test 8 first generation VADs Flashcards
Positive Displacement pumps
Propels fluid by changing the internal volume of a pumping chamber.
Provides PULSATILE FLOW
Requires 1 way valves to produce forward flow
Flow is about 5-10 liters per minute
Mean bp = 100-150 mmHg
Rate is <120 bpm
Mean filling pressure is appx 20mmHg.
Thoratec PVAD/IVAD provides support for what part of the body
Provides support for the right, left or both ventricles.
BIVAD – 10% of LVADs will need an 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.
FDA Approved as a BTT since 1995
Thoratec PVAD/IVAD Preop risk factors for Right Heart Failure
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
Indicators of BiVAD
Early insertion of LVAD before significant major organ dysfunction
Less likely to need RVAD too.
Higher pre-op bilirubin
Higher pre-op creatinine
Normalize w/in 2-3 weeks after implant of VAD
Emergent Implant
Intraop Bleeding
Greater transfusion requirements increases pulmonary vascular resistance and promotes the development of right heart failure.
Post op bleeding is common for BiVAD patients
Related to the severity of hepatic failure
Thoratec PVAD/IVAD stroke volume: beats: flow: placement:
65 mL Stroke volume pump chamber
Made of Thoralon Polyurethane
2 mechanical valves
Alternate positive and negative air pressure by console/ Portable driver
Beats 40-110 bpm
Flow is 1.3-7.2 Lpm
Placed in the anterior abdominal wall with cannulas crossing into the chest wall to connect the VAD to the heart and great vessels.
External location is suitable for use in smaller patients
BSA >0.73m2
Actuated by DDC (dual drive console) for in hospital use and portable TLCII for ambulatory use
TLCII approved in 2003.
Pump considerations for Implant: Thoratec PVAD/IVAD
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)
Anticoagulation : Thoratec PVAD/IVAD
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
Intracorporeal VAD (or Implantable VAD)
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
IVAD Difference from PVAD
Polished Titanium Body – makes it implantable
Reduced weight
339gms vs. 417 gms
Narrower Percutaneous leads
9mm vs. 20mmHeartmate XVE texture
Textured inner surface
Circulatory assistance without anticoagulation except an antiplatelet agent
Promotes pseudointimal layer
Limits thrombogenesis
CON: Immunologically active
Limit transplant candidacy due to increase in immunologic reactivity.
Heartmate XVE cannulation and method of displacement
Positive displacement pump
Made of titanium with a polyurethane diaphragm and a pusher plate actuator (which is responsible for producing mechanical energy).
Powered pneumatically (emergency) or ELECTRONICALLY
Cannulate LV Apex (apical cannula)
Dacron conduit with 25mm porcine valve
Cannulate ascending aorta
20mm Dacron outflow graft with porcine valve
Heartmate XVE electric power and system
Pneumatic
Uses 9kg driver console
Small emergency hand pump
Actuates pusher plate via drive line
Electric Motor
Rotates and displaces pusher plate
Air that is displaced by the diaphragm is vented to the atmosphere
Where the hand pump/ pneumatic driver plugs in.
Vent filter in place with electric motor operation.
Power
2 batteries (4-7hours of use)
External controller
Heartmate XVE stroke volume
Stroke Volume – 83mL
Fixed and Auto Modes
Auto - SV maintained at 97% full
Flow – 4-10 Lpm
Fixed – stroke volume depends upon filling
Rate is adjusted manually to keep stroke volume between 70-80mL
Psuedointima
Titanium microspheres and fibrillar textured surface
Promotes pseudointima
Thin layer of biologic matrix that resists thrombogenesis
Composed of cellular elements, collagen, and cells derived from circulating progenitor cells.
Immunologically active microenvironment
Heightened susceptibility to opportunistic infections.
Heartmate XVE implantation
Placed intraperitoneal or in peritoneal pocket in left upper quadrant
Must go through diaphragm with cannulas
Percutaneous leads exit to the right
AI and MS must be corrected at implantation
PFOs must be closed at implantation
Requires CPB
No cardioplegia or cooling
BSA: >1.5m2
Anticoagulation – ASA only
