Heparin monitoring in ImpellaTM-supported cardiogenic shock patients: the benefit of parallel dual testing
Authors: Van Edom C , Fiorelli F , Balthazar T , Jacquemin M , Meyns B , Monteagudo Vela M , Price S , Rosenberg A , Soliman-Aboumarie H , Tavazzi G , Tindale A , Van Der Linden L , Vanassche T , Panoulas V , Vandenbriele C 
Published: May 2024

Abstract

Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Fonds Wetenschappelijk Onderzoek Flanders.

Background
Coagulopathic complications often jeopardize the outcome of critically ill patients in cardiogenic shock (CS) during percutaneous mechanical circulatory support (pMCS). Therefore, meticulous management of heparin therapy is mandatory to ensure appropriate anticoagulation management. In this context, the most convenient and most frequently used test is the activated partial thromboplastin time (APTT). However, the APTT-test can be prolonged or shortened independent of the patient's anticoagulation status due to various confounding factors during critical illness (e.g., sepsis, liver failure, factor XI/XII consumption). Alternatively, the anti-Xa assay directly measures heparin activity. Therefore, to optimize heparin anticoagulation during critical illness, an anti-Xa-guided protocol for heparin titration combined with parallel APTT measurements to assess both bleeding and thrombotic risk has recently been proposed. (1)

Purpose
We aimed to investigate the correlation between parallel anti-Xa and APTT-measurements in an anti-Xa-guided heparin anticoagulated CS population during left-sided ImpellaTM support.

Methods
Between April-2017 and June-2022, all CS patients with isolated left-sided ImpellaTM-support (&gt;24h) and heparin anticoagulation monitored by anti-Xa with APTT in parallel were assessed at two high-volume tertiary institutions. Anti-Xa was considered in range between 0.20-0.30IU/mL or 0.31-0.50IU/mL based on the patient’s profile (per center protocol, underlying atrial fibrillation or venous thromboembolism). In range APTT values were considered 40-55s and 55-80s respectively. Correlation between parallel anti-Xa and APTT values was assessed by Pearson correlation. A Pearson correlation coefficient of 0.7 or lower was considered to confer a weak correlation.

Results
Ninety-three ImpellaTM-patient runs (77 men, 83%) with a median age of 56 years (IQR 46-66) were analyzed. Median support duration was 6 days (IQR 4-12). In total, 2447 parallel anti-Xa/APTT samples were analyzed, showing an overall Pearson correlation coefficient of 0.50 (p&lt;0.001) (Fig. 1A). For samples with in-range anti-Xa (N=1914), matching APPT was shortened in 460 (24%), in-range in 986 (52%) and prolonged in 468 (24%) samples (Fig. 1B).

Conclusions
We highlight a weak correlation between anti-Xa and APTT in an anti-Xa guided heparin anticoagulated CS population during left-sided ImpellaTM support. Heparin titration based on APTT alone would result in over- (24%) or undertitration (24%) in 48% of our cases, due to confounding factors influencing the APTT-assay in critically ill, exposing these patients to coagulopathy associated problems. Therefore, we strongly advocate a combined (anti-Xa/APTT) testing anticoagulation monitoring strategy to adequately manage the coagulation state of this critically ill population. Future trials will investigate whether this approach will effectively reduce the high coagulopathy associated morbidity and mortality on pMCS.