# A Case of the Utility of Viscoelastic Testing for the Management of the Impella Device in Heparin Anticoagulation

## TL;DR

This paper discusses using viscoelastic testing instead of traditional clotting time measurements to manage heparin therapy during Impella device use.

## Contribution

The study demonstrates the utility of viscoelastic testing as a more reliable alternative to ACT for monitoring heparin anticoagulation during Impella therapy.

## Key findings

- Viscoelastic testing provided consistent measures of heparin effect with clot time ratio (CTR) of 1.9.
- VET minimized variability compared to ACT and allowed effective management of unfractionated heparin dosing.
- VET was successfully used to guide UFH administration and discontinuation before surgery.

## Abstract

The main anticoagulant therapy with Impella is unfractionated heparin (UFH), with manufacturers recommending a target therapeutic range of 160-180 seconds for activated clotting time (ACT). However, the ACT assay does not have uniform criteria, and many available devices contain a variety of activators, making it difficult to compare them individually. We used Impella CP in the perioperative management of a post-myocardial infarction ventricular septal rupture in a 69-year-old man. A significant amount of UHF was used in this case, but as the ACT did not reach the recommended range, blood viscoelasticity testing (VET) was adopted as an alternative point-of-care test (POCT). The initial measurement results showed a clot time (CT) of 308 seconds, a heparinase clot time (CTH) of 161 seconds, and a clot time ratio (CTR) of 1.9, indicating that UFH was sufficiently active. Continuous administration of UFH was then performed with reference to VET, which was terminated three hours before surgery. As an alternative POCT to ACT, the VET may be suitable for assessing low doses of UFH effectiveness with heparinase assay, which provides specific measures of the heparin effect, such as CTR, and minimizes the variability in results as compared to ACT.