Topic 10: VAD Flashcards
Roller pumps aren’t good VADS
Limitations?
Tethering, Blood trauma, Adjust pump speeds due to changes in heart pressures.
1963–Spencer, et al. Reported using a roller pump to support a patient to recovery
1st successful clinical application of a true
VAD - who? when?
DeBakey, 1966
Pneumatically driven diaphragm pump Paracorporeal LA to Axillary Artery 37yo patient who could not be weaned from CPB s/p AVR/MVR Supported for 10 days Weaned and Discharged
1st used a Total Artificial Heart (TAH) to temporarily support a patient to transplant
Cooley, 1969
47yo man with failure to wean from CPB s/p LV Aneurysm repair
TAH had only been tested for up to 12 hours in an animal model
Implanted the “Liotta Heart” which was a pneumatic device
Supported the patient for 64 hours
University of Utah investigators were the first in the world to implant a permanent what? when?
TAH on 12/2/1982
Jarvik 7 TAH performed by Dr. William DeVries
Implanted into Dr. Barney Clark, 61yo dentist with end stage idiopathic dilated cardiomyopathy
Died of complications from aspiration pneumonia, Renal failure, colitis with septicemia.
Was supported for 112 days
1st planned TAH implant as a Bridge to
Transplant (BTT)
1985–Copeland at the University of Arizona
Syncardia, Cardiowest–Tucson, AZ
Drs. Olsen and Copeland revived the first TAH model
Modified and renamed–Cardiowest C70
Received FDA Approval as a BTT in 2004
Transplantation provided a stimulus for the development of what?
VADs for support until transplant
30% of patients died on the list
Became an incentive to develop devices that could be used for patients with acute cardiac decompensation while awaiting transplantation
9/1984–Stanford University
Oyer and Colleagues –Implanted the Novacor LVAD - which is what?
1st successful transplant s/p BTT with LVAD
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 (Implantable pneumatic)
Restored near normal hemodynamics.
What were its Limitations?
Devices dependent on large consoles for power and controller function
Patients confined to hospital until
transplantation despite being fully ambulatory
1991–Frazier at Texas Heart Institute
first to use what?
First to use an untethered vented electric LVAD for long term support
33 y/o patient
Battery operated Heartmate VE
500 days of support
Patient died of embolic cerebral vascular accident.
1990–Kormos at University of Pittsburg
Developed a program to do what?
transfer VAD patients to a monitored outpatient setting until transplantation
1994–What was the first FDA approved implantable device for bridge to
transplant?
Heartmate LVAD
Biological Barriers to VAD design (4)
- Blood versus Foreign surface
- Moving parts
- Changes to patients anticoagulation and immune system over time in response to the mechanical pump
- Pharmacologic modifications (Heparin, Coumadin, ASA)
Indications for VAD: 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.
Indications for VAD two options?
Bridge to Transplant
Destination Therapy
Contraindications for VAD - tons
High surgical risk Recent/evolving stroke Neurological deficits impairing the ability to manage device Coexisting terminal condition Abdominal aortic aneurysm (greater than 5cm) Active infection Fixed pulmonary hypertension Severe pulmonary dysfunction Multisystem organ failure Inability to tolerate anticoagulation HIT Psychiatric illness Lack of social support pregnancy
Design of a VAD must take into consideration? tons
Configured for their eventual application
(Shorter term vs partial assist vs long term support vs total support)
Different uses and device requirements impact design.
Anatomically compatible (Used over large variations in body mass, chest size/ shape, abdominal girth, etc.)
Structurally stable in a corrosive saline environment
Operate continuously w/o maintenance 4years.
Cannot fail under increased stress conditions
Reduce power requirements to save battery life
Must be efficient–reduce heat waste
2 different kinds of pumps for VAD
Positive displacements (Usually pneumatic) Rotary
Flow and Pressure - Positive Displacement - how?
Change volume in the chamber
Flow and Pressure - Rotary - how?
Rotating Impeller
Source of Energy Positive Displacement?
Air pressure/ Electricity
Source of Energy - Rotary:
Electricity
Is rotary of positive displacement smaller?
Rotary is smaller with a smaller cannula
Prime Volume:
Positive Displacement:
Large Prime Volume
Prime Volume - Rotary:
has a smaller Prime Volume than post displacement
Flow Ranges for rotary and post displacement?
Both plagued with thrombosis with decreased flow and hemolysis with increased flow
If Afterload changes what happens in- Post Displacement VAD pumps?
Unaffected by changes in afterload
If Afterload increases what happens in Rotary VAD pumps?
Flow drops with increased SVR
Comparison of Pump Types: Preload, Positive Displacement:
Passive filling, output follows venous return
Comparison of Pump Types: Preload, Rotary:
Flow increases with increased VR, but no active suction applied
Positive Displacement Pumps Flow? Mean BP? HR rate? Mean Filling Pressure?
Flow is about 5-10 liters per minute
Mean bp = 100-150 mmHg
Rate is <120 bpm
Mean filling pressure is appx 20mmHg
Positive Displacement Pumps - how does flow work?
Propels fluid by changing the internal volume
of a pumping chamber.
Compression of a sac/membrane, etc.
Provides pulsatile flow
Requires 1 way valves to produce forward flow
BIVAD–10% of LVADs will need a what?
RVAD
BiVAD is common after what events?
and least used with what?
transplant failure, postpartum, Acute MI, Cardiomyopathy, Myocarditis.
Used least with idiopathic CM and Ischemic CM
Thoratec PVAD/IVAD - provides what?
FDA Approved as a BTT since 1995
Provides support for the right, left or both
ventricles
Preop risk factors for Right Heart Failure? (3)
Hemodynamics-
-Low CI with inc. RA pressure not necessarily an indicator of Rt. Heart failure.
May improve when LV is unloaded with LVAD
-Ability of RV to generate pressure
-Low pulse pressure with high CVP–indicator of BiVAD
Indication of BiVAD from what two increased lab values?
Higher pre-op bilirubin
Higher pre -op creatinine
Indicators for a BiVAD - 3
Emergent Implant
Intraop Bleeding
Greater transfusion requirements increases pulmonary vascular resistance and promotes the development of right heart failure.
Post op what is common for BiVAD pts? and whats it related to?
Post op bleeding is common for BiVAD patients
Related to the severity of hepatic failure
Thoratec PVAD/IVAD Stroke volume pump chamber? Beats ? Flow is Lpm? BSA >?
65 mL
Beats 40-110 bpm
Flow is 1.3-7.2 Lpm
BSA >0.73m2
Thoratec PVAD/IVAD
Made of?
How many valves?
How does it pump?
Thoralon Polyurethane
2 mechanical valves
Alternate positive and negative air pressure by console/Portable driver
Thoratec PVAD/IVAD
where is it placed in patients?
Placed in the anterior abdominal wall w/ cannulas crossing into the chest wall to connect the VAD to the heart and great vessels.
External location is suitable for use in smaller pts
Actuated by DDC for in hospital use & portable TLCII for ambulatory use TLCII approved in 2003
Pump considerations for Implant: Thoratec PVAD/IVAD Cannulation? Temp? CPG/XC? LV Vent special indications? Ultrafiltrate to keep HCT to what?
-Ideally use bicaval cannulation
-Normothermic
-w/o cardioplegia or XC
-LV Vented
-De-aired via LV Apex cannula before connecting to the VAD
-Ultrafiltrate to keep hematocrit greater than 30% (in case clotting factors are needed to
assist coagulation)
Thoratec PVAD/IVAD
Anticoagulation w/what 1st & afterwards what?
INR?
Chronic Warfarin Anticoagulation
INR= 2.5-3.5
Starts with heparin–PTT 1.5x baseline until
GI function is stable and show low bleeding
risk (10-14 days)
Switch to warfarin and ASA
PVAD–used as what?
some other random facts:
Mostly what gender? ischemic/idiopathic CM%?
BTT and Post Cardiotomy
1982-2005 : 2900 patients implanted 1,941 Heart Failure patients awaiting transplant on PVAD support 73% are males Mean age: 48 years BSA: 1.89m2 Weight: 75 kg 30% are ischemic CM 21% are idiopathic CM
BIVADS - mean support? longest support?
–54%, LVADs-34%, RVAD–3%
Mean support: 51.8 days
Longest support: 3.3 years
PVAD can be used in pediatrics due to being what?
paracorporeal
Thoratec IVAD: Intracorporeal VAD (or Implantable VAD)
used when?
Approved for what?
BSA >?
Used when longer term support is anticipated
Approved in 2004 by the FDA as a BTT or BTR
BSA >1.3m2 b/c of intracorporeal position
Thoratec IVAD: Intracorporeal VAD (or Implantable VAD) Difference from PVAD? (4)
body? wt? leads? mm?
Polished Titanium Body–makes it implantable
Reduced weight - 339gms vs. 417 gms
Narrower Percutaneous leads
9mm vs. 20mm
