Drill of the Month Developed by Michael Lindsay An Overview of Ventricular Assist Devices & Pre Hospital Management
Student ObjectivesAt the conclusion of this Drill Students will be able to: • Define Heart Failure • Define Ventricular Assist Device (VAD) and their use in treating Heart Failure • Identify types of Ventricular Assist Devices • Explain the difference between Pulsatile and Nonpulsatile flow • Identify hemodynamic differences in patients with a VAD • List VAD related complications • Demonstrate how to assess a patient with a VAD • Describe how to treat VAD complications • Identify VAD resources that can be utilized when caring for these patients.
Heart Failure * Heart failure is a condition where the heart cannot pump enough blood throughout the body. * It develops over time as the pumping action of the heart grows weaker. * Most cases involve the left side where the heart cannot pump enough oxygen-rich blood to the rest of the body. * With right sided failure, the heart cannot effectively pump blood to the lungs where the blood picks up oxygen.
What is a VAD? A single system device that is surgically attached to the left ventricle of the heart and to the aorta for left ventricular support For Right Ventricular support, the device is attached to the right atrium and to the pulmonary artery
Ventricular Assist Device (VAD) • A mechanical pump that is surgically attached to one of the heart’s ventricles to augment or replace native ventricular function • Can be used for the left (L VAD), right (R VAD), or both ventricles (Bi VAD) • Are powered by external power sources that connect to the implanted pump via a percutaneous lead (driveline) that exits the body on the right abdomen • Pump output flow can be pulsatile or nonpulsatile
Why Do We Need VADs? • Heart disease is the leading cause of death in the Western world • ~5 million people in the US have congestive heart failure (CHF) • 250,000 are in the most advanced stage of CHF • ~500,000 new cases each year • ~50,000 deaths each year • only effective treatment for end stage CHF is heart transplant
Why Do We Need VADs? • But, in 2008: • 7318 people were waiting for a heart • 2210 received one • 623 died waiting • ~1200-1500 VAD implanted in 2008
Bridge to transplant (BTT) most common allow rehab from severe CHF while awaiting donor Bridge to recovery (BTR) unload heart, allow “reverse remodeling” can be short- or long-term “Destination” therapy (DT) permanent device, instead of transplant currently only in transplant-ineligible patients Bridge to candidacy (BTC)/Bridge to decision (BTD) when eligibility unclear at implant not true “indication” but true for many pts Indications for VAD
Pulsatile and Non Pulsatile Types of VADs
Pulsatile • Ventricle-like pumping sac device. • Blood enters via the inflow cannula and fills a flexible pumping chamber. • Electric motor or pneumatic (air) pressure collapses the chamber and forces blood into systemic circulation via the outflow cannula. • Can be LVAD, RVAD, or BiVAD • First-generation devices (in use since early 1980s) • Patients will have a palpable pulse and a measurable blood pressure. Both are generated from the VAD output flow.
Pulsatile VAD Key Parameters • Pump Rate: • How fast the VAD is pumping (filling & emptying) • Can be set at a fixed rate or can automatically adjust • Pulsatile VADs are loud and the rate can be assessed by listening • Output: • The amount of blood ejected from the VAD • Measured is liters per minute • Is dependent upon preload, afterload, and pump rate
Non-Pulsatile • Continuous-flow devices • Impeller (spinning turbine-like rotor blade) propels blood continuously forward into systemic circulation. • Axial flow: blood leaves impeller blades in the same direction as it enters (think fan or boat motor propeller). • Most implanted devices are LVADs only • Are quite and cannot be heard outside of the patient’s body. Assess VAD status by auscultation over the apex of the LV. The VAD should have a continuous, smooth humming sound. • The Patient may have a weak, irregular, or non-palpable pulse • The Patient may have a narrow pulse pressure and may not be measurable with automated blood pressure monitors. This is due to the continuous forward outflow from the VAD. • The Mean Arterial Pressure is the key in monitoring hemodynamics. Ideal range is 65-90 mmHg.
Non Pulsatile VAD Key Parameters • Flow: • Measured in liters per minute • Correlates with pump speed (speed=flow, ↓speed=↓flow) • Dependent on Preload and Afterload • Speed: • How fast the impeller of the internal pump spins • Measured in revolutions per minute (rpm) • Flow speed is set and determined by VAD clinical team and usually cannot be manipulated outside of the hospital
Non Pulsatile VAD Key Parameters • Power: • The amount of power the VAD consumes to continually run at a set speed • Sudden or gradual sustained increases in the power can indicate thrombus inside the VAD • Pulsatility Index (PI): • A measure of the pressure differential inside the internal VAD pump during the native heart’s cardiac cycle • Varies by patient • Indicates volume status, right ventricle function, and native heart contractility
Non Pulsatile VAD Key Parameters • The device parameters are displayed numerically on the VAD console or Controller • Will vary with each individual patient and VAD device
VAD Parameters • Parameters for pulsatile and non pulsatile devices vary with each device model • Patients and their care givers know the expectable parameter ranges and goals for their specific device • Contact the VAD Coordinator at the implanting medical center, they will be your best resource when treating a VAD patient.
Basic VAD Management • ALL VADs are: • Preload-dependent • EKG-independent • Afterload-sensitive • Anticoagulated • Prone to: • infection • bleeding • thrombosis/stroke • mechanical malfunction • Key differences depend on pulsatile vs. non-pulsatile device
Thoratec VAD (pVAD/iVAD) • Pneumatic, external(pVAD) or internal (iVAD), pulsatile pump(s) • right-, left-, or bi-ventricular support (RVAD/LVAD/BiVAD) • up to ~7.2 lpm flow • Short- to medium-term use (up to ~1-2 years) • bridge to recovery • bridge to transplant • hospital discharge possible iVAD pVAD
HeartMate XVE LVAS • Internally implanted, electric pulsatile pump • left heart support only • up to 10 lpm flow • Medium- to long-term therapy (months to years) • bridge to transplant • destination therapy (only FDA-approved DT device)
HeartMate II LVAS • Internally implanted, axial-flow (non-pulsatile) device • left heart support only • speed: 8000-15000 rpm • flow: ~3-8 lpm • Medium- to long-term therapy (months to years) • bridge to transplant (FDA-approved) • destination therapy (investigational)
Jarvik 2000 LVAD • Axial-flow (non-pulsatile) pump • electric, intra-ventricular • left heart support only • Speed: 8000-12000 rpm • flow: ~3-5 lpm • Medium- to long-term therapy (months to years) • bridge to transplant (investigational)
Problems/Complications • Major VAD Complications • Bleeding • Thrombosis • Infection • sepsis is leading cause of death in long-term VAD support • RV dysfunction/failure • Suckdown (low preload causes a nonpulsatle VAD to collapse the ventricle) • Device failure/malfunction (highly variable by device type) • Hemolysis (the VAD destroys blood cells)
Problems/Complications • Other Common Issues • Arrhythmias • A patient can be in a lethal arrhythmia and be asymptomatic. Treat the patient not the monitor. • Do not cardiovert/ defib. unless the patient is unstable with the arrhythmia. • Do not initiate chest compressions unless instructed by a physician or VAD coordinator. Chest compressions can disrupt the implanted equipment causing bleeding and death • Electrical shock from cardiovert/ defib. will not damage any of the VAD equipment
Problems/Complications • Other Common Issues • Hypertension • High afterload can limit VAD flow/ output • Do not administer antihypertensive medications or nitrates unless instructed by a physician or VAD Coordinator • Hypotension/ loss of Preload • All VADs are preload dependent. A loss or reduction in preload will compromise VAD function and limit flow/ output
Problems/Complications • Other Common Issues • Depression/ Adjustment Disorders • Living with a VAD is difficult to management for a lot of patients. • A large percentage of patients experience symptoms of depression • Portability/ Ergonomics • The external VAD equipment is heavy and cumbersome limiting a patient’s mobility and greatly impacting their quality of life.
Problems/Complications • Bleeding & Thrombosis • Careful control of anticoagulation is imperative • Patients are often on both anticoagulants and platelet inhibitors • Device thrombosis • rare in pulsatile devices • typically revealed by increased power and signs and symptoms of hemolysis
Problems/Complications • Bleeding & Thrombosis Tx • Assess for signs and symptoms of bleeding • Neuro Assessment to rule out CVA • Initiate IV therapy and administer fluid slowly to maintain preload • Device Thrombus is treated with low dose lytics and/ or increasing anticoagulation therapy
Problems/Complications • Infection *The leading cause of mortality in VAD patients *Higher incidence in pulsatile VADs *The driveline provides direct access into the body and into the blood stream *Often recurrent and difficult to treat
Problems/Complications • Preventing Infection * Always observe clean/ sterile technique when able * Make sure driveline exit site is covered with a clean, dry gauze dressing
Problems/Complications • Suckdown • LV collapse due to hypovolemia/hypotension or VAD overdrive • nonpulsatile devices only • indicators: hypotension, PVCs/VT, low VAD flows.
Problems/Complications • Treating Suckdown • Initiate a peripheral IV and slowly give volume to increase preload • If able and instructed by the VAD Coordinator, reduce the speed of the VAD • Assess for signs and symptoms of bleeding and sepsis
Problems/Complications • Device Failure • This is a true emergency requiring immediate transport to the implanting VAD center • Most common in pulsatile devices • Patients & caregivers are trained to identify signs and symptoms of device failure • May require the VAD to be replaced
Problems/Complications • Hemolysis • Blood cells are destroyed as they travel through the VAD • More common in non pulsatile devices
Problems/Complications • Treating Hemolysis • Initiate a peripheral IV and slowly give volume • If able and instructed by the VAD Coordinator, reduce the speed of the VAD • If thrombus is suspected to be causing hemolysis, administer lytics and anticoagulants as able/ ordered
Alarms • All VAD devices typically have two distingue alarms to indicate a problem and it’s severity • Advisory Alarms • Critical/ Hazardous Alarms
Alarms • Advisory Alarms are intermittent beeping sounds that have a corresponding YELLOW light that illuminates on the system controller • Not critical but the device requires attention • Likely due to low battery, cable disconnected, or device not functioning properly.
Alarms • Hazardous or Critical alarms are a loud, continuous, shrill sound that have a corresponding RED light that illuminates on the system controller • Indicating the device needs immediate attention • Often because the pump has stopped or a problem is detected with the system controller • Most likely intervention required is to change out the system controller
Field Management • All VADs are dependant on adequate preload in order to maintain proper functioning • Volume resuscitation in an unstable VAD patient is the first line of therapy before vasopressors but be cautious with fluid as to not over load the right ventricle in L VADs only.
Field Management • Nitrates can be detrimental to a VAD patient because of the reduction in preload • Results in decreased pump efficiency • Consult with medical control before administering nitrates per protocol
Field Management • Initiate IV therapy with all VAD patients if possible • Use aseptic technique due to the patient’s increased risks of infection
Field Management • VAD patients are susceptible to other injuries unrelated to the VAD • Contact the VAD Coordinator, they are your most valuable resource when encountering these patients • Consult with medical control about transport
Patient Transport • This is emergency, resource and protocol driven decision making • VAD patients require unique care that not all medical centers are equipped to handle. Transport to the implanting center when able or the closest VAD center • Make sure when transporting to bring all VAD related equipment • Secure VAD batteries and the controller to prevent dropping or damage • Make sure to keep all cables tangle and kink free
Preplanning • Medical Control • Inquire ahead of time the level of knowledge/ comfort with your medical directors regarding the management of VAD patient • Know Transport Options • Air vs. Ground • Know your tertiary facilities and their ability to management VAD patients
Remember… • EMS can walk into just about any situation • Depending on the individuals- the family may not be able to handle the emergency • Listen to the family members that can handle the emergency and “assist” them with whatever they need • The only resources/ tools you can truly rely on are the ones you bring to the call • Follow-up and educate yourself to new technologies that keep entering into the industry
Remember… • Ask for the contact number for the managing center’s VAD Coordinator as soon as you arrive, this should be on the person or close by. This is the coordinator they work very closely with and will be your best resource • Family, friends, co-workers- listen to them for direction, they should be educated/ trained to assist with most VAD related complications • 911 activation may not be for a VAD related emergency
Remember… • Emergency bag containing back-up VAD supplies needs to stay with the patient at all times. Should contain extra batteries and the spare system controller • Ask the family for any trouble shooting guidelines that maybe available. This often includes various alarms and interventions • Remember that the family/ friends are not emergency responders or maybe too upset to assist you • If a VAD patient calls 911 it will not be for something simple like a battery change. VAD related emergencies are serious life threatening events