# Prediction of Maximum Amplitude With Citrated Rapid Thromboelastography Reaction Time in Cardiac Surgery: A Retrospective Study

## TL;DR

This study shows that a quick blood test called CRT-R can predict clot strength in heart surgery patients, helping doctors decide on blood product transfusions faster.

## Contribution

The study identifies CRT-R thresholds that predict clot strength parameters, offering a faster alternative for transfusion decisions in cardiac surgery.

## Key findings

- CRT-R has strong inverse correlations with clot strength parameters like CFF-MA and CRT-MA.
- CRT-R thresholds of 1.19 and 1.28 minutes predict specific clot strength targets with high specificity.
- CRT-R and TEG-ACT are nearly perfectly linear, suggesting CRT-R can replace TEG-ACT in some cases.

## Abstract

Background: Rapid and accurate assessment of coagulation status is essential in cardiac surgery to guide transfusion therapy. The reaction time in citrated rapid thromboelastography (CRT-R) is obtainable within minutes; however, its predictive relationship with maximum amplitude (MA) parameters, particularly platelet- and fibrinogen-related clot strength, remains unclear.

Methods: We retrospectively analyzed TEG6s assays performed in the operating rooms and intensive care units of a single tertiary center from January 2018 to July 2024 in adult patients who underwent cardiac surgery. Pearson coefficients quantified the associations between CRT-R and MA values from the CRT, citrated kaolin with heparinase (CKH), and citrated functional fibrinogen (CFF) assays. Relationships with MA were modeled using an exponential‐decay fit, and CRT-R versus TEG-activated clotting time (TEG-ACT) was modeled linearly. Bootstrap resampling (1,000 iterations) estimated CRT-R thresholds corresponding to clinically relevant MA targets (CRT-MA=48 mm; CFF-MA=12 mm).

Results: Of the 2,453 initially identified paired measurements, 104 were excluded (missing values, n=80; CRT-R >5.5 min, n=24), leaving 2,349 paired measurements for analysis. CRT-R showed inverse associations with MA parameters (absolute Pearson r: CFF-MA 0.6224, CRT-MA 0.6215, CKH-MA 0.6022; all p<0.0001) and a weak association with CKH-R (r=0.2897). CRT-R and TEG-ACT were nearly perfectly linear (r=1.000). Bootstrap-derived CRT-R cutoffs were 1.1858 min (95% CI 1.1597-1.2135) for predicting CRT-MA=48 mm and 1.2832 min (95% CI 1.2487-1.3238) for predicting CFF-MA=12 mm. At these thresholds, CRT-R predicted CRT-MA <48 mm with 49.2% sensitivity and 93.8% specificity and predicted CFF-MA <12 mm with 56.9% sensitivity and 97.0% specificity.

Conclusion: CRT-R, obtainable within minutes of assay initiation, moderately predicts final clot strength, with the strongest link to fibrinogen-dependent CFF-MA. These CRT-R-based thresholds may enable earlier preparation of platelet and fibrinogen therapy within viscoelastic-guided transfusion workflows.