How does having a Left Ventricular Assist Device (LVAD) affect blood pressure measurement?

Blood Pressure Measurement in LVAD Patients

Blood pressure measurement in patients with a Left Ventricular Assist Device (LVAD) should be performed using Doppler ultrasound with a manual blood pressure cuff, as conventional automated blood pressure cuffs are unreliable due to the continuous flow physiology of these devices. 1

Why Conventional BP Measurement Doesn't Work with LVADs

• LVADs create continuous blood flow with reduced arterial pulse pressure and pulsatility
• This unique hemodynamic profile makes standard automated blood pressure measurements inaccurate
• Patients often have a pulse that is difficult or impossible to palpate, making traditional methods unreliable 2

Recommended BP Measurement Technique

1. Doppler Ultrasound Method:

   • Position a manual blood pressure cuff on the patient's upper arm
   • Apply ultrasound gel over the brachial or radial artery
   • Place the Doppler probe at a 45-60° angle over the artery
   • Inflate the cuff 20-30 mmHg above the point where the Doppler signal disappears
   • Slowly deflate the cuff (2-3 mmHg/second)
   • Record the pressure at which the Doppler signal returns 1

2. Interpretation of Doppler Readings:

   • If a pulse is palpable (PP ≥15 mmHg): Doppler reading correlates strongly with systolic BP
   • If no pulse is palpable (PP <15 mmHg): Doppler reading correlates with mean arterial pressure (MAP) 3

Alternative Method: Pulse Oximeter

• Research shows that replacing the Doppler probe with a finger-based pulse oximeter can yield BP measurements similar to Doppler-derived MAP
• This may be a reliable alternative when Doppler equipment is unavailable 4

Blood Pressure Targets for LVAD Patients

• Maintain mean arterial pressure between 70-90 mmHg
• MAP levels above 90 mmHg are associated with increased risk of aortic insufficiency, stroke, and pump thrombosis 1
• Hypertension should be aggressively managed to reduce neurological events 1

Clinical Pitfalls and Considerations

• During emergencies, if specialized equipment is unavailable, focus on clinical signs of perfusion rather than absolute BP numbers 1
• The interobserver agreement for the presence of a palpable pulse is only moderate (k = 0.41), so standardize assessment techniques 3
• Continuous electrocardiographic monitoring is considered standard of care for hospitalized LVAD patients, as arrhythmias may provide insight into VAD hemodynamics 2
• The artificial pulse of newer LVAD models (like HeartMate 3) is asynchronous with the cardiac cycle, which affects pulsatility assessment 2

By understanding these unique aspects of LVAD hemodynamics and using appropriate measurement techniques, clinicians can better manage these complex patients and potentially reduce complications related to inappropriate blood pressure management.