Ventricular Assist DevicesOverview, Patient Management and Emergency Care

Timothy Ryan, APRN-NP

Learning ObjectivesIdentify the components, their function, & theory of device operation of the LVADDescribe the path blood follows in patients with the LVADList two potential complications associated with the LVADIdentify the purpose and function of the System ControllerDiscuss Nursing Care of a Patient with a LVADDescribe appropriate interventions in the event of an emergency

Indication for UseBridge to TransplantNon-reversible left heart failureImminent risk of deathCandidate for cardiac transplantationDestination Therapy Not candidate for transplantLifelong support

ConsiderationsContraindication:Inability to tolerate anticoagulation

Other considerations:Nonreversible end organ failureAcceptance of blood productsPregnancySupport systemCompliance history

HeartMate II Pump

Anatomical Placement

HeartMate II LVAS System ComponentsHM II Components:Implantable titanium blood pumpSystem Controller

System Components:System MonitorDisplay ModulePower SourcesPower ModuleBatteries & ClipsAccessoriesShower BagTravel Bag

HeartMate II LVASValvelessAfterload sensitiveFollows native LV pulsePump flow varies over the cardiac cycle

HeartMate II LVASKey Design FeaturesRelatively Simple DesignValvelessOnly one moving part, the rotorBlood immersed bearings designed for minimization of blood damageAll motor drive and control electronics are outside of the implanted blood pumpSpeed range: 6,000 to 15,000 rpmFlow range: 3 10 L/min

Internal ViewRev. 12.0 (3/24/04)

Blood Flow PathInflow from LV

Inlet Stator3 vanes straighten the flow before it enters the rotor

RotorPropel blood toward outflow & spins it radially imparting kinetic energy

Outlet statorStraightens flow as leaves rotor and pressure is further increased

Outflow to ascending aorta

Pump Flow PrinciplesPump flow is a function of:The speed of the rotor Speed FlowSpeed 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 PointsValveless pumpRetrograde flow will occur if the pump stopsDegree of retrograde flow is determined by pressure differential across the pumpSimilar to acute aortic regurgitation

Significant negative pressures can be produced when insufficient blood is provided to the pumpDehydration or RV failure can cause suction eventsSuction events can cause arrhythmias

Equipment OverviewSystem ControllerPower SourcesSystem MonitorDisplay Module

System ControllerMicroprocessor that:Delivers power to the pumpControls pump speed and powerMonitors, interprets & responds to system performancePerforms diagnostic monitoringIndicates hazard and advisory alarmsProvides complete backup systemEvent recording capability

System Controller Perc LockDesign implemented to prevent accidental percutaneous lead disconnects from the system controller

HeartMate II Pocket System ControllerSafety by DesignBackup batteryPrioritized visual alarms with clear, actionable instructionsDriveline diagnostic capabilityProgrammed for use in 37 languagesDesigned for an active lifestyleLightweight and compact with single-side cable designDurable, shock-resistant outer case, cables, and electronicsIntuitive, discreet, and comfortable interface

HeartMate II System ControllerDelivers power to the pumpControls and monitors system operationIdentifies alarm conditions and initiates Hazard and Advisory AlarmsUser Interface displays the following available in 37 languages:Pump parameters (Flow, Speed, Power, PI) and status of Backup Battery chargeVisual alarms with clear, actionable instructionsAccessible alarm history of last six non-transient alarmsDisplay Module no longer requiredBackup battery housed within the controllerDriveline diagnostic capabilityRecords alarm data and device performance (240 events)

System Controller User Interface

Power ModuleSupplies mains power to LVADServes as the electrical interface between the System Controller and the System Monitor or Display ModuleWeights only 10 poundsCan run off of car powerProvides 30 minutes of backup powerTakes 12 hours to rechargeKeep plugged into grounded outlet at all timesInternal battery must be changed yearly

Batteries14-volt Li-Ion Battery10+ hours of support on a pair of batteriesFour hours recharge for fully discharged batteryService life of greater than 2 years (auto recalibration)

Battery Charger

Display ModuleParametersPump ModePump Speed (rpm)PI (Pulsatility Index)Estimated Flow (lpm)Too low ---Too high +++Power (watts)

Alarm conditionsHighest 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 ComplicationsHypovolemiaRight Heart failurePulmonary hypertensionCardiac tamponadeBleedingArrhythmiaInfectionHemolysisThromboembolismNeurologic dysfunction

Potential Late ComplicationsHypovolemiaArrhythmiaThromboembolismInfectionPsycho-social issuesNeurological dysfunction

Patient AssessmentPatient assessment includes:Pump functionPump speed, flow, motor power, pulse index (PI)Percutaneous lead connection to system controller and percutaneous lead lock in locked positionExit site status, immobilization of percutaneous leadVital signs, peripheral circulationMental status, level of consciousnessLab work

Exit Site CareDressing changeEvery Monday and ThursdayUse Sterile TechniqueSterile Gloves and maskChlorohexadine PrepSterile dressing

Care of the Percutaneous LeadDamage 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 cleanWipe off any dirt or grimeIf necessary, use a towel with soap and warm water to gently clean the percutaneous leadNever submerge the lead or other system components in water or liquid

Care of the Percutaneous LeadDo not pull on or move the lead at the exit site

Be mindful of where the system controller is at all timesProtect the controller from falling or pulling on the lead

Dont 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 damageCuts, holes, tears

Warnings & RestrictionsNo excessive jumping or contact sportsNo swimmingNo exposure to MRIAvoid strong static discharge (i.e. TV, computer screens, vacuuming carpets)No pregnancy

Patient AssessmentVital SignsNo pulseNo blood pressureCannot use automatic blood pressure machineDoppler used to get mean arterial pressureTarget mean pressure of 70-90 mmHgArterial line waveform dampened

Patient CareArrhythmiasAffect pump functionCan be caused by mechanical irritation of ventricular wall by inflow catheterMust be treated using usual careICDs are turned back on after implantCardioversion or defibrillation WILL NOT affect VAD function

Patient CareAnticoagulationBecause of risk of clot formation in pumpWarfarin with target INR 2.0 to 3.0 (higher if other conditions)Also on aspirin and dipyridamole therapy

Emergency CareAcute Pump FailureDepleted BatteriesLoss of home power and not switched to batteryController FailureRedundant SystemDriveline FailurePump Failure

Emergency CareAcute Pump FailureCauses acute regurgitation to LVIf some LV function, will maintain some blood pressure, but will most likely be in shockIf minimal LV function, regurgitate flow will cause LV to dilate leading to VFNeed to restart pump as soon as possible10 minute rule

Emergency CareCardiopulmonary ResuscitationMay perform cardioversion or defibrillation as needed. Will not affect VAD or controllerNo CPRUnless last resortMay dislodge inflow or outflow cannulas resulting in hemorrhageTreat like cardiogenic shock if pump failure

Emergency CareRouting of PatientsMost 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 issuesToll-Free Emergency Contact: 855-823-8662

Exercising And Cardiac RehabilitationNeed to have doppler to evaluate blood pressureNo limitations to equipment usedLimit exercise to no higher than Borg level of 13Initially may have higher meansWill decrease over timeStrongly encourage Phase III

The Nebraska Medical Center MCS ProgramTop 15% of Implanting Centers in the United States

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Survival with Primary CF LVAD

Success Storieshttp://www.omaha.com/article/20111025/NEWS2001/710199974http://www.youtube.com/watch?v=-zALZGINfAUhttp://youtu.be/539A2dMOGK8

**Youngest patients: pilot study 14 year old, pivotal trial 16 year oldSmallest patient: BSA 1.33 *The LVAD is implanted below the diaphragm and attaches to the LV apex and ascending aorta. The velour covered percutaneous lead exits in the right upper quadrant and connects to the system controller which, in this picture, is powered by 2 HM batteries worn in a shoulder holster.*The HeartMate I and II share many of the same components. Both the system monitor and display module can be upgraded with HM II software eliminating the need to purchase capital equipment.**The HeartMate II incorporates precision engineering, a simple design, and 30 years of clinical experience. The rotor spins on precision jeweled ruby bearings. These hydrodynamic bearings are blood immersed, lubricated by the plasma to prevent heat build up that could damage blood with the potential to cause thrombus formation.There is also the potential for significantly improved durabilityThe percutaneous lead attaches to the external system controller that controls electronics and motor drive.Outflow graft with snap on bend relief allows direct visualization during deairing and minimizes risk of kinking

The rotor is capable of providing flow from 3 to 10 liters per minute at a speed range of 6,000 to 15,000 rpm, covering the full cardiac output of a healthy heart. *The HeartMate II is driven by an electric motor that is integrated into the pump.Inside the pumps rotor is a cylindrical magnet. Current is passed through the motor winding, which creates a spinning magnetic field. This spinning magnetic field imparts torque to the rotor and causes the rotor to spin.

*Axial flow pumps, the spinning rotor is in the same linear path as the blood flow.HM II utilizes a high speed rotor incorporating integral vanes on the surface. These vanes produce the pressure necessary to create flow in a continuous manner.As blood enters the pump, seen here in slow motion, it is straightened by the inlet stator vanes prior to entering the path of the rotor. The rotor then spins the blood radially and propels it toward the outlet, where blood flow is straightened by the outlet stator vanes.*Rotary pumps have an interdependent relationship between the speed of the rotor, the difference in pressure between the inlet and outlet of the pump (differential pressure) and the amount of flow generated by the device. The pressure at the inlet of the pump is the left ventricular pressureThe pressure at the outlet of the pump is the aortic pressure

*Retrograde flow will occur if the pump is stopped. The degree is dependent on pressure differential across the pump. For example, during diastole the arterial pressure is approximately 70 mmHg while the ventricular pressure is 20 mmHg resulting in a pressure differential of 50 mmHg. Flow will occur from the aorta to the LV at approximately 1 1.5 liters per minute.Negative pressure can collapse the ventricle and prevent blood from entering the pump. Detection of this occurrence (PI event) will result in automatic reduction in pump speed to low speed limit.Occurrence of hemolysis should prompt evaluation to rule out pump obstruction and reassess fixed speed setting.*The system controller has 2 controller boards, one for the primary system operation and one for complete backup system operation in the event the primary system malfunctions or becomes inoperable.

The system controller power leads provide equal power to the pump. The white power lead contains a data link cable that transmits data from the controller to the System Monitor or Display Module when connected to the PBU. To save data &/or waveforms to a card: White lead - download data to the card Black lead save waveform (current trace) So as long as the cables are intact, transferring the event recorder should be ok with just the white. But for the complete waveform capture data both cables are required.*The perc lock is designed to prevent accidental disconnection of the percutaneous lead from the system controller by covering the metal release tab when in the locked position. It cannot not be turned to the lock position if the percutaneous lead is not fully engaged in the controller socket. It should always be in the locked position once the system controller is attached to the patients percutaneous lead.To lock it, rotate up until the metal tab is completely covered and you hear it click into place. To unlock it, rotate down until the metal tab is exposed and you hear it click into place. 37 language support 240 alarm history (vs. 120 in current controller) Six most recent alarms are accessible on the controller display Redundant processors Boards are connected to the case with shock mounts that protect from shock and vibration Case:Protects against water and moisture.Molded magnesium alloy coated for corrosion protection and durability 37 language support 240 alarm history (vs. 120 in current controller) Six most recent hazard alarms are accessible on the User Interface display for communication interpretation and troubleshooting Redundant processors Boards are connected to the case with shock mounts that protect from shock and vibration Case:Protects against water and moisture.Molded magnesium alloy coated for corrosion protection and durability 3 buttons to allow for checking battery status, silencing alarms, display control, and self test and asses last six alarms.5 LEDs: Low battery, cable connection status, loss of hemodynamic support, compromised controller operations, and controller status

**If low estimation is below green zone range, get ---. If flow estimation is above green zone range, get +++.During alarms, highest priority alarm message alternates with Flow & Power display on lower line.*Reimbursement lecture to review billing of dressing supplies.*