Left ventricular dimension decrement index early after axial flow assist device implantation: A novel risk marker for late pump thrombosis

Abstract

Background: It is increasingly recognized that pump thrombosis most likely represents the end stage of a complex interaction between the patient-pump interface. We hypothesized that early patient/pump mismatch, as manifested by suboptimal left ventricular (LV) unloading early after left ventricular assist device (LVAD) implantation, may be a harbinger of increased risk for later LVAD thrombosis.

Methods: In 64 patients (59 ± 11 years old, 78% men, 44% destination therapy) discharged alive without thrombosis or other device malfunction after first HeartMate II LVAD implantation (between January 2011 and June 2014), LV dimensions in end diastole (LVIDd) and end systole (LVIDs) were compared between pre-implant and optimal set speed pre-discharge echocardiography. LV dimension decrement indices (pre-implant dimension - optimal set speed dimension ÷ pre-implant dimension × 100) for LVIDd [LVIDdDI] and LVIDs [LVIDsDI] were calculated.

Results: The incidence of pump thrombosis was 0.06 per patient year (n = 18, median time 8 [interquartile range 2, 17] months). Baseline characteristics including pre-operative LVIDd and LVIDs were similar between LVAD thrombosis and no thrombosis groups. After ventricular assist device implantation, set speed and other ramp parameters did not differ between groups. However, LVIDdDI (19 ± 13% vs 25 ± 11%, p = 0.04) and LVIDsDI (16 ± 16% vs 27 ± 13%, p = 0.008) were significantly lower in patients with later pump thrombosis. A cutoff value of ≤15% using receiver operating characteristic curve analysis was 83% sensitive for LVIDdDI and LVIDsDI for predicting pump thrombosis. Patients with LVIDdDI of >15% vs ≤15% were significantly more likely to be free of pump thrombosis over a median follow-up period of 15 (interquartile range 9, 26) months (log-rank test, p = 0.045).

Conclusions: LV dimension decrement index at optimized speed setting on pre-discharge echocardiography is associated with LVAD thrombosis.

Keywords: echocardiography; heart failure; left ventricular dimension; pump thrombosis; ventricular assist device.