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

  • First generation LVADs had pulsatile flow
    • Subsequent designs use continuous flow - patient will not have a palpable pulse.
  • Pt will be on anticoagulation to prevent pump thrombus.
  • VADs are ECG independant, unlike ICD (most patients with a VAD will also have an ICD in place)
    • ICD discharges are common, and frequently inappropriate (possibly 2/2 LVAD interference)[3]

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

  • Driveline/Pocket infections: Treat for gram negative and positive coverage. Consider endocarditis for recently transplanted pts.
  • Pump Thrombosis (due to inappropriate anticoagulation)
    • Consider heparin/tPA if device thrombus is a high probability or seen on bedside echo
  • Bleeding (many patients are anticoagulated on the LVAD)
    • Acquired Von Willebrand disease (similar to patients on dialysis or with aortic stenosis)
    • Hypercoagulability due to coumadin
  • Dead Battery for Device
    • Usually a button to check remaining battery charge
  • Arrythmias: Okay to defibrillate (front-to-back), but not over pump
  • Acute Infarction

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. ↑ Partyka C, Taylor B. Review article: ventricular assist devices in the emergency department. Emerg Med Australas. 2014 Apr;26(2):104-12.
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