What does an LVAD (Left Ventricular Assist Device) control unit reading of increased power and decreased flow indicate?

LVAD Control Unit Reading of Increased Power and Decreased Flow: Implications and Management

An LVAD control unit reading of increased power and decreased flow indicates a potentially serious pump obstruction or thrombosis that requires immediate evaluation and intervention to prevent device failure and life-threatening complications.

Understanding the Significance of These Parameters

When an LVAD control unit shows increased power consumption with decreased flow, this combination strongly suggests resistance to pump function. This hemodynamic pattern is particularly concerning as it directly impacts patient morbidity and mortality.

Key Physiological Implications

• Pump Thrombosis: The most concerning cause is thrombus formation within the device, which increases resistance (requiring more power) while restricting blood flow 1

• Inflow Obstruction: Possible causes include:

  • Cannula malposition
  • Suction events (when the LV is excessively unloaded)
  • Inflow cannula obstruction by adjacent cardiac structures

• Outflow Obstruction: May occur due to:

  • Kinking of the outflow graft
  • Thrombus in the outflow graft
  • Aortic valve stenosis or insufficiency development 1

Immediate Assessment Steps

1. Device Parameter Documentation

   • Record all device parameters (power, speed, flow, pulsatility) 1
   • Compare with baseline parameters for the patient

2. Power Source Verification

   • Ensure adequate battery power or proper wall power connection 1
   • Rule out simple power supply issues before assuming device malfunction

3. Clinical Evaluation

   • Assess for signs of hemodynamic compromise:
     • Hypotension
     • Decreased organ perfusion
     • Signs of heart failure exacerbation
   • Check for LVAD "hum" - absence or change may indicate device malfunction

4. Laboratory Assessment

   • Obtain hemolysis markers (LDH, plasma free hemoglobin)
   • If thrombus is suspected, check lactate dehydrogenase levels immediately 1

Management Algorithm

Step 1: Determine Severity

• Emergent: Signs of hemodynamic instability, severe symptoms
• Urgent: Stable but concerning parameters
• Non-urgent: Mild parameter changes without symptoms

Step 2: Initial Interventions

• Contact LVAD coordinator/center immediately
• If controller alarms persist despite confirmed power source, consider controller exchange using backup controller 1
• Do not arbitrarily adjust pump speed without expert consultation

Step 3: Diagnostic Workup

• Echocardiography to assess:
  • LV filling
  • Position of inflow cannula
  • Aortic valve opening
  • Presence of thrombus
• Consider CT angiography if outflow obstruction suspected

Step 4: Definitive Management

Based on identified cause:

• Pump Thrombosis: Systemic anticoagulation, thrombolytics, or surgical pump exchange
• Suction Event: Reduce pump speed under expert guidance
• Cannula Malposition: Surgical revision may be required
• Aortic Insufficiency: Medical management or valve intervention

Special Considerations

• Arrhythmias: May cause flow variations and should be addressed 1
• Right Heart Failure: Can present with similar LVAD parameters and requires specific management 1
• Hypovolemia: Can cause suction events that increase power and decrease flow

Common Pitfalls to Avoid

1. Delayed Recognition: Failure to recognize the urgency of these parameters can lead to device failure and catastrophic outcomes
2. Inappropriate Speed Adjustments: Changing LVAD speed without understanding the underlying cause can worsen the situation
3. Overlooking Simple Causes: Battery depletion or controller issues should be ruled out before assuming internal pump problems
4. Isolated Management: Always involve the specialized LVAD team in decision-making

Continuous LVAD flow patterns create unique hemodynamic states that require specialized understanding. The combination of increased power and decreased flow represents a critical warning sign that warrants immediate attention to prevent serious complications and ensure optimal patient outcomes.