Left ventricular assist devices (LVADs) are an effective therapy for patients with advanced heart failure, increasing patient survival and quality of life. Left ventricular assist devices are associated with the risks of bleeding and thrombosis. We used lactate dehydrogenase (LDH) and brain natriuretic peptide (BNP) as biomarkers for developing a thrombosis risk index. Data from a single center was retrospectively queried between January 1, 2008, and 10/15, 2011, to identify LVAD patients and related complications. Of 75 consecutive patients implanted with an LVAD, nine had device thrombosis. Analysis of the relationship among international normalized ratio (INR), BNP, LDH, and device thrombosis was performed. Of nine patients with thrombosis, seven had at least 30% of INR readings below 1.5 and two had at least 22% below the therapeutic range from the time of LVAD implant to date of thrombosis. Timeline variability in INR, BNP, and LDH were used to calculate thrombosis risk index (TRI). The TRI retrospectively was able to accurately predict patients with impending device thrombosis. Indexed rise in BNP and LDH in LVAD patients may be useful to identify early device dysfunction and possible future thrombosis. Fibrinogen and D-dimer assays are currently being evaluated in these patients for their possible inclusion and added value to the TRI.