REVIEW URRENT C OPINION

Short-term continuous-flow ventricular assist devices Hiroo Takayama a, Koji Takeda a, Darshan Doshi b, and Ulrich P. Jorde b

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. Keywords cardiogenic shock, CentriMag, Impella, short-term VAD, TandemHeart

INTRODUCTION Nearly 15 years after the seminal SHould we emergently revascularize Occluded Coronaries for cardiogenic shock (SHOCK) trial established the benefits of early revascularization in cardiogenic shock [1], the overall in-hospital mortality rate for cardiogenic shock because of acute myocardial infarction (AMI) remains nearly unchanged at 50% and approaches nearly 100% in patients with the worst hemodynamics [2–4]. Furthermore, the recent Intraaortic balloon counterpulsation in AMI complicated by cardiogenic shock: design and rationale of the Intraaortic Balloon Pump in Cardiogenic Shock II (IABP-SHOCK II) trial suggested that the only routinely employed form of mechanical circulatory support (MCS), the intra-aortic balloon pump (IABP), confers no benefit in AMI and cardiogenic shock [5 ]. Clearly, more powerful MCS is needed in order to improve the outcomes [6]. The progress of MCS is highlighted by the implementation of implantable continuous-flow left ventricular assist device (LVAD) therapy in the management of patients with advanced chronic heart &

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failure. As the technology associated with continuous-flow LVADs continues to evolve, it may eventually contribute to the care of patients in the earlier, more acute stages of heart failure. However, at present, the use of devices designed to support long-term chronic heart failure in acutely decompensating patients does not appear promising [7]. Some of the characteristics of an implantable LVAD, such as inability to simultaneously assist the right ventricle (RV), the need for a complex surgical implant procedure, and high cost, make it an unfavorable device of choice for cardiogenic shock.

a

Division of Cardiothoracic Surgery and bDivision of Cardiology, New York Presbyterian Hospital, Columbia University Medical Center, New York, New York, USA Correspondence to Ulrich P. Jorde, MD, Medical Director, MCSD Programs, New York Presbyterian Hospital, Columbia University Medical Center, 622 West 168th Street, PH9-977, New York, NY 10032, USA. Tel: +1 212 305 0167; fax: +1 212 305 7139; e-mail: [email protected] edu Curr Opin Cardiol 2014, 29:266–274 DOI:10.1097/HCO.0000000000000060 Volume 29  Number 3  May 2014

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AV, aortic valve; AxA, axillary artery; FA, femoral artery; IABP, intra-aortic balloon pump; LA, left atrium; LV, left ventricle; pVAD, percutaneous ventricular assist device; RA, right atrium; RV, right ventricle; VA-ECMO, venoarterial extracorporeal membrane oxygenation.

LV distension High High Yes Yes No 15–30 Easy Inflow: 19–25 Fr in RA; outflow: 15–23 Fr in FA VA-ECMO

3–6

NA

No Very high

NA Yes

No Yes

No Maybe

Yes 120

NA Less difficult

Surgery Any surgical cannula in any cardiac chamber CentriMag surgical VAD

5 14 Fr sheath in FA Reitan pVAD

10

Relatively low Relatively low Maybe Near future Yes 15–30 Less difficult 12–21 Fr pump across AV, 11 Fr catheter in FA or AxA Impella pVAD

2.5–5

Low Low

High Yes

Yes No

Yes Maybe

Maybe 10

30–60 Difficult

Easy 0.5

Inflow: 21 Fr in LA; Outflow: 15–17 Fr in FA

3–4

7–9 Fr in descending aorta

Bed rest RV support LV unload Insertion time (min) Insertion technique Flow (l/min) Size, location

Currently available pVADs include the TandemHeart system (CardiacAssist Inc., Pittsburgh, Pennsylvania, USA) and the Impella system (Abiomed Inc., Pittsburgh, Pennsylvania, USA) (Table 1). Other pVADs under active investigation include the Reitan catheter pump (CardioBridge GmbH; Hechingen, Germany) and the Percutaneous Heart Pump (Thoratec, Pleasanton, California, USA). These pVADs are an appealing and promising therapeutic approach for cardiogenic shock, and have become increasingly popular. They can be inserted quickly, are less invasive for unstable patients, and may decrease morbidity compared with surgical VADs. However, in a meta-analysis of three randomized studies comparing pVAD (two studies with TandemHeart and one study with Impella 2.5) with IABP, pVAD did not improve 30-day mortality (relative risk 1.06, 95% confidence interval 0.68–1.66) [13].

Table 1. Characteristics of short-term mechanical circulatory support devices

PERCUTANEOUS SHORT-TERM VENTRICULAR ASSIST DEVICE

Bleeding risk

 Multidisciplinary approach is essential in order to improve the overall care of cardiogenic shock with MCS.

TandemHeart pVAD

 Rigorous clinical trials are needed to establish the role of short-term VADs in cardiogenic shock therapy.

IABP

Limb ischemia risk

 Various short-term, percutaneous, and surgical CF-VADs are available and in development.

High

Other

 Cardiogenic shock still continues to have high mortality.

Continuous-flow technology itself, however, has significantly advanced the use and popularity of MCS. In comparison with the first generation of short-term VADs, such as ABIOMED BVS5000, which was built on the basis of pulsatile flow pump technology, current generation short-term VADs consist exclusively of continuous-flow pumps. These pumps have improved durability, biocompatibility, and ease of maintenance. Furthermore, continuous-flow pump technology has allowed miniaturization of the actual pump body, which has been translated into some forms of percutaneous VADs (pVADs). Supported by these advancements, short-term VADs have become an accepted treatment option in cardiogenic shock [8–12]. The purpose of this review is to provide a comprehensive update on the current state of short-term continuous-flow ventricular assist devices (CF-VADs) as a treatment modality for patients in refractory cardiogenic shock.

Hemolysis

KEY POINTS

Surgical risks

Continuous-flow ventricular assist devices Takayama et al.

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Cardiac failure

This disappointing result may be a reflection of the limitations of studied pVADs, such as limited flow capacity, limited support period, need for bed rest, and need for an experienced interventionalist and cardiac catheterization laboratory. With the introduction of newer devices and technology, pVADs may eventually emerge as the standard of care in the immediate treatment of AMI and cardiogenic shock.

The TandemHeart percutaneous ventricular assist device The TandemHeart is an extracorporeal continuousflow pump that can generate up to 4 l/min of flow at 7500g. The LVAD system consists of a 21-Fr inflow cannula inserted from the femoral vein into the left atrium through a transseptal puncture, a 15-Fr or 17-Fr outflow cannula inserted into the femoral artery, and an extracorporeal pump (Fig. 1). A special cannula and an experienced pair of hands are necessary for the transseptal approach. Positioning the cannulas in the main pulmonary artery and the right atrium allows use of the device for a right VAD configuration. The hemodynamic effects of percutaneous LVAD support using the TandemHeart has been investigated by Thiele et al. [14] in 18 patients with cardiogenic shock because of myocardial infarction. Before support, cardiac index was 1.7  0.3 l/min/m2 Impella 2.5

and improved to 2.4  0.6 l/min/m2, and mean blood pressure increased from 63  8 to 80  9 mmHg (all P < 0.001). Pulmonary capillary wedge pressure, central venous pressure, and pulmonary artery pressure were reduced from 21  4, 13  4, and 31  8 to 14  4, 9  3, and 23  6 mmHg (all P < 0.001), respectively. In another study, patients with AMI and cardiogenic shock were randomized to either IABP (n ¼ 20) or TandemHeart LVAD (n ¼ 21) [15]. Cardiac power index, as well as other hemodynamic and metabolic variables, improved more substantially with TandemHeart LVAD support. However, complications, such as severe bleeding and limb ischemia, were more frequent with the pVAD. Thirty-day mortality was not significantly different (IABP 45% vs. pVAD 43%). More recently, Kar et al. [16] reported a total of 117 patients with cardiogenic shock supported with this device. Forty-eight percent (n ¼ 56) were undergoing active cardiopulmonary resuscitation immediately before or at the time of insertion. The average duration of support was 5.8  4.75 days. After implantation, a sizeable reduction of pulmonary capillary wedge pressure from 31.53  10.2 to 17.29  10.82 mm Hg was seen (P < 0.001), demonstrating the ability of the TandemHeart to adequately decompress the left ventricle (LV) from the left atrium. Additionally, the cardiac index, systolic blood pressure, mixed venous oxygen TandemHeart

FIGURE 1. Impella 2.5 and TandemHeart. The transvalvular, axial flow Impella 2.5 is shown on the left, whereas the left atrial-to-femoral artery centrifugal TandemHeart is shown on the right. Reproduced by courtesy of Abiomed, Inc. (for photograph of Impella 2.5) and CardiacAssist Inc. (CAI; for photograph of TandemHeart). 268

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Continuous-flow ventricular assist devices Takayama et al.

saturation, urine output, lactic acid level, and creatinine level all improved. The 30-day and 6-month mortality rates were 40.2% and 45.3%, respectively. However, widespread use seems to still be limited because of the technical complexity of a transseptal puncture in the emergent or urgent situation, as well as occasional dislodgement of the left atrial cannula back into the right atrium.

Impella left ventricular assist device system The Impella LVAD system is the clinical translation of miniaturized, rotary pump technology. The size of the pump starts as small as 12-Fr, which is amenable to total percutaneous insertion. A catheter-mounted continuous-flow axial pump is placed across the aortic valve with the inflow in the LV and the outflow in the ascending aorta under fluoroscopic and echocardiographic guidance (Fig. 1). The family of the Impella system includes 2.5 (12-Fr, 2.5 l/min of flow), Continuous Power (CP) (14-Fr, 3.5 l/min of flow), 5.0 (21-Fr, 5 l/min of flow), and Left Direct (LD) (21-Fr, 5 l/min of flow) as well as the Impella right ventricular assist device (RVAD) (23-Fr, 5 l/min of flow). These pumps are operated through an 11-Fr catheter. The Impella’s hemodynamic support results from its ability to augment active forward flow to increase net cardiac output, while simultaneously unloading the LV. With the outflow of the Impella device in the aortic root, it provides both an active flow and systemic pressure contribution leading to increased cardiac power output. The inflow of the device draws blood directly from the ventricle, resulting in reduced ventricular end-diastolic volume and pressure, which leads to a reduction of mechanical work, myocardial wall tension, and myocardial oxygen demand. As opposed to the TandemHeart system or venoarterial extracorporeal membrane oxygenation (VA-ECMO), in which a larger catheter is left placed in the femoral artery, the Impella system predisposes the patients to lower risk of limb ischemia. On the other hand, the internal pump of the Impella is susceptible to positional change, which requires frequent echocardiograms with positional adjustment. Additionally, higher shear stress because of higher operational speed of the impeller might cause damage to the blood components [17]. Contraindications for Impella placement include significant peripheral arterial disease (if device is to be placed percutaneously), at least moderate ( 30 min of on-going CPR Septic shock Predicted extremely short-term life expectancy due to comorbidities

No

Yes

Selection of bridge-to-decision device

No device support

Any of the following? • Unknown neurological status • Severe hemodynamical status • Severe hemodynamical instability • Severe coagulopathy

Yes

Percutaneous VA-ECMO

No

Exchange when longer-term support needed with certain destination

Surgical CentriMag BiVAD

Impella 2.5 LVAD for LV decompression

Destinations • Exchange to implantable VAD • Explant for myocardial recovery • Heart transplantation • Death

FIGURE 4. Algorithm for bridge-to-decision device therapy. CPR, cardiopulmonary resuscitation; LV, left ventricle; MCS, mechanical circulatory support; VA-ECMO, venoarterial extracorporeal membrane oxygenation. 272

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Continuous-flow ventricular assist devices Takayama et al.

with implantable LVAD technology, but also to the development of various short-term percutaneous CF-VADs (TandemHeart, Impella, and other investigational devices) and surgical CF-VADs (CentriMag). These devices have favorable features for the treatment of cardiogenic shock, as well as allowing bridge-to-decision therapy. More powerful and durable devices with tailored features for cardiogenic shock treatment are still in development. Clinical evidence for each device, as well as for overall MCS therapy as a treatment for cardiogenic shock, however, remains at the level of case reports. Equally important to the evolution of technology is the pursuit of rigorous clinical trials to quantify the contribution of device therapy to the treatment of cardiogenic shock. However, a multidisciplinary approach plays a pivotal role to streamline this complex and rapidly changing environment surrounding MCS therapy for cardiogenic shock. Acknowledgements None. Conflicts of interest U.P.J. has received consulting fees of less than $5000 annually each from Thoratec, HeartWare, and Jarvik. H.T., K.T., and D.D. have nothing to disclose.

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Short-term continuous-flow ventricular assist devices.

To provide a comprehensive update on the current state of short-term, continuous-flow ventricular assist devices (CF-VADs) in the treatment of refract...
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