Outcomes of a multicenter trial of the Levitronix CentriMag ventricular assist system for short-term circulatory support

Short-term continuous-flow ventricular assist devices

PURPOSE OF REVIEW

To provide a comprehensive update on the current state of short-term, continuous-flow ventricular assist devices (CF-VADs) in the treatment of refractory cardiogenic shock in Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) 1 patients.

RECENT FINDINGS

The mortality rate associated with refractory cardiogenic shock remains markedly elevated, with INTERMACS 1 profile repeatedly demonstrating the worst outcomes. Recent innovations in continuous-flow pump technology have not only contributed to improved outcomes with long-term left ventricular assist device technology, but have also led to the development of various short-term, percutaneous, and surgical CF-VADs. Short-term CF-VADs have several favorable features, but, most notably, they allow the effective temporary stabilization of otherwise refractory cardiogenic shock and serve as a bridge-to-decision therapy.

SUMMARY

Clinical evidence supporting the use of CF-VADs still remains at the level of small case series, but the data appear promising. However, further rigorous clinical investigation is necessary in order to prove the overall clinical efficacy of these devices in refractory cardiogenic shock.

The 'Inextricabilis Syndrome': a case with no solution

We describe a case of a 58-year-old man with cardiogenic shock who underwent triple vessel coronary artery bypass and a left ventricular assist device (LVAD) implantation. His course was complicated by stroke, worsening mitral regurgitation, aortic regurgitation, and multiple cardiac thrombi while on the device. We provide the details of the patient's hospital course, management, and echocardiographic findings. We also discuss the utility of echocardiography before LVAD insertion and its role for continued monitoring after insertion.

LEARNING POINTS

Ventricular assist devices (VADs) are used as bridge to decision, transplant, recovery, or destination therapy in patients with advanced heart failure and cardiogenic shock.VADs improve survival and the quality of life but have significant associated complications.Echocardiography plays an essential role before VAD insertion and for postoperative cardiac monitoring. Information provided by echocardiography is used in device selection, consideration for corrective surgical interventions, and device explantation.

Bridge-to-decision therapy with a continuous-flow external ventricular assist device in refractory cardiogenic shock of various causes

BACKGROUND

Mortality for refractory cardiogenic shock remains high. In this patient cohort, there have been mixed results in mechanical circulatory support device use as a bridge-to-decision therapy. We evaluated a continuous-flow external ventricular assist device (VAD), CentriMag VAD (Thoratec Corp., Pleasanton, CA), in patients with various causes of refractory cardiogenic shock.

METHODS AND RESULTS

This is a retrospective review of adult patients who underwent surgical CentriMag VAD insertion as bridge-to-decision therapy. From January 2007 through June 2012, 143 patients received CentriMag VAD. The cause of refractory cardiogenic shock was failure of medical management in 71 patients, postcardiotomy shock in 37, graft failure post-heart transplantation in 22, and right ventricular failure post-implantable left VAD in 13. Mean age was 52±16 years, and 71% were in INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) profile 1. Among 158 device runs, device configuration was BiVAD in 67%, isolated right VAD in 26%, and isolated left VAD in 8%. Median duration of support was 14 days (interquartile range, 8-26). Survival was 69% at 30 days and 49% at 1 year. The next destination after the CentriMag VAD was myocardial recovery in 30%, device exchange to an implantable VAD in 15%, and heart transplantation in 18%. The failure of medical management and the graft failure post-heart transplantation groups had higher 30-day survival compared with the postcardiotomy shock group. Major bleeding events occurred in 33% and cerebrovascular accidents in 14%. There was no CentriMag pump failure or thrombosis.

CONCLUSIONS

Bridge-to-decision therapy with CentriMag VAD is feasible in a variety of refractory cardiogenic shock settings. Patients with postcardiotomy shock have inferior survival.

Use of a single circuit to provide temporary mechanical respiratory and circulatory support in patients with LV apical thrombus and cardiogenic shock

Introduction:

Techniques to support patients with cardiogenic shock continue to improve. Patients with intracardiac thrombi pose a potential for additional complications. Novel methods of biventricular support are necessary to manage these patients.

Methods:

Two patients with refractory cardiogenic shock and left ventricular apical thrombi underwent mechanical circulatory support (MCS) as a bridge to decision, with a left ventricular assist device (LVAD) and extracorporeal mechanical oxygenation (ECMO). Instead of the conventional LV apical cannulation for LVAD, the left atrium (LA) was cannulated. The LA cannula was then integrated with the ECMO circuit via a ‘Y’ connection to a percutaneous right atrial cannula, enabling optimal drainage of both sides into one circuit through a single CentriMag® pump and ECMO into the aorta.

Results:

The first patient was converted to a durable LVAD and transplanted, while the second patient was explanted, after demonstrating significant LV recovery.

Conclusion:

We demonstrated the use of MCS as a bridge to decision in patients with LV thrombi, utilizing biatrial cannulation with a ‘Y’ connection to drain both right- and left-sided circulation through a single circuit and pump.

A comparison study of haemolysis production in three contemporary centrifugal pumps

One challenge in providing extracorporeal circulation is to supply optimal flow while minimising adverse effects, such as haemolysis. To determine if the recent generation constrained vortex pumps with their inherent design improvements would lead to reduced red cell trauma, we undertook a study comparing three devices. Utilizing a simulated short-term ventricular assist circuit primed with whole human blood, we examined changes in plasma free haemoglobin values over a six-day period. The three pumps investigated were the Maquet Rotaflow, the Levitronix PediVAS and the Medos Deltastream DP3.This study demonstrated that all three pumps produced low levels of haemolysis and are suitable for use in a clinical environment. The Levitronix PediVAS was significantly less haemolytic than either the Rotaflow (p<0.05) or the DP3 (p<0.05). There was no significant difference in plasma free haemoglobin between the Rotaflow and the DP3 (p=0.71).

The Impella device for acute mechanical circulatory support in patients in cardiogenic shock

BACKGROUND

Acute cardiogenic shock is associated with high mortality rates. Mechanical circulatory devices have been increasingly used in this setting for hemodynamic support. The Impella device (Abiomed Inc, Danvers, MA) is a microaxial left ventricular assist device that can be inserted using a less invasive technique. This study was conducted to determine the outcome of patients who have undergone placement of the Impella device for acute cardiogenic shock in our institution.

METHODS

A retrospective record review of 47 patients who underwent placement of the Impella device was performed from January 1, 2006, to December 31, 2011. Records were evaluated for demographics, operative details, and postoperative outcomes. Operative mortality was defined as death within 30 days of the operation.

RESULTS

The patients (33 male) were an average age of 60.23 ± 13 years. The indication for placement of the Impella device included cardiogenic shock in 15 patients (32%) and postcardiotomy cardiogenic shock in 32 (68%). Of the 47 patients, 38 (80%) received the Impella 5.0 and the rest the 2.5 device. Ventricular function recovered in 34 of 47 patients (72%), and the device was removed, with 4 patients (8%) transitioned to long-term ventricular assist devices. The 30-day mortality was 25% (12 of 47 patients). Complications occurred in 14 patients (30%), consisting of device malfunction, high purge pressures, tube fracture, and groin hematoma.

CONCLUSIONS

This is one of the largest series of patients undergoing placement of the Impella device for acute cardiogenic shock. Our outcomes showed improved results compared with historical data. Myocardial recovery was accomplished in most patients. Finally, the 30-day mortality and complication rate was acceptable in these critical patients. These benefits were all achieved with the Impella device in a less invasive method.

Mechanical Support for Heart Failure

Critically ill patients at extremes of physiology may benefit from mechanical support for heart failure and intensive care practitioners should be knowledgeable about these options. In this article we will discuss the mechanical support for critically ill patients in heart failure. Referral to a specialist centre should be considered early for maximal patient benefit.

Percutaneous Assist Devices for Left Ventricular Shock

Percutaneous ventricular assist devices (PVADs) are increasingly being used for hemodynamic support in patients with cardiogenic shock as well as for patients undergoing high-risk cardiovascular procedures. The currently available PVADs for left ventricular shock are reviewed; the evidence for supporting PVAD use is discussed, and the authors' perspective on their unique clinical applications is offered.

Partial mechanical circulatory support in children

Partial mechanical support devices are capable of partially unloading only one ventricle, often the systemic one, in the setting of acute circulatory failure. They are rarely used in the pediatric population, as the mode of circulatory failure in patients with congenital heart disease often involves biventricular or a predominantly right ventricular component. The devices include intra-aortic balloon pumping, Impella, TandemHeart, and CentriMag. They are rarely used as a bridge-to-recovery, but more often as a bridge-to-decision, or bridge-to-conversion to full mechanical support systems, such as extracorporeal membrane oxygenation or ventricular assist devices. Currently, lack of availability of more complete support devices, cost issues, or lack of infrastructure and personnel may still be indications to continue using partial mechanical support as opposed to more complete forms of biventricular circulatory support.

Left ventricular outflow tract occluding thrombus after biventricular mechanical circulatory support as a bridge to recovery

The role of mechanical circulatory support for cardiopulmonary failure is expanding. Anticoagulation in the setting of static blood, hypercoagulable states, extracorporeal circuits, and surgery presents an intricate and delicate balance. We present a patient with large, biventricular thrombi during and succeeding biventricular mechanical support. Management of the thrombi and device selection in this patient are discussed.

Preoperative Evaluation and Perioperative Management of Right Ventricular Failure After Left Ventricular Assist Device Implantation

Right ventricular (RV) failure continues to be a major cause of morbidity and mortality after left ventricular assist device (LVAD) implantation. Preoperative evaluation of RV function with a variety of clinical, laboratory, echocardiographic, and hemodynamic variables is essential to ensure appropriate patient selection for LVAD therapy but remains imperfect. Therefore, clinicians involved in the care of these patients need to be prepared to manage RV failure after LVAD placement. Perioperative management of RV failure after LVAD implantation requires minimization of intraoperative RV ischemia, maintenance of appropriate filling pressure, supportive therapy with pulmonary vasodilators and inotropes, and surgical interventions such as RV assist devices in select cases. This article reviews the incidence of RV failure with LVAD implantation, preoperative predictors of RV failure, and perioperative management strategies.

New generation extracorporeal membrane oxygenation with MedTech Mag-Lev, a single-use, magnetically levitated, centrifugal blood pump: preclinical evaluation in calves

We have evaluated the feasibility of a newly developed single-use, magnetically levitated centrifugal blood pump, MedTech Mag-Lev, in a 3-week extracorporeal membrane oxygenation (ECMO) study in calves against a Medtronic Bio-Pump BPX-80. A heparin- and silicone-coated polypropylene membrane oxygenator MERA NHP Excelung NSH-R was employed as an oxygenator. Six healthy male Holstein calves with body weights of about 100 kg were divided into two groups, four in the MedTech group and two in the Bio-Pump group. Under general anesthesia, the blood pump and oxygenator were inserted extracorporeally between the main pulmonary artery and the descending aorta via a fifth left thoracotomy. Postoperatively, both the pump and oxygen flow rates were controlled at 3 L/min. Heparin was continuously infused to maintain the activated clotting time at 200-240 s. All the MedTech ECMO calves completed the study duration. However, the Bio-Pump ECMO calves were terminated on postoperative days 7 and 10 because of severe hemolysis and thrombus formation. At the start of the MedTech ECMO, the pressure drop across the oxygenator was about 25 mm Hg with the pump operated at 2800 rpm and delivering 3 L/min flow. The PO2 of the oxygenator outlet was higher than 400 mm Hg with the PCO2 below 45 mm Hg. Hemolysis and thrombus were not seen in the MedTech ECMO circuits (plasma-free hemoglobin [PFH] < 5 mg/dL), while severe hemolysis (PFH > 20 mg/dL) and large thrombus were observed in the Bio-Pump ECMO circuits. Plasma leakage from the oxygenator did not occur in any ECMO circuits. Three-week cardiopulmonary support was performed successfully with the MedTech ECMO without circuit exchanges. The MedTech Mag-Lev could help extend the durability of ECMO circuits by the improved biocompatible performances.

Heart rescue: the role of mechanical circulatory support in the management of severe refractory cardiogenic shock

PURPOSE OF REVIEW

Cardiogenic shock is present in 3.5% of patients presenting with acute decompensated heart failure. Despite advances in therapy, mortality remains high, approaching 70% in some settings. Recent management strategies have incorporated the use of mechanical circulatory support (MCS), which has been associated with better survival in nonrandomized trials. MCS is increasingly used in the acute setting and has become an important treatment modality for cardiogenic shock.

RECENT FINDINGS

Small studies have demonstrated improved survival when MCS is instituted early in the management of cardiogenic shock. Numerous case reports support the benefit of MCS for various causes of cardiogenic shock, including acute myocardial infarction, cardiac allograft rejection, myocarditis and refractory arrhythmias.

SUMMARY

This article will review novel strategies in the management of cardiogenic shock including percutaneous MCS (intra-aortic balloon pump, Impella, TandemHeart, venoarterial extracorporeal membrane oxygenation) and surgically implanted devices (CentriMag) that are used for short-term management. We will review the mechanisms involved in cardiogenic shock and discuss management and device selection strategies.

Mechanical circulatory support for cardiogenic shock

Cardiogenic shock (CS) is a syndrome of progressive depression of myocardial function with systemic hypoperfusion. It occurs due to various aetiologies such as acute myocardial infarction, myocarditis, acute decompensated heart failure and postcardiotomy. Cardiogenic shock carries poor prognosis, and medical therapy alone is not effective. Mechanical circulatory support is required to unload the ventricles, decrease the myocardial demand, prevent further injury, improve the coronary perfusion, stabilise the haemodynamics and maintain the end-organ perfusion before definitive interventions such as coronary reperfusion can take place. Currently, there are several methods of mechanical circulatory support. These include extracorporeal life support, paracorporeal or extracorporeal ventricular-assist devices, percutaneous ventricular assist devices, intra-aortic balloon counterpulsation and total artificial heart. In this review, we discuss the role of each of these circulatory support devices in the management of acute cardiac failure.

The future of heart transplantation

The field of heart transplantation has seen significant progress in the past 40 years. However, the breakthroughs in long-term outcome have seen stagnation in the past decade. Through advances in genomics and transcriptomics, there is hope that an era of personalized transplant therapy lies in the future. To see where heart transplantation truly fits into the long term, searching for and understanding the alternative approaches for heart failure therapy is both important and inevitable. The application of mechanical circulatory support has contributed to the largest advancement in treatment of end stage heart failure. It has already been approved for destination therapy of heart failure, and greater portability and ease of use of the device will be the future trend. Although it is still not prime time for stem cell therapy, clinical experiences have already suggested its potential therapeutic effects. And finally, whole organ engineering is on the horizon as new techniques have opened the way for this to proceed. In the end, progress on alternative therapies largely depends on our deeper understanding of the mechanisms of heart failure and how to prevent it.

Myocardial recovery with left ventricular assist devices

OPINION STATEMENT

Advanced heart failure (HF) is a condition that is rarely thought of in terms of cure. Left ventricular assist devices (LVADs), like no therapy before them, provide complete decongestion of the left ventricle, with resulting favorable changes at all levels, from reversal of hypertrophy of cardiomyocytes to recovery of normal geometry and function of the ventricles. Although not a frequent phenomenon at most institutions, LV recovery is achieved in 20-25 % of LVAD recipients in some programs. Patients with good chances for recovery are usually young, with nonischemic cardiomyopathy and short duration of HF symptoms. After LVAD removal, patients with recovered function remain asymptomatic for years. To reach this level of sustainable restoration of cardiac function, several steps need to be taken: 1) myocardial recovery has to be recognized as a therapeutic goal, especially in patients with nonischemic cardiomyopathy; 2) HF medications have to be restarted and aggressively uptitrated after LVAD implantation; 3) regular monitoring for signs of myocardial recovery (eg, echocardiography or hemodynamics) should become a standard practice in LVAD centers; and 4) weaning protocols should be discussed and accepted at each LVAD program. While some protocols involve extensive several-day testing both at rest and with exercise, others are mostly guided by echocardiographic evaluation.

Temporary percutaneous right ventricular support using a centrifugal pump in patients with postoperative acute refractory right ventricular failure after left ventricular assist device implantation

OBJECTIVE

Acute right ventricular (RV) failure is a life-threatening condition with a poor prognosis, and sometimes the use of mechanical circulatory support is inevitable. In this article, we describe our experience using a centrifugal pump as a temporary percutaneous right ventricular assist device (RVAD) in patients with postoperative acute refractory RV failure after left ventricular assist device (LVAD) implantation.

METHODS

We retrospectively reviewed eight consecutive patients with acute RV failure who underwent temporary percutaneous RVAD implantation using a centrifugal pump after LVAD implantation between April 2008 and February 2011. A Dacron graft was attached to the main pulmonary artery and passed through a subxiphoid exit, where the outflow cannula was inserted. The inflow cannula was percutaneously cannulated using Seldinger's technique in the femoral vein. The chest was definitely closed. The technique allowed bedside removal, avoiding chest re-opening.

RESULTS

The median patient age was 52 years (range: 41-58). The median duration of support was 14 days (range: 12-14). RV systolic function improved; central venous pressure and mean pulmonary artery pressure decreased significantly after RVAD support. In three patients, an oxygenator was integrated into the RVAD due to impaired pulmonary function. Six patients were successfully weaned. Five patients survived to hospital discharge. Technical problems or serious complications concerning decannulation were not observed.

CONCLUSION

This report suggests that implantation of temporary percutaneous RVAD using a centrifugal pump is a safe alternative in the treatment of postoperative acute refractory RV failure. Ease of device implantation, weaning, explantation, and limited number of complications justify a liberal use.

Mechanical assistance of the circulation during cardiogenic shock

PURPOSE OF REVIEW

Cardiogenic shock still has a grave prognosis. We present the recent advances in mechanical circulatory support (MCS) for the treatment of refractory cardiogenic shock.

RECENT FINDINGS

The contraindications for short-term MCS in rapid-onset cardiogenic shock are becoming fewer and the threshold for its application has been progressively lowered. Short-term MCS is increasingly used in refractory cardiac arrest and will be probably integrated as the last means in the advanced cardiopulmonary resuscitation algorithm (provided there is experienced team and technical support). Improved device technology has contributed to improved results of long-term MCS. Emergent application of long-term MCS in patients with critical cardiogenic shock after a long history of progressively deteriorating end-stage chronic heart failure should be interpreted as delayed application associated with increased mortality.

SUMMARY

Although MCS can be life saving in cardiogenic shock, the results are still suboptimal. Mortality is associated with the critical presupport state and the adverse events during MCS. Early initiation of support that meets the patient's requirements, potent support in the early phase, adverse event prevention, global combined management (surgical, interventional, medical), balanced support duration, bridging to further therapeutic modalities including heart transplantation or longer-term support, and advanced technology could offer improved results.