Ventricular Assist Devices

Overview, Patient Management and Emergency Care

Timothy Ryan, APRN-NP

Learning Objectives• Identify the components, their function, & theory of

device operation of the LVAD• Describe the path blood follows in patients with the

LVAD• List two potential complications associated with the LVAD• Identify the purpose and function of the System

Controller• Discuss Nursing Care of a Patient with a LVAD• Describe appropriate interventions in the event of an

emergency

Indication for Use

• Bridge to Transplant– Non-reversible left heart failure– Imminent risk of death– Candidate for cardiac transplantation

• Destination Therapy – Not candidate for transplant

• Lifelong support

Considerations

• Contraindication:– Inability to tolerate anticoagulation

• Other considerations:– Nonreversible end organ failure– Acceptance of blood products– Pregnancy– Support system– Compliance history

HeartMate II Pump

Anatomical Placement

HeartMate II LVAS System Components

• HM II Components:– Implantable titanium blood

pump– System Controller

• System Components:– System Monitor– Display Module– Power Sources

• Power Module• Batteries & Clips

– Accessories• Shower Bag• Travel Bag

HeartMate II LVAS

• Valveless• Afterload sensitive• Follows native LV pulse• Pump flow varies over

the cardiac cycle

HeartMate II LVASKey Design Features

• Relatively Simple Design– Valveless– Only one moving part, the rotor– Blood immersed bearings designed for

minimization of blood damage– All motor drive and control electronics

are outside of the implanted blood pump

• Speed range: 6,000 to 15,000 rpm• Flow range: 3 – 10 L/min

Internal View

Rev. 12.0 (3/24/04)

Blood Flow Path

• Inflow from LV

• Inlet Stator– 3 vanes “straighten” the flow

before it enters the rotor

• Rotor– Propel blood toward outflow &

spins it radially imparting kinetic energy

• Outlet stator– “Straightens” flow as leaves rotor

and pressure is further increased

• Outflow to ascending aorta

Pump Flow Principles

• Pump flow is a function of:– The speed of the rotor

↑Speed → ↑Flow

↓Speed → ↓ Flow

– The difference in pressure across the pump ↑ Pressure gradient → ↓ Flow

↓ Pressure gradient → ↑ FlowAt any given speed, increased B/P will decrease flow

Typical Pump Parameters

Speed mean (range) 9,400 rpm (8,000 – 13,000)

Flow mean (range) 5.5 lpm (3.3 – 7.8)

Key Points• Valveless pump

– Retrograde flow will occur if the pump stops– Degree of retrograde flow is determined by

pressure differential across the pump– Similar to acute aortic regurgitation

• Significant negative pressures can be produced when insufficient blood is provided to the pump– Dehydration or RV failure can cause suction events– Suction events can cause arrhythmias

Equipment Overview

System ControllerPower Sources

System MonitorDisplay Module

System ControllerMicroprocessor that:• Delivers power to the pump• Controls pump speed and power• Monitors, interprets & responds to

system performance• Performs diagnostic monitoring• Indicates hazard and advisory

alarms• Provides complete backup system• Event recording capability

System Controller Perc Lock• Design implemented to prevent accidental percutaneous lead

disconnects from the system controller

HeartMate II Pocket System Controller•Safety by Design

•Backup battery

•Prioritized visual alarms with clear, actionable instructions

•Driveline diagnostic capability

•Programmed for use in 37 languages

•Designed for an active lifestyle

• Lightweight and compact with single-side cable design

•Durable, shock-resistant outer case, cables, and electronics

• Intuitive, discreet, and comfortable interface

HeartMate II System Controller• Delivers power to the pump

• Controls and monitors system operation

• Identifies alarm conditions and initiates Hazard and Advisory Alarms

• User Interface displays the following available in 37 languages:

• Pump parameters (Flow, Speed, Power, PI) and status of Backup Battery charge

• Visual alarms with clear, actionable instructions

• Accessible alarm history of last six non-transient alarms

• Display Module no longer required

• Backup battery housed within the controller

• Driveline diagnostic capability

• Records alarm data and device performance (240 events)

System Controller User Interface

Power Module

• Supplies mains power to LVAD• Serves as the electrical interface

between the System Controller and the System Monitor or Display Module

• Weights only 10 pounds• Can run off of car power• Provides 30 minutes of backup

power• Takes 12 hours to recharge• Keep plugged into grounded

outlet at all times• Internal battery must be changed

yearly

Batteries

• 14-volt Li-Ion Battery• 10+ hours of support on

a pair of batteries• Four hours recharge for

fully discharged battery• Service life of greater

than 2 years (auto recalibration)

Battery Charger

Display Module

• Parameters– Pump Mode– Pump Speed (rpm)– PI (Pulsatility Index)– Estimated Flow (lpm)

• Too low “---”• Too high “+++”

– Power (watts)

• Alarm conditions– Highest priority alarm message

alternates with flow and power

Fixed Speed 9600 PI 5.5 Flow 4.5 Power 8.2

Fixed Speed 9600 PI 5.5 LOW FLOW for < 1 min

Patient Management

Post Op Complications• Hypovolemia• Right Heart failure• Pulmonary hypertension• Cardiac tamponade• Bleeding• Arrhythmia• Infection• Hemolysis• Thromboembolism• Neurologic dysfunction

Potential Late Complications

• Hypovolemia• Arrhythmia• Thromboembolism• Infection• Psycho-social issues• Neurological dysfunction

Patient Assessment

• Patient assessment includes:– Pump function

• Pump speed, flow, motor power, pulse index (PI)– Percutaneous lead connection to system controller

and percutaneous lead lock in locked position– Exit site status, immobilization of percutaneous

lead– Vital signs, peripheral circulation– Mental status, level of consciousness– Lab work

Exit Site Care

• Dressing change– Every Monday and

Thursday– Use Sterile Technique– Sterile Gloves and

mask– Chlorohexadine Prep– Sterile dressing

Care of the Percutaneous Lead• Damage to the percutaneous lead, depending on the degree,

may cause the pump to stop

– Do not severely bend, kink or twist the percutaneous lead

– Do not “catch” the percutaneous lead in the zipper of the carrying case

– Allow for a gentle curve of the percutaneous lead. • Do not severely bend the lead multiple times or wrap it tightly.

– Keep the percutaneous lead clean• Wipe off any dirt or grime• If necessary, use a towel with soap and warm water to gently clean the

percutaneous lead• Never submerge the lead or other system components in water or liquid

Care of the Percutaneous Lead– Do not pull on or move the lead at the exit site

– Be mindful of where the system controller is at all times• Protect the controller from falling or pulling on the lead

– Don’t allow the percutaneous lead to catch or snag on anything that will pull on or move the lead

– Check the percutaneous lead daily for signs of damage• Cuts, holes, tears

Warnings & Restrictions

• No excessive jumping or contact sports• No swimming• No exposure to MRI• Avoid strong static discharge (i.e. TV,

computer screens, vacuuming carpets)• No pregnancy

Patient Assessment

• Vital Signs– No pulse– No blood pressure

• Cannot use automatic blood pressure machine• Doppler used to get mean arterial pressure

– Target mean pressure of 70-90 mmHg

– Arterial line waveform dampened

Patient Care

Arrhythmias• Affect pump function• Can be caused by mechanical irritation of ventricular

wall by inflow catheter• Must be treated using usual care• ICD’s are turned back on after implant• Cardioversion or defibrillation WILL NOT affect VAD

function

Patient Care

Anticoagulation• Because of risk of clot formation in pump

– Warfarin with target INR 2.0 to 3.0 (higher if other conditions)

– Also on aspirin and dipyridamole therapy

Emergency Care

• Acute Pump Failure– Depleted Batteries– Loss of home power and not switched to battery– Controller Failure

• Redundant System

– Driveline Failure– Pump Failure

Emergency Care

• Acute Pump Failure– Causes acute regurgitation to LV– If some LV function, will maintain some blood

pressure, but will most likely be in shock– If minimal LV function, regurgitate flow will cause

LV to dilate leading to VF– Need to restart pump as soon as possible

• 10 minute rule

Emergency Care

Cardiopulmonary Resuscitation• May perform cardioversion or defibrillation as

needed. Will not affect VAD or controller• No CPR

– Unless last resort– May dislodge inflow or outflow cannulas resulting in

hemorrhage

• Treat like cardiogenic shock if pump failure

Emergency Care

Routing of Patients• Most patients will need to be transferred to The

Nebraska Medical Center.• May first present to local ED for stabilization then

transferred to The Nebraska Medical Center, if needed.

• Other centers will not be able to treat pump related issues

• Toll-Free Emergency Contact: 855-823-8662

Exercising And Cardiac Rehabilitation

• Need to have doppler to evaluate blood pressure

• No limitations to equipment used• Limit exercise to no higher than Borg level of

13• Initially may have higher means

– Will decrease over time

• Strongly encourage Phase III

The Nebraska Medical Center MCS Program

Top 15% of Implanting Centers in the United States

Survival with Primary CF LVAD

Success Stories

• http://www.omaha.com/article/20111025/NEWS2001/710199974

• http://www.youtube.com/watch?v=-zALZGINfAU

• http://youtu.be/539A2dMOGK8