UNIVERSITY OF UTAH HEALTH CARE HOSPITALS AND CLINICS

Transcription

1 UNIVERSITY OF UTAH HEALTH CARE HOSPITALS AND CLINICS CARDIAC MECHANICAL SUPPORT PROGRAM GUIDELINES CARDIAC MECHANICAL SUPPORT: LVAD BASICS FREQUENT SCENARIOS AND TROUBLESHOOTING Review Date: July 2011 Chapter or section: Follow Up I. PURPOSE: Revision Date: A. To provide overview and guidelines of monitoring, assessment, frequent clinical scenarios, and troubleshooting issues in a continuous-flow LVAD patient. II. GUIDELINES: A. Any and all LVAD setting changes made to LVAD patients should be reported to the University of Utah Cardiac Mechanical Support Program (VAD Team) via phone call (801) or fax (801) The VAD Coordinator on call can be reached for immediate assistance in troubleshooting LVAD patient issues by calling (801) and asking for VAD Coordinator on call. 2. Echocardiogram reports, other cardiac testing reports, and clinic visit notes should be faxed to (801) B. When the continuous-flow LVAD patient is hemodynamically stable (i.e. euvolemic, no inotropic support), the range of speed of the LVAD is determined and set by the clinician based on patient s clinical status, LVAD parameters, and echocardiography. C. Considerations when assessing the LVAD patient: 1. Preload Assessment a. The following conditions can affect LV preload (and therefore LVAD flows) i) Right Heart Function A) RV function should be assessed by echocardiogram if patient has signs of poor forward flow or right heart failure. B) Avoid setting pump speed too high this will result in leftward shift of interventricular septum and abnormal RV geometry. C) In general, the LVAD speed is adjusted so that the LV is well unloaded decreased in size, interventricular septum is midline (no shift in either direction) and aortic valve opens approximately every second or third beat. 1) There will be some variation in the degree of unloading that can be achieved in individual patients. Some patients with very poor LV function will not have any aortic valve opening even at lower LVAD speeds. ii) Intravascular Fluid Volume Status A) It is important for LVAD patients to avoid dehydration. The LVAD is continuously flowing at a set speed (RPM) and can generate large negative pressures at the pump inlet in the left ventricle. B) Caution should be taken if a fluid restriction is ordered for a LVAD patient as dehydration and decreased preload in the left ventricle can cause the ventricle to suckdown or collapse around the inflow cannula resulting in obstruction, low flow, and arrhythmias. C) LVAD patients should be charting their weight daily and pay attention to symptoms such as orthostatic hypotension.

2 D) Fluctuations of weight (>3-5 lbs in hours) may indicate need to review diuresis and fluid intake with the patient. E) Caution should be taken when making speed changes to the LVAD in response to changes in patient s fluid status. Decisions on speed changes should be based on clinical status of a fluid optimized patient. iii) Arrhythmias A) LVAD patients may be at greater risk for ventricular arrhythmias. This is partly related to the presence of the inflow cannula in the LV. 1) Avoid setting pump speed too high. This may cause significant leftward septal shift, ventricular collapse (suction / PI event), and trigger ventricular arrhythmias. B) Ventricular tachycardia and ventricular fibrillation may not cause immediate hemodynamic instability and loss of consciousness, as the LV is being supported with the LVAD. However, it is important to resume a stable rhythm as soon as possible to prevent hemodynamic deterioration. 1) All LVAD patients can be cardioverted / defibrillated without stopping or disconnecting the LVAD. 2. Afterload / Systemic Vascular Resistance Assessment a. Arterial blood pressure should be controlled with medications and intravascular fluid volume management and NOT by LVAD pump speed. The LVAD patient s flow and cardiac output is sensitive to afterload. b. Non-invasive blood pressure monitoring i) If the patient has a palpable pulse, a standard automated BP machine may be used to obtain blood pressures. (It may be very difficult to hear the systolic/diastolic sounds using a manual cuff and stethoscope). A) NOTE: The pulse pressure is usually narrow in a continuous-flow LVAD patient. ii) If the patient does not have a palpable pulse, the most reliable form of non-invasive BP monitoring is obtaining an approximated Mean Arterial Pressure (MAP) with a Doppler and a sphygmomanometer. A) Place manual cuff on patient s arm. B) Find blood flow on radial or brachial artery using a Doppler. C) Pump cuff up (the blood flow sound from Doppler will disappear) D) The 1 st sound you hear as you deflate the cuff slowly is the approximated Mean Arterial Pressure (MAP) E) MAP target is mmhg. D. Troubleshooting Frequent Scenarios. 1. Assessing adequacy of pump speed and LVAD support by determining ventricular size. a. Volume Overload i) Increased PI, Power, Estimated Flow b. Dehydration ii) Arrhythmias iii) Decrease in PI c. Arrhythmias ii) Decrease in flow, power, and PI 2. Assessing valvular function a. Aortic insufficiency i) Dilated LV with high pump flow 3. Assessing RV function a. RV Failure ii) Displayed pump speed drops below fixed speed setting iii) Decreased pump flow 4. Assessing inflow and outflow abnormalities a. Tamponade

3 ii) Decreased pump flow E. Specific Device Management 1. HeartMate II LVAD a. When patient is connected to the HeartMate II Power Module and System Monitor touch screen, changes to the patient s speed can be made and the following parameters should be displayed: A) Fixed speed is a direct measurement through pump rotor. B) HeartMate II pump speed should be set at a range that provides a sufficient level of cardiac output support (usually 8,600-9,800 RPM). Speed changes should only be done slowly in increments of 200 RPMs. C) Optimum speed no rightward or leftward shift of the interventricular septum. ii) Estimated Flow A) Estimated based on power and speed and should only be used for trending. B) The normal flow range is patient specific and based on their cardiac output needs. C) The flow displayed is an estimate, and in some situations may not exactly reflect cardiac output. If there is discrepancy between the LVAD flow estimate and clinical assessment, invasive hemodynamic monitoring should be considered. D) +++ or may be displayed when the power values and estimated flow are above or below the expected physiologic limits at the current set speed. These readings are not of concern if the patient is NOT symptomatic. iii) Pump Power (watts) A) Directly measured by the LVAD system controller. C) Increase in power not related to an increase in the speed (RPM) can indicate thrombus or clot in the pump and cause erroneously high estimated flow readings. iv) Pulsatility Index (Pulse Index or PI) A) Correlation between the LV contractility and continuous-flow nature of the LVAD. Only useful in trending. 1) LV contractility increase yields increase in PI 2) LV contractility decrease yields decrease in PI 3) Significant drop in PI can also indicate LV suck-down or collapse due to high pump speed or drop in preload. (suction / PI Events see below) B) Normal PI values are patient specific but usually 3-6. b. PI or Suction Events i) The HeartMate II LVAD has a Low Speed Limit setting. This setting is usually set by the clinician at RPMs below the Fixed Speed Setting. When the pump senses a suction event or collapse of LV around the inflow cannula, the pump automatically decreases to Low Speed Limit and then slowly ramps back up to the Fixed Speed Setting. This is a PI or suction event. A) When these events occur, they will be recorded by the system controller (up to 120 events) and can be reviewed in the history screen on the System Monitor Touchscreen. B) Multiple events seen can indicate LVAD speed too high, inadequate preload from arrhythmias, RV dysfunction, or low intravascular volume. 2. HeartWare LVAD a. The patient s HeartWare controller displays the patient s pump parameters. In order to make speed or viscosity changes to the LVAD, the patient must be connected to the HeartWare touch screen monitor. HeartWare touchscreen monitors are only available at the implanting centers. A) Fixed speed is a direct measurement through pump rotor. B) HeartWare pump speed should be set at a range that provides a sufficient level of cardiac output support (usually 2,400-3,200 RPM). Speed changes should only be done slowly in increments of 20 RPMs. C) Optimum speed no rightward or leftward shift of the interventricular septum.

4 ii) Estimated Flow A) Estimated based on power, speed, and blood viscosity and should only be used for trending. B) The normal flow range is patient specific and based on their cardiac output needs. C) The flow displayed is an estimate, and in some situations may not exactly reflect cardiac output. If there is discrepancy between the LVAD flow estimate and clinical assessment, invasive hemodynamic monitoring should be considered. iii) Pump Power (watts) A) Direct measurement by the LVAD system controller of pump motor current. C) Increase in power not related to an increase in the speed (RPM) can indicate thrombus or clot in the pump and cause erroneously high estimated flow readings. b. Suction Detection Alarm i) HeartWare LVAD has a Ventricular Suction Detection Alarm that will trigger if the estimated flow drops approximately 40% below patient s estimated flow baseline. Suction event indicates a considerable reduction in left ventricular volume. ii) The suction alarm will automatically clear when the estimated flow reading returns to the patient s baseline. iii) Suction events can indicate LVAD speed too high, inadequate preload from arrhythmias, RV dysfunction, or low intravascular volume. 3. Jarvik 2000 LVAD a. The patient s controller displays the patients pump settings and allows the user to adjust the pump speed. There is no system monitor or touch screen. A) Speed setting dial/knob on side of controller B) Select speed settings 1 to 5. Setting 1 = 8,000 RPM, 2 = 9,000 RPM, 3 = 10,000, 4 = 11,000 RPM, 5 = 12,000 RPM. C) Patient may be instructed to increase one speed level setting during activity and decrease back to baseline post activity. ii) Pump Power (watts) A) Illuminated number on power bar located on top of controller indicates power usage level. C) Increase in power not related to an increase in the speed (RPM), outside of patient s normal trend, can indicate thrombus or clot in the pump and cause erroneously high estimated flow readings. iii) Flow A) There is no flow estimator displayed on a Jarvik 2000 LVAD controller. B) The following tabulated flow estimates are based on research measurements in healthy animals. Speed Dial Setting Speed (RPM) Flow (L/min) Power (watts) 1 8, , , , , b. Intermittent Low Speed (ILS) Phase i) Every minute for about 8 seconds the controller automatically drops the pump speed to ~ 7,500 RPM increasing the end-diastolic volume in the LV and in many patients permitting the aortic valve to open more effectively thereby washing blood flow through the aortic root. A) This is particularly important in the Jarvik patient who has had the LVAD placed via left thoracotomy with the outflow graft connected to the descending aorta instead of the ascending aorta. ii) Patients will commonly become more pulsatile during those 8 seconds. iii) The power displayed on the controller will subsequently drop to 3 during the slower ILS phase.

5 REFERENCES: Slaughter MS, Rogers JG, Milano CA, et al. Advanced heart failure treated with continuous-flow left ventricular assist device. N Engl J Med 2009;361: Slaughter MS, Pagani FD, Rogers JG, et al. Clinical management of continuous-flow left ventricular assist devices in advanced heart failure. J Heart Lung Transplant 2010;29:S1-S39. APPROVAL BODY: Solid Organ Transplant Program, Cardiac Mechanical Support Program Surgical and Medical Directors APPROVAL DATE: GUIDELINE OWNER: Cardiac Mechanical Program HISTORICAL INFORMATION ORIGIN DATE: 7/19/2011 REVIEW DATES: REVISION DATES: APPROVAL DATES: