From the Guidelines
A low flow alarm on a Left Ventricular Assist Device (LVAD) is most commonly caused by decreased preload, such as hypovolemia, which can be prevented by maintaining adequate fluid intake, as suggested by a recent study 1. When a low flow alarm occurs, it is crucial to assess the patient immediately for symptoms like dizziness, syncope, or signs of hypoperfusion.
- Check for hypovolemia by examining vital signs, jugular venous pressure, and performing a fluid challenge if appropriate.
- Administer IV fluids (typically 500-1000mL normal saline) if hypovolemia is suspected, as this can help restore adequate blood flow through the device. Other potential causes of a low flow alarm include increased afterload (hypertension) 1, pump thrombosis, right heart failure, or mechanical issues with the device itself.
- Evaluate for pump thrombosis by checking for hemolysis markers and power spikes.
- Rule out right ventricular failure by assessing for elevated central venous pressure, peripheral edema, and hepatomegaly.
- Arrhythmias can also cause low flow, so obtain an ECG and treat any identified rhythm disturbances according to standard protocols. It is essential to contact the LVAD coordinator or cardiac team immediately, as device malfunction may require specialized intervention. The management of a low flow alarm should prioritize maintaining optimal blood flow through the device to prevent serious complications, and this can often be achieved by addressing the underlying cause, such as hypovolemia, and ensuring the patient's volume status is optimized, as recommended in recent guidelines 1.
From the Research
Causes of Left Ventricular Assist Device (LVAD) Low Flow Alarm
- A low flow alarm on an LVAD can be caused by various factors, including ventricular fibrillation, as seen in a case study where a 50-year-old female presented to the ED with a low flow alarm on her LVAD and was found to be in ventricular fibrillation 2.
- Pump thrombosis is another potential cause of low flow alarms, as patients with pump thrombosis often present with elevated lactate dehydrogenase levels and higher power and/or low-/high-flow alarm at admission 3.
- Low flow alarms can also be related to patient characteristics, such as smaller body size and lower pump flows, as found in a study of HeartWare ventricular assist device patients 4.
- Other potential causes of low flow alarms may include right ventricular failure, as right ventricular failure can lead to decreased LVAD flow, although this can sometimes be treated with medications such as milrinone 5.
- LVAD failure itself can also lead to significant retrograde flow and induce adverse physiologic responses, including changes in hemodynamics and end-organ perfusion 6.
Key Factors Associated with Low Flow Alarms
- Ventricular fibrillation and other dysrhythmias
- Pump thrombosis
- Patient characteristics, such as smaller body size and lower pump flows
- Right ventricular failure
- LVAD failure and retrograde flow
Clinical Implications
- Low flow alarms on LVADs can be caused by a range of factors, and clinicians should consider these potential causes when evaluating patients with low flow alarms.
- Prompt treatment of underlying causes, such as ventricular fibrillation or pump thrombosis, is crucial to prevent adverse outcomes.
- Further studies are needed to fully understand the causes and consequences of low flow alarms on LVADs, as well as to develop effective strategies for prevention and treatment 4, 3.