VADs Flashcards
Development of balloon pump
1963
Followed Klaus’ atrial counter pulsation
First successful true VAD
1965 DeBakey
Pneumatically driven
Paracorporeal
First total artificial heart to temporarily support pt to transplant
1969 Cooley
Liotta heart
First permanent TAH
1982 University of Utah
Dr. William DeVries
First bridge to transplant decide
2004 Tucson
Dr. Olsen and Copeland
First successful BTT with LVAD
1984 Stanford University
Novacor
First FDA approved implantable LVAD
Heartmate
Biologic barriers to VAD design
Blood vs foreign surface
Moving parts
Patient coagulation and immune system in response to mechanical pump
Pharmacological modifications
Indications for BTT VAD
Worsening hemodynamics despite high level of IV inotropes and/or vasodilator therapy or refractor arrhythmias
Indications for destination therapy VAD
Not transplant candidates
EF <25%
NYHA class 4 symptoms despite optimal therapy
Contraindications to VADs
High surgical risk Recent stroke Neurological deficits Coexisting terminal condition Abdominal aortic aneurysm Active infection Fixed pulmonary hypertension Pulmonary dysfunction Organ failure Inability to tolerate anticoagulation HIT Psychiatric illness Lack of social support Pregnancy
Design considerations for VADs
Configured for application
Anatomically compatible
Structurally stable in corrosive saline environment
Operative continuously without regular maintenance for years
Don’t fail under increased stress
Reduce power requirements to save battery
Efficient: reduce heat waste
2 kinds of VAD pumps
Positive displacement
Rotary
Positive displacement pumps
Propel fluid by changing internal volume of pumping chamber Pulsatile flow One way valves 5-10LPM BP: 100-150mmHg HR: <120bpm Mean filling pressure: 20mmHg
Throatec PVAD/IVAD
Supports right, left, or both ventricles
BiVAD common after transplant failure, cardiomyopathy, acute MI, myocarditis
Preop risks for right heart failure
Ability of RV to generate pressure
Low pulse pressure with high CVP (use BiVAD)
Indicators for BiVAD
Early insertion of LVAD before significant organ failure High preop bilirubin High preop creatinine Emergent implant Intraop bleeding Greater transfusion requirements
Throatec PVAD/IVAD characteristics
SV: 65mL 2 mechanical valves 40-110 bpm 1.3-7.2LPM Placed in anterior abdominal wall External location suitable for small patients (BSA >.73m2)
Pump considerations for implant of Throatec PVAD/IVAD
Bicaval cannulation Normothermic No CPG or XC LV vented Ultrafiltrate to keep HCT greater than 30%
Anticoagulation for Thoratec
Chronic warfarin
INR: 2.5-3.5
Start with heparin until PTT is 1.5x baseline, GI fxn stable, and low bleeding risk (10-14 days)
Switch to warfarin and ASA
PVAD
Paracorporeal Bridge to transplant Mean support: 51.8 days Longest support: 3.3 years Can be used in Peds
IVAD
Intracorporeal (implantable) Used for longer term support Polished titanium body Reduced weight Narrower leads (9mm vs. 20mm)
Heartmate XVE
Circulatory assist without anticoagulation
Has antiplatelet agent
Promotes pseudointimal layer
Con: immunologically active
Characteristics of Heartmate XVE
Positive displacement pump Powered pneumatically or electrically Cannulate LV apex and ascending aorta SV: 83mL Flow: 4-10LPM
Pseudointima
Thin layer ofnbiologic matrix that resists thrombogenesis
Composed of cellular elements, collagen,progenitor cells
Immunologically active
Promoted by Heartmate XVE
Implantation of Heartmate XVE
Dacron grafts must be preclotted Placed interperitoneal or peritoneal pocket upper L quadrant Leads exit to right Must fix AI, MS, PFO Requires CPB No CPG or cooling BSA >1.5 Only use ASA
Survival of Heartmate XVE BTT
65% survive to transplant
If survive first month, 85% success
Micromed rotary pump
Limited foreign surface area
Few moving parts (reduces cost, more durable)
Axial flow
Small size so simple implantation and can be used on more patients
Development of Micromed
Debakey and NASA
Europe
Has ultrasonic probe encircling outflow graft
Use Coumadin for anticoagulation
Complication with Micromed
Fibrin deposition on impellar leading to thrombus
Treat with TPA and heparin
Heartmate II
Smaller than XVE Axial flow Electric motor Only moving part is magnetic rotor Must preclot Dacron grafts Flow is ESTIMATE
Implantation of Heartmate II
Below L costal margin under rictus abdominal muscle
Leave LV apex to diaphragm to pump
Approved for destination therapy
Survival with Heartmate II
1 year: 68%
2 years: 58%
VentrAssist
3rd generation
Not produced due to lack of funds
Heartware HVAD
Small continuous flow rotary pump
Placed in pericardial cavity at LV apex
First human Implant in 2006
DuraHeart LVAS
Continuous flow rotary pump
Upper hosing with levitation and impeller
Bottom housing has external drive motor
2-8LPM
1200-2400rpm
Placed in abdominal pocket
First device with centrifugal pump and magnetic levitation
Levacor VAD
Bearing less centrifugal pump with impeller magnetically levitated
Implanted in small subcostal, pre-peritoneal space
Not approved
Abiomed Impella 2.5/5.0
Intracatheter VAD
Pulls blood for LV tip to aorta
Abiomed Abiocor
First completely self contained replacement heart
Up to 12LPM
Internal motor and rechargeable battery
External battery pack
Tandem Heart
10cc centrifugal pump
8LPM
Cannula dependent
Floats on fluid bearing (10cc/hr saline drip into lower chamber that cools and lubricates)
Syncardia TAH
9.5 LPM through both ventricles After stable, patient is considered 1a 6 moving parts Never had a device failure All electronics outside body Pneumatic driver
Berlin heart
BTT
Available for compassionate use
Stock all sizes in hospital
