Two-dimensional echocardiographic estimates of left atrial function in healthy dogs and dogs with myxomatous mitral valve disease

Objectives

To provide reference intervals for 2-dimensional linear and area-based estimates of left atrial (LA) function in healthy dogs and to evaluate the ability of estimates of LA function to differentiate dogs with subclinical myxomatous mitral valve disease (MMVD) and similarly affected dogs with congestive heart failure (CHF).

Cardioversion of supraventricular tachycardia using lidocaine in five dogs

Sustained supraventricular tachycardia (SVT) may lead to life-threatening complications such as tachycardia-induced myocardial failure. We report the use of intravenous lidocaine in 5 dogs with SVT. Two dogs had evidence of an accessory conduction pathway, 2 were suspected of having an accessory pathway, and the mechanism of SVT was unknown in the remaining dog, which subsequently developed dilated cardiomyopathy 2 years later. In all cases there was rapid conversion to normal sinus rhythm, which was then maintained with oral mexilitene (4 dogs) or mexilitene combined with propranolol (1 dog).     

Survival time with pacemaker implantation for dogs diagnosed with persistent atrial standstill

Objectives

To evaluate survival time in dogs with persistent atrial standstill after pacemaker implantation and to compare the survival times for cardiac-related vs. non-cardiac deaths. Secondary objectives were to evaluate the effects of breed and the presence of congestive heart failure (CHF) at the time of diagnosis on survival time.

A Randomized Study Assessing the Effect of Diet in Cats with Hypertrophic Cardiomyopathy

Background

Diet might influence progression of hypertrophic cardiomyopathy (HCM).

Objective

To investigate whether diet composition could alter clinical, biochemical, or echocardiographic variables in cats with HCM.

Animals

Twenty‐nine cats with HCM (International Small Animal Cardiac Health Council stage 1b) examined at a university teaching hospital.

Methods

Randomized, placebo‐controlled trial. After physical examination, echocardiogram, and blood collection, cats were randomized to 1 of 3 diets, which varied in carbohydrate and fat content and ingredients. Measurements were repeated after 6 months.

Results

There were no significant differences among the 3 groups at baseline. After 6 months, there were no significant changes in the primary endpoints, left ventricular free wall (Group A, P = .760; Group B, P = .475; Group C, P = .066) or interventricular septal thickness in diastole (Group A, P = .528; Group B, P = .221; Group C, P = .097). Group A had significant increases in BUN (P = .008) and cholesterol (P = .021), while Group B had significant increases in BUN (P = .008), cholesterol (P = .007), and triglycerides (P = .005), and significant decreases in NT‐proBNP (P = .013) and hs‐troponin I (P = .043). Group C had significant decreases in body weight (P = .021), left atrial dimension (P = .035), interventricular septal thickness in systole (P = .038), and liver enzymes (P = .034–.038).

Conclusions and Clinical Importance

These data suggest that diet might influence some clinical, biochemical, and echocardiographic variables in cats with HCM.     

The Cardiac Biomarker NT-proBNP Is Increased in Dogs with Azotemia

Background: Amino‐terminal probrain natriuretic peptide (NT‐proBNP) has been proposed as a useful biomarker for heart disease in dogs. In humans, decreased glomerular filtration rate (GFR) increases NT‐proBNP. Objective: To investigate whether decreased GFR as indicated by plasma creatinine concentration is associated with increased NT‐proBNP in dogs without heart disease. Animals: Four groups of dogs: healthy (n= 39), azotemic (n= 36), heart disease (n= 37), and congestive heart failure (CHF) (n= 7) presented to 2 teaching hospitals. Methods: Prospective observational cohort study. Plasma creatinine concentration and NT‐proBNP were measured in every dog. Nonparametric tests were used to compare the differences among groups. The median and actual results for each group were compared with the manufacturer's recommended and previously published suggestions for cut‐off values for diagnosis of heart disease. Results: Median (range) plasma creatinine concentration was 1.47 (1.06–1.70), 4.36 (1.74–15.6), 1.22 (0.69–1.91), and 1.45 (0.63–1.64) mg/dL and median (range) NT‐proBNP was 118 (2–673), 556 (37–1,819), 929 (212–5,658), and 3,144 (432–5,500) pmol/L for the healthy, azotemic, heart disease, and CHF groups, respectively. Pair‐wise comparison indicated a significant difference among all groups for NT‐proBNP (P≤ .049). Plasma creatinine concentration was significantly higher in the azotemic group compared with other groups (P < .001) but there was no significant among other groups. Application of 3 recommended cut‐off values led to misclassification of dogs with azotemia as having heart disease. Conclusions: Azotemia results in NT‐proBNP being increased to concentrations reported as diagnostic of heart disease or heart failure in dogs. Care should be employed when interpreting the results of NT‐proBNP in patients with known or possible increased plasma creatinine concentration.     

Syncope secondary to transient atrioventricular block in a German shepherd dog with dilated cardiomyopathy and atrial fibrillation

This case report describes transient atrioventricular block as the etiology for syncopal events in a 6-year-old male German shepherd dog with atrial fibrillation and dilated cardiomyopathy. The arrhythmia diagnosis was obtained via Holter monitoring. Medical treatment with a sustained-release preparation of theophylline, as an additive to the standard congestive heart failure treatment (benazepril, furosemide and pimobendan) may have contributed to temporary remission of the syncopal events. However, the congestive heart failure progressed and the dog was euthanized. Veterinarians should be aware of the possibility of transient atrioventricular block causing syncope in dogs with DCM and AF and should be careful in empirically lowering the ventricular response rate if these dogs present with syncopal episodes.     

Prospective clinical evaluation of serum cardiac troponin T in dogs admitted to a veterinary teaching hospital

The purpose of this study was to measure serum cardiac troponin T (cTnT) with a commercially available human enzyme-linked immunoassay (ELISA) test in various groups of dogs, including those undergoing doxorubicin chemotherapy. Serum samples were obtained from 6 groups of dogs: (1) normal adult dogs (n = 15); (2) dogs with asymptomatic dilated cardiomyopathy (n = 5); (3) dogs with congestive heart failure (n = 10); (4) dogs with untreated neoplasia (n = 20); (5) dogs with skeletal muscle trauma (n = 10); and (6) dogs with neoplasia receiving doxorubicin chemotherapy (n = 4). One serum sample was obtained from each of the normal dogs, those with asymptomatic cardiomyopathy, those with congestive heart failure, and those with untreated neoplasia. Serum samples were obtained serially from the dogs that were undergoing doxorubicin chemotherapy; samples were collected before doxorubicin (30 mg/m2) administration and then 1, 5, 7, and 14 days after administration throughout 6 cycles for a cumulative total dose of 180 mg/m2. All normal dogs, dogs with untreated neoplasia, and dogs with asymptomatic dilated cardiomyopathy had cTnT concentrations below the lower limits of detection for the assay used (<0.05 ng/mL). Detectable concentrations of cTnT were found in 3 dogs with congestive heart failure and in 2 dogs with skeletal muscle trauma. Detectable concentrations also were found in both dogs that had received 180 mg/m2 of doxorubicin. We conclude that dogs with congestive heart failure and those with skeletal muscle trauma and dogs with neoplasia receiving high-dose doxorubicin chemotherapy may have increased serum cTnT concentration, which may be suggestive of myocardial damage.     

Left atrial volume and function in dogs with naturally occurring myxomatous mitral valve disease

Objective

Myxomatous mitral valve disease (MMVD) induces progressive left atrial (LA) enlargement. The LA modulates left ventricular filling and performance through its reservoir, conduit, and contractile function. Assessment of LA size and function may provide valuable information on the level of cardiac compensation. Left atrial function in dogs with naturally occurring MMVD remains largely unexplored. The objective of this study was to evaluate LA volume and function in dogs with naturally occurring MMVD.

Plasma endothelin-1 immunoreactivity in normal dogs and dogs with acquired heart disease

We sought to measure plasma endothelin-1 (ET-1) concentrations in normal dogs and to compare them with those measured in dogs with acquired heart disease with or without pulmonary edema. A sandwich enzyme-linked immunosorbent assay kit was validated and used to measure ET-1 immunoreactivity in plasma samples obtained from 32 normal dogs and 46 dogs with either dilated cardiomyopathy (DCM, n = 27) or degenerative valvular disease (CDVD, n = 19) with (n = 30) or without (n = 16) overt congestive heart failure (CHF). Plasma ET-1 concentrations (geometric mean, 95% confidence interval of geometric mean) were 1.17 (1.04-1.32) fmol/mL in the 32 normal control dogs, 1.25 (0.981-1.60) fmol/mL in 16 dogs with DCM (n = 9) or CDVD (n = 7) without CHF, and 2.51 (2.10-3.01) fmol/mL in 30 dogs with DCM (n = 18) and CDVD (n = 12) with CHE Plasma immunoreactivity of ET-1 was significantly higher in dogs with CHF in comparison with normal dogs (P < .001) and dogs with heart disease without CHF (P < .001). No significant difference was found between normal dogs and dogs with heart disease but without CHF (P > .05). Significant correlations were between plasma ET-I concentrations and left atrial:aortic ratio (P < .0001, r2 = .39), left ventricular internal dimension at end-diastole indexed to aortic diameter (P < .0001, r2 = .30) or body surface area (BSA) (P = .0071, r2 = .10), and left ventricular internal dimension at end-systole indexed to aortic diameter (P = .0003, r- = .17) or BSA (P = .0008, r2 = .15).     

Validation of heart rate spot-check protocol to measure circadian variation and heart rate in healthy dogs and dogs with atrial fibrillation

IntroductionAlternatives for out-of-clinic heart rate (HR) measurement are required to optimise the management of atrial fibrillation (AF) in dogs. Additionally, the presence of circadian variation (CV) in HR in pet dogs remains unknown.We aimed to identify the number and duration of spot-checks required for an accurate estimation of 24-hour HR in canine AF. Circadian variation in HR was examined in healthy dogs and dogs with AF, and spot-check-derived HR was compared with a CV-derived gold standard.Materials and methodsAmbulatory electrocardiogram data from healthy dogs and dogs with AF were retrospectively analysed. Heart rate was calculated from the entire recording and pre-defined periods (spot-checks) of one hour to 30 and 60 s in duration. Circadian variation in HR was determined by cosinor analysis. Bias and limits of agreement of means and median HR with mesor HR were determined by correlation and Bland–Altman analysis.ResultsCircadian variation in HR was identified not only in 18/22 healthy dogs and 14/21 AF dogs but only on ambulatory electrocardiogram recordings.Four-hourly spot-checks provided the most accurate estimate of mesor HR in healthy dogs (bias of the median over 30 s 7.70, limits of agreement 7.48), whereas, in dogs with AF, four, six and eight-hourly spot-checks provided reliable estimates of mesor HR (bias within −1.29 and −29.5).ConclusionsFour, six and eight-hourly HR spot-checks can estimate 24-hourly HR in dogs with AF. There was CV in HR in most healthy pet dogs and dogs with AF. Spot-check protocols cannot identify CV in HR.     

Regurgitant fraction measured by using the proximal isovelocity surface area method in dogs with chronic myxomatous mitral valve disease

Previous studies have demonstrated that regurgitant fraction can be measured by using the proximal isovelocity surface area (PISA) method. For this study, we utilized this Doppler echocardiographic method to estimate the magnitude of mitral regurgitation in dogs with myxomatous mitral valve disease. Seventeen older, small dogs with chronic mitral regurgitation and no to mild myocardial failure were studied. A blinded observer judged the clinical severity of mitral regurgitation to be mild, moderate, or severe by using echocardiographic assessment of left heart size. The regurgitant fraction was calculated by using the PISA method and spectral Doppler echocardiography. The regurgitant fraction was compared to the clinical assessment of severity for each dog and to calculations of left atrial size. Five dogs had clinically mild mitral regurgitation. Four of these dogs had a regurgitant fraction between 22 and 41%, whereas 1 had a regurgitant fraction of 73%. The 3 dogs with clinical evidence of moderate mitral regurgitation had a regurgitant fraction of 46-65%. All 9 dogs with clinically severe mitral regurgitation had a regurgitant fraction greater than 75% (78-88%). The regurgitant fraction was statistically different between each group (P < .001). A good but curvilinear relationship was found between left atrial size and regurgitant fraction (r2 = 0.72). In this study, dogs with clinically severe mitral regurgitation consistently had hemodynamically severe regurgitation (regurgitant fraction > 75%), whereas dogs with clinically mild to moderate disease had lesser degrees of regurgitation. Good correlation was found between regurgitant fraction and left atrial size. We conclude that the major determinant of left atrial size and disease severity in dogs with mitrial regurgitation is the degree of mitral regurgitation.     

Radiocardiography in dogs with atrial fibrillation

In 54 of 99 dogs with atrial fibrillation heart function was examined scintigraphically. Data on the ejection fraction (EF), end-diastolic volume (EDV) and regurgitation fraction (RF) are presented. Of these animals 37 had a seriously decreased EF (less than 30%) with a more or less normal RF value, whereas a smaller group (17) had a moderately decreased EF (but greater than or equal to 30%) and a seriously increased RF value. In both groups the EDV was increased.     

Radiocardiography in dogs with atrial fibrillation

Summary

In 54 of 99 dogs with atrial fibrillation heart function was examined scintigraphically. Data on the ejection fraction (EF), end‐diastolic volume (EDV) and regurgitation fraction (RF) are presented. Of these animals 37 had a seriously decreased EF (< 30%) with a more or less normal RF value, whereas a smaller group (17) had a moderately decreased EF (but ≥ 30%) and a seriously increased RF value. In both groups the EDV was increased.     

Intravenous amiodarone treatment in horses with chronic atrial fibrillation

Six horses without underlying cardiac disease were presented because of atrial fibrillation of between 5 and 12 months duration. These horses received an intravenous amiodarone treatment of 5mg/kg/h for 1 h followed by 0.83mg/kg/h for 23h and subsequently 1.9mg/kg/h for 30h. During treatment, clinical signs were monitored and a surface ECG and an intra-atrial electrogram were recorded. Infusion was discontinued when sinus rhythm or side effects occurred. Four horses successfully cardioverted, of which one showed symptoms of hind limb weakness and weight shifting. Two horses did not cardiovert and showed similar side effects. In all horses, side effects disappeared within 6h after termination of treatment. Cardiac side effects, such as pro-arrhythmia, were not seen in any of the horses. Total bilirubin slightly increased in three horses and normalised within four days. It was concluded that amiodarone has the potential to treat naturally occurring chronic atrial fibrillation in horses, although further research is needed to refine the infusion protocol.     

Plasma big endothelin-1, atrial natriuretic peptide, aldosterone, and norepinephrine concentrations in normal Doberman Pinschers and Doberman Pinschers with dilated cardiomyopathy

BACKGROUND: Dilated cardiomyopathy (DCM) results in progressive myocardial and circulatory dysfunction causing activation of a number of neurohormonal systems, including the endothelin (ET) system, which is only beginning to be described in clinical veterinary medicine. Measurement of these circulating neurohormones possesses potential utility in the diagnosis, staging, and assessment of prognosis in cardiac disease. HYPOTHESIS: We hypothesized that plasma big ET-1, norepinephrine (NE), aldosterone, and atrial natriuretic peptide (ANP) concentrations in normal Dobermans would differ from those in Dobermans with DCM, and that concentrations of these hormones would be associated with time to congestive heart failure (CHF) or death. ANIMALS: Thirty client-owned Dobermans (10 each of normal, occult DCM, and overt DCM) were included in the study. METHODS: Dogs underwent an echocardiogram, ECG, and blood sample collection. Neurohormones were measured by high-pressure liquid chromatography (NE) or commercial assays. RESULTS: Dogs with occult DCM had significantly higher ANP concentrations compared with normal dogs (least squares means [95% confidence interval, CI]: occult female 53.7 pg/mL [40.2-71.7] versus normal female 31.6 pg/mL [24.8-40.3], P = .026; occult male 86.1 pg/mL [64.7-115] versus normal male 12.1 pg/mL [5.1-28.7], P = .011). Dogs with overt DCM had significantly higher concentrations of all neurohormones compared with the normal group. Furthermore, increasing big ET-1 (risk ratio [RR] 2.7, CI 1.3-8.6, P = .01) and NE concentrations (RR 3.9, CI 1.1-18.1, P = .03) over 1 month were associated with a shorter survival time. CONCLUSIONS AND CLINICAL IMPORTANCE: High ANP concentrations can identify dogs with advanced occult DCM. Increasing big ET-1 or NE concentrations over time can be useful predictors of poor prognosis.     

Estimation of left ventricular filling pressure by Doppler echocardiography in dogs with pacing-induced heart failure

BACKGROUND: Congestive heart failure (CHF) is a common clinical syndrome characterized by elevated filling pressure. HYPOTHESIS: Doppler echocardiographic (DE) variables of left ventricular (LV) filling can predict a decline of LV end-diastolic pressure (LVEDP) induced by acute preload reduction in dogs with compensated CHF. ANIMALS: Five male hound dogs. METHODS: Dogs previously instrumented with a transvenous cardiac pacemaker and a LV pressure gauge were paced at 160-180 bpm to induce mild CHF characterized by LVEDP > 20 mmHg. LVEDP and 9 DE variables of LV filling derived from diastolic time intervals, transmitral and pulmonary venous flow, and tissue Doppler imaging were measured simultaneously at baseline and 30, 60, 120, and 240 minutes after furosemide (4 mg/kg, IV) or placebo (0.9% saline, IV). Repeated measures analysis of variance and correlation analysis were used to determine the association between the decline of LVEDP after furosemide and DE measures of LV filling pressure (LVFP). RESULTS: Furosemide but not placebo decreased LVEDP (P < .001). The ratio of early transmitral flow velocity to LV isovolumic relaxation time (E : IVRT) predicted LVEDP best (R(2)= .50; P < .001). Correlations were also found between LVEDP and IVRT, E, ratio between E and late diastolic transmitral flow velocity (E : A), and early diastolic velocity of the mitral annulus (Ea). The ratio of E to Ea (E : Ea) was not useful in the prediction of LVEDP in this model. CONCLUSION AND CLINICAL IMPORTANCE: E : IVRT can be used to predict LVFP in dogs with mild left-sided CHF induced by rapid pacing.     

Transcutaneous direct current cardioversion in a foal with lone atrial fibrillation

There are rare published reports of atrial fibrillation (AF) in foals, all of which are associated with structural heart disease or within the adaptive period of newborns. This report describes a 3-month-old Thoroughbred filly with AF and a structurally normal heart on echocardiography. Medical cardioversion of the foal's AF was attempted with three 20mg/kg doses of quinidine sulfate therapy without success. Timed, transcutaneous, direct current cardioversion was successfully performed using adhesive patches on the midthorax in conjunction with intravenous procainamide at a total dose of 20mg/kg. A normal sinus rhythm was maintained through discharge from the hospital and at recheck 5 months after cardioversion. Transcutaneous direct current cardioversion presents a feasible alternative to quinidine sulfate or transvenous electrical cardioversion in young or lower body weight equids.