Carlo R Bartoli1, David Zhang2, Jooeun Kang3, Samson Hennessy-Strahs4, David Restle5, Jessica Howard4, Gretchen Redline4, Christian Bermudez4, Pavan Atluri4, Michael A Acker4. 1. Division of Cardiovascular Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: carlo.bartoli@uphs.upenn.edu. 2. MD/PhD Program, Washington University in St. Louis, St. Louis, Missouri. 3. MD/PhD Program, Vanderbilt University School of Medicine, Nashville, Tennessee. 4. Division of Cardiovascular Surgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania. 5. Health Sciences Center, School of Medicine, Stony Brook University, Stony Brook, New York.
Abstract
BACKGROUND: Recent data suggest that hemolysis contributes to left ventricular assist device (LVAD) thrombosis, but the mechanism is unknown. In a clinical study, we measured plasma free hemoglobin (pfHgb) and the incidence of LVAD thrombosis. In an in vitro study, we examined biophysical relationships between shear stress, pfHgb and von Willebrand factor (vWF) metabolism toward understanding mechanisms of LVAD thrombosis. METHODS: In the clinical study, blood samples were obtained from continuous-flow LVAD patients (n = 30). Plasma free hemoglobin was measured via enzyme-linked immunosorbent assay. Plasma lactate dehydrogenase (LDH) was measured with a fluorimetric assay. In the in vitro study, to investigate mechanism, human plasma (n = 10) was exposed to LVAD-like shear stress (175 dyne/cm2) with and without free hemoglobin (30 mg/dL). ADAMTS-13 (the vWF protease) activity was quantified with Förster resonance energy transfer. vWF size was quantified with immunoblotting. vWF clotting function was quantified with an enzyme-linked immunosorbent assay. RESULTS: In the clinical study, LVAD support caused subclinical hemolysis. In all patients, LDH increased significantly from 213 ± 9 U/L to 366 ± 31 U/L at 10 days of support (p < 0.0001) and remained significantly elevated at 280 ± 18 U/L at 1 month of support (p < 0.01). In 21 patients that did not develop LVAD thrombosis, pfHgb increased early but decreased over time (pre-LVAD: 5.2 ± 0.8 mg/dL; 1 week: 19.8 ± 4.4 mg/dL, p < 0.01; 3 months: 9.3 ± 2.2 mg/dL, p = 0.07). In 9 patients that developed LVAD thrombosis, pfHgb was significantly elevated versus patients without thrombosis before (p < 0.001) and after 3 months (p < 0.05) of support (pre-LVAD: 20.2 ± 6.3 mg/dL; 1 week: 17.3 ± 3.7 mg/dL; 3 months: 21.5 ± 7.8 mg/dL). Similarly, after 3 months, patients that did not develop LVAD thrombosis had an LDH of 271 ± 28 U/L, whereas patients that later developed LVAD thrombosis had a significantly higher LDH of 625 ± 210 U/L (p = 0.02). In the in vitro study, shear stress degraded vWF similarly to an LVAD. Free hemoglobin inhibited ADAMTS-13 activity during shear stress (633 ± 27 ng/mL to 565 ± 24 ng/mL; p < 0.001). vWF was thereby protected from degradation, 4 vWF fragments decreased significantly (p ≤ 0.05), and vWF clotting function increased (1.15 ± 0.09 U/mL to 1.29 ± 0.09 U/mL, p = 0.06). CONCLUSIONS: These are the first data to demonstrate mechanistic relationships between subclinical hemolysis and a procoagulant state during continuous-flow LVAD support. Patients with high pfHgb and LDH were more likely to develop LVAD thrombosis. In vitro experiments demonstrated that free hemoglobin inhibited ADAMTS-13, protected vWF from degradation, increased vWF clotting function, and created a procoagulant state. As such, pfHgb may be a clinical target to prevent LVAD thrombosis.
BACKGROUND: Recent data suggest that hemolysis contributes to left ventricular assist device (LVAD) thrombosis, but the mechanism is unknown. In a clinical study, we measured plasma free hemoglobin (pfHgb) and the incidence of LVAD thrombosis. In an in vitro study, we examined biophysical relationships between shear stress, pfHgb and von Willebrand factor (vWF) metabolism toward understanding mechanisms of LVAD thrombosis. METHODS: In the clinical study, blood samples were obtained from continuous-flow LVADpatients (n = 30). Plasma free hemoglobin was measured via enzyme-linked immunosorbent assay. Plasma lactate dehydrogenase (LDH) was measured with a fluorimetric assay. In the in vitro study, to investigate mechanism, human plasma (n = 10) was exposed to LVAD-like shear stress (175 dyne/cm2) with and without free hemoglobin (30 mg/dL). ADAMTS-13 (the vWF protease) activity was quantified with Förster resonance energy transfer. vWF size was quantified with immunoblotting. vWF clotting function was quantified with an enzyme-linked immunosorbent assay. RESULTS: In the clinical study, LVAD support caused subclinical hemolysis. In all patients, LDH increased significantly from 213 ± 9 U/L to 366 ± 31 U/L at 10 days of support (p < 0.0001) and remained significantly elevated at 280 ± 18 U/L at 1 month of support (p < 0.01). In 21 patients that did not develop LVAD thrombosis, pfHgb increased early but decreased over time (pre-LVAD: 5.2 ± 0.8 mg/dL; 1 week: 19.8 ± 4.4 mg/dL, p < 0.01; 3 months: 9.3 ± 2.2 mg/dL, p = 0.07). In 9 patients that developed LVAD thrombosis, pfHgb was significantly elevated versus patients without thrombosis before (p < 0.001) and after 3 months (p < 0.05) of support (pre-LVAD: 20.2 ± 6.3 mg/dL; 1 week: 17.3 ± 3.7 mg/dL; 3 months: 21.5 ± 7.8 mg/dL). Similarly, after 3 months, patients that did not develop LVAD thrombosis had an LDH of 271 ± 28 U/L, whereas patients that later developed LVAD thrombosis had a significantly higher LDH of 625 ± 210 U/L (p = 0.02). In the in vitro study, shear stress degraded vWF similarly to an LVAD. Free hemoglobin inhibited ADAMTS-13 activity during shear stress (633 ± 27 ng/mL to 565 ± 24 ng/mL; p < 0.001). vWF was thereby protected from degradation, 4 vWF fragments decreased significantly (p ≤ 0.05), and vWF clotting function increased (1.15 ± 0.09 U/mL to 1.29 ± 0.09 U/mL, p = 0.06). CONCLUSIONS: These are the first data to demonstrate mechanistic relationships between subclinical hemolysis and a procoagulant state during continuous-flow LVAD support. Patients with high pfHgb and LDH were more likely to develop LVAD thrombosis. In vitro experiments demonstrated that free hemoglobin inhibited ADAMTS-13, protected vWF from degradation, increased vWF clotting function, and created a procoagulant state. As such, pfHgb may be a clinical target to prevent LVAD thrombosis.
Authors: James P Buerck; Dustin K Burke; David W Schmidtke; Trevor A Snyder; Dimitrios V Papavassiliou; Edgar A O'Rear Journal: J Artif Organs Date: 2021-01-09 Impact factor: 1.731
Authors: Mark S Goodin; Michael S Showalter; David J Horvath; Barry D Kuban; Christine R Flick; Anthony R Polakowski; Kiyotaka Fukamachi; Jamshid H Karimov Journal: ASAIO J Date: 2021-11-10 Impact factor: 3.826
Authors: Noah Weingarten; Cindy Song; Amit Iyengar; David Alan Herbst; Mark Helmers; Danika Meldrum; Sara Guevara-Plunkett; Jessica Dominic; Pavan Atluri Journal: Indian J Thorac Cardiovasc Surg Date: 2022-09-21
Authors: Carlo R Bartoli; Samson Hennessy-Strahs; Jeff Gohean; Maryann Villeda; Erik Larson; Raul Longoria; Mark Kurusz; Michael A Acker; Richard Smalling Journal: Ann Thorac Surg Date: 2018-12-23 Impact factor: 5.102
Authors: Takuma Miyamoto; Yuichiro Kado; David J Horvath; Barry D Kuban; Shiva Sale; Kiyotaka Fukamachi; Jamshid H Karimov Journal: JTCVS Open Date: 2020-06-20