Objective—To evaluate markers of hemostasis and
their relationship to the degree of mitral regurgitation
(MR) and platelet function in Cavalier King Charles
Spaniels (CKCSs) with myxomatous mitral valve disease.
Animals—76 clinically healthy CKCSs and 24 control
Procedure—All dogs underwent echocardiographic
examination; various hemostatic, hematologic, and
biochemical variables were evaluated in blood. The
CKCSs were allocated to 1 of 3 groups on the basis of
MR severity. In 8 control dogs and 8 CKCSs, plasma
von Willebrand factor (vWF) multimer analysis was
Results—Compared with control dogs, plasma fibrinogen
concentration was higher in all CKCSs and
related to left ventricular end diastolic diameter and
left atrial-to-aortic root ratio among all CKCSs. The
activated partial thromboplastin times and plasma Ddimer
concentration were similar among the 4
groups. Plasma vWF concentration was lower in
CKCSs with moderate to severe MR, compared with
that of CKCSs with no MR and control dogs. There
was a relationship between plasma vWF concentration
and platelet function in CKCSs but not in control
dogs. In 4 CKCSs with moderate to severe MR and
low plasma vWF concentration, amounts of vWF
high-molecular-weight multimers (HMWMs) were
Conclusions and Clinical Relevance—In CKCSs,
MR appeared to be associated with a low plasma
vWF concentration and likely a loss of vWF HMWMs
(possibly through their destruction via shear stress to
the blood). The importance of the changes in plasma
fibrinogen concentration and the thromboembolic risk
in dogs with MR remain to be investigated. (Am J Vet
Objective—To investigate whether plasma activity of matrix metalloproteinase (MMP)-2 and -9 was associated with severity of myxomatous mitral valve disease (MMVD) in dogs and to assess potential associations between MMP activity and dog characteristics, echocardiographic variables, systolic arterial blood pressure (SAP), heart rate, cardiac troponin I (cTnI) concentration, and C-reactive protein concentration.
Animals—75 client-owned dogs.
Procedures—Severity of MMVD was assessed by use of echocardiography. Plasma activity of latent (pro-MMP) and active MMP-2 and -9 was analyzed via zymography. Plasma concentration of cTnI was analyzed with a high-sensitivity cTnI assay, and C-reactive protein concentration was analyzed with a canine-specific ELISA.
Results—Pro-MMP-9, active MMP-9, and pro-MMP-2 were detected, but active MMP-2 was not. No significant differences were found in MMP concentrations among the 4 MMVD severity groups. Activity of pro-MMP-9 decreased with decreases in SAP and was higher in male dogs than in female dogs. Activity of MMP-9 decreased with increases in left ventricular end-systolic dimension and with decreases in SAP and cTnI concentration. Left ventricular end-systolic dimension was the variable most strongly associated with MMP-9 activity. No associations were found between the activity of pro-MMP-2 and investigated variables.
Conclusions and Clinical Relevance—Plasma MMP-9 activity decreased with increases in the end-systolic left ventricular internal dimension and decreases in SAP. Hence, evaluation of MMP-9 activity has the potential to provide unique information about the myocardial remodeling process in dogs with MMVD.
OBJECTIVE To investigate serum and plasma serotonin concentrations, percentage of serotonin-positive platelets, level of surface-bound platelet serotonin expression (mean fluorescence intensity [MFI]), and platelet activation (CD62 expression) in platelet-rich plasma from Cavalier King Charles Spaniels with myxomatous mitral valve disease (MMVD).
ANIMALS Healthy dogs (n = 15) and dogs with mild MMVD (18), moderate-severe MMVD (19), or severe MMVD with congestive heart failure (CHF; 10).
PROCEDURES Blood samples were collected from each dog. Serum and plasma serotonin concentrations were measured with an ELISA, and surface-bound platelet serotonin expression and platelet activation were determined by flow cytometry.
RESULTS Dogs with mild MMVD had higher median serum (746 ng/mL) and plasma (33.3 ng/mL) serotonin concentrations, compared with MMVD-affected dogs with CHF (388 ng/mL and 9.9 ng/mL, respectively), but no other group differences were found. Among disease groups, no differences in surface-bound serotonin expression or platelet activation were found. Thrombocytopenic dogs had lower serum serotonin concentration (482 ng/mL) than nonthrombocytopenic dogs (731 ng/mL). In 26 dogs, a flow cytometry scatterplot subpopulation (FSSP) of platelets was identified; dogs with an FSSP had a higher percentage of serotonin-positive platelets (11.0%), higher level of surface-bound serotonin expression (MFI, 32,068), and higher platelet activation (MFI, 2,363) than did dogs without an FSSP (5.7%, 1,230, and 1,165, respectively). An FSSP was present in 93.8% of thrombocytopenic dogs and in 29.5% of nonthrombocytopenic dogs.
CONCLUSIONS AND CLINICAL RELEVANCE A substantive influence of circulating serotonin on MMVD stages prior to CHF development in Cavalier King Charles Spaniels was not supported by the study findings. An FSSP of highly activated platelets with pronounced serotonin binding was strongly associated with thrombocytopenia but not MMVD.
OBJECTIVE To evaluate heart rate, heart rate variability, and arrhythmia frequency as well as changes in cardiac biomarker values and their association with heart rate in horses before and after an endurance ride.
DESIGN Cross-sectional study.
ANIMALS 28 Arabian horses competing in a 120- or 160-km endurance ride.
PROCEDURES ECG recordings were obtained from each horse before (preride) and after (recovery) an endurance ride to evaluate changes in heart rate and the SD of normal R-R intervals (SDNN) during the initial 12 hours of recovery. Frequencies of supraventricular and ventricular premature complexes before and after the ride were evaluated. Blood samples were obtained before the ride and twice during recovery. Hematologic analyses included measurement of serum cardiac troponin I concentration and creatine kinase isoenzyme MB activity.
RESULTS Heart rate was significantly increased and SDNN was decreased during the recovery versus preride period. Frequency of ventricular premature complexes increased during recovery, albeit not significantly, whereas frequency of supraventricular premature complexes was not significantly different between preride and recovery periods. Serum cardiac troponin I concentration and creatine kinase isoenzyme MB activity were significantly increased in the recovery versus preride period. No associations were identified between cardiac biomarkers and velocity, distance, or mean heart rate.
CONCLUSIONS AND CLINICAL RELEVANCE Heart rate increased and SDNN decreased in horses after completion of an endurance ride. These and other cardiac changes suggested that prolonged exercise such as endurance riding might have cardiac effects in horses. Additional studies are needed to clarify the clinical relevance of the findings.