from 14.7% in 2006–2007 to 41.6% in 2011–210313 (Table 84-1) At the same time, the proportion of

patients listed for transplantation decreased significantly: from 42.4% to 21.7%. Patients undergoing

implantation of an MCS device in the presence of cardiogenic shock (i.e., INTERMACS levels 1 and 2)

had worse outcomes compared with device implantation in patients with more stable forms of advanced

heart failure (INTERMACS levels 3 through 7)13 (Fig. 56-7; Table 84-2). These observations highlight

the importance of proper patient selection and timing of initiation of MCS therapy on outcomes.

Patients with significant organ dysfunction at the time of MCS device implant, accompanied by a

greater degree of hemodynamic compromise, have a significantly higher risk of requiring BiVAD

support, higher risk of major adverse events, and significantly higher risk of death during VAD support.

Figure 84-5. Actuarial survival for primary device implant, stratified by device type. Error bars indicate ± 1 SE. Patients are

censored at transplant and recovery. CF, continuous flow; LVAD, left ventricular assist device; PF, pulsatile flow; TAH, total

artificial heart. (From Kirklin JK, Naftel DC, Pagani FD, et al. Sixth INTERMACS annual report: a 10,000-patient database. J Heart

Lung Transplant 2014;33:1304–1311, with permission.)

Figure 84-6. Actuarial survival for primary continuous-flow devices, stratified by strategy at implant: BTR, bridge to recovery; DT,

destination therapy; BTT, bridge to transplant; BTC, bridge to candidacy. Error bars indicate ± 1 SE. (From Kirklin JK, Naftel DC,

Pagani FD, et al. Sixth INTERMACS annual report: a 10,000-patient database. J Heart Lung Transplant 2014;33:1304–1311, with

permission.)

WEANING PATIENTS FROM MCS

Weaning From Short-Term MCS

A number of factors are considered when weaning patients from MCS. Major cardiac abnormalities not

addressed before or during support render the chances of weaning from MCS negligible. Optimization of

volume status, afterload, cardiac rhythm, and degree of inotropic support as well as exclusion of

obvious surgical pathology, such as tamponade, is paramount before attempting separation from MCS.

In addition, extracardiac causes, such as pulmonary edema, elevated pulmonary vascular resistance,

acute respiratory distress syndrome (ARDS), and pneumonia, may worsen right ventricular function and

prevent successful weaning from MCS.

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Once a patient’s status has been optimized, weaning from MCS aided with echocardiographic

monitoring is preferred. As device flows are reduced, transesophageal echocardiogram provides

information on ventricular filling and performance and valve function. If patients maintain satisfactory

hemodynamics with reduction of pump flow, they can be considered for weaning. In the setting of

biventricular support, it is important that device flows on the right side be reduced before lowering leftsided device flows. This prevents pulmonary edema in the event of inadequate LV function. As device

flows are reduced, native heart function begins to support the circulation. When weaning from MCS is

not possible, patients should be evaluated for heart transplantation and/or bridged to a long-term MCS

device.

Figure 84-7. Survival analysis for patients on mechanical circulatory support by INTERMACS Profile. Error bars indicate ± 1 SE.

See Table 84-2 for a description of INTERMACS Profiles. (From Kirklin JK, Naftel DC, Pagani FD, et al. Sixth INTERMACS annual

report: a 10,000-patient database. J Heart Lung Transplant 2014;33:1304–1311, with permission.)

Table 84-1 MCS Device Implants by Implant Era and Indications for MCS Device

Implantation in the INTERMACS Registry

Weaning From Long-Term MCS

Anecdotal observations from the cumulative experience with long-term MCS for BTT and recent small

clinical studies have demonstrated that long-term MCS, associated with sustained mechanical unloading

of the LV, can improve myocardial function even in those patients thought to have irreversible, dilated

cardiomyopathies.55–57 Several studies have demonstrated that long-term MCS can restore ventricular

geometry, improve myocyte function, orientation, and size, reduce myocyte apoptosis, reduce

myocardial cytokine gene and protein expression, reverse abnormal neurohormonal patterns associated

with advanced heart failure, and improve myocardial mitochondrial function.55–57 These observations

have led clinicians to consider MCS alone, or in conjunction with other future possible therapies (novel

medications; gene therapy; myocyte or stem cell implantation), as a potential modality to reverse endstage cardiomyopathy. Whether these observation hold under future rigorous experimental scrutiny

remains unknown at this time.

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MCS DEVICES

The devices currently approved by the FDA are broadly grouped into two categories on the basis of

their durability and the intended length of support and use.

Devices Intended for Short-Term MCS (Temporary Devices)

IABP

Since its first reported clinical use by Kantrowitz in 1968, the IABP has become the most frequently

utilized MCS device (Fig. 84-8).58 The IABP can be inserted percutaneously and is positioned within the

descending thoracic aorta. It augments ventricular performance and cardiac output increasing diastolic

coronary blood flow, decreasing myocardial oxygen consumption, and reducing left ventricular

afterload. Inflation of the balloon during diastole increases diastolic pressure and coronary blood flow

and deflation of the balloon during systole reduces arterial afterload facilitating LV ejection. Although

the IABP has been the mainstay of circulatory support for decades, the utility of IABP in cardiogenic

shock complicating acute myocardial infarction was recently challenged by the results of the SHOCKIABP Trial.59 This prospective study randomized 600 patients to IABP counterpulsation or no IABP

counterpulsation in addition to revascularization and optimal medical therapy. The study revealed no

difference in 30-day mortality, length of stay in the intensive care unit, serum lactate level, incidence of

renal failure, or duration of catecholamine therapy.59 Complications from the use of the IABP include

leg ischemia, balloon rupture, infection, bleeding, false aneurysm formation, femoral neuropathy, vessel

perforation with hemorrhage, and aortic dissection. Female gender, peripheral vascular disease,

diabetes, smoking, advanced age, obesity, and cardiogenic shock are predisposing factors for tissue

malperfusion and limb ischemia. The IABP has several disadvantages. The augmentation of cardiac

output is generally small (approximately 15% in optimal circumstances) when compared with that of

conventional VADs and mobilization of the patient is very limited with percutaneous approaches

through the femoral arteries. The use of the axillary or subclavian arteries with direct operative

placement or percutaneous insertion may permit some degrees of patient mobility.

Extracorporeal Life Support

Extracorporeal life support, traditionally referred to as “extracorporeal membrane oxygenation” is a

temporary form of MCS that provides circulatory assistance while allowing for both oxygenation and

carbon dioxide removal from blood.60–63 The ECLS circuit is conceptually similar in concept to CPB;

however, the inclusion of membrane or hollow-fiber oxygenators has allowed for safe application for

extended periods of time (usually days to weeks). Since the first successful use of prolonged ECLS,

reported by Hill in 1972,63 ECLS has been used in a variety of both pediatric and adult clinical settings,

including respiratory support, postcardiotomy support, and as a bridge to an LVAD or heart and/or lung

transplantation.64

ECLS Achieves Circulatory by Unloading the RV. The blood is drained from the venous circulation,

oxygenated it, and returned to the arterial circulation. Although it does reduce LV preload by decreasing

the pulmonary venous return, ECLS does not directly unload the LV. In patients with severe LV

dysfunction, the use of an IABP and catecholamines helps reduce LV afterload and improves myocardial

contractility, thus preventing blood stasis and thrombus formation within the LV. If LV function is so

severely reduced that there is essentially no ejection, an atrial septostomy or insertion of a left-atrial

venting system can be performed to relieve LV distention. Maintenance of some degree of pulmonary

blood flow during ECLS is important in preventing pulmonary artery and vein thrombosis, while

minimal ventilatory settings ensure that the oxygen saturation of the blood ejected from the left

ventricle is adequate. Venovenous ECLS, unlike venoarterial ECLS, maintains flow through the heart

and is used solely for pulmonary support.

Table 84-2 INTERMACS Profiles: Description of Heart Failure Symptoms and

Hemodynamic Status at the Time of MCS Device Implantation and

Including the Time Frame for Intervention

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Current ECLS circuits are typically composed of a centrifugal pump with either a hollow fiber or

membrane oxygenator, oxygen blender, pump console, heat exchanger, and pump cart. A roller pump is

used by some centers. Cannulation technique for ECLS is extremely variable and depends on the clinical

situation and the nature of support required. Percutaneous cannulation of the femoral vein and artery

allows for rapid initiation of MCS in cases of acute cardiac and/or respiratory arrest. In less urgent

situations, cut-down on the internal jugular and carotid artery or respective femoral vessels can be

performed. In cases of postcardiotomy failure in the operating room, venous access can be obtained by

insertion of cannula in the right atrium and arterial outflow obtained by cannulation of the ascending

aorta. Even though many ECLS perfusion systems are available, new portable ECMO systems such as

CardioHelp (Maquet GmbH and Company, Rastatt, Germany) have now attained the FDA approval and

may find a useful role in emergency situations due to the relative ease of implantation and initiation.

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Figure 84-8. Intra-aortic balloon pump. A: Aortic pressure tracing during intra-aortic balloon pump support. Balloon

counterpulsation is occurring after every other heartbeat (1:2 counterpulsation). With correct timing, balloon inflation (IP) begins

immediately after aortic valve closure, signaled by the dicrotic notch of the arterial waveform. Compared with unassisted ejection,

the pump augments diastolic blood flow by increasing peak aortic pressure during diastole. Balloon deflation before systole

decreases ventricular afterload, with lower aortic end-diastolic pressure and lower peak systolic pressure. B: Console for the intraaortic balloon pump. C: Catheter-mounted balloon is positioned within the thoracic aorta through a percutaneous or surgical

approach via the femoral artery. (Photo courtesy of Maquet Cardiac Assist, Fairfield, NJ.)

Numerous large clinical series have reported successful use of ECLS for cardiac and/or respiratory

support in adult, pediatric, and neonatal patients. In the largest series reported to date, Gray and

colleagues

64 at the University of Michigan reported on the outcome of 2,000 patients supported with

ECLS from 1973 through 2010. Of the 2,000 patients, 74% were weaned from ECLS and 64% survived

to hospital discharge. In patients with respiratory failure, survival to hospital discharge was 84% in 799

neonates, 76% in 239 children, and 50% in 353 adults. Survival in patients with cardiac failure was 45%

in 361 children and 38% in 119 adults. ECLS during extracorporeal cardiopulmonary resuscitation was

performed in 129 patients, with 41% surviving to discharge. Survival decreased from 74% to 55%

between the first and second 1,000 patients. The most common complication was bleeding at sites other

than the head, with an incidence of 39%, and the least frequent complication was pump malfunction,

with a 2% incidence. Intracranial bleeding or infarction occurred in 8% of patients, with a 43% survival

rate.

Venovenous ECLS was the preferred method of respiratory support since 1988. For patients with

cardiac failure, survival in adult patients was improved by utilizing ECLS as a bridge to longer-term

implantable devices in patients who did not demonstrate early recovery of myocardial function.65–67

Conversely, the availability of long-term implantable devices has extended the use of ECLS in situations

where recovery of myocardial function is unlikely.65–67

Percutaneous Short-Term MCS Devices

The 2015 SCAI/ACC/HFSA/STA clinical expert consensus statement endorses the use of percutaneous

MCS in carefully selected patients with severe hemodynamic compromise in a variety of clinical

scenarios, including complications of acute MI, severe heart failure in the setting of nonischemic

cardiomyopathy, acute allograft rejection, posttransplant RV failure, inability to separate from CPB

after cardiac surgery, refractory arrhythmia, and prophylactic use during high-risk coronary

interventions.1 The choice of the device depends on the clinical setting, the ease of implantation, the

hemodynamic effects of the device, and the goals of therapy. Expert operators may choose percutaneous

LVAD systems over IABP to minimize pressor use and myocardial oxygen demand and improve systemic

perfusion while substantially decompressing the dysfunctional ventricle and effectively augmenting the

cardiac output and tissue perfusion. It is important to note, however, that the extent of clinical data

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pertaining to the effectiveness and safety of these devices is still limited. In addition, the cost of the

devices and the operating costs substantially exceed those of the IABP.

The Tandem Heart pVAD (Cardiac Assist Technologies, Inc., Pittsburgh, PA) is currently the only

available percutaneous left atrial-to-femoral artery VAD68 (Fig. 84-9). This dual-chamber, low-speed

continuous-flow, centrifugal device bypasses the LV by pumping blood extracorporeally from the left

atrium to the femoral arterial system via a catheter placed across the atrial septum into the left atrium.

It is a dual-chamber pump composed of an upper and a lower housing assembly, providing a conduit for

inflow and outflow of blood and communication with the controller, respectively. The controller

ensures hydrodynamic bearing support of the LVAD impeller and rotation at 3,000 to 7,500 rpm, as well

as its cooling and delivery of local anticoagulation. The controller is a micropressor-based

electromechanical drive operated on AC current or internal batteries.

Figure 84-9. A: The Tandem Heart pVAD centrifugal pump (CardiacAssist Corporation, Pittsburgh, PA). The TandemHeart pVAD is

an extracorporeal, continuous-flow rotary pump with centrifugal design providing temporary mechanical circulatory support to the

left ventricle (left atrium to femoral artery). The TandemHeart pVAD utilizes a bearing design in the pump for impeller

positioning and rotation. B: Schematic representation of the cannulation of the femoral artery and femoral vein with the

transseptal placement of the inflow catheter within the left atrium from the femoral vein. The centrifugal pump of the Tandem

Heart pVAD is secured to the patient’s right thigh. (Photographs courtesy of CardiacAssist Corporation, Pittsburgh, PA.)

Implantation of the device is performed percutaneously via the right femoral vein. A standard

Brockenbrough catheter inserted into the superior vena cava allows for interatrial septostomy, through

which a venous inflow cannula is introduced. An arterial perfusion catheter, ranging in size from 15F to

19F, is inserted percutaneously into the right femoral artery.

Hemodynamic effects of this device are based on the parallel flow contribution to the aorta of both

the device and the LV itself. This results in reduction of LV preload, myocardial oxygen consumption,

filling pressures, and ventricular wall stress.69 Depending on the size of the arterial cannula, the device

flow varies from 3.5 to 5.0 L/min.

In a randomized comparison of IABP with the Tandem Heart pVAD, Thiele and colleagues

68 reported

a more effective improvement in cardiac power index as well as other hemodynamic and metabolic

variables with the Tandem Heart pVAD compared with the IABP. Even though 30-day mortality rate

was similar between the two groups, complications like severe bleeding and limb ischemia were

encountered more frequently during VAD support.68 The Tandem Heart pVAD is FDA-approved for

temporary MCS for cardiogenic shock in patients refractory to optimal medical therapy and IABP.

Impella LVAD (Abiomed Corporation, Danvers, MA) is a continuous flow rotary pump wit axial design

that propels blood from the LV across the aortic valve and into the ascending aorta70,71 (Fig. 84-10). It

is currently available in three delivery platforms for LV support including a 12F (Impella LP 2.5), 21F

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(Impella LP 5.0), and 14F (Impella CP) system and Impella RP, a system uniquely designed for RV

support. While the Impella 2.5 and 5.0 provide maximal flow rates of 2.5 and 5.0 L/min, respectively,

the Impella CP achieves maximal flows of approximately 4 L/min despite its smaller platform. The two

smaller devices can be inserted percutaneously, while the larger device may require surgical cut-down.

The preferred site of introduction is the femoral artery; however, the devices have been introduced via

the axillary artery or directly into the aorta. The LVAD is positioned across the aortic valve with the

inlet port below and outlet above the aortic valve.

The hemodynamic effects of Impella devices are based on LV unloading and augmentation of forward

flow. This reduces myocardial oxygen consumption, improves mean arterial blood pressure, and reduces

pulmonary capillary wedge pressure.72 Similar to the TandemHeart, proper function of the Impella

LVAD requires adequate RV function or RV support to provide sufficient preload for the devices. In a

prospective, randomized clinical trial comparing the Impella LP2.5 to IABP, cardiac index was

significantly increased in patients with the LP2.5 compared with patients supported with an IABP.

Overall mortality rate at 30 days was similar in both groups.70

The Impella RP (Fig. 84-10) is a novel RVAD designed using the Impella system but adapted for right

ventricular support. The pump supports the pulmonary circulation with intent to reduce right

ventricular work and potentially recover right ventricular contractility. The pump is inserted

percutaneously via the femoral vein and capable of delivering up to 4 L/min of blood flow from the

right atrium to the pulmonary artery.

Figure 84-10. The Impella left ventricular assist device (Abiomed Inc., Danvers, MA). A: Diagram demonstrating positioning of the

device across the aortic valve. Device inflow is within the left ventricle and device outflow is above the aortic valve. B: Impella

5.0. C: Impella RP. (Photographs courtesy of Abiomed Inc., Danvers, MA.)

The CentriMag VAD (Levitronix LLC; Waltham, MA) is an extracorporeal, continuous flow rotary pump

composed of a centrifugal blood pump, a motor, a console, a flow probe, and a circuit73,74 (Fig. 84-11).

The device is based on a magnetically levitated “bearingless motor” design. The rotor located within the

upper pump housing is magnetically coupled to the lower motor housing to produce rotor levitation and

spin which combines the drive, the magnetic bearing and the rotor function into a single unit. The

motor generates the magnetic bearing force that levitates the rotor into the pump housing while also

generating the torque necessary to produce the unidirectional flow. This device can produce flows of up

to 10 L/min under normal physiologic conditions, with a priming volume of 31 mL. Both left and right

ventricular systems exist and have been used as a BTR, BTT, or bridge to a long-term MCS. Single-center

reports have demonstrated successful use of both left and right ventricular Centri-Mag systems as a BTT,

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BTR, or bridge to a long-term implantable MCS.73,74 The Centri-Mag system can be utilized in series

with an oxygenator as an ECLS system.

Implantable Devices Intended for Long-Term MCS for Out-of-Hospital Use (BTT and DT

Indications)

Historical Perspective

The majority of patients receiving long-term MCS in the 1990s and early 2000s were supported by

devices engineered with pulsatile, volume displacement designs. These first-generation devices, now

obsolete in clinical practice, were engineered with an internal reservoir chamber and inflow and

outflow valves that permit cyclic filling and emptying of the device with pump actuation elicited by

either pneumatic or electrical drive systems.

Extended periods of MCS highlighted limitations in the design of pulsatile, volume displacement

pumps that included a large pump size restricting mobility, requirement for extensive surgical dissection

for implant leading to bleeding and infection complications, a large body habitus of the recipient

limiting options for device therapy for women or smaller patients, the presence of a large-diameter

percutaneous lead for venting air, and audible pump operation. A critical limitation of these devices was

the high incidence of reoperation for device exchange for device malfunction.75 To overcome these

limitations, newer device designs incorporating continuous-flow rotary pump technology with an axial

or centrifugal blood path represent the next generation of devices for long-term MCS therapy.

Implantable, Continuous-Flow Rotary MCS Devices

9 Implantable, continuous-flow, rotary pumps with axial or centrifugal blood flow design represent a

new generation of implantable VAD technology that have now completely replaced pulsatile devices for

long-term MCS indications.46–50,76 Rotary pumps have an internal impeller within the blood flow path

that is suspended by contact bearings or in more recent cases by hydrodynamic or magnetic forces.

Rotary pumps offer several advantages over pulsatile, volume displacement pumps. These advantages

include smaller size, fewer moving parts, durability, absence of valves to direct blood flow, smaller

blood contacting surfaces, and reduced energy requirements. Blood flow is accomplished by the

spinning of an internal rotor as high speed that imparts significant kinetic energy to the blood. The

spinning of the rotor is accomplished by actuating an electrical current and magnetic field around the

rotor that contains internal magnets. Blood flow from left ventricle to the aorta occurs continuously

during the systolic and diastolic phases of the cardiac cycle. Although blood flow is continuous during

the cardiac cycle, phasic changes in the flow of blood occur during the cardiac cycle due to changes in

ventricular pressure and aortic afterload. These phasic changes in blood flow impart a diminished

pulsatility to the aortic waveform. The ability to design smaller pumps using rotary pump technology is

a result of the elimination of a large blood chamber necessary with pulsatile systems. An additional

important feature of these pumps is the lack of need for a compliance chamber. This feature alleviates

the problem of internal compensation that is associated with conventional pulsatile pumps that, to date,

has significantly hindered total internalization.

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Figure 84-11. The CentriMag VAD. The CentriMag VAD is an extracorporeal, continuous-flow rotary pump with centrifugal design

utilized for temporary mechanical circulatory support. The CentriMag can provide univentricular or biventricular support. A: The

CentriMag console (background) and pump/motor (foreground). B: Schematic representation of the CentriMag pump. The rotor

located within the upper pump housing is magnetically coupled to the lower motor housing to produce rotor levitation and spin.

(Photograph courtesy of Levitronix LLC, Waltham, MA.)

Rotary pump designs incorporating pump technology with an axial blood path have accumulated

significant human clinical experience. Reports from clinical trials with rotary pumps have demonstrated

efficacy in providing hemodynamic support, a favorable risk to benefit assessment, and improvement in

mechanical performance.46–50,76 Furthermore, the human experience with the newer generation of

rotary pumps with axial or centrifugal design has established the long-term safety of MCS with minimal

pulse pressure.77,78 Results from clinical studies have demonstrated early improvement followed by

long-term stability of renal and hepatic function and no adverse effects on neurocognitive

performance.46–50 These improvements in device technology with continuous-flow rotary pumps have

increased the acceptance and adoption of LVAD therapy for long-term MCS indications.

Implantable, Continuous-Flow MCS Devices (Rotary Pumps with Axial Flow Design)

HeartMate II. The HeartMate II LVAD (Thoratec Corporation, Pleasanton, CA)38,39,47–50 (Fig. 84-12) is

continuous-flow rotary pump with axial design and mechanical bearing support of the internal impeller.

The sealed inflow conduit of the pump is attached to the apex of the LV and the pump sealed outflow

graft is connected to the ascending aorta, creating a circuit parallel to the native circulation. A magnet

within the pump’s rotor assembly is rotated by the electromotive force generated by the motor itself.

This rotation is the driving force propelling the blood from the left ventricle through the pump into the

ascending aorta. The flow generated by the pump depends on the rotational speed of the rotor as well

as the pressure difference between the inlet and outlet of the pump. The internal pump surfaces are

lined with smooth polished titanium, while the sealed inflow conduit and outflow elbow have a textured

titanium microsphere surface. The percutaneous lead (drive-line) transmits commands and power from

the external System Controller and power source to the LVAD itself. The system can be powered by

portable batteries.

The HeartMate II was approved for BTT therapy in 2008 and for DT in 2010, following two pivotal

safety and efficacy trials, and is the most utilized and studied LVAD pump to date. In a prospective,

multicenter, controlled study of HeartMate II as BTT, 133 patients with end-stage heart failure while on

the waiting list for heart transplantation underwent implantation of the LVAD. The primary end point

(the proportions of patients who had undergone transplantation, had cardiac recovery, or had ongoing

mechanical support while remaining eligible for transplantation) was evaluated at 180 days

postimplantation. Three quarters of the patients reached the primary end point. Of these 100 patients,

only one recovered myocardial function and had the VAD explanted. The rest were either transplanted

(56 patients) or continued requiring LVAD support (43 patients). Overall actuarial survival for patients

continuing to receive LVAD support was 89% at 1 month, 75% at 6 months, and 68% at 12 months.49 A

follow-up report of the initial 133 patients in addition to 148 patients entered through the Continuous

Access Protocol38 reveals that at 18-month follow-up, 157 patients (55.8%) had received a heart

transplant, 58 patients (20.6%) remained alive with ongoing LVAD support, 56 patients (19.9%) died, 7

patients (2.5%) recovered cardiac function and underwent device explantation, and 3 patients (1%)

were withdrawn from the study after device explantation and exchange for another type of LVAD.

Overall survival rate for the patients who continued on LVAD support was 82% (95% confidence

interval [CI]: 77% to 87%) at 6 months, 73% (95% CI: 66% to 80%) at 1 year, and 72% (95% CI: 65%

to 79%) at 18 months. The most common adverse effects were bleeding, stroke, infection, and neurocognitive dysfunction, while sepsis and stroke were the primary causes of mortality. The post–FDAapproval study of the HeartMate II for Bridge to Transplant indication reported comparable results with

HeartMate II in a commercial setting to those of other available devices for the same indication. The

cohort of 338 patients was followed for at least 12 months or until death or transplantation. Both the

30-day mortality rate and the in-hospital mortality rate were significantly lower among the LVAD

patients (4% vs. 11%, and 6% vs. 15%, respectively). Patients supported with the HeartMate spent less

time in the hospital, were more likely to be discharged home, and reported better quality of life.47

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