Left ventricular assist device complications

Background

  • Commonly referred to as an LVAD
  • Developed in 1960s as bridge to cardiac transplant
    • LVAD (left ventricle), RVAD (right ventricle), BiVAD (both venticles via separate pumps)[1]
  • VADs have 3 major variables:
  1. Speed
  2. Flow
  3. Power
  • Other parameters:
  1. Battery level - typically powered by two batteries, with power base unit that can be plugged into wall
  2. Pulsatility index:
    • Decreased index, may indicate low preload
    • Increased index, may indicate volume overload
    • Pump speed and pulsatility index are inversely related

Applications

  • Modern applications have expanded beyond original purpose:
    • Bridge to cardiac transplant
    • Temporizing measure for cardiomyopathies that are expected to resolve
    • Destination therapy for patients who will not undergo cardiac transplant
  • Indication is New York Heart Association class 4 heart failure, ejection fraction <25%, VO2 max less than 15 among other criteria[2]
  • Goal of a VAD is to assist the ventricle and augment cardiac output

Components

  • Pump = Internal pump (usually placed in preperitoneal space), takes blood from a cannula in the apex of the left ventricle and pumps it into the aorta
  • Driveline = Percutaneous cable that exits the abdominal wall, connects pump to external components (controller, battery)
  • Controller = External "box" containing computer for the device that monitors pump performance, has a display screen and controls for settings/alarms/diagnostics, and will display will show pump speed in RPM and pump output in L/min
  • Power Supply = Controller can be connected to batteries for patient mobility, or to a "power base station" that plugs into the wall for home use

Devices Overview

Heartmate I
Heartmate II
Thoratec-VAD

HeartMate I or XVE

  1. Use: Destination Therapy
  2. Flow Type: Pulsatile
  3. Backup Method: Hand Pump
  4. Battery: 12volt MiMH - 10hrs
  5. Defib/Cardioversion: Use hand pump during defib/cardioversion

HeartMate II

(Most common type in use today)

  1. Use: Bridge to transplant or destination therapy
  2. Flow type: Continuous
  3. Backup Method: No external method
  4. Battery: 14V Li-Ion - 10 hrs
  5. Defib/Cardioversion: No precautions
  6. Target INR: 1.8 to 2.5

Thoratec VAD (HeartMate III)

  1. Use: Bridge to Transplant
  2. Flow Type: Pulsatile
  3. Backup Method: No external method
  4. Battery: 12V lead acid gel battery - 7.2 Ah - up to 3 hrs
  5. Defib/Cardioversion: No precautions

HeartWare HVAD

  1. Use: Bridge to Transplant
  2. Anatomy: Designed to be implanted completely in pericardial space, no need for pump pocket formation
  3. Flow Type: Centrifugal pump
  4. Target INR: 2.0-3.0

Complications/Differential Diagnosis[3]

  • Bleeding - most common reason for ED visit, most common in first month after implant (frequency 42%[4])
  • Infection - driveline and pocket are most common sites[4]
  • Pump Thrombosis, estimated at 2-13%, average first thrombosis ~1 year after implant depending on device[7]
    • Low output state with falsely elevated pump flow estimates on controller
    • Diagnose with echo or cardiac CTA
    • Treatment with heparin and antiplatelet therapy
    • Consider tPA in life-threatening situations
    • Causes:
      • Mechanical - post-surgical ventricular debris, cardiac emboli, inflow cannula malposition
      • Inadequate anticoagulation and/or antiplatelet treatment
        • As optimal dosing and monitoring not well defined due to lack of clinical trials
        • Will occur despite rigid regimen and compliance of anticoagulation/antiplatelet
      • Prosthetic material inflammatory reaction with serum
      • Intrinsic endothelial activation in response to continuous flow-VAD
  • Arrhythmia - very common
    • Get labs to evaluate electrolytes and troponin
    • Treat atrial fibrillation as in any other patient
    • Treat ventricular arrhythmias with volume replacement and pharmacological or electrical cardioversion
      • Place pads anterior/posterior if going to cardiovert/defibrillate

Evaluation[3]

  • Assess perfusion and general state (mental status, skin temp/color, capillary refill, etc)
    • LVADs are preload dependant - if symptoms of hypoperfusion, give fluid blous
  • HR measured via ECG or auscultation (may be difficult secondary to pump noise)
  • Get 12-lead ECG on all LVAD patients
    • Demonstrates primary cardiac disease[8]
    • Generally, VAD does not influence underlying cardiac rhythm
  • Imaging:
    • Bedside echo if able, formal echo if available, with the following suggestive of thrombosis:
      • Cannula flow velocity > 2 m/s
      • More frequent opening of aortic valve than at baseline
      • Increasing LV internal dimension in diastole without manual speed changes
    • CT with contrast to look for thrombus, discuss with radiologist to protocol
  • Blood pressure measured with manual BP cuff and Doppler ultrasound - MAP is identified when constant flow is heard
  • Basic lab should be obtained on all LVAD patients
  • Cardiac labs - BNP, troponin
  • Include thrombolysis, coagulopathy labs
    • CBC
    • CMP, indirect bilirubin
    • PT/INT/PTT
    • LDH
    • Haptoglobin
    • Fibrinogen
    • UA, hematuria
    • Quantitative plasma free hemoglobin
    • Consider TEG
  • LDH elevation over 1,150 IU/L suggestive of pump thrombosis[9]
    • Approximate sensitivity of ~80% and specificity of 90%
    • Hemolysis within thrombosed pump releases LDH
  • Assess LVAD status
    • Auscultate for pump noise
    • Device parameters (found on controller)
      • Pump speed - varies by device - 2,000-10,000 RPM
      • Power - normal 4-6 Watts
      • Flow - normal 4-6 L/min
      • Pulsatility Index (PI) - normal 1-10
        • Measures magnitude of pulsatile flow provided by native cardiac contractions
        • Higher PI = less LVAD support
    • Clinical status more important than LVAD parameters

Management

  • Immediately contact hospital or patient's LVAD coordinator to help coordinate care
  • Take special care to not twist, bend, cut, or otherwise damage the driveline
  • First generation LVADs had pulsatile flow
    • Subsequent designs use continuous flow - patient will not have a palpable pulse
  • Patient will be on anticoagulation and antiplatelet therapy secondary to high risk of pump thrombus, CVA, and other thromboembolic events
  • VADs are ECG independant, unlike ICD (many patients with a VAD will also have an ICD in place)
    • ICD discharges are common, and frequently inappropriate (possibly secondary to LVAD interference)[8]
  • Ensure that patient or family bring in any additional batteries and charging elements as these will not be available in most hospital settings
  • Thrombosis, tPA in emergencies
    • Breadth of literature supporting is overall small
    • When patient not responding to continuous anticoagulation (heparin, argatroban drip)
    • AND when going directly to LVAD exchange or catheter-directed thrombolysis are not possibilities
    • Consider tPA if not contraindicated for survival and avoidance of needing LVAD exhange[10]
      • 5 mg IV bolus tPA
      • 3 mg/hr infusion in NS for 10 hours
      • 1 mg/hr for up to 48 hours, never exceeding 100 mg max total dosage
      • In single center study cited above, there was:
        • 70% that had hemolysis resolve and no need for LVAD exchange at 30 days
        • 95% survival at 30 days
        • 10% hemorrhagic stroke with no difference between tPA and control group
    • Alternative dosing, while plus/minus continuing heparin drip[11]
      • Initial dosing of 10 mg IV bolus
      • Followed by 1 mg/min for 20 min
      • Then 1 mg/hr for 24 hours
      • Monitor LDH levels and discontinue heparin drip when LDH acceptably lowered

Cardiac Arrest[3]

  • Unconscious, apneic, no evidence of LVAD function (auscultate for mechanical noise)
  • Immediately evaluate LVAD components and attach to reliable power source
    • Some first-generation LVADs have external hand pumps that can be used to provide circulation
  • Otherwise follow ACLS as in a normal patient
    • Patient should be intubated, given IV fluids and drugs, etc
  • Avoid chest compressions unless absolutely necessary - evaluate other causes of pump failure or lack of perfusion (e.g. pump thrombus) first
    • Compressions can potentially damage LVAD, disrupt its connection to the heart (risk of exsanguination), etc
    • Some studies available[12][13] indicate that CPR may not be as harmful as previously thought, or that abdominal compressions are an alternative[14] but further investigation needed
    • Use clinical judgement for initiation of compressions

Disposition

  • Immediately contact the patient's VAD coordinator
  • Almost all LVAD patient presenting to the ED will require admission or transfer to a site of expertise

See Also

External Links

References

  1. ↑ Mechem CC. Prehospital assessment and management of patients with ventricular-assist devices. Prehosp Emerg Care. 2013 Apr-Jun;17(2):223-9.
  2. ↑ Mancini D, Lietz K. Selection of cardiac transplantation candidates in 2010. Circulation. 2010;122(2):173-83.
  3. ↑ 3.0 3.1 3.2 Partyka C, Taylor B. Review article: ventricular assist devices in the emergency department. Emerg Med Australas. 2014 Apr;26(2):104-12.
  4. ↑ 4.0 4.1 Rose EA, Gelijns AC, Moskowitz AJ et al. Long-term use of a left ventricular assist device for end-stage heart failure. N. Engl. J. Med. 2001; 345: 1435–1443.
  5. ↑ Suarez J., Patel C.B., Felker G.M., Becker R., Hernandez A.F., Rogers J.G. Mechanisms of bleeding and approach to patients with axial-flow left ventricular assist devices. Circ Heart Fail. 2011;4:770–784.
  6. ↑ Jennings, D, et al. Safety of Anticoagulation Reversal in Patients Supported with Continuous-Flow Left Ventricular Assist Devices. ASAIO Journal. July 2014. 60:381–384
  7. ↑ Nair N et al. Thrombolytics in VAD management — A single-center experience. Int J Cardiol Heart Vasc. 2016 Jun; 11: 49–54.
  8. ↑ 8.0 8.1 Pistono M, Corrà U, Gnemmi M, Imparato A, Temporelli PL, Tarro Genta F, Giannuzzi P. How to face emergencies in heart failure patients with ventricular assist device. Int J Cardiol. 2013 Oct 15;168(6):5143-8
  9. ↑ Zoler ML. Cardiology News. STS: Lactate dehydrogenase of 1,150 IU/L flags LVAD thrombosis. https://www.mdedge.com/ecardiologynews/article/106621/heart-failure/sts-lactate-dehydrogenase-1150-iu/l-flags-lvad. Published Feb 19, 2016.
  10. ↑ Nair N et al. Thrombolytics in VAD management — A single-center experience. Int J Cardiol Heart Vasc. 2016 Jun; 11: 49–54.
  11. ↑ Webber BT et al. Intravenous thrombolytic therapy for patients with ventricular assist device thrombosis: An attempt to avoid reoperation. Ann Card Anaesth. 2016 Jan-Mar; 19(1): 192–196.
  12. ↑ Shinar Z, Bellezzo J, Stahovich M, Cheskes S, Chillcott S, Dembitsky W. Chest compressions may be safe in arresting patients with left ventricular assist devices (LVADs). Resuscitation. 2014 May;85(5):702-4.
  13. ↑ Mabvuure NT, Rodrigues JN. External cardiac compression during cardiopulmonary resuscitation of patients with left ventricular assist devices. Interact Cardiovasc Thorac Surg. 2014 Aug;19(2):286-9.
  14. ↑ Eric M Rottenberg, Jarrett Heard, Robert Hamlin, Benjamin C Sun, and Hamdy Awad. Abdominal only CPR during cardiac arrest for a patient with an LVAD during resternotomy: A case report. J Cardiothorac Surg. 2011; 6: 91.
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