Noninvasive assessment of left ventricular assist devices with cardiovascular computed tomography and impact on management

Abstract

Background: Left ventricular assist devices (LVADs) provide a bridge to recovery or heart transplantation but require serial assessment. Echocardiographic approaches may be limited by device artifact and acoustic window. Cardiovascular computed tomography (CCT) may provide improved non-invasive imaging of LVADs. We evaluated the diagnostic findings and clinical impact of CCT for non-invasive assessment of patients with LVADs.

Methods: CCT examinations performed between 2005 and 2008 in patients with LVADs were identified. Acquisitions were completed on the identical 64-detector-row scanner with intravenous contrast administration. Electrocardiographic gating was used in patients with pulsatile devices, and peripheral pulse gating was used in patients with continuous-flow devices. Comparison was made between CCT results and 30-day outcomes, including echocardiographic and intraoperative findings.

Results: We reviewed 32 CCT examinations from 28 patients. Indications included evaluation of low cardiac output symptoms, assessment of cannula position, low flow reading on the LVAD, and surgical planning. CCT identified critical findings in 6 patients, including thrombosis and inlet cannula malposition, all confirmed intraoperatively. CCT missed 1 case of intra-LVAD thrombus. Using intraoperative findings as the gold standard, CCT's sensitivity was 85% and specificity was 100%. Echocardiographic LVAD evaluation did not correlate with findings on CCT (kappa = -0.29, 95% confidence interval, -0.73 to 0.13).

Conclusions: This preliminary observational cohort study indicates that non-invasive imaging using CCT of LVADs is feasible and accurate. CCT warrants consideration in the initial evaluation of symptomatic patients with LVADs.

Figure 1

A 56 year-old patient with LVAD had low cardiac output signaling of the device. Initial transesophageal echocardiography shows the proximal inflow cannula at the LV apex (a, arrow). The outflow cannula could not be visualized. Normal inflow cannula flow is suggested by color Doppler (b, arrow); velocities (not shown) were less than 1.5 m/s. However, CCT revealed extensive thrombus in the outflow cannula (c, sagittal plane reformat). Isotropic spatial resolution of CCT images allows reformatting in an oblique sagittal plane (d) to demonstrate the entire outflow graft, further illuminating the extensive thrombus burden. The device itself and portions of the inflow cannula are also seen.

Figure 2

The inflow cannula abuts the anteroapical wall of the left ventricle (a, b), obstructing inflow. Clinically, this patient had poor cardiac output and borderline shock; flow improved and symptoms resolved with intra-operative repositioning of the inflow cannula. In a different patient, proper positioning of the inflow cannula in relation to the walls of left ventricle is illustrated (c, d).

Figure 3

After thrombus removal in patient 1A, the outflow cannula is unobstructed (a, arrow). LA = left atrium. The inflow cannula (b), while angled slightly toward the LVOT, is otherwise unobstructed.