Evaluation of the Cardiac reader® as a point-of-care instrument for measurement of fibrin D-dimers in dogs

Fibrinolysis in Dogs with Intracavitary Effusion: A Review

Simple Summary

In blood vessels there is a balance between clot formation and its dissolution. Fibrinolysis normally allows the breakdown of blood clots during the healing of injured blood vessels. This process is mediated by the activation of a blood enzyme (plasmin) which breaks down a meshed protein (fibrin) which holds blood clots at the site of the vessel injury. In some diseases, the activation of plasmin becomes excessive, leading to bleeding tendencies (hyperfibrinolysis). Under normal conditions, abdominal and thoracic cavities are filled with a small amount of fluid deriving from the blood. The results of recent studies have shown that, in dogs, all types of pathologic intracavitary fluids have an increased fibrinolytic activity. This increased fibrinolytic activity is also present in their blood, in some cases reaching a hyperfibrinolytic state. Hyperfibrinolysis and bleeding tendencies have also been documented in cardiopathic dogs with ascites. The latter result is surprising considering that thrombotic events are commonly documented in humans and cats with some cardiac diseases.

Abstract

Physiologic fibrinolysis is a localized process in which stable fibrin strands are broken down by plasmin in response to thrombosis. Plasmin activation can also take place separately from the coagulation process, resulting in pathologic fibrinolysis. When plasmin activation exceeds the neutralizing capacity of plasmin inhibitors, severe bleeding can potentially take place. Although the processes which regulate coagulation and fibrinolysis in the blood are well known, it is less clear as to what extent the same processes take place in the body cavities and whether they influence systemic hemostasis. The results of the studies herein cited demonstrate that coagulation followed by fibrinogenolytic/fibrinolytic activity takes place in all kinds of canine ascitic and pleural fluids. Moreover, systemic clotting abnormalities suggesting primary fibrinolysis/primary hyperfibrinolysis (i.e., elevated plasma fibrin/fibrinogen degradation products [FDPs] and normal D-dimer concentrations with fibrinogen concentrations ≤ 100 mg/dL or above this cut-off, respectively) occur in dogs with intracavitary effusion. Enhanced fibrinolytic activity in dogs with intracavitary effusion can also be detected using rotational thromboelastometry (ROTEM), although the degree of agreement between ROTEM and FDPs, D-dimer and fibrinogen concentrations is poor. Finally, contrary to the thrombotic events commonly documented in some humans and cats with cardiac diseases, bleeding tendencies due to primary fibrinolysis/primary hyperfibrinolysis have been documented in dogs with cardiogenic ascites.

A review of hyperfibrinolysis in cats and dogs

The fibrinolytic system is activated concurrently with coagulation; it regulates haemostasis and prevents thrombosis by restricting clot formation to the area of vascular injury and dismantling the clot as healing occurs. Dysregulation of the fibrinolytic system, which results in hyperfibrinolysis, may manifest as clinically important haemorrhage. Hyperfibrinolysis occurs in cats and dogs secondary to a variety of congenital and acquired disorders. Acquired disorders associated with hyperfibrinolysis, such as trauma, cavitary effusions, liver disease and Angiostrongylus vasorum infection, are commonly encountered in primary care practice. In addition, delayed haemorrhage reported in greyhounds following trauma and routine surgical procedures has been attributed to a hyperfibrinolytic disorder, although this has yet to be characterised. The diagnosis of hyperfibrinolysis is challenging and, until recently, has relied on techniques that are not readily available outside referral hospitals. With the recent development of point-of-care viscoelastic techniques, assessment of fibrinolysis is now possible in referral practice. This will provide the opportunity to target haemorrhage due to hyperfibrinolysis with antifibrinolytic drugs and thereby reduce associated morbidity and mortality. The fibrinolytic system and the conditions associated with increased fibrinolytic activity in cats and dogs are the focus of this review article. In addition, laboratory and point-of-care techniques for assessing hyperfibrinolysis and antifibrinolytic treatment for patients with haemorrhage are reviewed.

Cardiopulmonary and inflammatory biomarkers in the assessment of the severity of canine dirofilariosis

The prognosis and success of adulticide treatment depends on the baseline severity of infection with Dirofilaria immitis in dogs and can influence the therapeutic protocol to choose. A study was conducted to assess the utility of the cardiopulmonary biomarkers N-terminal of the prohormone brain natriuretic peptide (NT-proBNP), cardiac troponin I (cTnI), myoglobin, and D-dimer, as well as the biomarker of inflammation C-reactive protein (CRP) to evaluate the severity of canine heartworm disease in different stages. Serum samples were collected from 20 heartworm-infected dogs for measurement of these biomarkers. Dogs were assigned to four groups (n=5/group) according to the severity of the disease: Class I and Class II dogs showed concentrations of biomarkers generally within normal ranges for healthy dogs, except CRP in dogs classified as Class II, which showed values slightly above laboratory reference values (19.46±5.69mg/l). Dogs of Class III showed elevated levels of NT-proBNP (1220.12±465.18pmol/l) (p<0.05), cTnI (0.99±0.39ng/ml), CRP (33.98±7.99mg/l) (p<0.05), and 40% of these dogs (2/5) presented pathological values of D-dimer and myoglobin (p<0.05). Dogs of Class IV (caval syndrome) presented elevated levels of NT-proBNP (>2530.8pmol/l), cTnI (1.99±0.32ng/ml), and CRP (80.24±47.69mg/l); all Class IV dogs showed pathological elevations of D-dimer (0.81±0.46ng/ml), and 60% (3/5) of these dogs showed pathological elevations of myoglobin (significant elevations [p<0.05] for all biomarkers with respect to reference values and values for dogs in Classes I, II, and III). In canine heartworm disease, chronic presence of D. immitis causes a proliferative endoarteritis, thromboembolisms, pulmonary hypertension, and right-sided congestive heart failure. As the severity of the disease worsens, serum values of cTnI, myoglobin, and NT-proBNP increase, indicating significant cardiac damage. The finding of pathological concentrations of D-dimer suggests the presence of thromboembolism and/or disseminated intravascular coagulation. CRP increases according to the severity of the disease, indicating inflammatory processes that could contribute to the progression of the disease. These preliminary results demonstrate the utility of cardiopulmonary and inflammation biomarkers to assist in the establishment of the severity of canine heartworm disease.

Evaluation of cardiopulmonary biomarkers during classic adulticide treatment versus the American Heartworm Society recommended treatment protocol in dogs infected by Dirofilaria immitis

Adulticide treatment of dogs with canine heartworm disease causes the death of the adult Dirofilaria immitis lodged in the vascular system of the host. During the death of the worms, pulmonary thromboembolisms (PTE), pulmonary inflammation, congestive heart failure, or renal disease are possible consequences. The aim of this study was to evaluate cardiopulmonary biomarkers and renal parameters during adulticide treatment of canine heartworm to compare the classic two-injection treatment protocol versus the American Heartworm Society (AHS) recommended protocol. Fourteen heartworm-infected dogs with high parasite burdens were divided in three groups and allocated to adulticide protocols as follows: Group A (n=5) was treated with the classic two-injection protocol; group B (n=5) was treated using the AHS recommended protocol, and group C (n=4) was treated as for group B but received diminishing anti-inflammatory doses of prednisone. To assess cardiorespiratory status, cardiac troponin I (cTnI), myoglobin, and D-dimer were measured. Renal function was evaluated by measuring urea, creatinine, and urine protein:creatinine (UP:C). Serum and urine samples were collected day 0 (day of diagnosis), 7 and 14 days after the first dose of adulticide, and 1 month after the last adulticide injection. Dogs that received classic treatment presented pathologic concentrations of D-dimer more frequently and showed higher average D-dimer levels, which may indicate the presence of more severe PTE. Group C showed the highest levels of D-dimer during treatment, which may be due to an exacerbation of PTE caused by the administration of prednisone. CTnI and myoglobin values remained above reference values in all groups during the study but reached the lowest values 1 month after the last injection. Levels of urea and creatinine were within normal ranges in all groups, and 28.5% of the dogs were proteinuric on day 0, progressing to better UP:C values at the end of the treatment, except in group A. The results of this study justify the treatment of canine heartworm disease using the AHS recommended adulticide guidelines and recommends re-evaluation of the role of glucocorticosteroids in the prevention and treatment of PTE.