Auscultation in mild mitral regurgitation in dogs: observer variation, effects of physical maneuvers, and agreement with color Doppler echocardiography and phonocardiography

Observer variation in diagnosing mild mitral regurgitation in dogs by cardiac auscultation was assessed by having 6 veterinarians with different levels of experience examine 57 Cavalier King Charles Spaniels. Comparisons with color Doppler echocardiography and phonocardiography were made, and the effects of 2 physical maneuvers on the auscultatory findings were evaluated. Using mildly diseased dogs, interobserver agreement in diagnosing the presence or absence of left-sided murmurs ranged from 63% to 88%. The agreement with phonocardiography (range, 53-91%) increased with the amount of observer experience. The 2 most experienced observers could discern soft ejection murmurs from regurgitant murmurs and were able to diagnose 89% of the dogs with regurgitant jets larger than 30% of the left atrial area. In general, less experienced observers diagnosed most jets larger than 50%. In many dogs with small jets, no murmur was found by auscultation and phonocardiography. The audibility of mild regurgitation was significantly reduced in dogs that were difficult to auscultate. Early systolic murmurs were typical of mild regurgitation, whereas holosystolic murmurs typified severe regurgitation. In a few dogs, late systolic murmurs alternated with holosystolic murmurs. Systolic clicks were found phonocardiographically in 18 dogs with mild to moderate regurgitation, but the audibility apparently was low. In many mildly affected dogs, physical maneuvers increased murmur intensity. Thus, some form of dynamic auscultation might facilitate the diagnosis of mild regurgitation. Auscultatory findings in mild regurgitation appear to depend on observer experience, circulatory status, and how difficult the dog is to auscultate.     

Changes in platelet life span in dogs with mitral valve regurgitation

Platelet life span was measured in dogs with experimentally-induced mitral regurgitation (MR) by using an in vitro whole-blood biotinylation technique to evaluate the effects of shear stress induced by MR. Mitral regurgitation was created in healthy dogs by ablation of the mitral valve chordae tendineae. Mitral regurgitation was identified by auscultation and postoperative color Doppler echocardiography. Platelets were biotinylated. and derivatized blood was reinfused into the dogs. Biotinylated platelet disappearance was measured over time to determine platelet life span. Pre- and postablation platelet life span was compared in each dog. Platelet life span was shorter in dogs with experimentally induced MR. Shear stress from MR was postulated to shorten platelet life span. Alternations in platelet function and life span may contribute to the progression of cardiovascular disease in dogs with MR. Further studies are required to determine if platelet dysfunction is related to disease progression in these patients.     

Cardiac troponin-I concentration in dogs with cardiac disease

Cardiac troponin-I (cTnI) is a highly sensitive and specific marker of myocardial injury and can be detected in plasma by immunoassay techniques. The purpose of this study was to establish a reference range for plasma cTnI in a population of healthy dogs using a human immunoassay system and to determine whether plasma cTnI concentrations were high in dogs with acquired or congenital heart disease, specifically cardiomyopathy (CM), degenerative mitral valve disease (MVD), and subvalvular aortic stenosis (SAS). In total, 269 dogs were examined by physical examination, electrocardiography, echocardiography, and plasma cTnI assay. In 176 healthy dogs, median cTnI was 0.03 ng/mL (upper 95th percentile = 0.11 ng/mL). Compared with the healthy population, median plasma cTnI was increased in dogs with CM (0.14 ng/mL; range, 0.03-1.88 ng/mL; P < .001; n = 26), in dogs with MVD (0.11 ng/mL; range, 0.01-9.53 ng/mL; P < .001; n = 37), and in dogs with SAS (0.08 ng/mL; range, 0.01-0.94 ng/mL; P < .001; n = 30). In dogs with CM and MVD, plasma cTnI was correlated with left ventricular and left atrial size. In dogs with SAS, cTnI demonstrated a modest correlation with ventricular wall thickness. In dogs with CM, the median survival time of those with cTnI >0.20 ng/mL was significantly shorter than median survival time of those with cTnI <0.20 ng/mL (112 days versus 357 days; P = .006). Plasma cTnI is high in dogs with cardiac disease, correlates with heart size and survival, and can be used as a blood-based biomarker of cardiac disease.     

Assessment of global and regional left ventricular volume and shape by real-time 3-dimensional echocardiography in dogs with myxomatous mitral valve disease

Background: Left ventricular (LV) remodeling occurs in response to chronic volume overload. Real‐time 3‐dimensional (RT3D) echocardiography offers new modalities for LV assessment. Objective: To investigate LV changes in shape and volume in response to different severities of naturally acquired myxomatous mitral valve disease (MMVD) in dogs by RT3D echocardiography. Animals: Sixty‐five client‐owned dogs. Methods: Prospectively recruited dogs were classified by standard echocardiography into healthy, mild, moderate, and severe MMVD groups. Endocardial border tracking of LV RT3D dataset was performed, from which global and regional (automatically acquired basal, mid, and apical segments based on LV long‐axis length) end‐diastolic (EDV) and end‐systolic volumes (ESV), LV long‐axis length, and sphericity index were obtained. Results: Global and regional EDV and ESV (indexed to body weight) were most prominently increased in dogs with severe MMVD. All 3 regional LV segments contributed to increased global EDV and ESV with increasing MMVD severity, but mid‐EDV contributed the most to the global EDV increase. Furthermore, LV long‐axis length and LV sphericity index increased with increasing MMVD severity. Basal and apical EDV segments displayed the strongest association with sphericity index (P < .0001). Conclusions and Clinical Importance: The most prominent LV volume expansion was found in dogs with severe MMVD. Increased EDV, primarily in the mid‐segment, leads to rounding of LV apical and basal segments in response to increasing MMVD severity. Assessment of LV volume and shape potentially could allow early detection of dogs at risk for rapid progression into congestive heart failure.     

Serum Serotonin Concentrations in Dogs with Degenerative Mitral Valve Disease

Background: Increased serotonin (5HT) signaling has been implicated in valvular disease of humans and animals, including canine degenerative mitral valve disease (DMVD). High circulating 5HT concentration is a potential source of increased signaling, and serum 5HT concentrations have not been previously reported in dogs with DMVD.
Hypothesis: Dogs with DMVD and small breed dogs predisposed to DMVD have higher serum 5HT concentrations than large breed controls.
Animals: Fifty dogs affected with DMVD, 34 dogs predisposed to DMVD but without cardiac murmur or echocardiographic evidence of DMVD, and 36 healthy large breed control dogs.
Methods: Prospective analysis. Serum 5HT concentration was measured by an ELISA test.
Results: Median serum 5HT concentration was significantly higher in dogs with DMVD and in dogs predisposed to DMVD as compared with controls (DMVD, 765.5 ng/mL [interquartile range, 561.3–944.4]; predisposed, 774.9 ng/mL [528.3–1,026]; control, 509.8 ng/mL [320.8–708.8]; P = .0001). Subgroup analysis of predisposed dogs indicated significantly higher serum 5HT concentrations in Cavalier King Charles Spaniel (CKCS) dogs than in other breeds (CKCS, 855.0 ng/mL [635.8–1,088]; non-CKCS, 554.2 ng/mL [380.6–648.4]; P = .0023). Age, platelet count, and platelet morphology were not correlated with 5HT concentration in any group.
Conclusions and Clinical Importance: Dogs with DMVD had significantly higher serum 5HT concentrations when compared with large breed control dogs. Healthy CKCS dogs had significantly higher serum 5HT concentrations than other healthy dogs predisposed to DMVD. Additional investigation into a possible role of 5HT in the pathogenesis of DMVD is warranted.     

Echocardiographic measurement of cardiac valvular thickness in healthy cows,cows with bacterial endocarditis,and cows with cardiorespiratory diseases

ObjectiveTo determine valvular thickness in healthy cows, cows with bacterial endocarditis, and cows with various cardiorespiratory diseases.Animals40 healthy Holstein adult cows (CONTROL), 6 adult cows with confirmed bacterial endocarditis (BE), and 10 cows with other cardiorespiratory disorders (NONBE).MethodsProspective study using right transthoracic echocardiographic examination in CONTROL, BE and NONBE cows. The valvular thicknesses of all cows were assessed in four different locations for all cardiac valves, and the maximal value was used for further analysis.ResultsThe mean [±standard deviation (SD)] maximal thicknesses of the tricuspid, mitral, aortic, and pulmonary valves in the CONTROL group were 0.69 ± 0.10 cm, 0.85 ± 0.21 cm, 0.72 ± 0.17 cm, and 0.58 ± 0.12 cm, respectively. The maximal valvular thicknesses were less than 0.97 cm for the tricuspid, less than 0.91 cm for pulmonary, less than 1.05 cm for the aortic, and less than 1.28 cm for the mitral. In BE cows, the maximal valvular thickness of affected valves (median: 4.22 cm; range: 2.52–6.97 cm) and non affected valves (median: 0.75 cm; range: 0.45–1.52 cm) were significantly different (P = 0.0004). The maximal valvular thicknesses of the NONBE valves as well as the unaffected valves in the BE group were not significantly different compared to the CONTROL group valves.ConclusionsUsing the mean ± 2SD formula for each valve in healthy cows, a thickness of tricuspid, mitral, aortic or pulmonary valves greater than 0.85 cm, 1.27 cm, 1.06 cm or 0.82 cm respectively should raise the suspicion of valvular bacterial endocarditis.