test 8 VAD indications, design, and comparing pump types

Question 1

Three different uses for VADs

Answer 1

 Bridge to Recovery (BTR)
 Bridge to Transplant (BTT)
 Destination Therapy (DT)

Question 2

Bridge to Transplant

Answer 2

 Worsening hemodynamics despite high level of IV inotropic support and/or vasodilator therapy or refractor arrhythmias.

Question 3

Destination Therapy

Answer 3

 Patients who are not transplant candidates. Have an EF less than 25% and NYHA Class IV symptoms despite optimal therapy.

Question 4

VAD Contraindications

Answer 4

 High surgical risk
 Recent/evolving stroke
 Neurological deficits impairing the ability to manage device
 Coexisting terminal condition
 Abdominal aortic aneurysm (greater than 5 cm)
 Active infection
 Fixed pulmonary hypertension
 Severe pulmonary dysfunction
 Multisystem organ failure
 Inability to tolerate anticoagulation
 HITT
 Psychiatric illness
 Lack of social support
 pregnancy

Question 5

VAD design

Answer 5

 Devices need to be configured for their eventual application
 Shorter term versus partial assist versus long term support versus 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 without regular maintenance for years.
 Cannot fail under increased stress conditions
 Reduce power requirements to save battery life
 Must be efficient – reduce heat waste.

Question 6

3 different kinds of pumps for VADs

Answer 6

Positive displacements
Usually pneumatic
Rotary
Centrifugal

Question 7

Flow and Pressure comparisons for
Positive displacement:
Rotary/ Centrifugal:

Answer 7

 Positive Displacement: Change volume in the chamber

 Rotary/ Centrifugal: Rotating Impeller

Question 8

Source of Energy comparisons for
Positive displacement:
Rotary/ Centrifugal:

Answer 8

 Positive Displacement: Air pressure/ Electricity

 Rotary/ Centrifugal: Electricity

Question 9

Size comparisons for
Positive displacement:
Rotary/ Centrifugal:

Answer 9

 Rotary is smaller with a smaller cannula

 Centrifugal can be placed in pericardium!

Question 10

Prime Volume comparisons for
Positive displacement:
Rotary/ Centrifugal:

Answer 10

 Positive Displacement: Large Prime Volume

 Rotary/ Centrifugal: Smaller Prime Volume

Question 11

Flow Ranges comparisons for
Positive displacement:
Rotary/ Centrifugal:

Answer 11

 Both plagued with thrombosis with decreased flow and hemolysis with increased flow

Question 12

Afterload comparisons for
Positive displacement:
Rotary/ Centrifugal:

Answer 12

 Positive Displacement: Unaffected by changes in afterload

 Rotary/ Centrifugal: Flow drops with increased SVR

Question 13

Preload comparisons for
Positive displacement:
Rotary/ Centrifugal:

Answer 13

 Positive Displacement: Passive filling, output follows venous return
 Rotary/ Centrifugal: Flow increases with increased VR, but no active suction applied