Increased Plasma‐Free Hemoglobin Levels Identify Hemolysis in Patients With Cardiogenic Shock and a Trans valvular Micro‐Axial Flow Pump

Hemolysis is a potential limitation of percutaneously delivered left-sided mechanical circulatory support pumps, including trans valvular micro-axial flow pumps (TVP). Hemolytic biomarkers among durable left ventricular assist devices include lactate dehydrogenase (LDH) >2.5 times the upper limit of normal (ULN) and plasma-free hemoglobin (pf-Hb) >20 mg/dL. We examined the predictive value of these markers among patients with cardiogenic shock (CS) receiving a TVP. We retrospectively studied records of 116 consecutive patients receiving an Impella TVP at our institution between 2012 and 2017 for CS. Twenty-three met inclusion/exclusion criteria, and had sufficient pf-Hb data for analysis. Area under receiver-operator characteristic (ROC) curve for diagnosing hemolysis were calculated. Mean age was 62 ± 14 years and ejection fraction was 15 ± 5%. Mean duration of support was 5.4 ± 3.5 days. Pre-device LDH levels were >2.5x ULN in 71% (n = 5/7) of 5.0 and 29% of CP patients, while pre-device pf-Hb levels were >20 mg/dL in 14% (n = 1/7) of 5.0 and 25% (n = 4/16) of CP patients. Given elevated baseline LDH and pf-Hb levels, we defined hemolysis as a pf-Hb level >40 mg/dL within 72 h post-implant plus clinical evidence of device-related hemolysis. We identified that 30% (n = 7/23) had device-related hemolysis. Using ROC curve-derived cut-points, an increase in delta pf-Hb by >27mg/dL, not delta LDH, within 24 h after TVP implant (delta pf-Hb: C-statistic = 0.79, sensitivity: 57%, specificity: 93%, p <0.05) was highly predictive of hemolysis. In conclusion, we identified a change in pf-Hb, not LDH, levels is highly sensitive and specific for hemolysis in patients treated with a TVP for CS.