Resting and dobutamine stress test induced serum concentrations of brain natriuretic peptide in German Shepherd dogs

Studies of clinical uses of brain natriuretic peptide (BNP) represent one of the most important advances in cardiology since the introduction of echocardiography as a clinical diagnostic procedure. Defining the clinical potential of BNP in canine cardiology has not been completed yet. The aim of this study is to measure BNP concentrations in healthy German Shepherd dogs of different ages as a baseline in resting and when conventional protocol of the dobutamine stress test (DST) is applied to dogs. Concentrations of BNP were measured in blood serum by the radioimmunoassay method. The values of BNP concentrations were compared to cardiac parameters obtained by standard cardiac diagnostic procedures (radiology, electrocardiography and echocardiography). No significant differences in serum BNP concentrations existed in dogs of different ages. A statistically significant increase in BNP concentrations was registered after DST. These changes in BNP concentrations were related to ST/T electrocardiographic changes, and correlated to changes in the left ventricular internal diameter in systole (LVESD). These data suggest that BNP is not increased in aged dogs with normal cardiac systolic function and renal function, and that myocardial ischemia leads to a significant increase in BNP concentrations even in dogs with normal left ventricular function.     

Usefulness of dobutamine stress tests for detection of cardiac abnormalities in dogs with experimentally induced early left ventricular dysfunction

OBJECTIVE: To determine whether dobutamine stress tests (DST) can be used to detect cardiac dysfunction in dogs with early left ventricular dysfunction (ELVD) induced by rapid right ventricular pacing (RRVP). ANIMALS: 7 adult male Beagles. PROCEDURE: A pacemaker was surgically implanted in each dog at the level of the right ventricular apex. Electrocardiography, Doppler sphygmomanometry, and Doppler echocardiography were performed before and during a DST prior to activation of the pacemaker and every 3 to 4 days during the period of RRVP. Dobutamine stress tests were performed by infusing dobutamine at incremental dosages ranging from 12.5 to 42.5 microg/kg of body weight/min. RESULTS: Clinical signs of congestive heart failure were not observed during the pacing period. However, all dogs developed ELVD associated with significant changes in values for most Doppler echocardiographic variables obtained prior to DST Adverse cardiac effects were not detected during DST. Most Doppler echocardiographic indices of cardiac function were significantly altered in response to dobutamine infusion during the pacing period, compared with prepacing values. However, a dobutamine-induced 2-fold increase in cardiac output was maintained. CONCLUSIONS AND CLINICAL RELEVANCE: Dobutamine stress tests can be safely performed in dogs with experimentally induced ELVD. Dobutamine stress tests may be a sensitive, noninvasive diagnostic method, complementary to standard clinical examinations, for detection of early cardiac dysfunction in dogs asymptomatic for dilated cardiomyopathy.     

Assessment of plasma brain natriuretic peptide concentration in Boxers with arrhythmogenic right ventricular cardiomyopathy

OBJECTIVE: To determine whether Boxers with a clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC) have increased plasma concentrations of brain natriuretic peptide (BNP), compared with concentrations in clinically normal dogs. ANIMALS: 13 Boxers with ARVC, 9 clinically normal Boxers, 10 clinically normal non-Boxer dogs, and 5 hound dogs with systolic dysfunction. PROCEDURE: All Boxers were evaluated via 24-hour ambulatory electrocardiography and echocardiography; the number of ventricular premature contractions (VPCs) per 24 hours was assessed. Hound dogs with cardiac pacing-induced systolic dysfunction (positive control dogs) and clinically normal non-Boxer dogs (negative control dogs) were evaluated echocardiographically. Three milliliters of blood was collected from each dog for measurement of plasma BNP concentration by use of a radioimmunoassay. RESULTS: Mean +/- SD plasma BNP concentration for the ARVC-affected Boxers, clinically normal Boxers, negative control dogs, and positive control dogs was 11.0 +/- 4.6 pg/mL, 7.9 +/- 3.2 pg/mL, 11.5 +/- 4.9 pg/mL, and 100.8 +/- 56.8 pg/mL, respectively. Compared with findings in the positive control group, plasma BNP concentration in each of the other 3 groups was significantly different. There was no significant difference in BNP concentration between the 2 groups of Boxers. A significant correlation between plasma BNP concentration and number of VPCs per 24 hours in the ARVC-affected Boxers was not identified. CONCLUSIONS AND CLINICAL RELEVANCE: A significant difference in BNP concentration between Boxers with ARVC and clinically normal Boxers was not identified. Results suggest that BNP concentration may not be an indicator of ARVC in Boxers.     

Hormonal response to dobutamine cardiac stress testing in a conscious canine model of early left ventricular dysfunction induced by chronic rate overload

The aims of this study were to investigate (1) hormonal activation before and during dobutamine cardiac stress testing (DST) in a canine model of early left ventricular dysfunction (ELVD) induced by rapid right ventricular pacing (RRVP) and (2) the relationship between this hormonal profile and carnitine concentrations.Before the pacing period, the 6 dogs were assigned to 2 groups according their baseline total plasma carnitine concentration. A DST was performed on each dog before activation of the pacemaker and every 3 to 4 days during development of 3 progressive stages of ELVD (stages 1, 2 and 3). Plasma atrial natriuretic factor (ANF), angiotensin II (ANG II) and endothelin-1 (ET-1) levels were measured at the start and at the end of each DST. Effects of ELVD, DST and plasma carnitine concentration on these measurements were tested.The RRVP induced a significant increase of ANF and ANG II and a non significant trend toward increase of ET-1 in all dogs.Before the pacing period, ANF remained constant during the DST in dogs with normal total plasma carnitine concentration, while it significantly decreased in dogs with low total plasma carnitine concentration. Dobutamine stress testing induced a significant decrease in ANF in all dogs in ELVD. Dobutamine infusion induced a significant increase in ANG II in all dogs before as well as during the pacing period while ET-1 was unchanged.These results suggest that investigation of the hormonal profile before and after a dobutamine challenge might provide important diagnostic information in dogs with asymptomatic or mildly symptomatic cardiac dysfunction of different origins.     

Peri-operative changes in echocardiographic measurements and plasma atrial and brain natriuretic peptide concentrations in 3 dogs with patent ductus arteriosus

Peri-operative changes in echocardiographic measurements and plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were investigated for 1 month in 3 dogs with patent ductus arteriosus (PDA). Post-operative left ventricular end-diastolic dimention and fractional shortening decreased in all cases. Pre-operatively increased plasma ANP concentrations reduced dramatically after the operation. Peri-operative changes in plasma BNP levels had slightly S-shaped curves in all cases. These observations suggest that post-operative responsiveness of ANP and cardiac function are rapid in comparison with cardiac morphological changes, and BNP has a different pathophysiological significance from ANP in dogs with PDA.     

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.     

Evaluation of NT-pro BNP and CT-ANP as markers of concentric hypertrophy in dogs with a model of compensated aortic stenosis

Background: Serum C-terminal atrial natriuretic peptide (CT-ANP) and N-terminal pro B-type natriuretic peptide (NT-pro BNP) concentrations have not been measured serially in dogs with chronic pressure overload of the heart.
Hypothesis: We investigated whether serial evaluation of CT-ANP and NT-pro BNP concentrations is a useful guide to the risk of cardiac remodeling in dogs with a model of aortic stenosis.
Animals: Six male Beagles.
Methods: After anesthesia, the aorta was constricted with a polyester band and mean left ventricular systolic pressure (LVPs) was 50 mmHg above baseline. Echocardiographic and intracardiac catheter examinations and blood sampling were performed before surgery and 3 and 6 months after surgery.
Results: LVP and left ventricular end-diastolic pressure (LVEDP) were significantly higher at 6 months. Compared with baseline, end-diastolic intraventricular septum thickness (IVSd), left ventricular posterior wall thickness (LVPWd), and relative wall thickness (RWT) were significantly increased 3 and 6 months after aortic constriction. Serum CT-ANP concentrations were increased significantly at 3 months and serum NT-pro BNP concentrations were significantly higher 3 and 6 months after aortic constriction. Serum NT-pro BNP concentration was significantly correlated with LVEDP and IVSd whereas serum CT-ANP concentration was not correlated with any measurement. Stepwise regression analysis showed that LVEDP, IVSd, and RWT could predict serum NT-pro BNP.
Conclusions and Clinical Importance: This study indicated the differential regulation of NT-pro BNP and CT-ANP concentrations during pressure overload. NT-pro BNP assay may be used as an additional screening method to stratify early-stage ventricular remodeling because of aortic constriction.     

Neurohormonal, hemodynamic, and electrocardiographic evaluations of healthy dogs receiving long-term administration of doxorubicin

OBJECTIVE: To evaluate diagnostic testing that could be used to establish an early diagnosis of cardiotoxicosis induced by long-term administration of doxorubicin. ANIMALS: 13 adult mixed-breed dogs. Procedures-7 dogs were administered doxorubicin chloride (30 mg/m(2), IV, q 21 d for 168 days [cumulative dose, 240 mg/m(2)]), and 6 dogs received saline (0.9% NaCl) solution (5 mL, IV, q 21 d for 168 days; control group). Echocardiography, ECG, arterial blood pressure, plasma renin activity (PRA), and plasma concentrations of norepinephrine and brain natriuretic peptide (BNP) were assessed before each subsequent administration of doxorubicin and saline solution. RESULTS: Dogs that received doxorubicin had a significant decrease in R-wave amplitude, compared with values for the control group, from 30 to 210 mg/m(2). Doxorubicin-treated dogs had decreases in fractional shortening and left ventricular ejection fraction evident as early as 30 mg/m(2), but significant differences between groups were not detected until 90 mg/m(2)was reached. There was also a significant increase in PRA (>or= 120 mg/m(2)) and left ventricular end-systolic and end-diastolic dimensions (>or= 60 and >or= 180 mg/m(2), respectively). Systemic arterial pressure, remaining echocardiographic variables, and concentrations of norepinephrine and BNP had significant variations, but of no clinical importance, during doxorubicin administration. CONCLUSIONS AND CLINICAL RELEVANCE: Doxorubicininduced cardiotoxicosis developed at 120 mg/m(2), but there were no clinical signs of dilated cardiomyopathy or congestive heart failure. Echocardiography and determination of PRA were able to detect early cardiac alterations during the development of dilated cardiomyopathy, despite apparently differing degrees of sensitivity to development of doxorubicin-induced cardiotoxicosis.     

Evaluation of left ventricular function with cardiac magnetic resonance imaging and echocardiography after administration of dobutamine and esmolol in healthy beagle dogs

Unlike echocardiography, cardiac magnetic resonance imaging (cardiac MRI) results in a near-exact assessment of cardiac structures and function. However, most veterinary studies have focused on dogs with normal cardiac function. We hypothesized that there would be significant differences in cardiac measurements between cardiac MRI and echocardiography when left ventricular (LV) function was abnormal. This study was undertaken to compare measurements of LV function produced by cardiac MRI and echocardiography in dogs whose LV function was altered by pharmacological agents. This study was conducted with six healthy beagle dogs. We increased left ventricular contractility by administration of dobutamine; we decreased cardiac contractility with esmolol. Stroke volume measurements were made by using both cardiac MRI and echocardiography under seven different conditions with general anesthesia: control, three doses of esmolol (100, 200, and 500 µg/kg/min), and three doses of dobutamine (10, 20, and 50 µg/kg/min). Experiments involving each condition were conducted at least 1 week apart. When LV contractility was normal, ejection fraction (EF) and stroke volume (SV), as measured by echocardiography and cardiac MRI, were not significantly different. However, when contractility was changed by pharmacological agents, EF and SV were overestimated by echocardiography, compared to MRI. Evaluation of cardiac function in patients treated with pharmacological agents should be conducted carefully because EF and SV measured by echocardiography can be overestimated, compared with EF and SV obtained by cardiac MRI.     

Myocardial Function of Horses Under Sedation with Romifidine Using Two-Dimensional Speckle Tracking

Two-dimensional speckle tracking echocardiography (2DST) provides the assessment of the left ventricle deformation parameters strain (St) and strain rate (SR). The objective of this study was to evaluate St and SR under the influence of romifidine in healthy horses and horses affected with heart disease. The study subjects were 45 privately owned horses. Valvular insufficiencies were identified by color Doppler in 21 out of 45 horses. Dimensional changes were identified in 13 of these 21 horses. These dimensional changes included dilatations of the left ventricle (130 ± 8.95 mm) and/or the left atrium (141 ± 4.8 mm). The other 24 horses were without echocardiographic findings and had normal heart dimensions. Based on clinical signs, echo-, and electrocardiographic examinations, 24 horses were categorized as group 1 (healthy), 13 as group 2 (heart disease without dimensional changes), and 8 as group 3 (heart disease with dimensional changes). The radial St and SR were assessed in the left ventricular free wall and the interventricular septum using 2DST. After application of romifidine, a significant reduction of St and the systolic peak of SR were found in all three groups. Group 3 showed the most significant reduction of these parameters (41.5%). The reduction of St and SR under romifidine showed a reduced myocardial function, which is more obvious in horses with cardiac dilatation. It can be assumed that heart disease with myocardial dilatation leads to decreasing myocardial function, which becomes more obvious after romifidine application and of clinical importance in horses with severe heart disease and cardiac dilatation.     

QUANTITATIVE CROSS-SECTIONAL ECHOCARDIOGRAPHY IN THE NORMAL DOG

Two-dimensional echocardiography was performed on 18 unanesthetized, normal dogs (4.5 to 30 kg). Measurements of wall thickness, intracavitary dimensions, and cross-sectional area of the left atrium, left ventricle, and aorta were made. Satisfactory data were obtained from 17 dogs, and were used to determine normal values. Normal data were tested for significant correlation to body weight (kg) by linear regression. Repeatability was studied in six dogs examined, on three separate occasions, during a 5-day period. Differences between values obtained on different days were evaluated by analysis of variance.
Satisfactory qualitative echocardiograms were repeatedly obtained by using consistent sites of transducer placement and by identifying internal cardiac structures. These tomographic planes were highly reproducible, with only ventricular length, and some views of the ventricular septum, showing statistically significant (P < 0.05) differences. Almost all linear and area measurements were significantly correlated to body size, while most indices of left ventricular function were independent of body weight. Dimensions obtained from the left and right parasternal position were nearly identical. Cross-sectional echocardiography allows repeatable assessment of cardiac anatomy, and it should prove useful for identification and quantitation of heart disease in the dog.     

Changes of cardiac function in diabetic dogs

Objective

This study aimed to evaluate cardiac function and compare the concentration of cardiac biomarkers including cardiac troponin I (cTnI), galectin-3 (Gal-3), and N-terminal pro B-type natriuretic peptides (NT-proBNP) in diabetic and control dogs.

Influence of detomidine on echocardiographic function parameters and cardiac hemodynamics in horses with and without heart murmur

30 warmblood horses were examined before and after sedation with 20 micrograms/kg BW detomidine, to determine changes of cardiac function parameters, using B-mode, M-mode and Doppler echocardiography. 15 horses showed a heart murmur, but no clinical signs of cardiac heart failure, 15 horses had neither a heart murmur nor other signs of cardiac disease. After sedation with detomidine we could recognise a significant increase of end-diastolic left atrium diameter, an increase of end-systolic left ventricular diameter and aortic root diameter. The end-systolic thickness of papillary muscle and interventricular septum showed a decrease. Fractional shortening and amplitude of left ventricular wall motion was decreased after sedation. The mitral valve echogram revealed a presystolic valve closure and an inflection in the Ac slope (B-notch) in xy horses before sedation. Both increased after sedation with detomidine. Doppler echocardiography showed a decrease of blood flow velocity and velocity time integral (VTI) in the left and right ventricular outflow tract after sedation. Regurgitant flow signals were intensified following sedation in xy horses, especially at the mitral valve.     

Clinical evaluation of left ventricular moderator band in 12 dogs

We retrospectively examined clinical data for 12 dogs in which echocardiography revealed the presence of left ventricular moderator bands (LMB). Physical examinations, electrocardiography and echocardiography revealed slight cardiac murmurs, increasing QRS complex and left ventricular turbulent flow (6 of the dogs), respectively. No differences were observed with respect to gender, and no specific clinical symptoms or types of dog that frequently develop this disorder were found.     

MITRAL ANNULUS MOTION AS DETERMINED BY M-MODE ECHOCARDIOGRAPHY IN NORMAL DOGS AND DOGS WITH CARDIAC DISEASE

M-mode echocardiography was used to assess apical mitral annulus motion (MAM) in 103 normal dogs and 101 dogs with cardiac disease, to obtain information on systolic left ventricular long axis function. In normal dogs, a close relationship was found between MAM and body weight (r = 0.80, P < 0.001). There was a weak correlation between MAM and heart rate (r = -0.25, P < 0.05), but no correlation between MAM and age or left ventricular shortening fraction (P > 0.05). Mean MAM (95% confidence intervals) were established for normal dogs of differing body weight, and were 0.70 cm (0.65 to 0.75) in dogs < 15 kg, 1.08 cm (1.03 to 1.13) in dogs weighing 15 to 40 kg, and 1.51 cm (1.21 to 1.81) in dogs > 40 kg. "Cut-off" values to define decreased MAM for normal dogs of differing body weight were 0.45 cm (dogs < 15 kg), 0.80 cm (dogs 15-40 kg), and 1.20 cm (dogs > 40 kg). In dogs with cardiac disease, median MAM was normal in mitral valve endocardiosis or aortic stenosis, but significantly decreased (P < 0.05) in dilated cardiomyopathy. All dogs with mitral valve endocardiosis (n = 54) or aortic stenosis (n = 26) had MAM above the above-mentioned "cut-off" values, suggesting normal or increased left ventricular longitudinal systolic shortening, whereas 81% (17/21) of dogs with dilated cardiomyopathy had MAM below the "cut-off" value, indicating decreased long axis systolic function. It is concluded that MAM may be used to evaluate systolic left ventricular long axis performance in dogs and may add useful information on global left ventricular contraction dynamics.     

Cardiovascular effects of acute pulmonary obstruction in horses with recurrent airway obstruction

BACKGROUND: Recurrent airway obstruction (RAO) is common in horses. Although pulmonary artery (PA) pressure increases during RAO, cardiac function in horses with RAO has received limited attention. HYPOTHESIS: The purpose of this study was to noninvasively determine the cardiovascular effects of acute pulmonary obstruction (APO) in horses with RAO and their reversibility. ANIMALS: Five geldings with RAO, inducible by exposure to moldy hay, were studied. METHODS: Pulmonary mechanics, echocardiography, serum troponin I concentrations, arterial blood gases, and hematocrit were obtained before and after 7 days of APO. Heart rate, PA diameter and flow characteristics, right and left ventricular luminal dimensions and wall thicknesses, global cardiac performance, and evidence of myocardial damage were evaluated. Pulmonary mechanics and echocardiography were reevaluated during remission. RRESULTS: Severe, transient APO did not induce chronic cor pulmonale in horses, because cardiac anatomy and function were normal between episodes. An acute episode of APO produced anatomical and functional cardiac changes in both the right and left heart (including increased PA diameter, abnormal septal motion, and decreased left ventricular diameter and estimated stroke volume), possibly because of the development of pulmonary hypertension, without apparent myocardial damage. The decrease in stroke volume was offset by the increase in heart rate. CONCLUSIONS AND CLINICAL IMPORTANCE: With APO of 7 days' duration, cardiovascular abnormalities and the functional airway changes that produce them are reversible when the offending allergens are removed.     

Noninvasive estimation of cardiac systolic function using continuous-wave Doppler echocardiography in dogs with experimental mitral regurgitation

OBJECTIVE: To evaluate the feasibility of noninvasive estimation of cardiac systolic function using transthoracic continuous-wave Doppler echocardiography in dogs with mitral regurgitation. PROCEDURE: Seven mongrel dogs with experimental mitral regurgitation were used. Left ventriculography and measurement of pulmonary capillary wedge pressure were performed under inhalational anaesthesia. A micromanometer-tipped catheter was placed into the left ventricle and transthoracic echocardiography was carried out. The peak rate of left ventricular pressure rise (peak dP/dt) was derived simultaneously by continuous-wave Doppler and manometer measurements. The Doppler-derived dP/dt was compared with the catheter-measured peak dP/dt in the dogs. RESULTS: Classification of the severity of mitral regurgitation in the dogs was as follows: 1+, 2 dogs; 2+, 1 dog; 3+, 2 dogs; 4+, 1 dog; and not examined, 1 dog. We were able to derive dP/dt from the transthoracic continuous-wave Doppler echocardiography in all dogs. Doppler-derived dP/dt had a significant correlation with the catheter-measured peak dP/dt (r = 0.90, P < 0.0001). CONCLUSION: It was demonstrated that transthoracic continuous-wave Doppler echocardiography is a feasible method of noninvasive estimation of cardiac systolic function in dogs with experimental mitral regurgitation and may have clinical usefulness in canine patients with spontaneous mitral regurgitation.     

Tissue Doppler Imaging and Two-Dimensional Speckle Tracking of Left Ventricular Function in Healthy Horses After Clenbuterol Application

The cardiac effects of high dosages of the ß²-adrenergic agent clenbuterol have been the focus of several histological, biochemical and echocardiographic studies in the past. Possible effects of a therapeutic dosage on myocardial contractility and velocities have not been evaluated using tissue Doppler imaging (TDI) and two-dimensional speckle tracking (2DST) in equine medicine. Twenty-five healthy horses were treated over 14 days with clenbuterol in a normal dosage (0.8 μg/kg every 12 hours). Before and after the treatment, an echocardiographic examination was performed using B-mode, M-mode, color flow Doppler, and tissue Doppler imaging (TDI). In all horses, the radial and circumferential myocardial functions were recorded in the right parasternal short-axis view (SAX). Pulsed-wave (PW) and color TDI were used for evaluation of peak and mean myocardial velocities; myocardial deformation was documented in 2DST. An improvement of diastolic function after clenbuterol treatment was demonstrated by a significant increase of the early diastolic radial wall motion velocity (E_m) in all myocardial sections except the right ventricular free wall (RVFW) in TDI, as well as an increase of the E/A quotient in the left ventricular free wall (LVFW) and the interventricular septum (IVS). Shortened time intervals, in particular in the LVFW and a tendency of increase of all deformation parameters showed improved relaxation characteristics of the cardiac muscle after treatment. The results can be interpreted as beginning physiologic cardiac hypertrophy due to clenbuterol treatment. No signs of increased rigidity or reduced compliance of the heart muscle could be found at the applied dosage. This study demonstrates the sensitivity of TDI and 2DST in equine cardiology to detect myocardial remodeling before the appearance of obvious findings in conventional echocardiographic techniques. This technique can be used to detect pharmacologic effects on myocardial function.     

Electrocardiographic and echocardiographic features of trypanosomiasis in dogs inoculated with North American Trypanosoma cruzi isolates.

Purebred Beagles were inoculated with Trypanosoma cruzi isolates from a North American opossum or armadillo (Tc-W), and dog (Tc-D). Although Tc-D established infection in dogs, the dogs did not develop cardiac abnormalities. Dogs inoculated with Tc-W developed acute myocarditis associated with increases in P-R interval, atrioventricular block, depression of R wave amplitude and shifts in mean electrical axis. Echocardiograms were normal during this stage. Three Tc-W-inoculated dogs died during the acute stage. Following the acute stage, 5 of 8 Tc-W-inoculated dogs entered an indeterminate stage in which ECG changes were minor and echocardiograms were normal. Progression to the chronic stage in 5 of the 8 Tc-W-inoculated dogs was indicated by development of ventricular-based arrhythmias, mainly ventricular premature contractions, between postinoculation days 60 and 170. In some dogs, ventricular premature contractions were multifocal. Electrocardiographic abnormalities progressively degenerated to various forms of ventricular tachycardia. Worsening ECG coincided with loss of left ventricular function as measured by echocardiography. Mean percent ejection fraction and percentage of fractional shortening decreased to 63% and 52% of control values, respectively. The left ventricular free wall (LVFW) thickness decreased and % septal: % LVFW thickening ratio increased, indicating a relative preservation of septal wall motion and LVFW hypokinesis.     

Plication of the free wall of the left ventricle in dogs with doxorubicin-induced cardiomyopathy

OBJECTIVE: To evaluate plication of the free wall of the left ventricle, which reduces the left ventricular area and volume, as a method to improve the left ventricular systolic function without cardiopulmonary bypass. ANIMALS: 8 mixed-breed adult dogs. PROCEDURE: Dilated cardiomyopathy (DCM) was induced in each dog by administration of doxorubicin (30 mg/m2, i.v., q 21 d for 168 days).Two dogs died during induction of cardiomyopathy. Plication surgery was performed in 4 dogs. Two dogs did not ondergo to surgery (control group). Values for cardiac output (CO), 2-dimensional and M-mode echocardiography, arterial blood pressure, electrocardiography, blood cell counts, and serum biochemical analyses were recorded after induction of DCM (baseline) and 1, 2, 7, 15, 21, 30, 60, 90, 120, 150, and 180 days after plication surgery. Ambulatory ECG (Holter) recordings were conducted for 24 hours on the day of surgery. RESULTS: 1 dog died after plication surgery. The remaining dogs undergoing ventricular plication had a significant improvement in CO, ejection fraction, and fractional shortening and reductions of left ventricular area and volume after surgery. Electrocardiographic and Holter recordings revealed premature ventricular complexes, which resolved without treatment during the first week after surgery. Clinical condition of the control dogs declined, and these 2 dogs died approximately 40 days after induction of cardiomyopathy. CONCLUSIONS AND CLINICAL RELEVANCE: Plication of the free wall of the left ventricle improved left ventricular systolic function in dogs with doxorubicin-induced cardiomyopathy. Additional studies are needed to evaluate its application in dogs with naturally developing DCM.