- Antibiotics are given to prevent and treat infections. - The driveline exit site is cleaned and dressed regularly. - If infection occurs inside the body, removal of the device may be required followed by long term antibiotics. - Prevention of infection is the key - cleanliness of the exit site, prophylactic antibiotics etc. are important. 4) Bleeding: - Patients need to take blood thinning medications like warfarin to prevent clots. This increases the risk of bleeding. - Bleeding can occur from the exit site, during surgery or internally. It needs immediate medical attention. - Blood transfusions may be required to replace lost blood volume.

1. INTRODUCTION
A Ventricular Assist Device (VAD) is a mechanical circulatory device that is
used to partially or completely replace the pumping action of a failing human heart.
Unlike artificial heart, which completely takes over all the functions of the human heart,
a Ventricular Assist Device, as the name suggests, aids the functioning of the ventricles
of the heart. Any abnormality present in the ventricles can be effectively dealt by a
Ventricular Assist Device.
Cardiac problems are a very common ailment in today’s world. People from
all walks of life suffer from a plethora of cardiac complications. Ventricular malfunction
is a common disease which leads to several problems viz. Lower Cardiac output, Angina
Pectoris, poor circulation of oxygen and nutrients to the body, poor supply of
deoxygenated blood to the lungs, etc. which leads to further physiological diseases.
Ventricular Assist Device can effectively treat all such problems by treating the root
cause of such ailments, the Ventricles. Proper contraction of Ventricular muscles will
lead to a higher Cardiac output, which helps in delivering a higher volume of blood to
the lungs, followed by proper delivery of oxygenated blood from the Left Ventricle.
Thereby solving all the problems related to insufficient supply of oxygen and nutrients
to the body.
All such aspects, classifications, working mechanisms, presently used
Ventricular Assist Devices in the surgical arena, future of Ventricular Assist Devices
and their shortcomings will be elaborated in the following pages. Although Ventricular
Assist Devices have been in the world of cardiac surgery for more than a decade, this
seminar work will stress upon Advanced Ventricular Assist Devices, which are
technologically different from the conventional Ventricular Assist Devices. Technical
details and methodology will be discussed as you browse through the pages to follow.
Happy reading and discovery!
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2. HISTORY AND PRESENT STATE OF VENTRICULAR ASSIST DEVICES
The very first Ventricular Assist Device was manufactured in the year 1994, the
name coined was “HeartMate IP LVAS”. This device and its sister devices emulated the
heart by using a pulsatile action where blood is alternately sucked into the pump from
the left ventricle and then forced out of the aorta. FDA in the US had approved of such
devices in October 1994. Such devices were termed as “First Generation VADs”.
Currently used Ventricular Assist Devices employ continuous flow pumps which
can be classified into 2 types: Centrifugal pumps and Axial flow impeller driven pumps.
These pumps have advantage over the former pulsatile action pumps because of their
simplicity in working mechanism. Due to simplicity their sizes are also smaller. These
devices are popularly known as “Second Generation VADs” or Advanced Ventricular
Assist Devices. Working mechanism and classifications of Advanced Ventricular Assist
Devices will be explained in details in the subsequent sections.
Ventricular Assist Devices are implanted to patients who have practically lost the
ability of contraction of ventricles. The entire contraction mechanism of heart is taken
over by this device, be it the right ventricle, the left ventricle or both. Since it takes over
a major functionality of the normal heart, one might ask what is the difference between
an artificial heart and a Ventricular Assist Device? The answer is, an artificial heart is a
device that carries out all the functions of a healthy heart: intake of deoxygenated blood
from the Vena Cavae, sending it to the lungs through pulmonary artery, receiving
oxygenated blood from the pulmonary veins and finally releasing it through the aorta.
The normal heart merely has a physical existence in this case. Ventricular Assist Device
on the other hand performs with the impaired heart, it only assists the releasing/pumping
of oxygenated blood from the impaired right ventricle to the aorta or pumping out the
deoxygenated blood from right ventricle to the pulmonary artery. Basically, a
Ventricular Assist Device is provided to support mere existence of the normal heart.
Patients being implanted with Ventricular Assist Device must have their heart
transplanted sooner or later because their heart has been severely damaged. Permanent
Ventricular Assist Device do not have a huge utility because heart transplantation is the
best solution for such an ailment rather than living on an artificial life support system.
2

3. CLASSIFICATION OF VENTRICULAR ASSIST DEVICES
Advanced Ventricular Assist Devices can be classified under the following heads:
1) On the basis of period of use
Temporary Ventricular Assist Device: Ventricular Assist Devices which are
meant for short term use, i.e when a patient is undergoing cardiac surgery or
recovering from any cardiac ailment.
Permanent Ventricular Assist Device: Ventricular Assist Devices which are
permanently transplanted into the human body for proper functioning of
ventricles.
2) On the basis of impaired ventricle
Left Ventricular Assist Device ( LVAD): Ventricular Assist Device which helps
in restoring the proper functioning of left ventricle.
Right Ventricular Assist Device (RVAD): Ventricular Assist Device which helps
in restoring the proper functioning of right ventricle.
Bi- Ventricular Assist Device (BiVAD): Ventricular Assist Device which helps
in restoring the proper functioning of both the left and right ventricles.
3) On the basis of Pumping Mechanism
Pulsatile Ventricular Assist Device: Ventricular Assist Devices which mimic the
pumping action of the ventricles are termed as Pulsatile Ventricular Assist
Devices.
Non-pulsatile Ventricular Assist Device: Centrifugal pumps or Axial flow pumps
are employed to carry out the blood circulation through the ventricles.
3

4. 4) On the basis of suspension of rotors
Rotors are an important component of Ventricular Assist Device’s pump. This
classification is of relevance to Advanced Ventricular Assist Devices only
because the earlier versions did not propel the blood using rotors.
Bearing suspension: Advanced Ventricular Assist Devices use such rotor
suspension technique where the rotor is suspended in the pumping chamber over
a bearing chamber. As the rotor rolls over the bearings it creates a translatory
motion in the chamber which pumps the blood out.
Electromagnetic or Hydrodynamic suspension: These technologies are still under
research and has not been implemented in the device.
NEED OF VENTRICULAR ASSIST DEVICES
As mentioned in the introduction, cardiac ailments have become a major cause of
mortality in the recent times, out of which ventricular problems find a great percentage.
Invention of the Ventricular Assist Device has been able to solve this problem quite
largely. Statistics of the US regarding cardiac ailments are listed below:
 5 million people suffer from Congestive Heart Failure (CHF).
 2,50,000 patients are in the advanced stage of CHF
 5,00,000 new cases arrive each year
 50,000 deaths are caused due to ventricular failure alone
 Only-effective treatment for end stage ventricular failure is total Heart transplant.
But in the year 2008-2009:
 7318 patients required a heart
 2210 received one
 623 perished waiting
4

5. ADVANCED VENTRICULAR ASSIST DEVICE
Advanced Ventricular Assist Device is also termed as “Non-pulsatile Ventricular Assist
Device”, because the main difference between the puslatile ones and the advanced is the
pumping mechanism. Pulsatile Ventricular Assist Devices used positive displacement
pumps to circulate blood which almost emulated the real contraction phenomenon of
ventricles. But Advanced Ventricular Assist Devices uses continuous flow pumps which
are of two types: Centrifugal and Axial flow pumps. The replacement of pulsatile
technology with non-pulsatile technology was due to a few factors:
1) Irregular Haemodynamic flow of blood through the pulsatile pump.
Such a turbulent flow lead to haemolysis of blood corpuscles which lead to severe
complications like clotting, emboli formation, thrombus formation. All such undesirable
side effects lead to abandonment of the technology.
2) Large size
Large size of the pulsatile Ventricular Assist Device was undesirable as it had to
be implanted within the body (most cases). Non pulsatile ones have smaller size.
3) Operating sound
Pulsatile Ventricular Assist Devices emitted sound during their operation which
had an unaesthetic appeal. Non pulsatile have practically no sound during
operation or at most may have a faint humming sound.
4) Large sized battery
Owing to its primitive design and working mechanism, the power consumption
of pulsatile Ventricular Assist Device was high, thereby requiring a larger battery
for its supply. Non pulsatile ones do not suffer from this problem.
Due to such positive desirable factors Non-pulsatile Ventricular Assist Devices became
popular and are widely used now.
5

6. Key features of Advanced Ventricular Assist Device:
 Enabled with Continuous flow pumps
 ECG independent
 LVADs are the most popular Advanced Ventricular Assist Devices
 Operation is practically soundless
 Patient generally has a weak or non palpable pulse owing to the continuous
pumping mechanism of the Ventricular Assist Device.
 Patient may have a narrow pulse pressure and may not be measurable by normal
blood pressure measuring instruments.
 Mean arterial pressure is in the range of 65 to 90 mm Hg.
Although the systolic pressure is quite below the normal range of a healthy human
being, one must not compare the blood pressure with that of a healthy human because
the patient who is being put on a Ventricular Assist Device has practically lost his heart
contraction ability. A mean blood pressure of 65 to 90 mm Hg is sufficient to circulate
the blood through the entire body because the pumping action is continuous rather than
pulse variant.
Components of an Advanced Ventricular Assist Device:
 Outflow tube: attached to aorta
 Inflow tube: attached to the apex (bottom) of left ventricle
 Power source: driving the continuous flow pump, placed outside the body.
 Driveline: connects the pump to the controller, placed outside the body.
6

7.  Controller: controls the pump’s functioning, displays the status of the system and
has alarm system.
Fig1: Arrangement of Advanced VAD (Axial Pump) and its external components.
7

8. 8

9. Fig 2: Arrangement of Advanced VAD (Centrifugal Pump) and its external components.
The Pump:
This is the heart of the Advanced Ventricular Assist Device. These devices use
Continuous flow pumps, which are of two types:
1) Centrifugal flow pumps:
A central rotor is present which is suspended on bearings inside the pump
chamber. Controlled electric currents running through coils contained in the
pump housing apply forces to the electromagnets which causes the rotors to spin.
9

10. Fig 3.: Centrifugal flow pump.
2) Axial flow pump:
10

11. This type of pumps are mostly preferred in manufacturing Advanced Ventricular
assist devices. Similar to the centrifugal ones, the rotors are suspended over a
bearing set but here the blades are helical in shape and are parallely aligned with
the rotor’s axis.
Fig. 4: Axial flow pump.
Key features of the continuous flow pumps:
11

12. 1) Flow:
 Measured in liters per minute (lpm): General range: (3-10)lpm
 Flow is directly proportional to pump speed: Higher the pump speed greater is
the flow rate.
2) Speed:
 Measured in revolutions per minute (rpm): General range: (8000-15000) rpm
 Flow speed is determined and fixed by the surgeons and cannot be manipulated.
If, however this speed changes, it indicates thrombus formation inside the pump.
3) Power:
 The amount of power a VAD consumes to run continuously at the set speed.
4) Pulsatility Index (PI):
It is the measure of the pressure difference inside the Ventricular Assist Device
pump and the heart’s ventricle(s) if it is functioning partially. Patients suffering
from severe cardiac problem have a PI of Zero.
Such important parameters are displayed on the Ventricular Assist Device’s console or
controller.
LIST OF VENTRICULAR ASSIST DEVICES USED:
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13. Device Manufacturer Type
Approval Status as of
July 2009
Novacor World Heart Pulsatile.
Was approved for use in
North America, European
Union and Japan. Now
defunct and no longer
supported by the
manufacturer.
HeartMate XVE Thoratec Pulsatile.
FDA approval for BTT in
2001 and DT in 2003. CE
Mark Authorized. Rarely
used anymore due to
reliability concerns.
HeartMate II Thoratec
Rotor driven continuous
axial flow, ball and cup
bearings.
Approved for use in North
America and EU. CE Mark
Authorized. FDA approval
for BTT in April 2008.
Recently approved by FDA
in the US for Destination
Therapy (as at January
2010).
HeartMate III Thoratec
Continuous flow driven
by a magnetically
suspended axial flow
rotor.
Clinical trials yet to start,
uncertain future.
Incor Berlin Heart
Continuous flow driven
by a magnetically
suspended axial flow
rotor.
Approved for use in
European Union. Used on
humanitarian approvals on
case by case basis in the
US. Entered clinical trials
in the US in 2009.
Jarvik 2000 Jarvik Heart
Continuous flow, axial
rotor supported by
ceramic bearings.
Currently used in the
United States as a bridge to
heart transplant under an
FDA-approved clinical
13

14. investigation. In Europe,
the Jarvik 2000 has earned
CE Mark certification for
both bridge-to-transplant
and lifetime use. Child
version currently being
developed.
MicroMed
DeBakey VAD
MicroMed
Continuous flow driven
by axial rotor supported
by ceramic bearings.
Approved for use in the
European Union. The child
version is approved by the
FDA for use in children in
USA. Undergoing clinical
trials in USA for FDA
approval.
VentrAssist Ventracor
Continuous flow driven
by a hydrodynamically
suspended centrifugal
rotor.
Approved for use in
European Union and
Australia. Company
declared bankrupt while
clinical trials for FDA
approval were underway in
2009. Company now
dissolved and intellectual
property sold to Thoratec.
MTIHeartLVAD
MiTiHeart
Corporation
Continuous flow driven
by a magnetically
suspended centrifugal
rotor.
Yet to start clinical trials.
C-Pulse Sunshine Heart
Pulsatile, driven by an
inflatable cuff around the
aorta.
Currently in clinical trials
in the US and Australia.
HVAD HeartWare
Miniature "third
generation" device with
centrifugal blood path
and hydromagnetically
suspended rotor that may
be placed in the
pericardial space.
Obtained CE Mark for
distribution in Europe,
January 2009. Initiated US
BTT trial in October 2008
(completed February 2010)
and US DT trial in August
2010.
14

15. DuraHeart Terumo
Magnetically levitated
centrifugal pump.
CE approved, US FDA
trials underway as at
January 2010.
Thoratec PVAD
(Paracorporeal
Ventricular Assist
Device)
Thoratec
Pulsatile system includes
three major components:
Blood pump, cannulae
and pneumatic driver
(dual drive console or
portable VAD driver).
CE Mark Authorized.
Received FDA approval for
BTT in 1995 and for post-
cardiotomy recovery (open
heart surgery) in 1998.
IVAD -
Implantable
Ventricular Assist
Device
Thoratec
Pulsatile system includes
three major components:
Blood pump, cannulae
and pneumatic driver
(dual drive console or
portable VAD driver).
CE Mark Authorized.
Received FDA approval for
BTT in 2004. Authorized
only for internal implant,
not for paracorporeal
implant due to reliability
issues.
COMPLICATIONS AND SIDE EFFECTS
Like every technology, this technology too has its share of shortcomings. Some of the
complications are:
15

16. 1) Coagulation and Thrombosis:
This is one of the most predominant side effects of the Advanced Ventricular
Assist Device. This happens mainly due to the flow of blood over non-biological
surfaces. This problem has been eliminated by constructing the pump
components with anticoagulant coated materials viz. Heparin or a fibrin based
compound and polyurethane compounds.
2) Haemolysis:
It is a phenomenon where red blood corpuscles are destroyed due to non-laminar
flow of blood. The non-laminar flow occurs across various sections of the
Ventricular Assist Device viz. the pump, the conduits carrying the blood from
the ventricles or to the aorta. Such a problem is eliminated by using elastic
conduits which more or less resemble the elastic nature of normal blood vessels
and by using blood straightener devices before and after the pump which creates
a laminar flow.
3) Infection:
Ventricular Assist Devices infections can be caused by a large number of
different organisms viz.:
 Gram positive bacteria (Staphylococci, etc)
 Gram negative bacteria (Pseudomonas aeruginosa, etc)
 Fungi (Candida, etc)
Treatment of Ventricular Assist Device related infection is very difficult despite
optimal treatment. But every effort is made to contain proliferation of such
organisms. Practicing sterile procedures during every step of the operation and
also during maintenance is necessary.
4) Portability:
This remains one of the major disadvantages of this technology. The majority of
the Advanced Ventricular Assist Devices present today are somewhat bulky,
therby rendering normal movement of human a bit difficult and uneasy. The
16

17. smallest device, the HeartMate II weighs about 0.45 kg and measures 7.6 cm.
This has been proven the best device for women and children for whom other
devices would be bulky. As technology progresses we hope to see even more
compact and reliable devices being discovered and used.
CONCLUSION
17

18. Advanced Ventricular Assist Devices have been a boon to cardiac patients
suffering from severe ventricular failure. It has been a long time since this device was
first designed, the device has evolved and through extensive research and development it
has reached almost a supreme state. But as other technologies and methodologies would
develop this present technology would gradually become outdated. For instance, the
latest form of Ventricular Assist Devices, still under development, employs
Hydrodynamic suspension of the rotor and its blades within the pump. This technology
would drastically decrease the power consumption of the device, probably would
eliminate the usage of blood flow straighteners, thereby making the devices more
compact. FDA and other medical bodies would be there to ascertain the credibility of
such a technology and its implications. Till then, this present technology would continue
to serve innumerable patients suffering from ventricular ailments and gift them better
lives.
REFERENCES
18

19. 1) www.thoratec.com
2) www.jarvikheart.com
3) www.google.com
4) Google Scholar
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