VADs Flashcards by Chelsea Furnish

Development of balloon pump

1963

Followed Klaus’ atrial counter pulsation

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First successful true VAD

1965 DeBakey
Pneumatically driven
Paracorporeal

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First total artificial heart to temporarily support pt to transplant

1969 Cooley

Liotta heart

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First permanent TAH

1982 University of Utah

Dr. William DeVries

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First bridge to transplant decide

2004 Tucson

Dr. Olsen and Copeland

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First successful BTT with LVAD

1984 Stanford University

Novacor

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First FDA approved implantable LVAD

Heartmate

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Biologic barriers to VAD design

Blood vs foreign surface
Moving parts
Patient coagulation and immune system in response to mechanical pump
Pharmacological modifications

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Indications for BTT VAD

Worsening hemodynamics despite high level of IV inotropes and/or vasodilator therapy or refractor arrhythmias

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Indications for destination therapy VAD

Not transplant candidates
EF <25%
NYHA class 4 symptoms despite optimal therapy

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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

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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

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2 kinds of VAD pumps

Positive displacement

Rotary

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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

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Throatec PVAD/IVAD

Supports right, left, or both ventricles

BiVAD common after transplant failure, cardiomyopathy, acute MI, myocarditis

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Preop risks for right heart failure

Ability of RV to generate pressure

Low pulse pressure with high CVP (use BiVAD)

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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