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Original article
Heartmate II axial-flow left ventricular assist system:management, clinical review and personal experienceAntonino Loforte, Andrea Montalto, Federico Ranocchi, Giovanni Casali,Giampaolo Luzi, Paola Lilla Della Monica, Fabio Sbaraglia, Vincenzo Polizzi,Giada Distefano and Francesco Musumeci
Objectives The excellent results with left ventricular assist
devices (LVADs) have revolutionized the treatment options
for end-stage heart failure. The use of pulsatile devices is
associated with significant comorbidity and limited
durability. The axial-flow HeartMate II LVAD represents the
new generation of devices. The clinical use of this pump
resulted in superior outcomes. We review the HeartMate II
technology, management, clinical usage and our
experience.
Methods Between 3/2002 and 12/2008, 18 transplantable
adult patients were supported on long-term HeartMate II
LVAD at our institution (13 men, age 52 W 8.4 years, range:
31–64 years). Primary indications were: ischemic
cardiomyopathy (CMP) (n U 13), idiopathic CMP
(n U 5). All patients were in New York Heart Association
(NYHA) Class IV heart failure. None of patients had prior
open-heart surgery. Implantation via cannulation of the left
ventricular apex and the ascending aorta was always
elective.
Results Mean support time was 217 W 212.3 days (range:
1–665 days). Early (30-day) mortality was 27.7% (five
patients) with multiple organ failure and sepsis as main
causes of death. Bleeding requiring reoperation occurred in
six (33.3%) cases. Cerebral hemorrhage occurred in one
patient. There were two driveline infections and no device
opyright © Italian Federation of Cardiology. Unau
1558-2027 � 2009 Italian Federation of Cardiology
failure. Twelve (66.6%) patients were successfully
discharged home. Overall nine patients (50%) were
transplanted and two patients are actually waiting for a
suitable organ (n U 2 patients discharged home and n U 1
patient in hospital). At latest, follow-up survival rate after
heart transplantation is 66.6% (six patients).
Conclusion Long-term HeartMate II LVAD provides good
mid-term, long-term results. This new technology requires
delicate management. Functional status and quality of life
greatly improve in patients who survive the perioperative
period. J Cardiovasc Med 10:765–771 Q 2009 Italian
Federation of Cardiology.
Journal of Cardiovascular Medicine 2009, 10:765–771
Keywords: heart failure, left ventricular assist device, mechanical support
Department of Cardiac Surgery and Heart Transplantation, San Camillo Hospital,Rome, Italy
Correspondence to Dr Antonino Loforte, Cardiac Surgeon, Department ofCardiac Surgery and Heart Transplantation, S. Camillo Hospital, P.za C. Forlaninin.1, 00151 Rome, ItalyTel: +39 06 5870 4401; fax: +39 06 5870 4706;e-mail: [email protected]
Received 23 January 2009 Revised 6 April 2009Accepted 23 April 2009
IntroductionThe HeartMate II left ventricular assist system (LVAS)
(Thoratec, Inc.; Pleasanton, California, USA) is a rotary
blood pump with axial flow design that represents a
second generation of implantable assist devices designed
to be a small, more reliable device suitable for long-term
outpatient circulatory support. The major advantage of
the HeartMate II LVAS is the axial flow design that
reduces significantly its size and weight compared with
the current generation of implantable, pulsatile pumps
(e.g. HeartMate XVE, Thoratec, Inc., Pleasanton,
California, USA; Novacor LVAD, World Heart, Inc.,
Ottawa, Canada; Thoratec IVAD, Thoratec, Inc.), princi-
pally through elimination of a blood sac or reservoir
necessary for pulsatile systems.
The initial development of the HeartMate II LVAS
began in the early 1990s as a collaborative project
between the engineering and clinical teams of Nimbus,
Inc. (Rancho Cordova, California, USA) and the Univer-
sity of Pittsburgh [1–4]. Early development of the pump
was supported by the National Institutes of Health-Small
Business Innovative research grants and later in 1997 by
an award from the National Institutes of Health program
for innovative ventricular assist development [4]. In 1998
Nimbus, Inc. was acquired by ThermoCardiosystems,
Inc. (Woburn, Massachusetts, USA). Initial animal test-
ing suggested that the HeartMate II LVAS had good
hemodynamic performance with excellent potential for
5-year durability [5,6]. In 2001 ThermoCardiosystems,
Inc. was acquired by Thoratec Corporation (Pleasanton,
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DOI:10.2459/JCM.0b013e32832d495e
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766 Journal of Cardiovascular Medicine 2009, Vol 10 No 10
California, USA), which currently leads development and
clinical testing of the HeartMate II LVAS.
In this report we review the HeartMate II technology,
management, clinical usage and our initial experience
with the device.
Device descriptionThe left ventricular assist system consists of an internal
blood pump with a percutaneus lead that connects the
pump to an external system driver (computer controller)
and power source (batteries or power base unit/battery
charger) [1–4]. The blood pump component of the
HeartMate II LVAS is a 12-mm-diameter straight tube
made of titanium alloy [1–4,7]. The 12-mm straight tube
incorporates the hydraulic components of the pump that
include the inlet stator (the fixed component that forms
the pivot or housing for the rotor), a pump rotor (the
rotational component that includes the impeller blades)
that incorporates a pump magnet, and an outlet stator.
Blood entering the tube passes through the inlet stator
supported by three guide vanes that straighten the flow of
blood as it passes across the inlet stator. The blood next
flows around the pump’s internal rotor. As the blood flows
around the pump rotor, the spinning action of the pump
rotor with its three curving blades introduces a radial or
tangential velocity to the blood flow and imparts kinetic
energy to the blood, which then flows past the outlet
stator vanes. The twisted shape of the outlet stator vanes
converts the radial velocity of the blood flow to an axial
direction [5]. As the blood flow is being turned through
the outlet stators, its kinetic energy is converted to static
pressure, producing a blood flow field that increases
pressure across the pump. The other components of
the pump assembly include the inlet cannula that carries
blood from the left ventricular apex to the pump inlet,
and outlet cannula that returns blood from the pump
outlet to the ascending aorta.
The power to drive the pump rotor is developed by an
integrated electric motor located in the hub of the rotor.
The motor magnet is located within the pump rotor and
orientated at the center line of the axis of the pump
windings and centered longitudinally with respect to the
coil’s length. Electric current is sequentially commutated
to the coils and this creates a spinning magnetic field.
This action creates tourque and angular velocity to the
motor magnet located within the pump rotor. The pump
rotor spins on two bearings located at the inlet and outlet
stators that consist of a ball-and-socket hydrodynamic
composite design. These bearings support radial and
axial loads from the pump rotor. The stationary element
of each bearing is located in the hub of the respective
inlet and outlet stators. The boundaries between the
static and moving surfaces of the ceramic bearings are
washed by the flow of blood. A major advantage of this
pump design is that the rotor that spins within the
yright © Italian Federation of Cardiology. Unauth
magnetic field on the inlet and outlet bearings represents
the only moving component of the pump.
The outlet cannula of the pump, screw-connected to the
pump by a rigid elbow, is made of woven Dacron and
requires preclotting. The inlet cannula has several
important design features that include a flexible joint
between the intraventricular portion of the cannula and
its union to a titanium 908 elbow joining the pump, and an
intraventricular rigid cannula that has been extended in
length and is intended to open the mid left ventricular
cavity. The longer intraventricular cannula is believed to
improve reliability of continuous flow throughout cardiac
systole and diastole and at varied levels of left ventricular
filling. The flexible portion of the inlet cannula is made of
woven Dacron and is compressed into accordion-like
ridges. The flexible portion of the inlet cannula was
added to reduce the risk for malalignment of the intra-
ventricular portion of the inlet cannula caused by the
pump. The pump rotor, blood tube within the pump
housing, and inlet and outlet stators are smooth titanium
surfaces. The inlet and outlet elbows and the intraven-
tricular cannula are textured with titanium microsphere
coatings similar to the HeartMate XVE design [8,9].
The system driver sends power and operating signals to
the pump and receives information from the pump. The
driver is wearable and is powered by a power base unit or
by two 12-volt rechargeable batteries that can provide
approximately 2–4 h of power under normal operating
conditions. The system monitor communicates to a sys-
tem driver and pump through the power base unit and is
made up of a series of display screens for checking and
altering pump functions.
An assessment of pump flow for the HeartMate II LVAS
is provided through use of a flow estimator that is based
on the relationship between pump motor rpm speed and
time-varying electrical power consumption of the pump
motor [10,11]. For any given pump rpm speed, pump flow
is related linearly to power over a limited power range,
and there is an anticipated range of flow and power
consumption for the pump. The relationship between
pump motor speed and power consumption does not
accurately predict estimates of pump flow less than
3 l/min. An additional relationship to understand for
pump operation is the term pulsatility index. Pulsatility
index is a measure of flow pulse through the pump and is
described by the relationship: pulsatility index¼ (maxi-
mum flow – minimum flow)/mean flow. When preload
increases in the native left ventricle, the Starling curve is
impacted and the pulsatility increases. When preload
decreases, the pulsatility of the left ventricle decreases.
Pump flow for the HeartMate II LVAS is not measured
directly through use of a sensor or flow meter. This
indirect assessment of pump flow can have significant
limitations in providing useful clinical information if the
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HeartMate II LVAD mechanical support Loforte et al. 767
pump is operating in a power range that is not typical for
the pump motor speed. In clinical situations in which
assessment of hemodynamic performance of the pump is
needed, invasive monitoring with a Swan–Ganz catheter
or use of echocardiography is thus important to trouble-
shoot potential patient or pump problems.
The approximate weight of the pump is 350 g and the
approximate size of the pump is 7.0 cm in length and
4.0 cm in diameter at its largest diameter. The pump has
an operating rpm range of 6000–15 000 and is capable of
generating up to 10 l/min of flow at an approximate
pressure of 100 mmHg. In addition, the axial flow design
and absence of a blood sac eliminates the need for
venting, currently for the first generation of implantable
pumps, thus reducing the size of the percutaneous drive
lead and eliminating the need for internal one-way
valves. These design features facilitate future conversion
to a completely implantable system because of the
absence of a requirement for a compliance chamber.
Design modificationsFuture design enhancements include development
and refinement of a computer algorithm for auto mode
operation of the system to optimize left ventricle (LV)
unloading [10,11] and potential conversion to a totally
implantable system with transcutaneous energy trans-
mission system (TETS) technology [12].
Device implantation and operativeconsiderationsThe pump is designed to be surgically implanted below
the left costal margin and under the left rectus abdominus
muscle in a preperitoneal position. The inflow cannula
exits the left ventricular apex and crosses the diaphragm
at the costophrenic angle and enters a subrectus pocket
under the left rib margin to attach to the pump. The
pump is intended to lie parallel to the diaphragm. The
outflow cannula is tunnelled back under the sternum to
the ascending aorta. The percuteous driveline consists of
a small-diameter electrical cable that is tunneled through
the abdominal wall and exits the right upper quadrant at
the midclavicular line approximately 3–4 cm below the
costal margin. The percutaneous driveline then is con-
nected to an external system driver and power source.
The system also can be configured to be a completely
implantable system using TETS technology and an
implantable system driver [12].
AnticoagulationThe anticoagulation regimen used for the pilot clinical
investigation includes initiation of heparin therapy within
12–24 h of pump implantation when chest tube drainage
decreased to approximately less than 50 ml/h. The
recommendations are to achieve a partial thromboplastin
time (PTT) of 45 s (1.2–1.4 times control) during the
initial 24 h of therapy and gradually increase over 48–72 h
opyright © Italian Federation of Cardiology. Unau
to a target goal PTT of approximately 55 to 65 s (1.5–1.8
times control. Antiplatlet therapy with aspirin 81 to
100 mg daily and dipyridamole 75 mg three times daily
is initiated at 48–72 h following pump implantation.
Conversion of heparin to warfarin therapy is initiated
at the discretion of the physician (approximately at day
five) to achieve a target international normalized ratio
(INR) of 2.0 to 3.0. Heparin is discontinued after obtain-
ing a stable therapeutic INR.
Special management issuesPump thrombusAn abnormal power increase unrelated to actual changes
in pump flow (e.g. thrombus on the pump rotor) produces
an inaccurate estimate of pump flow. With thrombus on
the rotor (resulting in significant rotor drag), power con-
sumption would increase, causing an inaccurately high
estimate of pump flow and decrease in pulsatility index
caused by the reduction in cyclic power consumption
(continuously high power consumption caused by the
thrombus). The patient’s aortic pulse pressure may
remain unchanged in this situation. With inlet obstruc-
tion (e.g. inlet cannula malalignment to thrombus on
the orifice of the inlet cannula) or outflow obstruction
(e.g. kinking of the aortic outflow graft or anastomotic
narrowing), power consumption, pump flow and pulsati-
lity index all decrease and are associated with an increase
in the patient’s aortic pulse pressure. Diagnosis of this
scenario can be aided with echocardiography demonstrat-
ing a dilated LV and changes in LV unloading perhaps
not responsive to increasing pump rpm speeds.
Ventricular suctionThe HeartMate II LVAS additionally incorporates a suc-
tion detection algorithm to reduce the risks for unwonted
suction events. The system monitors sudden changes in
pump flow pulsatility indirectly through analysis of the
time-dependent current trace and its derivatives (pulsa-
tility index). If a sudden change in pump flow pulsatility
is detected, the pump speed automatically reduces to
9000 rpm to avoid suction. Immediately following an
event, the operating speed displayed on the monitor is
lower than the set speed and then slowly returns to the set
pump speed. During a suction event, pump flow, power
consumption, and pulsatility index decrease. The patient
may or may not have a change in the aortic pulse pressure.
MethodsBetween March 2002 and December 2008, we enrolled
18 patients with severe heart failure. There were 15 men
and three women with a mean age of 52� 8.4 years
(range, 31–64 years), and a mean body surface area
(BSA) of 1.76� 0.18 m2 (range, 1.54–1.96 m2). The
indication for use was bridge to transplantation (BTT)
in all patients. The diagnosis was ischemic cardiomyo-
pathy in 13 patients and idiopathic cardiomyopathy in
five. A viable area less than 20% of the total heart area was
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768 Journal of Cardiovascular Medicine 2009, Vol 10 No 10
detected by positron emission tomography (PET) with
fluorodeoxyglucose (FDG) in ischemic cardiomyopa-
thies, all with functional moderate mitral regurgitation
and no graftable target vessels, and consequently con-
sidered not suitable for conventional surgical procedures
according to Hausmann et al. [13]. Additionally, the
correction of functional mitral valve regurgitation with
annuloplasty alone results in partial reversal of left ven-
tricular remodeling and the long-term benefit of this
procedure has yet to be demonstrated by randomized
trials comparing optimal medical management with
mitral valve surgery, and a recent retrospective study
showed no demonstrable decrease in long-term mortality
in patients affected by severe mitral regurgitation and
considerable left ventricular dysfunction and undergoing
mitral valve repair [14].
At the time of preoperative evaluation, all 18 patients
were classified in New York Heart Association (NYHA)
functional class IV and were receiving optimal medical
management in the hospital. Nine patients were being
supported by an intraaortic balloon pump (Datascope), and
one patient had been supported by Jostra RotaFlow
(Maquet Cardiopulmonary AG, Hirrlingen, Germany)
extracorporeal membrane oxygenation (ECMO) system
before receiving the LVAD. The HeartMate II was placed
in one patient after a HeartMate XVE device failed.
Implantation via cannulation of the left ventricular apex
and the ascending aorta was performed traditionally.
Patients received routine, postimplantation medical sup-
port after their operation. The anticoagulation protocol
proposed by Thoratec Inc. was adopted [5]. Once
patients are stabilized and become ambulatory, proper
nutrition, rehabilitation and education become a focus of
care. After discharge from the hospital, patients return to
our heart failure clinic for routine follow-up monthly and
at a decreasing frequency, depending on their needs.
Serial echocardiographic studies are performed at regular
intervals for inpatients and outpatients to evaluate the
adequacy of ventricular unloading.
Statistical analysisAll values are expressed as means� standard deviation.
All analyses were performed using SPSS for Windows
Release 11.5 (SPSS Inc., Chicago, Illinois, USA).
ResultsThe average duration of support was 217� 212.3 days
(range, 1–665 days). All patients survived the operation.
Of the 18 implanted patients, 13 (72.2%) survived the
operation without significant complications in the early
postoperative period and 12 (66.6%) were discharged from
the hospital in NYHA functional class I. Overall, survived
HeartMate II recipients were discharged a mean of 38 days
(range, 25–110 days) after implantation. Nine (50%)
patients underwent heart transplantation (Htx). At latest,
yright © Italian Federation of Cardiology. Unauth
follow-up survival rate after Htx is 66.6% (six patients).
Two patients died of early primary graft failure unsuccess-
fully treated with peripheral ECMO support and one
patient died suddenly of unknown causes 8 months after
Htx. There were three episodes in three different patients
of rejection greater than International Society of Heart and
Lung Transplantation (ISHLT) grade 3A, during the
posttransplant first year, treated successfully with medi-
cations. LVAD support is ongoing in three discharged
home patients who are waiting for a suitable organ. One
of these patients was recently readmitted to hospital due to
fever and suspicion of infection. None of the patients died
while receiving device support. Five patients died during
the early postoperative period (30-day mortality) because
of a combination of right-sided heart failure and multiple
system heart failure, leading tosepsis. Re-thoracothomy for
bleeding occurred in six (33.3%) patients. Thrombus
generation in thenoncoronary sinus occurred in one patient
with extremely poor myocardial contractility associated
with a constant lack of aortic valve opening in the early
postoperative period, treated successfully intravenously
with a higher dosage infusion of heparin for a few days.
Heparin-induced thrombocytopenia occurred in one
patient who underwent temporary bivalirudin infusion.
None of the removed devices at the time of transplantation
showed incidence of thrombus. In the early postoperative
period, one patient developed ventricular arrhythmias and
ventricular fibrillation, possibly generated by contact of the
intraventricular cannula with the endocardium due to too
low a volume of the left ventricle chamber, which needed
electric cardioversion for resuscitation. Cerebral hemor-
rhage occurred in one patient. Two patients underwent
right ventricular assist device (RVAD) (Levitronix Cen-
triMag, Levitronix LLC, Waltham, Massachusetts, USA)
placement intraoperatively due to preoperative laboratory,
hemodynamicandechocardiographic assessment ofa mod-
erate right ventricle dysfuntion considered not ideal for
LVAD placement according to the Berlin algorithm [15].
Both patients were weaned successfully from RVAD,
which was removed through a right lateral minithoracoth-
omy without reopening the sternum (13 and 17 days of
CentriMag support, respectively). Superficial driveline
infection occurred in two (11.1%) patients, all treated
successfully with aggressive daily local wound care. The
Heartmate XVE to HeartMate II pump-exchange patient
has been discharged, transplanted and is doing well.
Hemodynamic function improved from preoperative
levels in all patients during support with HeartMate II.
By48 h afterdevice implantation, the averagecardiac index
had increased significantly; from 1.8� 0.26 to 3.5� 0.9 l/
(min�m2), and pulmonary wedge pressure had decreased
significantly, from 23.7� 10 to 17.4� 5.2 mmHg. Inotropic
support was reduced after implantation, and all patients
were weaned within the first week. Serial echocardio-
graphic studies showed improvement in left ventricular
dimensions.
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HeartMate II LVAD mechanical support Loforte et al. 769
In the 12 patients who were discharged, hemoglobin,
hematocrit, and end-organ function had reached normal
levels by the time of discharge and remain normal in all
current outpatients.
The technical performance of the HeartMate II has been
excellent, and patients have been satisfied with this small
and quiet pump.
Before discharge, all patients were trained in the care and
use of their equipment and batteries. The patients
participated in a physical rehabilitation program that
was composed of graduated ambulation within the hos-
pital and treadmill exercise under observation. There
were no life-threatening arrythmias during rehabilitation.
No device malfunction or system problem has been seen
in the outpatient setting.
DiscussionThe first human implantation of the HeartMate II LVAS
was performed in 2000 in Israel. This experience was
followed by nine additional implants at two European
sites [16]. In the initial experience, the HeartMate II
LVAS was designed with sintered or textured surfaces on
the inlet and outlet stators that resulted in significant
incidence of pump thrombus formation. Following rede-
sign and application of smooth surfaces to the inlet and
outlet stators, a clinical pilot trial of the redesigned
HeartMate II LVAS was initiated in humans in Novem-
ber 2003 and completed in November 2004 [17,18]. The
most recent data analysis of the pilot trial was performed
on 27 May, 2005. A total of 34 patients were enrolled at 11
clinical sites; 24 (71%) patients were enrolled from
clinical sites in the United States and 10 (29%) patients
were enrolled from European centers. Notably, of the 34
patients enrolled in the study, 15 (44%) patients were
women, representing a larger pencentage of women than
typically treated with the current generation of implan-
table pulsatile pumps [19]. The median body surface area
was 1.8 m2 (1.63 m2 for females and 1.99 m2 for males).
The causes and severity of heart failure mirrors other
recent trials. As expected, hemodyamic measurements at
24 h following HeartMate II LVAS implantation were
improved significantly, with no significant change in
systolic blood pressure or central venous pressure. An
initial significant increase in serum total bilirubin was
noted at 7 days, which normalized by day 30 following
pump implantation. There was a significant improvement
in functional activity reflected by a greater proportion of
patients able to complete a 6-min walk at day 30 com-
pared with baseline, greater distance achieved during the
6-min walk, and improvement in NYHA functional class.
Ten (29%) patients died while on LVAD support. A total
of 22 (65%) were discharged home during LVAD support.
The median duration of pump support was 160 days, with
a range of 6–562 days. No pump failures were reported in
the early experience. The importance of adequate right
opyright © Italian Federation of Cardiology. Unau
ventricular function is underscored by the four (12%)
patients who required a RVAD for right-sided circulatory
failure, of which one patient weaned and survived and
three patients expired. Six (18%) patients experienced
eight neurological events, including two transient
ischemic events, one stroke, a perioperative encephalo-
pathy, and two perioperative seizures. Hemolysis,
defined as two consecutive plasma free-hemoglobin
values greater than 40 md/dl, occurred in only two
(6%) patients. In one of these patients, right-sided cir-
culatory failure with significant left ventricular collapse
was present for an extended period. There were a total of
10 deaths; the most frequent cause was multisystem
organ failure (five patients).
All pumps were operated in a fixed rpm speed during the
clinic pilot trial. The pumps were maintained at a mean
pump speed of 9.172 rpm at 24 h following implant,
9.255 rpm at day 7, and 9.366 at day 30. The minimum
and maximum pump speeds during the trial were 7.790
and 10.200 rpm, respectively.
The results of the initial pilot trial of the HeartMate II
LVAS demonstrated the efficacy of rotary pumps with
axial flow design for hemodynamic improvement and
organ recovery in humans. In addition the HeartMate
II LVAS provided excellent support in the outpatient
setting with significant improvement in functional
activity, easy use, and comfort related to the smaller size
of the driveline. The early experience with the Heart-
Mate II LVAS has also exposed a need for developing a
better understanding of the parameters to assess optimal
LV unloading, to maximize patient functional abilities
and LV recovery and prevent suction events or right-
sided circulatory failure. The HeartMate II LVAS cur-
rently is undergoing further clinical investigation in two
pivotal phase trials that include a multicenter, nonrando-
mized evaluation of the HeartMate II LVAS in patients
awaiting heart transplantation and a multicenter, random-
ized evaluation of the HeartMate II LVAS compared
with the HeartMate XVE in patients meeting criteria for
destination therapy. Recently, according to the data
presented at ISHLT 28th annual meeting 2008, Boston,
Massachusetts, USA, as ‘one year follow-up’ of above
multicenter evaluation of HeartMate II LVAS [20], 327
heart failure patients had undergone implantation of the
axial flow pump as BTT and 194 had reached 1 year since
implant. The median support was 131 days (longest: 844
days). Forty-two patients have been supported for more
than 1 year and five patients more than 2 years. At
12 months, 149 (77%) of the 194 patients survived, with
53% undergoing transplantation, 2% cardiac recovery
with device removal, and 22% ongoing device support.
Adverse events included percutaneous lead (12%) and
pocket (2%) infections, device thrombosis (2%), perio-
perative (3%) and postoperative (6%) stroke, and need for
RVAD (5%). The median time to Htx in the first year was
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770 Journal of Cardiovascular Medicine 2009, Vol 10 No 10
102 days. HeartMate II improved significantly 6-min
walk distance and NYHA functional class. Of the 42
patients supported for more than 1 year, nine have under-
gone transplantation, two recovered, five died, and 26
remain ongoing with a median duration of 513 days.
In a retrospective analysis of the first 101 consecutive
cases in Europe [21] the perioperative mortality post-
implant was 20% in BTT patients and 7% in the destina-
tion therapy arm. After 1 year a comparable survival was
observed in both groups (69% destination therapy, 63%
BTT). Main cause of death was multiple organ failure.
Our initial experience with the redesigned HeartMate II
has been favorable and has shown this model to be well
tolerated, durable and effective. The technical function
of the device has been excellent. We did not see any
pump failure or operational problems with this technol-
ogy to date.
In our series, 12 patients were discharged from the
hospital, and problems with the HeartMate II system
have been minimal. Arrythmia has been noted, particu-
larly if the patient becomes volume depleted or if the
pump’s unloading of the ventricle is excessive. Lowering
the rpm and ensuring adequate volume status, especially
during postoperative period, can solve this issue.
The small size and reduced weight of this technology
have enabled us to implant the device in women and
young smaller patients who suffer from end-stage heart
failure. The HeartMate II allows an easy intrapericardial
fitting of the device. We eventually open the left pleura
to gain more space, as done in three patients.
Again, a positive goal we reached in our experience with
the HeartMate II has been the possibility to discharge
home several patients, thus recovering a good social life
(this was not the case with the paracorporeal devices).
Discharging patients home is an important therapeutic
option both for the individual and to optimize health-care
resources, considering the long time on the waiting list
for Htx.
The progress of rotary blood pump technology has been
so fast that during the past 5 years all so-called second-
generation rotary blood pumps with blood immersed
bearings, such as the earlier discussed HeartMate II
(Thoratec), the MicroMed (Houston, Texas, USA)
DeBakey VAD, and the Jarvik 2000 FlowMaker (Jarvik
Heart), the development of which had been started in
1995, have already been implanted in several selected
end-stage cardiac patients for bridge to transplantation
and for destination therapy. Although considered unphy-
siological as cardiac support, the continuous flow or
reduced pulsatility continues to work in humans for a
duration of as long as 5.5 years [22]. Beyond second-
yright © Italian Federation of Cardiology. Unauth
generation devices, third-generation mechanical noncon-
tact devices utilizing magnetic suspension mechanisms,
such as the Terumo DuraHeart and the Berlin Heart
INCOR system, and hydrodynamic bearing mechanisms,
such as Arrow International’s (Reading, Pennsylvania,
USA) CorAide and Ventracor’s (Chatswood, New South
Wales, Australia) Ventr-Assist VADs, are actually making
their way into clinical applications [22].
All the continuous-flow technology has shown defini-
tively that ambulatory, effective circulatory support can
be achieved in the long-term in patients with advanced
heart failure who require cardiac support. However, by
changing the internal physiology, this therapy introduces
physiologic phenomena and accompanying clinical pro-
blems, such as arteriovenous malformations leading to
gastrointestinal bleeding, septal shift with resultant right-
sided heart-failure, thrombosis of the aortic valve non-
coronary sinus, aortic valve fusion, and aortic valve insuf-
ficiency. These problems are medically manageable, but
physicians must be aware of them when applying this
life-saving technology.
Miyamoto et al. [23] showed that increases in the amount
of left ventricular unloading led to incremental decreases
in the derivative of right ventricular pressure (right ven-
tricular dP/dt), effectively reducing right ventricular
function. Unlike pulsatile ventricular assist devices, com-
plete left ventricular unloading is avoided with Heart-
Mate II LVAS and other second- and third-generation
axial flow pumps. Our sense and that of other investi-
gators [24] is that there is less right ventricular failure with
the axial flow pumps owing to maintenance of left ven-
tricular end-diastolic volume, maintained septal position,
and preservation of right ventricular mechanics. There-
after, according to the recently developed Berlin echo-
cardiographic algorithm for biventricular support [15], in
our opinion, a temporary right ventricular support at the
same time of LVAD placement should be considered in
the case of a moderate preoperative right ventricular
dysfunction assessment and mainly a preoperative left
ventricle end-diastolic diameter less than 68 mm which is
unable to eventually avoid a leftward septum shift, as we
recently performed in only two patients. Five patients, at
the beginning of our experience, complicated by multiple
organ failure, had similar preoperative echocardiographic
ventricle geometry and dimensions as the earlier ones but
were not supported immediately by a temporary RVAD
placement and the outcome was bad.
We pay particular attention to the proper level of anti-
coagulation, recently focusing on thromboelastogram and
platelet aggregation test monitoring to reach the correct
equilibrium among the three systems involved: the plate-
lets, the procoagulant system, and the fibrinolytic system.
The effect on the blood and the coagulation system varies
from pump to pump, depending on its materials, pumping
orized reproduction of this article is prohibited.
C
HeartMate II LVAD mechanical support Loforte et al. 771
methodology, texture of the surface and design. The
patients vary dramatically in their comorbidities, genetic
composition, drug intake and level of compliance. All
of these complexities make it impossible to develop
a universal anticoagulation/antiaggregation regimen for
patients who have mechanical circulatory assist devices.
Rotary blood pumps show a greater tendency for shear
stress, which is actually optimized by tuning the gaps and
the angles of the impeller blades, thus minimizing turbu-
lence and vortex formation, and using particle image
velocimetry and flow visualization, and monitoring the
results with in vitro testing of blood parameters, such as
hemolysis testing. Consequently, an important array of
methodologies should actually be available for monitoring
the anticoagulation and antiaggregation status of patients
to provide the correct management.
Another delicate issue is the measurement and control of
blood pressure, even by means of Doppler testing per-
ipherally, in patients without a detectable pulse. To date,
experience with these pumps in a limited patient popu-
lation has suggested an increased incidence of hemor-
rhagic stroke [25]. This may be related to the difficulty of
properly monitoring blood pressure due to absent or
dampened pulses imparted by this technology. If hyper-
tension is present but not easily measurable, inadequate
pharmacologic control of blood pressure may result, in
turn subjecting these patients to an increased risk of
hypertensive hemorrhagic stroke. An additional concern
is that the altered stress on the aortic valve may result in
valve leaflet fusion and aortic insufficiency and stenosis.
This has been particularly reported in patients with
pulsatile assist pumps, but also seen in patients with
continuous-flow pumps.
Our initial experience with the 18 patients described here
has been favorable. We are encouraged by our results
with the use of the redesigned HeartMate II in the
treatment of patients with advanced heart failure. We
believe that this small, axial-flow blood pump is durable
and well tolerated and will offer an extended, improved
quality of life for critically ill heart failure patients of
varying size and clinical status.
AcknowledgementsThe authors are grateful to Mr Carlo Contento and all the
Cardio-Perfusion Team for the enormous contribution in
the technical and clinical management of VAD patients.
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