Comparison of viscoelastic coagulation parameters, blood loss and surgical time between asymptomatic heartworm antigen-positive and negative dogs presented for elective gonadectomy

Abstract

Objectives: The primary objective of this study was to evaluate viscoelastic profiles in heartworm antigen-positive versus antigen-negative dogs using a point-of-care viscoelastic device. A secondary objective was to compare intraoperative bleeding and surgical duration between these same groups.

Materials and methods: Dogs presented for elective surgical gonadectomy were screened for the presence of heartworm antigen using a commercial antigen detection test. Viscoelastic testing was performed in equal numbers of asymptomatic heartworm antigen-positive and -negative dogs. Viscoelastic data recorded included Clot Time, Clot Formation Time, α-angle, Maximum Clot Formation, Amplitude at 10 minutes (A10), Amplitude at 20 minutes (A20), Lysis Index at 30 minutes (LI30) and Lysis Index at 45 minutes (LI45). Other data included intraoperative blood loss via the gravimetric technique and surgical time (incision to closure).

Results: A total of 60 dogs (30 heartworm antigen-negative and 30 heartworm antigen-positive) were enrolled in the study. There were no significant differences between Clot Time, Clot Formation Time, α-angle, LI30 and LI45 between heartworm antigen-positive and -negative dogs; however, Maximum Clot Formation, A10 and A20 were higher in heartworm antigen-positive dogs. All viscoelastic results were within previously published normal reference ranges. No significant differences in surgical gonadectomy duration or intraoperative blood loss were observed between groups for male or female dogs.

Clinical significance: Apparently healthy heartworm antigen-positive dogs were relatively hypercoagulable as defined by viscoelastic testing compared to heartworm antigen-negative dogs. There was no apparent additional risk of bleeding in dogs with subclinical heartworm infection.

FIG 1

Mean VCM Vet values at each time point across all heartworm‐positive and heartworm‐negative patient samples. The solid black tracing represents the average heartworm negative data. The solid yellow tracing represents the average heartworm‐positive dog data. The amplitude at 10 minutes (A10), amplitude at 20 minutes (A20) and maximum clot formation (MCF) are labelled with a blue line. To make this tracing, the positive values of the data (after multiplying by −1) were used to create the traditional image of a thromboelastogram. The CSV files from the VCM Vet were plotted against time from 1 to 3600 seconds; therefore, for each patient data set, there are 3600 measurements along the curve. The average data are simply the mean values at each time point (from 1 to 3600 seconds) across all heartworm‐positive and heartworm‐negative patient samples.