Left ventricular assist device (Doppler ultrasound)

In patients with a left ventricular assist device (LVAD), spectral Doppler waveforms are altered due to continuous flow provided by the pump in the device:

• waveforms are monophasic with a constant antegrade flow and no flow below the baseline

• the waveform is typically parvus-tardus with a slow systolic upstroke and rounded systolic peak

  • less commonly there may be non-pulsatile flow with no systolic peak

  • the systolic peak is thought to be due to intrinsic residual myocardial reserve pumping some of the blood, whereas lack of a systolic peak is thought to occur when the left ventricle is simply acting as a passive conduit and all blood is being pumped by the device

• peak systolic velocity (PSV) is reduced

These findings have been demonstrated diffusely in multiple arterial beds, including the carotid, vertebral, subclavian and common femoral arteries.

Radiographic features

Ultrasound

Echocardiography

Spectral Doppler-derived indices of intracardiac hemodynamics, measured as part of repeated comprehensive echocardiographic studies, are used to serially assess cardiac structure and function. Echocardiography is typically performed in the following settings ³:

• pre-operative assessment

  • typically a routine transthoracic echocardiography protocol, with a particular focus on variables which would contraindicate surgical placement of the LVAD, including ³

    • moderate to severe mitral valve stenosis

    • moderate to severe aortic valve regurgitation

    • tricuspid valve stenosis

• perioperative monitoring

  • conducted using a transesophageal approach 

  • allows continuous assessment of the positioning and angulation of the cannulae during introduction ⁴

    • subsequent (spectral and color flow) Doppler assessment of the flow egress through the inflow cannula should reveal a laminar flow pattern, with a maximum velocity <2 m/s 

    • the patency of the outflow cannula should also be sought

  • color flow Doppler is also used to screen for the presence of the following, which may portend a complicated clinical course: 

    • occult patent foramen ovale (PFO)

    • significant aortic insufficiency

    • right ventricular dysfunction

• post-surgical evaluation

• routine surveillance