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.     

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.     

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.     

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).

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.     

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).     

Cardioversion with lidocaine of vagally associated atrial fibrillation in two dogs

Two dogs with acute onset atrial fibrillation (AF) were cardioverted to sinus rhythm by the administration of 2 mg/kg lidocaine given intravenously. Each dog was believed to have AF initiated because of elevated vagal tone. This report has potential clinical impact for a subset of dogs because it offers a treatment to circumvent persistent AF. Furthermore, this encouraging result of a pharmacologic cardioversion suggests that further investigation would be of interest to ascertain the effectiveness and mechanism of the antiarrhythmic action of lidocaine in vagally induced AF.     

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.

Prevalence,geographic distribution,and impact on lifespan of a dilated cardiomyopathy-associated RNA-binding motif protein 20 variant in genotyped dogs

IntroductionThe study objectives were to determine the prevalence and geographic distribution of a dilated cardiomyopathy (DCM)-associated RNA-binding motif protein 20 (RBM20) variant in canine DNA samples submitted for testing and to evaluate the influence of the genotype on cardiac phenotype and lifespan.AnimalsSamples from 2136 dogs including 1834 Standard Schnauzers (SSNZ), 266 Giant Schnauzers (GSNZ), and 36 dogs of other breeds.MethodsThe University of Missouri Canine Genetics Laboratory's sample-accession spreadsheet and Orthopedic Foundation for Animals' database were retrospectively reviewed for samples submitted for RBM20 genotyping from November, 2013, through May, 2018. Data analyzed included breed, date of birth, RBM20 genotype (homozygous wild-type, heterozygous variant [HET], or homozygous variant [HOM]), geographic origin of submission, pedigree, cardiac phenotype, and date of death or current age if alive.Results and DiscussionThe RBM20 variant was only detected in SSNZ and GSNZ. A total of 389 SSNZ were variant-positive (prevalence = 21.2%), with 361 HET (19.7%) and 28 HOM (1.5%). Of the HOM SSNZ, DCM was confirmed in 26 of 28 (92.9%), with the remainder lost to follow-up. The median lifespan of HOM SSNZ (3.06 years) was significantly shorter than that for HET (15.11 years) and wild-type (15.18 years) SSNZ. Twenty-six GSNZ were variant-positive (prevalence = 9.8%), with 23 HET (8.6%) and three HOM (1.1%). Nine GSNZ belonged to one family, including the three HOM GSNZ that all had DCM.ConclusionsThe HOM genotype is associated with DCM and premature death in SSNZ and GSNZ.     

Verapamil administration for acute termination of supraventricular tachycardia in dogs

Verapamil, a calcium channel-blocking drug, was administered IV at a dosage that ranged from 0.05 to 0.15 mg/kg of body weight to 14 dogs with supraventricular tachycardia. The dosage was titrated, administering 0.05 mg/kg every 5 to 30 minutes following the initial 0.05 mg/kg dose in all but 1 dog. The drug terminated the arrhythmia in 12 dogs and slowed the ventricular rate in 1 dog. One dog was unresponsive to verapamil administration and became transiently hypotensive after the administration of a total dose of 0.15 mg/kg over 5 to 6 minutes. Various arrhythmias occurred after verapamil administration, but none required additional treatment or caused serious sequelae. Verapamil was an effective treatment for acutely converting supraventricular tachycardia to sinus rhythm in these dogs. It appears to be safe when administered in the aforementioned dosage range.     

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.     

QT instability,an indicator of augmented arrhythmogenesis,increases with the progression of myxomatous mitral valve disease in dogs

Objectives

To investigate QT instability in dogs with myxomatous mitral valve disease (MMVD) and to determine if this is associated with arrhythmogenesis.

Total bilirubin is an independent predictor of death in dogs with degenerative valvular disease and dilated cardiomyopathy

IntroductionThere is little published regarding the association between canine cardiovascular disease and the hepatic system. The objective of the study was to evaluate the relationship between hepatic parameters, survival, and disease stages of dogs with either dilated cardiomyopathy (DCM) or degenerative valvular disease (DVD).Animals, materials, and methodsRetrospective study analyzing hepatic parameters in dogs with DVD or DCM in American College of Veterinary Internal Medicine stage B or C and healthy control dogs. Associations between liver parameters, type and stage of disease, and survival were investigated.ResultsNinety-nine dogs were included in the study: 61 DVD, 22 DCM, and 16 controls. Differences in liver parameter concentrations between DCM, DVD, and disease stages were found. Univariate analysis identified alanine aminotransferase (P < 0.001), aspartate aminotransferase (P = 0.02), and total bilirubin (P = 0.005) as predictors of mortality. In the multivariate analysis, total bilirubin remained an independent predictor of mortality.ConclusionsThe observed differences between DCM, DVD, and disease stages are likely consistent with disease-specific hemodynamics and progression of disease. This and the role of total bilirubin as an independent predictor for mortality indicate that in dogs with DVD and DCM the cardiovascular–hepatic interaction might be of relevance for disease progression and outcome, as reported for humans with cardiac disease. Further studies into the role of hepatic function in canine cardiac disease are required.     

Clinical, echocardiographic, and neurohormonal effects of a sodium-restricted diet in dogs with heart failure

The use of low-sodium diets in dogs with heart failure is common practice, but randomized, double-blind studies have not been conducted to examine the benefits or problems with this approach. The purpose of this study was to determine the effects of a low-sodium diet on clinical, echocardiographic, and neurohormonal parameters in dogs with heart failure. Dogs with stable chronic heart failure were fed exclusively a low-sodium (LS) and a moderate-sodium (MS) diet for 4 weeks each in a randomized, double-blind, crossover design. At days 0, 28, and 56, echocardiography and thoracic radiography were performed, and blood was analyzed for electrolytes and neurohormones. Fourteen dogs completed the study (9 with chronic valvular disease and 5 with dilated cardiomyopathy). Electrolyte abnormalities were common during the study, and serum sodium and chloride concentrations decreased significantly on the LS diet. Neurohormones did not change significantly between diet groups. Maximum left atrial (P = .05) and standard left atrial (P = .09) size decreased on the LS diet. For dogs with chronic valvular disease, vertebral heart score (P = .05), left ventricular internal dimension in diastole (P = .006) and systole (P = .02), standard left atrial dimension (P = .03), maximum left atrial dimension (P = .02), end-diastolic volume index (P = .02), and end-systolic volume index (P = .04) decreased significantly on the LS diet compared to the MS diet. Although analysis of these data suggests some benefits of a low-sodium diet, future studies with improved study design are needed to further evaluate the advantages and disadvantages of sodium restriction in dogs with heart failure.     

Cardiac troponin I in feline hypertrophic cardiomyopathy

Measurement of plasma cardiac troponin I concentration ([cTnI]) is a sensitive and specific means for detecting myocardial damage in many mammalian species. Studies have shown that [cTnI] increases rapidly after cardiomyocyte injury. The molecular structure of cTnl is highly conserved across species, and current assays developed for its detection in humans have been validated in many species. In this study, [cTnI] was quantified using a 2-site sandwich assay in plasma of healthy control cats (n = 33) and cats with moderate to severe hypertrophic cardiomyopathy (HCM) (n = 20). [cTnI] was significantly higher in cats with HCM (median, 0.66 ng/mL; range, 0.05-10.93 ng/mL) as compared with normal cats (median, <0.03 ng/mL; range, <0.03-0.16 ng/mL) (P < .0001). An increase in [cTnI] was also highly sensitive (sensitivity = 85%) and specific (specificity = 97%) for differentiating cats with moderate to severe HCM from normal cats. [cTnI] was weakly correlated with diastolic thickness of the left ventricular free wall (r2 = .354; P = .009) but not with the diastolic thickness of the interventricular septum (P = .8467) or the left atrium: aorta ratio (P = .0652). Furthermore, cats with congestive heart failure at the time of cTnI analysis had a significantly higher [cTnI] than did cats that had never had heart failure and those whose heart failure was controlled at the time of analysis (P = .0095 and P = .0201, respectively). These data indicate that cats with HCM have ongoing myocardial damage. Although the origin of this damage is unknown, it most likely explains the replacement fibrosis that is consistently identified in cats with moderate to severe HCM.     

Arterial thromboembolism in cats: acute crisis in 127 cases (1992-2001) and long-term management with low-dose aspirin in 24 cases

Records of 127 cats with arterial thromboembolism (ATE) were reviewed. Abyssinian, Birman, Ragdoll, and male cats were overrepresented. Tachypnea (91%), hypothermia (66%), and absent limb motor function (66%) were common. Of 90 cats with diagnostics performed, underlying diseases were hyperthyroidism (12), cardiomyopathy (dilated [8], unclassified [33], hypertrophic obstructive [5], hypertrophic [19]), neoplasia (6), other (4), and none (3). Common abnormalities were left atrial enlargement (93%), congestive heart failure (CHF, 44%), and arrhythmias (44%). Of cats without CHF, 89% were tachypneic. Common biochemical abnormalities were hyperglycemia, azotemia, and abnormally high serum concentrations of muscle enzymes. Of 87 cats treated for acute limb ATE, 39 (45%) survived to be discharged. Significant differences were found between survivors and nonsurvivors for temperature (P < .00001), heart rate (P = .038), serum phosphorus concentration (P = .024), motor function (P = .008), and number of limbs affected (P = .001). No significant difference was found between survivors and nonsurvivors when compared by age, respiratory rate, other biochemical analytes, or concurrent CHE A logistic regression model based on rectal temperature predicted a 50% probability of survival at 98.9 degrees F (37.2 degrees C). Median survival time (MST) for discharged cats was 117 days. Eleven cats had ATE recurrences, and 5 cats developed limb problems. Cats with CHF (MST: 77 days) had significantly shorter survival than cats without CHF (MST: 223 days; P = .016). No significant difference was found in survival or recurrence rate between cats receiving high-dose aspirin (> or = 40 mg/cat q72h) and cats receiving low-dose aspirin (5 mg/cat q72h). Adverse effects were less frequent and milder for the lower dosage.     

Cor triatriatum dexter of unusual morphology in a miniature schnauzer

A five-year-nine-month-old, male entire, miniature schnauzer presented for further investigation of pleural effusion. Echocardiography revealed a perforated membrane dividing the right atrium into two chambers: the true right atrium (a small, lower-pressure, cranioventral chamber communicating with the tricuspid valve and right ventricle) and the accessory right atrium (a larger, higher-pressure, caudodorsal chamber), consistent with a cor triatriatum dexter. This was confirmed using computed tomography angiography. Imaging studies revealed that both the cranial and caudal vena cava entered the higher-pressure accessory right atrium and the coronary sinus entered both the accessory and true right atrial chambers. This differed from the more usual canine cor triatriatum dexter presentation with the cranial vena cava entering the lower-pressure cranial chamber and the caudal vena cava entering the higher-pressure caudal chamber. Balloon membranostomy was successful in reducing the pressure gradient between the two right atrial chambers with subsequent resolution of the clinical signs. The patient continues to do well after three-years of follow-up.