1. Ventricular Assist Devices (VADs)
Cooper University Hospital: School of Perfusion 2014
By: Michael F. Hancock, CCP

2. Types of Mechanical Assist Devices:
Intra-Aortic Balloon Pump (IABP)- first line of assist
Cardiopulmonary Support (CPS)- a kind of extended CPB/ECMO
Need oxygenator and heat exchanger
Cannulate femoral artery and vein
Maximum support = 48 hours
ACTs- ~180s
Ventricular Assist Device (VAD)- used for more profound ventricular failure
35-70% of patients receiving a mechanical support device are either successfully weaned or receive a heart transplant

3. Types of VADs LVAD- used for failing Left Heart
20% of patients receiving an LVAD will require an RVAD
RVAD- used for failing Right Heart
Bi-VAD- used when both ventricles are failing

4. Scenarios for VAD Indication
Ventricular failure after MI
Bridge to cardiac transplant
When weaning off CPB is impossible
VADs considered when:
Maximum pharmacological support is employed
2 or more of the following drugs are maxed
Dobutamine (10 mcg/kg/min)
Dopamine (10 mcg/kg/min)
Epinephrine (0.2 mcg/kg/min)
Amrinone (10 mcg/kg/min after loading dose)
Milrinone (0.75 mcg/kg/min after loading dose)

5. Preoperative Predictors for VAD Insertion
EF <30%
Severe valvular disease with end-stage myocardial impairment
CAD that may not be reversible with CABG surgery
Anticipated long CPB run

6. Intra-operative Predictors for VAD Insertion
Pre-CPB Ischemia
Prolonged CPB run
Incomplete valve repair or bypass graft
Embolus in coronary artery
Large ventricular aneurysm resection

7. Criteria for Acute Ventricular Failure
Left Ventricular Failure:
CI < 1.8 L/min/m2
Systolic BP < 90 mm Hg
LAP > 20 mm Hg
LAP = PCWP
RAP < 15 mm Hg
RAP = CVP
HR > 80 bpm
Few or no dysrhythmias

8. Criteria for Acute Ventricular Failure
Right Ventricular Failure:
CI < 1.8 L/min/m2
Systolic BP < 90 mm Hg
LAP < 15 mm Hg
LAP = PCWP
RAP > 20 mm Hg
RAP = CVP
HR > 80 bpm
Few or no dysrhythmias
May or may not be with pulmonary hypertension
The work done by the RV is related to the difference between the right atrial and pulmonary artery mean pressure
As the difference approaches zero, pulmonary blood flow is passive and RVF is present

9. Criteria for Acute Ventricular Failure
Bi-Ventricular Failure:
LAP > 20 mm Hg
RAP > 20 mm Hg
Ventricular tachycardia or fibrillation
Severely impaired right and left ventricular function by echo

10. Types of VADs Pulsatile Pumps
The pumps are blood sacs which will force blood into the outflow cannula due to external pressure applied to these sacs
The direction of blood flow is controlled by the prosthetic valves which operate like a normal ventricular valve
The blood sac is compressed externally by 2 forces:
Air (Pneumatic Pumps)
Systole- blood sac is squeezed by increased gas pressure within the pump case causing ejection
Diastole- the pump is maintained ata negative pressure, causing blood to be drawn into the pump
Electric Pusher Plates(Electric Motor Pumps)

11. Types of Pulsatile VADs
Abiomed BVS5000
Extracorporeal pneumatically drive pump with 2 chambers
Passively filled atria
Pumping chamber
Contain 2 trileaflet, Angioflex polyurethane valves which are made without seams to minimize clotting
Valve chamber volumes are 100 cc
Stroke volume is 82 cc
Priming volume of the BVS system is < 660 cc
Patients must remain on bedrest
Maintain ACTs of seconds

12. Abiomed BVS5000 Pros- Cons- Used for LH, RH or both Pulsatile flow
Long periods of support (7-10 days)
Cons-
Cannulas limit flows of 4-6 L/min
Hemolysis, thromboembolism, infection
Anticoagulation required

13. Abiomed AB5000
Abiomed AB5000
Site-
Smaller Ventricle
Allows patients to walk around with the console

14. Pulsatile VADs Heart Mate I- made by Thoratec
Implantable Pulsatile LVAD in patient’s abdomen
Blood pumping chamber and an electric pusher plate torque motor
Pump ejection requires one revolution of the torque motor
After ejection, motor stops to allow passive filling into the chamber

15. Heart Mate I External power source Max pump flow is 10 L/min
Max Pump Heart Rate is 120 bpm
Max stroke volume is 83 cc
Uses 25mm porcine xenograft heart valves
Uses a textured blood contacting surface to promote antithrombotic substance
Contraindication- BSA <1.5
Mobile device to allow patients to move around and go home

16. Non-Pulsatile (Centrifugal Pump) VADs
Causes rotational acceleration of the blood by means of a spinning impeller
Uses a centrifugal pump such as:
Medtronic BioMedicus Pump
Heart Mate II
CentriMag by Thoratec
Flows up to 9.9 L/min
31 cc priming volume
Run ACTs 1.5 times normal with continuous heparin infusion

17. Impella by Abiomed http://www. abiomed
Minimally invasive cathetar based assist device
Improves ejection fraction
Improves cardiac output
Lowers PCWP
Increases MAP
Available in 2.5 or 5.0 L versions
Indications:
High risk PCI
Acute MI patients
Cardiogenic shock patients

18. Impella 2.5 Directly unloads the left ventricle
Reduces the workload of the heart and reduces myocardial oxygen consumption
Floated up through the femoral artery, into the ascending aorta, across the aortic valve and sits in the LV
Generates flows up to 2.5 L/min
Pump motor is 12 fr.
Cathetar is 9 fr.

19. Heart Mate II by Thoratec
The Heart Mate II made by Thoratec is an FDA approved Left Ventricular Assist Device
It is an axial-flow blood pump that produces non-pulsatile flow
The LVAD has only one moving part: The Rotor
Vanes on the spinning Rotor move blood through the pump
Produces flow up to 10 L/min

20. Heart Mate II Approved for: Bridge to Transplant Destination Therapy
(for patients that are not transplant candidates)

21. Heart Mate II to Patient
Cannulation:
Drainage- LV Apex
Return- Ascending Aorta
Anticoagulation:
Long-term Warfarin therapy must be maintained to achieve an INR of 1.5 – 2.5

22. Operation Pump Speed is adjusted on the controller
Flow is determined by pressure differences between inflow and outflow (Preload/Afterload) and Pump Speed

23. Levitronix CentiMag (now Thoratec)
Flow up to 9.9 LPM
Approved up to 14 days
Used for LVAD and/or RVAD
Also used for ECMO
Simple centrifugal pump
Little hemolysis or clotting

24. Tandem Heart Made by Cardiac Assist Inc.
Centrifugal Pump capable of delivering up to 5 LPM
Spins up to 7500 RPM
Low 10cc priming volume
Typically used as an LVAD to assist a failing Left Ventricle
Typically used for high risk PCIs or postcardiotomy cardiac failure
Can provide immediate cardiac support unlike an IABP
Can be used to wait for recovery or as a bridge to a more long-term device
Less invasive and traumatic that a typical VAD
Uses Percutaneous Cannulation (pVAD)

25. Tandem Heart
Cannulate Femoral Vein and feed it across the septum to sit in the LA
Cannulate Femoral Artery for return
Device is a simple centrifugal head, that has its own infusion of anticoagulant to the head so that you do not need systemic anticoagulation
Lubricant separates the rotor chamber from the blood chamber
Heparin can be added to this lubrication line to decrease risk of pumphead thrombosis
The lubricant is mixed with the blood and eventually ends up in the pumphead outflow line

26. Cannulation for VADs LVAD RVAD Inflow- Outflow-
Left Atrium- patients expecting to recover ventricular function
Left Superior Pulmonary Vein- patients expecting to recover ventricular function
Left Ventricle (Apex)- used as bridge to transplant, not expecting to recover ventricular function
Outflow-
Ascending Aorta
RVAD
Right Atrium
Pulmonary Artery

27. VAD Complications
Bleeding- most common cause, often leads to patient death
Long CPB runs cause activation of the platelet and coagulation systems due to exposure of blood to artificial surfaces and turbulent flow patterns
Leads to severe coagulopathy characterized by platelet dysfunction
Replenish clotting factors and platelets as necessary
Platelet counts above 100,000 with prolonged bleeding time indicates platelet dysfunction
Desmopressin (DDAVP)- a synthetic analog of the hormone arginine vasopressin will help augment platelet function to improve hemostatic plug formation
Mode of action is mediated by factor VIII complex, so you need enough Factor VIII present
Dose is 0.3 mcg/kg over 10 minutes
Reduction in bleeding time should occur after 30 minutes

28. VAD Complications
Infection- 2 large diameter tubes passing through the abdominal wall is a serious infection risk
Longer the circulatory support, greater chance of infection
Coagulation- depends on anticoagulant used
Probe patent foramen ovale-
Pneumatic vacuum applied to LA will reduce LAP below RAP which can often lead to severe intercradiac shunting between RA and LA
Presence of a PFO should always be checked via TEE
Collapsed or Obstructed Inflow Cannula-
Thrombus formation inside the cannula, or extrinsic compression of the cannula or atrium by clot or tissue can prevent adequate flow of blood into the pump

29. VADs Weaning off of a VAD Additional Information on VADs
Reduce the flow, which will pull less blood into the VAD and allow the native ventricles to take over
Patient must be able to have a 2.2 cardiac index in order to be taken off of the VAD
ACTs are increased as we lower flow on the VAD to prevent thromboembolism
Additional Information on VADs
Blood transfusions should be done only when HCT is < 20%
Should use blood that has been in storage for < 1 week and use a white blood cell filter during administration

30. Anticoagulation on VAD
Initiate heparin therapy (or other anticoagulant) as soon as bleeding is controlled (chest tube output < 100cc hr with normal coagulation factors), but always within 24 hours
Goal of anticoagulation is 1.5 – 2.5 times baseline
Draw baseline ACT at bedside and give heparin bolus to achieve ACT seconds. Follow with heparin infusion to maintain ACT at seconds
If flows are less than 3 liters per minute or the patient is in AFIB or VFIB, increase ACT
If resistance to heparin is noted (increased need for heparin to maintain ACT level), ATIII deficiency is possible
Consider administration of FFP

31. Helpful Clinical Tips
Thermodilution Cardiac Output and Continuous Cardiac Output will be inaccurate on Bi-VAD or RVAD support
Maintain filling pressures on the high side of normal
(CVP 12-15mmHg; PCWP/LAP 10-14mmHg)
Maintain SVR between dynes per second and PVR between dynes per second

32. Helpful Clinical Tips
For patients on univentricular support, watch for signs of failure of the unassisted ventricle
Do not apply direct heat or cold to blood pumps
Use tubing covers as needed
No Chest Compressions or Pre-cordial thumps
Consider placing sign at head of bed
To assist PA catheter insertion in a patient on RVAD or BiVAD
Decrease flow through the right blood pump by turning on the weaning mode
Decrease flow to approximately 2 liters to fill the patient's ventricle and allow the catheter to pass into the pulmonary artery
Once catheter is in place, return to full support by turning off the weaning mode
When assisting with TEE, reduce flow to approximately 2 liters to fill the ventricle in order to assess ventricular wall motion. Reduce flow by utilizing the weaning mode

33. BVS 5000 VAD Insertion Hand VAD kit to scrub nurse
Have IV pole and priming reservoir ready by OR table
Nurse will pass you “Atrial” tubing
Connect that to BOTTOM of reservoir
Nurse will pass you “Arterial” tubing
Connect that to TOP of reservoir
Nurse will pass you the Blood Pump
Power on the console and let it do the self checks
DO NOT press “ON” until the self checks are done
Battery life of BVS5000 console is 1 hour

34. BVS 5000 VAD Insertion Priming
Clamp distal to outflow port of reservoir
Drop 2000cc of room temp priming solution (warm saline or plamalyte)
Blood Pump should now be inverted and placed at the same level as the reservoir
Remove the clamp and slowly lower the pump to move fluid through the pump and expel air
Once fluid is through the pump, return it to its normal position
Connect the Drive Line to its correct port on the back of the console
Will be either Left or Right port depending on type of VAD
Turn console ON
Allow fluid to recirculate for at least 5 minutes
Flow will not be greater than 3 L/min
Manipulate the pump to expel all air bubbles, check carefully in the valve sinuses

35. BVS 5000 VAD Insertion Connecting to the Cannulas
Nurse will clamp both the silicone tubing and blood pump line tubing and roll the silicone tubing off
Blood pump tubing can now be connected to the cannulas
Arterial cannula comes packaged with a 10 or 12 mm precoated graft to allow an end to side anastomosis of the PA or aorta
Surgeon will now externalize cannulas by putting a “Bullet” on the end of the cannula tubing to run the tubing through the skin

36. BVS 5000 VAD Insertion Initiating VAD Flow
Place patient in Trendelenberg
Submerge cannula sites in blood or saline to prevent entraining air
Place blood pump at the level of the atrium
If on CPB, reduce flows to allow filling pressures >10 mm Hg
Need volume in the heart to go into the VAD inflow
Surgeon must be ready at VAD aortic cannula to clamp if air is entrained into the system
The foot pedal is used to initiate flow slowly to prevent air embolus
Turn console OFF first, press OFF button twice
Open rear cover and move the Transfer Lever up into the horizontal position
Pull out the foot pedal and put it on floor
If air is observed, you may need to reconnect blood pump lines to the recirculating circuit to rid it of air then reconnect to the patient when its air free
Once flow is generated and no air is observed, put foot pedal back and move Transfer Lever DOWN and turn console ON to begin autopumping