Evaluation of the NuCLEUS-X™ balloon valvuloplasty catheter for severe pulmonic stenosis in dogs

INTRODUCTION/OBJECTIVES

Balloon instability is commonly encountered during balloon pulmonary valvuloplasty (BPV) and may result in an unsuccessful procedure. The NuCLEUS-X™ catheter is a recently developed BPV catheter with a unique barbell shape and an ordered pattern of inflation that stabilizes the balloon to span the valve annulus before expansion of the balloon center.

ANIMALS

Ten client-owned dogs with severe valvular pulmonic stenosis (PS).

MATERIALS AND METHODS

Prospective observational study. The BPV procedure was performed by standard technique with use of NuCLEUS-X™ catheters targeting a balloon-to-annulus ratio between 1.2 and 1.5. Balloon stability, safety, and procedural success were assessed. Procedural success was defined as either a reduction in the Doppler transpulmonic PG by at least 50% of the pre-procedural PG or <80 mmHg one month post procedure.

RESULTS

Balloon stability centered at the pulmonic valve on the first inflation was achieved in 10/10 cases. The mean PG before BPV was 141 mmHg ±41 mmHg, and the PG after BPV at one month was 83 mmHg ±41 mmHg. Procedural success was achieved in 56% of patients. All dogs survived the BPV, and no major procedural complications were encountered using the NuCLEUS-X™ catheter.

CONCLUSIONS

The use of the NuCLEUS-X™ catheter is feasible for BPV in dogs with severe PS. The unique balloon shape provided catheter stability on the first inflation in all dogs, which may be beneficial when stabilization of a conventional BPV catheter cannot be achieved.

Prevalence of major complications and procedural mortality in 336 dogs undergoing interventional cardiology procedures in a single academic center

INTRODUCTION

Overall complication rates associated with a wide range of diagnostic and therapeutic interventional cardiac procedures in a contemporary academic setting have not been reported.

ANIMALS, MATERIALS AND METHODS

Consecutive interventional procedures performed for client-owned dogs were retrospectively analyzed to characterize procedural complications and mortality.

RESULTS

Three hundred sixty-four procedures were performed on 336 dogs. Interventions included attempted or completed transvenous pacemaker (PM) implantation (n = 134) with subsequent pacing system revision (n = 8), pulmonic balloon valvuloplasty (BVP) (n = 117) with a subset of patients undergoing an additional BVP (n = 14), transarterial closure of left-to-right shunting patent ductus arteriosus (PDA) (n = 66), diagnostic angiography and/or cardiovascular pressure measurement (n = 9), transvenous temporary pacing (n = 7), septal defect occlusion (n = 5), heartworm extraction (n = 3), and BVP catheter fragment retrieval (n = 1). The prevalence of major perioperative and postoperative complications for all procedures was 5% and 6%, respectively, and the procedural mortality rate was 2%. The overall rate of major complications was 12% for the PM group, 11% for the BVP group, and 2% for the PDA occlusion group. Both PM implantation and BVP have higher rates of major complications overall compared with PDA occlusion (p=0.0151).

CONCLUSIONS

The results of this study indicate that the prevalence of major complications and mortality associated with interventional cardiac procedures is low; however, significant differences exist in complication rates between procedures.

Detection by ELISA of C-terminal proBNP in plasma from cats with cardiomyopathy

The B-type natriuretic peptide prohormone (proBNP) is enzymatically cleaved into an inactive N-terminal peptide and a biologically active C-terminal peptide with many beneficial cardiorenal effects. The purpose of this study was to develop and test in cats with cardiomyopathy an immunoassay to quantify the concentrations of C-terminal proBNP in feline plasma. An anti-canine proBNP monoclonal antibody (UI-1021) was shown to have adequate binding affinity to proBNP 80-106 for use in a solid-phase immunoassay, and by epitope mapping to bind within positions 84-87 of feline proBNP. UI-1021 was paired with an affinity-purified rabbit polyclonal detection antibody to feline proBNP 100-106, in a sandwich ELISA with feline proBNP 80-106 standard. The linearity and analytical range and sensitivity of the assay were confirmed from 1.4 to 85 pmol/L. Spike recovery averaged 106.5% (95% confidence interval 78-135%). Within run and intra-assay coefficients of variation were <12%. A protease inhibitor mixture preserved proBNP 80-106 immunoreactivity for at least 5 days in plasma. Clinical verification of the ELISA was done using plasma from 13 cats with cardiomyopathy, whose C-terminal proBNP concentrations ranged from 1.7 to 78.8 pmol/L vs. <1.4-1.8 pmol/L in plasma from 18 healthy cats. Concentrations were found to be substantially lower than reported N-terminal proBNP concentrations, and similar to those of human heart failure patients where relative C-terminal BNP deficiencies have been proposed as contributory to the progression of the disease.

Biologic variability in NT-proBNP and cardiac troponin-I in healthy dogs and dogs with mitral valve degeneration

BACKGROUND

The N-terminal fragment of the prohormone B-type natriuretic peptide (NT-proBNP) and cardiac troponin-I are candidate biomarkers for cardiac disease in dogs. The degree of biologic variation in these biomarkers has not previously been reported in healthy dogs or dogs with mitral regurgitation.

OBJECTIVES

The purpose of the study was to derive estimates of intrinsic biologic variability and reference change values for NT-proBNP and cardiac troponin-I in healthy dogs and dogs with mitral regurgitation grade IB and II according to the International Small Animal Cardiac Health Council (ISACHC) grading system.

METHODS

Plasma and sera were collected weekly for up to 7 weeks from 12 control dogs and 9 dogs with mitral regurgitation. NT-proBNP and troponin-I (C-TnI) concentrations were determined. Indices of biologic variation such as reciprocal index of individuality (r-IoI) and reference change values (RCV) were calculated in both the groups.

RESULTS

Individuality was high in control dogs and dogs with grade IB and II mitral valve regurgitation for both C-TnI (r-IoI 1.6 and 2) and NT-proBNP (1.5 and 2.7), while the 2-sided RCV for NT-proBNP was significantly lower in dogs with mitral regurgitation (52.5% vs 99.4%, P<0.01.).

CONCLUSIONS

High individuality of these cardiac biomarkers suggests that, following diagnosis, these assays are best interpreted by serial determination in individual canine patients rather than by comparison to a population-based reference interval. The smaller RCV values for dogs with mitral regurgitation suggest that smaller relative changes in NT-proBNP are clinically meaningful in these patients.

Validation of a commercially available enzyme immunoassay for measurement of plasma antidiuretic hormone concentration in healthy dogs and assessment of plasma antidiuretic hormone concentration in dogs with congestive heart failure

OBJECTIVE

To validate the use of a human enzyme immunoassay (EIA) kit for measurement of plasma antidiuretic hormone (ADH) concentration in dogs and evaluate plasma ADH concentrations in dogs with congestive heart failure (CHF) attributable to acquired cardiac disease, compared with findings in healthy dogs.

ANIMALS

6 healthy dogs and 12 dogs with CHF as a result of chronic degenerative valve disease or dilated cardiomyopathy.

PROCEDURES

Plasma samples from the 6 healthy dogs were pooled and used to validate the EIA kit for measurement of plasma ADH concentration in dogs by assessing intra-assay precision, dilutional linearity, and spiking recovery. Following validation, plasma ADH concentrations were measured in the 6 healthy dogs and in the 12 dogs with CHF for comparison.

RESULTS

The EIA kit measured ADH concentrations in canine plasma samples with acceptable intra-assay precision, dilutional linearity, and spiking recovery. The intra-assay coefficient of variation was 11%. By use of this assay, the median plasma concentration of ADH in dogs with CHF was 6.15 pg/mL (SD, 3.2 pg/mL; range, 4.18 to 15.47 pg/mL), which was significantly higher than the median concentration in healthy dogs (3.67 pg/mL [SD, 0.93 pg/mL; range, 3.49 to 5.45 pg/mL]).

CONCLUSIONS AND CLINICAL RELEVANCE

Plasma ADH concentrations in dogs can be measured with the tested EIA kit. Plasma ADH concentrations were higher in dogs with CHF induced by acquired cardiac disease than in healthy dogs. This observation provides a basis for future studies evaluating circulating ADH concentrations in dogs with developing heart failure.

Doppler-derived deformation imaging in unsedated healthy adult dogs

OBJECTIVES

To evaluate feasibility, repeatability and reproducibility (R&R) of Doppler-derived deformation imaging (DI) in healthy adult dogs.

ANIMALS, MATERIALS AND METHODS

Forty-nine dogs underwent physical examination, ECG, blood pressure measurement and echocardiography. Doppler-derived DI parameters obtained from six selected Regions of Interest (ROI) within the left ventricle (LV) were: strain (S), systolic strain rate (SSR), strain rate E wave (SRE), and strain rate A wave (SRA). The averages of the six ROIs were calculated and labeled avS, avSSR, avSRE, and avSRA. Randomly selected dogs underwent two echocardiographic studies to evaluate intraoperator (n=14) and interoperator (n=17) variability.

RESULTS

DI data were obtained in 87.2% of dogs and 77.2% of ROIs. Compared to controls, avSSR was significantly reduced in Doberman Pinchers (DP) and it was increased in dogs < 30 kg, compared to dogs > 30 kg. The intraoperator Coefficient of Variability (CV) for some ROIs was greater than 15% but for averaged measurements it was < or = 5.0%. Interoperator CV varied widely but were all < 15% for avSSR, avS, and avSRA.

CONCLUSIONS

The CV for Doppler-derived DI varied widely. Averaging values from multiple ROIs improved R&R. DI may help elucidate differences in LV mechanics between canine breeds.

Canine heterophilic antibodies as a source of false-positive B-type natriuretic peptide sandwich ELISA results

BACKGROUND

Interference by heterophilic antibodies is a well-known cause of false-positive sandwich ELISA results in human medicine. They are considered rarely in veterinary species and have not been characterized but could become important as newer, highly sensitive sandwich immunoassay technologies are developed.

OBJECTIVES

The goals of this study were to use a B-type natriuretic peptide (BNP-32) sandwich ELISA to determine the effect of heterophilic antibodies on test performance; to characterize canine heterophilic antibodies; and to develop and test a method for heterophilic antibody removal.

METHODS

A sandwich ELISA was developed using a mouse IgG(1)K monoclonal and a rabbit polyclonal antibody to two synthetic peptides of canine BNP-32. The effects on false-positive results of heterophilic antibody depletion and blocking by various techniques were compared. The titers of canine heterophilic antibodies were compared with various blood antigens from other species and the relative amount of canine IgG was compared with that of IgM heterophilic antibody.

RESULTS

Heterophilic antibodies in dog plasma were shown to be capable of causing false-positive ELISA results. They reacted with blood proteins from a variety of animal species at relatively low titers and consisted of both IgG and IgM. Protein A agarose antibody precipitation, in conjunction with mouse IgG(1)K blocking antibody, was effective in eliminating false-positive sandwich ELISA results while retaining adequate test performance.

CONCLUSIONS

Canine heterophilic antibodies can interfere with sandwich ELISA assays and cause false-positive test results. An effective technique for their removal that has a potentially broad application was developed, and allows measurement of canine blood constituents at low picomolar concentrations.

Carvedilol in dogs with dilated cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is characterized by reduced systolic function, heightened sympathetic tone, and high morbidity and mortality. Little is known regarding the safety and efficacy of beta-blocker treatment in dogs with DCM.

HYPOTHESIS

Carvedilol improves echocardiographic and neurohormonal variables in dogs with DCM over a 4-month treatment period.

METHODS

Prospective, placebo-controlled, double-blinded randomized study. Dogs with DCM underwent echocardiography, ECG, thoracic radiographs, and neurohormonal profiling, followed by titration onto carvedilol (0.3 mg/kg q12h) or placebo over a 4-week period and subsequently received 3 months of therapy. Primary study endpoints included left ventricular volume and function.

RESULTS

Sixteen dogs received carvedilol and 7 received placebo. At study end, 13 carvedilol dogs and 5 placebo dogs were alive. There was no difference in the mean percentage change in left ventricular volume at end-diastole (LVVd), left ventricular end-systolic volume (LVVs), and ejection fraction (EF) between treatment groups, suggesting that both groups experienced similar amounts of disease progression. Carvedilol treatment did not result in significant changes in neurohormonal activation, radiographic heart size, heart rate, or owner perceived quality-of-life. Baseline B-type natriuretic peptide (BNP) predicted dogs in the carvedilol-treated group that maintained or improved their EF over the study duration.

CONCLUSIONS AND CLINICAL IMPORTANCE

Carvedilol administration did not improve echocardiographic or neurohormonal indicators of heart function. The lack of effect may be related to severity of disease, carvedilol dose, or brevity of follow-up time. Statistical power of the present study was adversely affected by a high fatality rate in study dogs and small sample size.

Distinguishing cardiac and noncardiac dyspnea in 48 dogs using plasma atrial natriuretic factor, B-type natriuretic factor, endothelin, and cardiac troponin-I

BACKGROUND

It is challenging to differentiate congestive heart failure (CHF) from noncardiac cause of dyspnea.

HYPOTHESIS

Circulating concentrations of atrial natriuretic peptide (NT-proANP), B-type natriuretic peptide (BNP), endothelin-I (ET-1), and cardiac troponin-I (cTnI) can be used to help distinguish between cardiac and noncardiac causes of dyspnea in dogs.

ANIMALS

Forty-eight client-owned dogs admitted to a veterinary teaching hospital for respiratory distress.

METHODS

Blood samples from patients were prospectively obtained. The etiology of dyspnea was determined by using physical examination, thoracic radiographs, and echocardiography.

RESULTS

CHF was diagnosed in 22 dogs, and dyspnea of noncardiac origin (noHD group) was diagnosed in 26 dogs. Analyses revealed significant difference between groups for NT-proANP (geometric mean, 95% confidence [CI]; no HD: 0.26 nmol/mL, 95% CI 0.17-1.09; CHF: 1.38 nmol/mL, 95% CI 1.09-1.74 nmol/mL; P < .0001), BNP (noHD: 12.18 pg/mL, 95% CI 10.91-16.17 pg/mL; CHF: 34.97 pg/mL, 95% CI 23.51-52.02 pg/mL; P < .0001), and ET-1 (noHD: 0.32 fmol/mL, 95% CI 0.23-0.46 fmol/mL; CHF: 1.26 fmol/mL, 95% CI 0.83-1.91 fmol/mL; P < .0001). Plasma cTnI concentrations were not significantly different between groups (noHD: 0.29 ng/mL, 95% CI 0.12-0.72 ng/mL; CHF: 0.42 ng/mL, 95% CI 0.18-0.97, P = .53). Receiver operating curves indicated areas under the curve for NT-proANP, BNP, and ET-1 of 0.946, 0.886, and 0.849, respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

Plasma NT-proANP, BNP, and ET-1, but not cTnI, appear useful for distinguishing between dogs with cardiac and noncardiac causes of dyspnea, with plasma NT-proANP having the highest sensitivity (95.5%) and specificity (84.6%).

Correlation of mitochondrial protein expression in complexes I to V with natural and induced forms of canine idiopathic dilated cardiomyopathy

OBJECTIVE

To identify qualitative and quantitative differences in cardiac mitochondrial protein expression in complexes I to V between healthy dogs and dogs with natural or induced dilated cardiomyopathy (DCM).

SAMPLE POPULATION

Left ventricle samples were obtained from 7 healthy dogs, 7 Doberman Pinschers with naturally occurring DCM, and 7 dogs with DCM induced by rapid right ventricular pacing.

PROCEDURES

Fresh and frozen mitochondrial fractions were isolated from the left ventricular free wall and analyzed by 2-dimensional electrophoresis. Protein spots that increased or decreased in density by 2-fold or greater between groups were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry or quadrupole selecting, quadrupole collision cell, time-of-flight mass spectrometry.

RESULTS

A total of 22 altered mitochondrial proteins were identified in complexes I to V. Ten and 12 were found in complex I and complexes II to V, respectively. Five were mitochondrial encoded, and 17 were nuclear encoded. Most altered mitochondrial proteins in tissue specimens from dogs with naturally occurring DCM were associated with complexes I and V, whereas in tissue specimens from dogs subjected to rapid ventricular pacing, complexes I and IV were more affected. In the experimentally induced form of DCM, only nuclear-encoded subunits were changed in complex I. In both disease groups, the 22-kd subunit was downregulated.

CONCLUSIONS AND CLINICAL RELEVANCE

Natural and induced forms of DCM resulted in altered mitochondrial protein expression in complexes I to V. However, subcellular differences between the experimental and naturally occurring forms of DCM may exist.

Characterization of canine mitochondrial protein expression in natural and induced forms of idiopathic dilated cardiomyopathy

OBJECTIVE

To map canine mitochondrial proteins and identify qualitative and quantitative differences in heart mitochondrial protein expression between healthy dogs and dogs with naturally occurring and induced dilated cardiomyopathy (DCM).

SAMPLE POPULATION

Left ventricle samples were obtained from 7 healthy dogs, 7 Doberman Pinschers with naturally occurring DCM, and 7 dogs with induced DCM.

PROCEDURES

Fresh and frozen mitochondrial fractions were isolated from the left ventricular free wall and analyzed by 2-dimensional electrophoresis. Protein spots that increased or decreased in density by >or= 2-fold between groups were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry or quadrupole selecting, quadrupole collision cell, time-of-flight mass spectrometry.

RESULTS

Within narrow pH gradients of control canine heart mitochondrial samples, a total of 1,528 protein spots were revealed. Forty subunits of heart mitochondrial proteins that differ significantly from control tissues were altered in tissue specimens from dogs with naturally occurring and induced forms of DCM. The most affected heart mitochondrial proteins in both groups were those of oxidative phosphorylation (55%). Upregulation of manganese superoxide dismutase was suggestive of heart oxidative injury in tissue specimens from dogs with both forms of DCM. Evidence of apoptosis was associated with overexpression of the heart mitochondrial voltage-dependent anion channel-2 protein and endonuclease G in tissue specimens from dogs with induced DCM.

CONCLUSIONS AND CLINICAL RELEVANCE

Alterations of heart mitochondrial proteins related to oxidative phosphorylation dysfunction were more prevalent in tissue specimens from dogs with induced or naturally occurring DCM, compared with those of control dogs.

Prospective screening for occult cardiomyopathy in dogs by measurement of plasma atrial natriuretic peptide, B-type natriuretic peptide, and cardiac troponin-I concentrations

OBJECTIVE

To evaluate the use of measuring plasma concentrations of atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), and cardiac troponin-I (cTnI) to detect dogs with occult dilated cardiomyopathy (DCM).

ANIMALS

118 client-owned dogs.

PROCEDURES

Dogs were prospectively examined by use of ECG; echocardiography; and evaluation of concentrations of ANP, BNP, and cTnI. Occult DCM was diagnosed by evaluation of echocardiographic left ventricular dimensions and detection of ventricular arrhythmias on ECG. Sensitivity and specificity of assays for measurement of plasma concentrations of ANP, BNP, and cTnI to detect dogs with occult DCM were determined.

RESULTS

Occult DCM was diagnosed in 21 dogs. A concentration of > 6.21 pg/mL for BNP had a sensitivity of 95.2% and specificity of 61.9% for identifying dogs with occult DCM. In contrast, concentrations of ANP and cTnI had relatively low predictive values.

CONCLUSIONS AND CLINICAL RELEVANCE

Blood-based screening for occult DCM in dogs can be accomplished by use of a BNP assay. Additional studies should be performed to optimize this method of screening dogs to detect occult DCM.

Physiologic VDD versus nonphysiologic VVI pacing in canine 3rd-degree atrioventricular block

Historically, ventricular demand, nonphysiologic (VVI) pacing has been the most commonly used modality to treat 3rd-degree atrioventricular (AV) block. The goal of this study was to determine the feasibility of using a commercial, single-lead, physiologic (VDD) pacemaker in dogs with 3rd-degree AV block. Furthermore, we hoped to characterize and identify differences in the radiographic, echocardiographic, neurohormonal, and quality of life consequences of physiologic versus nonphysiologic pacing. We evaluated 10 dogs during a 12-week crossover study. Acutely, rate-matched physiologic pacing reduced pulmonary capillary wedge pressure by 19% compared with nonphysiologic pacing. VDD pacing significantly reduced left atrial size normalized to body weight, left atrial-to-aortic root ratio, and left ventricular end-systolic dimension and increased fractional shortening, aortic Doppler velocity, cardiac output, and stroke volume compared with VVI pacing. Variable rate VDD pacing resulted in a significantly slower heart rate (HR) during echocardiography than fixed-rate (100 bpm) VVI pacing. AV synchronous pacing reduced circulating N-terminal proatrial natriuretic peptide (ANP), norepinephrine (NOR), and epinephrine (EPI) concentrations compared with asynchronous pacing. There were no significant differences in systemic blood pressure, thoracic radiographs, or owner-perceived quality of life. The median percentage of AV synchronous pacing during the VDD modality was 99.8% (range, 1.2 to 99.9%). This study confirms the potential to achieve physiologic pacing with a commercial, single-lead system in dogs. VDD pacing improved hemodynamics and neurohormonal profiles over asynchronous pacing although the long-term clinical benefits of these changes remain to be determined.

ASSESSMENT OF CARDIAC CHAMBER SIZE USING ANATOMIC M-MODE

Anatomic M-mode (AMM) is an echocardiographic technique that is capable of generating M-mode studies from two-dimensional (2D) cine loops. Unlike conventional M-mode (CMM) whose scan line must lie along the axis of the ultrasound signal, AMM produces M-mode studies independent of the orientation of the ultrasound beam. We sought to determine the ability of AMM to measure cardiac dimensions in normal dogs and to assess the accuracy and variability of AMM and CMM vs. 2D measurements. Thirty-eight healthy dogs underwent physical exam and 2D, CMM, and AMM echocardiographic studies. The end-diastolic and end-systolic dimension of the left ventricle and the diameter of the left atrium (LAD) and aortic root were evaluated from the right parasternal short- and long-axis views. Results of the AMM and CMM study were compared with the 2D study via linear regression and calculation of a coefficient of correlation. AMM increased the level of correlation with both the left ventricular dimensions and LAD. Bland-Altman analysis revealed that AMM increased the level of agreement with 2D measurements and CMM greatly underestimated LAD vs. AMM. In healthy dogs, cardiac AMM measurements are associated with greater accuracy and less variability than CMM. AMM has the potential to improve quantification of cardiac dimensions.

Measurements of plasma endothelin immunoreactivity in healthy cats and cats with cardiomyopathy

Plasma concentrations of endothelin-1 (ET-1), the most potent endogenous pressor substance discovered to date, are abnormally high in humans with congestive heart failure (CHF), and they correlate with the degree of functional impairment. We sought first to validate a human sandwich ELISA kit that targets that portion of the amino acid sequence that is identical in cats. The assay demonstrated linearity (R2 = .9968) and parallelism (P = .5339), recovery of spiked human ET-1 in cat plasma averaged 98.7%, and intraassay precision had a coefficient of variation <10%. We subsequently determined ET-1 immunoreactivity in healthy cats and in cats with myocardial disease with and without CHF, systemic thromboembolism (STE), or both. Plasma ET-1 immunoreactivity was measured in 12 healthy cats and in 28 cats with primary myocardial disease, including hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), or restrictive or unclassified cardiomyopathy (RCM and UCM), respectively. Plasma ET mean (95% CI) concentrations were 0.777 (0.6536-0.924) fmol/mL in the control cats, 1.427 (0.922-2.209) fmol/mL in 12 cats with cardiomyopathy (HCM = 11, RCM/UCM = 1) but without CHF or evidence of STE, and 2.360 (1.666-3.343) fmol/mL in 16 cats with cardiomyopathy (HCM = 8, RCM/UCM = 7, DCM = 1) and CHF (n = 15) or STE (n = 4). Plasma immunoreactivity of ET-1 was significantly higher in cats with myocardial disease without CHF/STE versus normal cats (P < .05) and in cats with myocardial disease with CHF/STE versus normal cats (P < .001).

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.

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).

Echocardiographic estimation of mean left atrial pressure in a canine model of acute mitral valve insufficiency

High mean left atrial pressure (MLAP) due to canine degenerative mitral valve disease is associated with clinically relevant morbidity and mortality. The ability to noninvasively measure MLAP would assist in the diagnosis and treatment of disease. Doppler echocardiography allows measurement of early transmitral blood flow (E) and the velocity of the mitral valve annulus (Ea). The ratio of early mitral inflow velocity to early mitral annular velocity (E: Ea) correlates well with MLAP in human subjects. We sought to determine the ability of E: Ea to predict MLAP in dogs with experimentally induced mitral regurgitation. Nine anesthetized purpose-bred dogs underwent placement of a Swan-Ganz catheter into the left atrium and recording of MLAP. Simultaneous transthoracic echocardiographic and hemodynamic studies were performed after acute chordae tendineae rupture and during IV infusion with nitroprusside (2.5-5.0 microg x kg(-1) x min(-1)) or hydralazine (1-1.5 mg/kg). Mitral regurgitant fraction, measured by single-plane angiography and thermodilution, ranged from 17% to 81%. MLAP increased from 5.4 +/- 2.5 mm Hg to 17.4 +/- 9.4 mm Hg after creation of mitral valve regurgitation (MR; P = .018). Forty sets of echocardiographic measurements were obtained from 7 dogs, and E, as well as E: Ea, were linearly related to MLAP. The R2 value for the linear regression equation containing E: Ea as the dependent variable (0.83) was greater than that for E (0.73). The 95% confidence intervals were calculated for predicting MLAP = 20 mm Hg from E:Ea, and E:Ea >9.1 or <6.0 indicated a 95% probability that MLAP was >20 mm Hg or <20 mm Hg, respectively. Echocardiography can be used to predict MLAP in isoflurane-anesthetized dogs with experimentally induced acute mitral valve insufficiency.

Neuroendocrine evaluation of cardiac disease

Current evidence favors the view that regardless of etiology, there is a predictable sequence of neuroendocrine activation that operates in most dogs and cats with progressive heart disease and that it is largely, but not entirely, independent of etiology. The natriuretic peptides and sympathetic nervous system seem to be early responders to developing cardiac and hemodynamic perturbations in both species. BNP plays a particularly prominent role in cats, possibly as a reflection of disease etiology. Shortly thereafter, plasma endothelin concentrations rise, reflecting the impact of the hemodynamic alterations on the vasculature. Endothelin and the natriuretic peptides directly suppress plasma renin release but have divergent effects on aldosterone. Activation of the tissue RAAS may operate early on to further the progression of heart failure, but evidence of plasma RAAS activation occurs comparatively late and near the time of development of overt CHF. Finally, in animals with severe CHF that are prone to hypotension,vasopressin levels may also rise, contributing to the retention of free water and congestion that is refractory to diuretics. Although oversimplified, this scenario seems to be consistent with data obtained in human, canine, and feline patients. These observations provide some impetus for evaluating ACE inhibitors in cats and beta-receptor-blocking drugs in dogs and cats. Perhaps we are also a little closer to identifying useful biochemical markers that can aid in the diagnosis of heart disease, guide therapy, and improve our understanding of the biologic processes occurring in our patients.

Immunohistochemistry of atrial and brain natriuretic peptides in control cats and cats with hypertrophic cardiomyopathy

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are cardiac hormones involved in electrolyte and fluid homeostasis. Our laboratory has investigated the use of ANP and BNP as diagnostic markers of cardiac disease in cats. We hypothesize that the cardiac distribution of ANP and BNP increases in cats with hypertrophic cardiomyopathy (HCM). Accordingly, we evaluated the immunohistochemical distribution of ANP and BNP in hearts of four cats with naturally occurring HCM relative to five healthy controls. Indirect immunoperoxidase was performed with polyclonal immunoglobulin G against feline ANP (1-28) and proBNP (43-56). In control cats, ANP and BNP immunoreactivity was restricted to the atria. Staining for both peptides was most intense adjacent to the endocardial surface. Auricles stained more diffusely than atria for both peptides. The interstitial capillaries and nerve fibers within the heart were positive only for BNP. Atrial immunoreactivity for ANP and BNP was more diffuse and had a less distinctly layered pattern in HCM than in control cats. Ventricular cardiomyocytes of HCM cats were negative for ANP but stained lightly and diffusely for BNP. The capillaries and nerve fibers remained positive for BNP. We conclude that in cats with HCM, the cardiac distribution of ANP and BNP is more diffuse in the atria and that novel expression of BNP in the ventricular cardiomyocytes occurs.

Juvenile hyperthyroidism in a cat

An 8-month-old, male domestic shorthaired cat presented for chronic weight loss, intermittent dyspnea, chronic diarrhea, hyperactivity, and weakness. The cat had a palpable thyroid nodule and increased serum total thyroxine and 3,5,3' triiodothyronine levels. The cat was diagnosed with hyperthyroidism, and a unilateral thyroidectomy was performed followed by radioactive iodine at a later date. The clinical signs resolved following radioactive iodine, and the cat subsequently developed clinical hypothyroidism.

Evaluation of canine congenital heart disease using an echocardiographic algorithm

Evaluation of canine congenital heart disease presents a diagnostic challenge to many ultrasonographers. To assist clinicians attempting to examine these patients, an echocardiographic algorithm containing the six most common canine congenital heart diseases (i.e., patent ductus arteriosus, subaortic stenosis, pulmonic stenosis, ventricular septal defect, tricuspid dysplasia, and tetralogy of Fallot) is presented. The algorithm focuses on the underlying disease pathogenesis and the resultant changes in cardiac structure and function that can be readily identified during echocardiographic examination. Use of this algorithm provides a framework from which the ultrasonographer gains both experience and confidence in diagnosing congenital heart disease via echocardiography. This algorithm is supported by a number of still figures within the article as well as real-time echocardiographic images available for viewing at AAHA's website, www.aahanet.org.

Cardiopulmonary evaluation of the use of medetomidine hydrochloride in cats

OBJECTIVE

To evaluate the cardiovascular effects of the alpha2-adrenergic receptor agonist medetomidine hydrochloride in clinically normal cats.

ANIMALS

7 clinically normal cats.

PROCEDURE

Cats were anesthetized with isoflurane, and thermodilution catheters were placed for measurement of central venous, pulmonary, and pulmonary capillary wedge pressures and for determination of cardiac output. The dorsal pedal artery was catheterized for measurement of arterial blood pressures and blood gas tensions. Baseline variables were recorded, and medetomidine (20 microg/kg of body weight, IM) was administered. Hemodynamic measurements were repeated 15 and 30 minutes after medetomidine administration.

RESULTS

Heart rate, cardiac index, stroke index, rate-pressure product, and right and left ventricular stroke work index significantly decreased from baseline after medetomidine administration, whereas systemic vascular resistance and central venous pressure increased. However, systolic, mean, and diastolic arterial pressures as well as arterial pH, and oxygen and carbon dioxide tensions were not significantly different from baseline values.

CONCLUSIONS AND CLINICAL RELEVANCE

When administered alone to clinically normal cats, medetomidine (20 microg/kg, IM) induced a significant decrease in cardiac output, stroke volume, and heart rate. Arterial blood pressures did not increase, which may reflect a predominant central alpha2-adrenergic effect over peripheral vascular effects.

Practices and outcome of artificial cardiac pacing in 154 dogs

Artificial pacing (AP) is a treatment for symptomatic bradyarrhythmias unresponsive to medical therapy. This retrospective study was designed to define the practices and outcome of AP in dogs at 7 referral institutions participating in the Companion Animal Pacemaker Registry and Repository (CANPACERS). The indications, implantation techniques, complications, long-term outcome, and owner satisfaction were examined. One hundred fifty-four dogs were identified as undergoing AP from January 1, 1991, to January 1, 1996. Third-degree atrioventricular (AV) block (n = 91; 59%) and sinus node dysfunction (n = 45; 29%) were the most common indications for AP Transvenous endocardial AP systems were implanted in 136 dogs (88%), and epicardial systems were implanted in 18 (12%). Complications associated with AP were reported in 84 dogs (55%). Major complications occurred in 51 dogs (33%), including dislodgement of the pacing lead (n = 15; 10%), generator failure (n = 10; 6%), cardiac arrest during implantation (n = 9; 6%), and infection (n = 7; 5%). Minor complications occurred in 47 dogs (31%), including seroma formation (n = 18; 12%), muscle twitch (n = 17; 11%), and inconsequential arrhythmias (n = 15; 10%). Fourteen dogs (9%) experienced both major and minor complications. Survival analysis revealed 1-, 2-, and 3-year survival rates of 70, 57, and 45%, respectively. Age and presence of preexisting congestive heart failure (CHF) had a negative effect on survival (P = .001). Sixty percent of dogs with preexisting CHF died within 1 year of implantation, whereas 25% of dogs without heart failure died during the same period. Owners rated their satisfaction with the procedure as high in 80% of the dogs.

Paraneoplastic thrombocytosis-induced systemic thromboembolism in a cat

A six-year-old cat presented with clinical signs consistent with distal aortic thromboembolism while clinical signs of cardiovascular disease were absent. Diagnostics, including thoracic radiographs, electrocardiography, and echocardiography revealed no cardiovascular anomalies. Thoracic radiographs revealed multifocal pulmonary lesions consistent with neoplasia. Complete blood cell count demonstrated a marked thrombocytosis, leukopenia, and neutropenia. Histopathology of the pulmonary lesions confirmed multiple bronchoalveolar carcinomas. Myelodysplasia with megakaryocytic hyperplasia and ineffective myelopoiesis was noted on bone-marrow histopathology from multiple sites. The absence of other causes suggested a paraneoplastic thrombocytosis. The diagnosis of paraneoplastic thrombocytosis-induced thromboembolism was made due to the lack of underlying cardiac disease and the presence of a marked thrombocytosis. The presence of thrombocytosis and thromboembolism associated with neoplasia is discussed.