Left ventricular assist device complications

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Background

  • Developed in 1960s and used as a bridge to Cardiac Transplant but have evolved into permanent, or “destination therapy.”
  • Indication is New York Heart Association class 4 heart failure, ejection fraction <25%, VO2 max less than 15 among other criteria.[1]
  • Goal of a VAD is to assist the ventricle and augment cardiac output.
    • LVAD (left ventricle), RVAD (right ventricle), BiVAD (both venticles via separate pumps)[2]
VADs have 3 major variables:
  1. Speed
  2. Flow
  3. Power

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 "brains" of the device. Monitors pump performance. Usually also has display screen and controls for settings, alarms, and diagnostics. Display will show pump speed in RPM and pump output in L/min.
  • Power Supply = Controller can be connected to batteries for pt 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

Thoratec VAD

  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

Special Considerations

  • 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.
  • Pt will be on anticoagulation and antiplatelet therapy 2/2 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 2/2 LVAD interference)[3]

Cardiac Arrest[4]

  • 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
    • Pt 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, etc.
    • Some studies available[5][6] indicate that CPR may not be as harmful as currently thought, or that abdominal compressions are an alternative[7] but further investigation needed
    • Use clinical judgement for initiation of compressions

Assessment of the LVAD Patient[4]

  • Assess perfusion and general state (mental status, skin temp/color, capillary refill, etc).
    • LVADs are preload dependant - if sx of hypoperfusion, give fluid blous
  • HR measured via EKG or auscultation (may be difficult 2/2 pump noise)
  • Get 12-lead EKG on all LVAD patients
    • Demonstrates primary cardiac disease[3]
    • Generally, VAD does not influence underlying cardiac rhythm
  • Blood pressure measured with manual BP cuff and doppler ultrasound - MAP is identified when constant flow is heard
  • Basic labs (CBC, CMP, Coags) should be obtained on all LVAD patients
  • 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

Complications[4]

  • Bleeding - most common reason for ED visit (frequency 42%[8])
    • GI Bleed, epistaxis, ICH, intrathoracic bleeding
    • Mechanisms
      • acquired Von Willebrands Disease
      • supratherapeutic anticoagulation
      • lack of pulsatile flow → AV malformations in GI tract
    • Immediately consult VAD team/coordinator
    • Tx - anticoagulation reversal based on specific agents used
      • In life-threatening bleeds, consider TXA, PCC, Desmopressin, FFP
  • Infection - driveline and pocket are most common sites[8]
    • Usually gram positive bacteria, but also need to cover for fungal infection
  • Pump Thrombosis
    • Low output state with falsely elevated pump flow estimates on controller
    • Dx with echo or cardiac CTA
    • Tx with heparin and antiplatelet therapy
    • Consider tPA in severe (life-threatening) situations
  • Arrhythmia - very common
    • Get labs to evaluate electrolytes and troponin
    • Tx atrial fibrillation as in any other patient
    • Tx ventricular arrhythmias with volume replacement and pharmacological or electrical cardioversion
      • Place pads anterior/posterior if going to cardiovert/defibrillate

References

  1. ↑ Mancini D, Lietz K. Selection of cardiac transplantation candidates in 2010. Circulation. 2010;122(2):173-83.
  2. ↑ Mechem CC. Prehospital assessment and management of patients with ventricular-assist devices. Prehosp Emerg Care. 2013 Apr-Jun;17(2):223-9.
  3. ↑ 3.0 3.1 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
  4. ↑ 4.0 4.1 4.2 Partyka C, Taylor B. Review article: ventricular assist devices in the emergency department. Emerg Med Australas. 2014 Apr;26(2):104-12.
  5. ↑ 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.
  6. ↑ 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.
  7. ↑ 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.
  8. ↑ 8.0 8.1 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.
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