Left ventricular assist device complications

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.
• Goal of a VAD is to assist the left ventricle and augment cardiac output.

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. Pulse: Has pulse but may not match ECG rhythm
4. Backup Method: Hand Pump
5. Battery: 12volt MiMH - 10hrs
6. Defib/Cardioversion: Use hand pump during defib/cardioversion
7. Anticoagulation: patient on aspirin

HeartMate II

(Most common type in use today)

1. Use: Bridge to transplant or destination therapy
2. Flow type: axial flow
3. Backup Method: No external method
4. Pulse: No palpable pulse or BP. Dopplerable Only
5. Battery: 14V Li-Ion - 10 hrs
6. Defib/Cardioversion: No precautions necessary
7. Anticoagulation: Warfarin

Thoratec VAD

1. Use: Bridge to Transplant
2. Flow Type: Patient will have pulse and BP but may not match ECG rhythm
3. Backup Method: No external method
4. Battery: 12V lead acid gel battery - 7.2 Ah - up to 3 hrs
5. Defibrillation/Cardioversion: No precautions
6. Anticoagulation: Warfarin

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.
• Pre-load dependant - give fluid bolus if sx of poor perfusion.
• Auscultate for hum or whirling sound. (indicates lvad is on)
• Check MAP with doppler and BP cuff, goal is ~65-90
• VADs are ECG independant, unlike ICD (most patients with a VAD will also have an ICD in place)

Complications

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

Management

1. Assess perfusion (mental status, skin temp/color, and machine flow indicator).
2. Consider inotropes and after load reduction to improve forward flow.
3. Fluid challenge for pre-load augmentation.
4. Place on monitor +/- defibrillate

Urgent Echo: Consider your own bedside ED echo.

References

• mylvad pdf
• Givertz,MM. Ventricular Assist Devices. Circulation. 2011; 124: e305-e311.
• 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(4 Suppl):S1-39.
• VAD Review
• EMCrit LVAD Management
• Patients with a Ventricular Assist Device Need Special Considerations