Left Ventricular Assist Device Performance Under Pressure: Troubleshooting Outflow Graft Dysfunction

A 38-year-old morbidly obese male with nonischemic cardiomyopathy status-post HeartMate 3 (Abbott Laboratories, Abbott Park, IL) left ventricular assist device (LVAD) as destination therapy in September 2018, presented 18 months later with cardiogenic shock. Initial right heart catheterization, at an LVAD speed of 6200 rpm, suggested elevated biventricular pressures with reduced cardiac output. Transthoracic echocardiogram noted an enlarged left ventricle with a rightward septum, aortic valve opening, and no significant aortic regurgitation. The patient was started on dobutamine, but fluid removal was difficult. Repeat transthoracic echocardiogram and right heart catheterization at LVAD speed 6300 rpm and higher vasoactives revealed a larger left ventricle and continued poor hemodynamics.

In the setting of left ventricular dilation with aortic valve opening despite high speeds, and mild increase in lactic dehydrogenase levels, concern for LVAD malfunction was raised. Logfile analysis was unrevealing. Chest X-Ray did not demonstrate obvious device defects when compared to prior. Computed tomography angiography to evaluate for outflow graft obstruction was deferred due to persistent renal dysfunction. Instead, the patient underwent invasive hemodynamic assessment of the outflow graft. There was no obvious deformity of the outflow graft by digital-subtraction angiography, but end-hole catheter pullback measurement revealed a significant pressure gradient (98 mm Hg peak/80 mm Hg mean) in the proximal portion near the LVAD bend relief (Figure 1A and 1B; Movie I in the Data Supplement). The patient went to the operating room where outflow graft twisting was noted 3 cm from the connector to the device body. The connector was rotated 120 degrees to fully untwist the obstruction (Figure 2). The patient was monitored afterwards in the ICU as vasoactive medications were weaned off and his LVAD function, renal function, and volume status improved.

Figure 1.

(A) Invasive hemodynamic pressure measurement of left ventricular assist device (LVAD) outflow graft. (B) Fluoroscopy of cardiac catheter position within LVAD outflow graft. Arrow indicates catheter tip at point of pressure gradient.

Figure 2. Operative images of outflow graft kink (A) before and (B) after untwisting.

The arrow in (A) indicates outflow graft kink; and the arrow in (B), outflow graft after untwisting of kink.

Measurement of the gradient in the outflow graft can be used to differentiate pump thrombosis from an outflow graft abnormality in patients with a clinical concern for device malfunction.