomplete emergent surgical revascularization. While the patient was on left ventricular assist device support, a complex angioplasty was done on a surgically inaccessible right coronary artery, with subsequent cardiac recovery.

Mechanical support for postcardiotomy cardiogenic shock

Postcardiotomy cardiogenic shock (PCCS) results in substantial morbidity and mortality. Despite intraaortic balloon pump and inotropic support, some patients with PCCS continue to have a refractory low cardiac output. For these patients, more effective ventricular assistance is imperative to prevent death. Multiple systems are available for the short-term support of patients with PCCS. Regardless of the device employed, only 25% of these patients survive and are discharged home. Two strategies, however, may improve the outcome of PCCS. One is long-term support by an implantable assist device, which can allow optimal ventricular unloading. Unfortunately, not all cardiac surgery centers offer this type of support. Therefore, the other strategy is the creation of postcardiotomy referral centers that offer long-term support or heart transplantation. Such centers would conserve scarce donor organs, maximize the chance of myocardial recovery, and yield expertise applicable not only to device recipients but also to critically ill heart-failure patients who do not need an implantable pump.