Ventricular Assist Devices Flashcards
Carrell and Lindbergh and Demikhov
1930s Experimented with mechanical support in animal models
Gibbon
1953
O 1st use of CPB
O Inability to wean fueled interest in prolonged mechanical support in order to promote myocardial recovery
Spencer
1963 Reported using a roller pump to support a patient to recovery
O Roller pumps aren’t good VADS O Limitations
O Tethering, Blood trauma, Adjust pump speeds due to changes in heart pressures.
de bakey
1966 O 1st successful clinical application of a true
VAD
O Pneumatically driven diaphragm pump
O Paracorporeal O LA to Axillary Artery
O 37yo patient who could not be weaned from CPB s/p AVR/MVR
O Supportedfor10days O Weaned and Discharged
Klaus
- Introduced the concept of atrial counter
pulsation
O Rapid systolic unloading of the ventricle with diastolic augmentation.
O Lead to the development of the balloon pump which was developed in 1963 and applied clinically in 1967.
1958–
O Total artificial heart was used in a dog model O Supported for 90 min.
1962
Reporting survival up to 24 hours with TAH
cooley
1969 – 1st used a TAH to temporarily support a patient to transplant O 47yo man with failure to wean from CPB s/p LV Aneurysm repair O TAH had only been tested for up to 12 hours in an animal model O Implanted the “Liotta Heart” which was a pneumatic device O Supported the patient for 64 hours.
first in the world to implant a permanent TAH on 12/2/1982.
university of Utah
Jarvik 7 TAH performed by
Dr. William DeVries
first person to receive TAH
Implanted into Dr. Barney Clark, 61 yo dentist with
end stage idiopathic dilated cardiomyopathy
O Died of complications from aspiration pneumonia, Renal failure, colitis with septicemia.
O Was supported for 112 days.
5 patients received permanent TAH under FDA trial
O Longest survival
620 days
– Copeland at the University of
Arizona
- 1st planned TAH implant as a Bridge to Transplant (BTT)
Syncardia, Cardiowest – Tucson, AZ
Drs.OlsenandCopelandrevivedthe
model
O Modifiedandrenamed–Cardiowest C70
O Received FDA Approval as a BTT in 2004
Norman
1978 Device used for 5 days of support O Intracorporeal pneumatic device O Patient died of multi-organ system failure s/p transplant.
Early 1980s
ansplantation became a widely applied therapy.
O 30% of patients died on the list
O Became an incentive to develop devices that could be used for patients with acute cardiac decompensation while awaiting transplantation.
1980–NIHsentoutrequestforproposals
To develop an “implantable, integrated, electrically powered left heart assist system” that could be used on a long term basis and allow extensive patient mobility.
9/1984–StanfordUniversity
Oyer and Colleagues – Implanted the Novacor
LVAD O 1st successful transplant s/p BTT with LVAD
O Followed by Hill and colleagues who implanted a Pearce-Donachey pneumatic LVAD.
1992 – Frazier and colleagues
1st to report successful BTT with Thoratec
Heartmate IP VAD O Implantable pneumatic
O Restorednearnormalhemodynamics.
limitations of thoratec heartmate ip
O Devicesdependentonlargeconsolesforpower and controller function
O Patients confined to hospital until transplantation despite being fully ambulatory.
Kormos at University of Pittsburg
1990 Developed a program to transfer VAD patients to a monitored outpatient setting until transplantation.
Frazier at Texas Heart Institute
1991 First to use an untethered vented electric LVAD for long term support
O 33y/opatient O Battery operated Heartmate VE O 500 days of support O Patient died of embolic cerebral vascular accident.
1990s – FDA sponsored
several multi- institution trials of assist devices as bridge to transplant and bridge to recovery.
1994 – Heartmate
LVAD was the first FDA approved implantable device for bridge to transplant.
Biological Barriers to VAD design
Blood versus Foreign surface
O Blood contact surface cannot harm the patient
O Minimum generation of blood clots
Changes to patients anticoagulation and immune system over time in response to the mechanical pump
O Coagulopathy immediately after implantation because of bypass
O Period of hypercoagulability
O Returning to baseline
Pharmacologic modifications
(Heparin, Coumadin, ASA)
O Need to anticoagulate on some level.
Indications for VAD
O Bridge to Transplant
Worsening hemodynamics despite high level of IV inotropic support and/or vasodilator therapy or refractor arrhythmias.
Indications for VAD Destination Therapy
Patients who are not transplant candidates. Have an EF less than 25% and NYHA Class IV symptoms despite optimal therapy.
Contraindications
High surgical risk O Recent/evolving stroke O Neurological deficits impairing the ability to manage device O Coexisting terminal condition O Abdominal aortic aneurysm (greater than 5 cm) O Active infection O Fixed pulmonary hypertension O Severe pulmonary dysfunction O Multisystem organ failure O Inability to tolerate anticoagulation O HIT O Psychiatric illness O Lack of social support O pregnancy
design requirements
Devices need to be configured for their eventual application
O Shorter term versus partial assist versus long term support versus total support.
O Different uses and device requirements impact design. O Anatomicallycompatible
O Used over large variations in body mass, chest size/ shape, abdominal girth, etc.
O Structurally stable in a corrosive saline environment O Operate continuously without regular maintenance for
years. O Cannot fail under increased stress conditions O Reduce power requirements to save battery life O Must be efficient – reduce heat waste.
2 different types of pumps
Positive displacements O Usually pneumatic
O Rotary
Comparison of Pump Types
Prime Volume:
Positive Displacement: Large Prime Volume O Rotary: Smaller Prime Volu
flow ranges for different pump types
Both plagued with thrombosis with decreased flow and hemolysis with increased flow
afterload differences between pumps
Positive Displacement: Unaffected by changes in
afterload O Rotary: Flow drops with increased SVR
preload differences between pumps
Positive Displacement: Passive filling, output
follows venous return
O Rotary: Flow increases with increased VR, but no active suction applied
Positive Displacement pumps
O Propels fluid by
changing the internal volume of a pumping chamber.
O Compression of a sac/membrane, etc. O Provides pulsatile flow O Requires 1 way valves to produce forward flow
Positive Displacement pumps specs
Flow is about 5-10 liters per minute O Mean bp = 100-150 mmHg O Rate is <120 bpm O Mean filling pressure is appx 20mmHg.`
Thoratec PVAD/IVAD
FDA Approved as a BTT since 1995 O Provides support for the right, left or both
ventricles.
10% of thoratec Lvad will need
RVAD
BiVAD is common after
transplant failure, postpartum Cardiomyopathy, Acute MI, Myocarditis. Used least with idiopathic CM and Ischemic CM.
According to the Thoratec Registry, 25% received BiVAD support with
hybrid RVAD and LVAD or Thoratec BiVAD.
BiVADusehasincreased
18%since2000.
Preop risk factors for RHF
Hemodynamics – Low CI with inc. RA pressure not necessarily an indicator of Rt. Heart failure.
O May improve when LV is unloaded with LVAD
O Ability of RV to generate pressure
O Low pulse pressure with high CVP – indicator of BiVAD
Indicators of BiVAD
Early insertion of LVAD before significant major organ dysfunction
O Less likely to need RVAD too. O Higher pre-op bilirubin O Higher pre-op creatinine
O Normalize w/in 2-3 weeks after implant of VAD O Emergent Implant O Intraop Bleeding
O Greater transfusion requirements increases pulmonary vascular resistance and promotes the development of right heart failure.
O Post op bleeding is common for BiVAD patients O Related to the severity of hepatic failure
Thoratec PVAD/IVAD STROKE VOLUME
65 mL
Thoratec PVAD/IVAD BEATS/FLOW
40-110bpm, 1.3-7.2Lpm
THORATEC PVAD/IVAD placed
the anterior abdominal wall with cannulas crossing into the chest wall to connect the VAD to the heart and great vessels. Externallocationissuitableforuseinsmallerpatients O BSA >0.73m2
THORATEC PVAD/IVAD actuated by
DDC for in hospital use and portable TLCII for ambulatory use
O TLCII approved in 2003
Pump considerations for Implant: Thoratec PVAD/IVAD
Ideally use bicaval cannulation O Normothermic O w/o cardioplegia or XC O LV Vented
O De-aired via LV Apex cannula before connecting to the VAD
O Ultrafiltrate to keep hematocrit greater than 30% (in case clotting factors are needed to assist coagulation)
Anticoagulation : Thoratec PVAD/IVAD
Chronic Warfarin Anticoagulation
O INR=2.5-3.5
O Starts with heparin – PTT 1.5x baseline until GI function is stable and show low bleeding risk (10-14 days)
O Switch to warfarin and ASA
Thoratec IVADs
Intracorporeal VAD (or Implantable VAD) O Used when longer term support is anticipated O Approved in 2004 by the FDA as a BTT or BTR O BSA>1.3m2b/cofintracorporealposition
Thoratec IVADs Difference from PVAD
Polished Titanium Body – makes it implantable O Reducedweight
O 339gms vs. 417 gms O Narrower Percutaneous leads O 9mm vs. 20mm
Heartmate XVE
O Placed in
5000 patients worldwid
Heartmate XVE Textured inner surface
O Circulatoryassistancewithout
anticoagulation except an antiplatelet agent
Heartmate XVE Promotes
Promotes
Heartmate XVE CON
mmunologicallyactive
O Limit transplant candidacy due to increase in immunologic reactivity.
WHAT TYPE OF PUMP IS HEARTMATE XVE
Positive displacement pump
O Made of titanium with a polyurethane diaphragm and a pusher plate actuator (which is responsible for producing mechanical energy).
HOW IS HEARTMATE XVE POWERED AND CANNULATION TECHNIQUE
Powered pneumatically (emergency) or electrically
O Cannulate LV Apex (apical cannula) O Dacron conduit with 25mm porcine valve
O Cannulate ascending aorta O 20mm Dacron outflow graft with porcine valve
Heartmate XVE
O Pneumatic
Uses 9kg driver console
O Small emergency hand pump O Actuatespusherplateviadriveline
Heartmate XVE Electric Motor
Rotates and displaces pusher plate
O Air that is displaced by the diaphragm is vented to the atomosphere
O Wherethehandpump/pneumaticdriverplugsin. O Vent filter in place with electric motor operation.
Heartmate XVE POWER
2 batteries (4-7hours of use) O External controller
Heartmate XVE
O Stroke Volume
83mL
Heartmate XVE MODES
Fixed and Auto Modes. Auto - SV maintained at 97% full O Flow–4-10Lpm
O Fixed – stroke volume depends upon filling
O Rate is adjusted manually to keep stroke volume between 70-80mL
Heartmate XVE
O Psuedointima
Titaniummicrospheresandfibrillartextured
surface O Promotespseudointima
O Thin layer of biologic matrix that resists thrombogenesis
Heartmate XVE
O Psuedointima COMPOSED OF
cellular elements, collagen, and cells derived from circulating progenitor cells.
O Immunologically active microenvironment
O Heightened susceptibility to opportunistic infections.
Heartmate XVE
O Implantation
Dacron grafts must be pre-clotted
O Placed intraperitoneal or in peritoneal pocket in left upper quadrant
O Must go through diaphragm with cannulas O Percutaneous leads exit to the right O AI and MS must be corrected at implantation O PFOs must be closed at implanation O Requires CPB O No cardioplegia or cooling O BSA: >1.5m2 O Anticoagulation – ASA only
Heartmate XVE
Identification of pump malfunctions is important because
Bearings wear out in 18-24 months
O Requires replacement
O Vent filters are changed regularly and sent to Thoratec for evaluation
O Test for signs of motor dust
O Excessive motor dust is an indication of bearing wear
O Other signs of bearing wear/ failure O Increaseincurrentusage O Change of pump motor sounds/ rhythm
O If pump shows signs of wear, patients must be admitted in case of failure
O Pneumatic driver at bedside.
Heartmate XVE: BTT Survival
65% survive to transplant/ recovery O If they survive the first month, they have an
85% chance of a successful outcome. O Success is related to patient selection:
O LVAD screening scale
Heartmate XVE
O Limitation to XVE
O Devicemalfunction
Rotary VAD in _____ 1st described continuous flow circulatory pumps.
1960
developed a small axial flow LVAD that went into clinical trials in 1998.
DeBakey and Noon
axial flow LVAD was followed by
Jarvik 2000 in 1999. O Nimbus/ HMII axial flow pump in 2000.
Rotary pumps
O Uses
rotating impellers to propel blood forward
O Supported with bearings O Powered by spinning shaft/ magnetic forces
Micromed
advantages
limited contact surface area O Fewer moving parts O Reduces cost O Potentially more durable? Expands the pool of qualified patients O Simplifies implantation
micromed design
O Axial flow design O Smaller size
Development of Micromed- DeBakey
O Collaboration between
NASA engineers and Dr. DeBakey and Dr. George Noon
O Establishedin6/1996withNASAlicense O Implanted in 1998 in Europe
O Clinical evaluations as a BTT in Europe and the US
Micromed- DeBakey DESCRIPTION
Mini electromagnetically actuated titanium pump with ball and cup bearings weighing less than 93 grams
O Has Elbow shaped inflow cannula, pump housing unit, dacro outflow, ultrasonic flow probe encircling outflow graft, flexible drive line to controller.
Micromed- DeBakey anticoagulation
Coumadin
Heartmate II what type of device
Axial flow device (2nd generation VAD)
O Reduced size/ weight compared to XVE
Heartmate II developed in_____ by______
theearly1990s O Collaboration between engineers at Nimbus, Inc and
Univeristy of Pittsburg O Initially developed thru NIH gran
Heartmate II motor
Electric Motor O Rotor spins within magnetic field on inlet
and outlet of bearings O Only moving part of pump
O Dacron grafts may require pre-clotting
heartmate 2 power and flow
PBU for power and to charge batteries
O Same system monitor and PBU as HM XVE
O Flow is an ESTIMATE
heart mate 2 flow estimate because
Relationship between pump motor RPM speed and time-varying electrical power consumption of pump motor
O Not accurate when flow is less than 3LPM
Heartmate II
O Implant is below
the L. Costal Margin under the rectus abdominus muscle
O Leave LV Apex to diaphragm to pump
heartmate 2 issues
Thrombus formation
O See abnormal power increase unrelated to change in pump flow
heart mate 2 Other variations
Jarvik 2000
Ventr Assist
Ventracor Ltd, NSW, Australia O 3rd generation device. Sadly, device development stopped due to lack of company funds.
Heartware HVAD
Small continuous flow rotary pump with a centrifugal and non- contact bearing design.
O Impellar is held in place by passive magnetic and hydrodynamic bearing systems, avoiding mechanical contact and wear.
O Physical contact between the housing and the impeller is prevented by thin blood film generated by the hydrodynamic bearings.
Heartware HVAD placed in
pericardial cavity at the apex of the LV O No need for abdominal pocke
DuraHeart LVAS by
Terumo Heart, Inc. O 2nd gen (DH II) Acquired by Thoratec July 2013
DuraHeart LVAS type of flow
continuous rotary
duraheart LVAS upper housing
levitation system and impeller
duraheart LVAS BOTTOM housing
containing the external-drive motor
duraheart LVAS FLOW RATES
2-8lpm with motor speeds of 1200-2400rpm.
O Flow rate can vary with physiological changes
duraheart LVAS First device to reach clinical trial that combined
centrifugal pump and magnetic levitation technology
duraheart LVAS Placed in
abdominal pocket
Levacor VAD
O By
WorldHeartCorp.
Levacor VAD TYPE OF PUMP
Bearinglesscentrifugalpumpwithanimpellercompetely
magnetically levitated.
LEVACOR VAD Implanted
in small subcostal, pre-peritoneal space
Feb 9, 2011 – announced a pause to the study pending FAA
review of “device refinements”
Projections of the inflow cannula into the ventrical
O Elimination of false alarms leading to controller change outs
O Optimization of surface finishing/ coating manuracturing processes
Abiomed Impella 2.5/5.0
Intracatheter VAD
O Can pump 2.5/5.0 Lpm
O Pulls blood from the LV tip to the aorta.
Abiomed Abiocor
O First completely
self- contained replacement heart
Abiomed Abiocor capable of pumping
12 liters per minute
Abiomed Abiocor motor and battery
Internal motor O Internal rechargeable battery O External battery pack O Labeled as a destination device??? O FDA Approval under an HDE
Tandem Heart
10cc hydrodynamic centrifugal pump
O Integratedmotor
Tandem Heart flow
8LPM flow
O Cannuladependent O Tandem Heart transeptal cannula
and 17fr arterial cannula = 5LPM
Tandem Heart floats on
fluid bearing
tandem heart saline drip
10cc/hr saline drip into lower chamber
O Cools and lubricates
Tandem Heart controller
Step by step setup on screen
O 21 pounds O Mounts on standard iv pole at
bedside
Tandem Heart battery backup
1 hour
tandem heart other characteristics
Transonic flow probe
O Selfdiagnostic O Displays alarms and problems
O Integrated air bubble detector
Syncardia TAH flow
9.5 liters per minute through both ventricles
Syncardia TAH after implant is stable
fter implant and stable, patient is moved to
1A , top of the l
syncardia device failures
In 30 years, no device failures
syncardia electronics
all outside body
syncardia driver
pneumatic
Berlin Heart FDA approved in
2011
Berlin heart originally used as
for compassionate use
O Apply for approval, order from Germany
O Now can stock all sizes of devices in hospitals
O Bridge to Transplant
