Valved apico-aortic conduit for relief of left ventricular hypertension caused by discrete subaortic stenosis in dogs

A double-outlet left ventricle (LV), with a valved conduit interposed between the LV apex and the aorta, was created in 7 dogs with subaortic stenosis. Of 8 dogs in which the implantation was attempted, 1 died following thoracotomy but before conduit implantation could be performed, 1 died from hemorrhage 24 hours after surgery, 1 died from septicemia as a sequel to pneumonia 10 days after surgery, 1 died from "shock-lung" 4 days after surgery, and 4 were functionally normal 22, 12, 6, and 2 months after surgery. In the 7 dogs in which the implantation was completed, the mean LV to aorta (LV-Ao) pressure gradient was significantly (P less than 0.01) reduced by the implantation. Diastolic and systolic murmurs were detected over the prosthetic valve area in 3 of the 4 surviving dogs 1 to 4 days postoperatively, but the murmurs gradually decreased in intensity until they disappeared after 1 month. The 4 survivors had no angiographic evidence of prosthetic valve insufficiency at 2 months or at 1 year. In 3 of the survivors, the LV-Ao pressure gradients 2 months postoperatively were 45, 20, and 0 mm of Hg, as compared with 120, 90, and 50 mm of Hg preoperatively. Postoperative pressure measurements were not obtained on 1 surviving dog.     

Heterotopic implantation of a porcine bioprosthetic heart valve in a dog with aortic valve endocarditis

CASE DESCRIPTION: A 5-year-old male German Shepherd Dog was evaluated because of a 5-month history of progressive lethargy, weight loss, and heart failure. CLINICAL FINDINGS: On physical examination, bounding femoral pulses and systolic and diastolic murmurs were detected. Echocardiography revealed severe aortic valve insufficiency (AVI) and a large vegetative lesion on the aortic valve consistent with aortic valve endocarditis. The AVI velocity profile half-time was 130 milliseconds; the calculated peak systolic pressure gradient across the aortic valve was 64 mm Hg. Left ventricular diameter during diastole was 63.6 mm (predicted range, 40.2 to 42 mm) and during systole was 42.9 mm (predicted range, 25.4 to 27 mm). Systolic, diastolic, and mean arterial blood pressures were 120, 43, and 65 mm Hg, respectively. TREATMENT AND OUTCOME: To palliate severe AVI, the descending aorta was occluded (duration, 16.75 minutes) and heterotopic implantation of a porcine bioprosthetic heart valve in that vessel was performed. After surgery, systolic, diastolic, and mean arterial blood pressures were 115, 30, and 61 mm Hg, respectively, in the forelimb and 110, 62, and 77 mm Hg, respectively, in the hind limb. Within 6 months, the AVI velocity profile half-time had increased to 210 milliseconds, indicating diminished severity of AVI. After 24 months, the dog was able to engage in vigorous exercise; no pulmonary edema had developed since surgery. CLINICAL RELEVANCE: Heterotopic bioprosthetic heart valve implantation into the descending aorta during brief aortic occlusion appears feasible in dogs and may provide substantial palliation for dogs with severe AVI.     

Cardiac remodeling and angiotensin II-forming enzyme activity of the left ventricle in hamsters with chronic pressure overload induced by ascending aortic stenosis

Cardiac remodeling and angiotensin II-forming enzyme activity of the left ventricle on chronic pressure overload were studied in male Syrian hamsters, whose chymase activity is similar to that of dogs. Pressure overload was achieved by banding at the ascending aorta (aortic stenosis). Echocardiography, histological analysis, and analysis of cardiac angiotensin-converting enzyme and chymase-like activities were performed. At 10 weeks after banding, concentric hypertrophy of the left ventricle was evident. At 20 weeks after banding, the ventricular weight-to-body ratio, cardiac fibrosis, and cardiac chymase-like activity were significantly increased, while cardiac angiotensin-converting enzyme activity was significantly decreased. This suggests that cardiac chymase, compared with cardiac angiotensin-converting enzyme, was activated against the chronic pressure overload and was responsible for the cardiac remodeling through the formation of angiotensin II. Considering the utility of the rodents, the interspecies similarity of the Ang II-forming pathway, and the effect of chymase in the hamsters, the present model is considered useful for studies evaluating the effect of Ang II and chymase in the canine heart with chronic pressure overload.     

Technique and outcome of mitral valve replacement in dogs

Eight dogs with naturally occurring severe mitral regurgitation underwent mitral valve replacement with a mechanical valve prosthesis during cardiopulmonary bypass. Dogs received warfarin orally after surgery to maintain a prothrombin time-based international normalized ratio from 2.5 to 3.5. Seven dogs survived surgery. Left ventricular diastolic volume index decreased significantly from 206 +/- 91 mL/m2 before surgery to 121 +/- 47 mL/m2 after surgery. Left atrium-to-aorta ratio decreased significantly from 2.66 +/- 0.4 before surgery to 1.73 +/- 0.65 after surgery. Left ventricular systolic volume index was not significantly different after surgery (56 +/- 36 mL/m2), compared with before surgery (40 +/- 32 mL/m2). Median survival after surgery was 4.5 months (range, 0.75 months to 5.25 years). Six dogs died of confirmed or suspected thrombosis of the valve prosthesis. Dogs with severe mitral regurgitation tolerated mitral valve replacement well, but a high incidence of prosthetic valve thrombosis limited long-term outcome.     

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.     

Echocardiographic evaluation of equine aortic insufficiency

Echocardiographic evaluation of 23 horses with aortic insufficiency was performed, using M-mode (n = 23) and 2-dimensional real-time echocardiography (n = 14 of 23). Echocardiograms were evaluated for abnormalities of aortic and mitral valves and alterations in motion of these valves. Changes in left ventricular chamber size and function, as well as aortic root size, were evaluated. The presence of other cardiac disease was also evaluated. Horses with aortic insufficiency had significant increases (P less than 0.01) in mean values of left ventricular chamber size, aortic root diameter, and shortening fraction. Left ventricular free wall thickness also was significantly decreased (P less than 0.01). Valvular abnormalities were seen echocardiographically in all 23 horses. Eighteen horses with aortic insufficiency had thickened valves, whereas two horses had lesions associated with vegetative endocarditis. High-frequency vibrations of the septal leaflet of the mitral valve were noticed in all horses, whereas similar vibrations of the aortic valve were seen in six horses. The presence of a bounding arterial pulse correlated significantly (P less than 0.05) with increased left ventricular chamber size at end diastole and shortening fraction, indicating a marked left ventricular volume overload. A reliable diagnosis of aortic insufficiency can be made with the detection of bounding arterial pulses in concert with a holodiastolic decrescendo grade II to V/V murmur with maximal intensity over the aortic valve area, radiating toward the left cardiac apex.     

Closed Transventricular Dilation of Discrete Subvalvular Aortic Stenosis in Dogs

Discrete subvalvular aortic stenosis with peak systolic pressure gradients of more than 60 mm Hg was treated by closed transventricular dilation in six young dogs. Peak systolic pressure gradients were measured by direct catheterization before surgery, immediately after dilation, and 3 months after surgery. Maximum instantaneous pressure gradients were measured by continuous wave Doppler echocardiography before surgery and 6 weeks to 9 months after surgery. All dogs survived the procedure, and two dogs were clinically normal after 9 and 14 months. Two dogs died at week 6 and month 7. One dog was receiving medication for pulmonary edema 15 months after surgery. One dog underwent open resection of the subvalvular ring at month 3, and was clinically normal 6 months after the second procedure. Complications included intraoperative ventricular fibrillation in one dog, and mild postoperative aortic insufficiency in one dog. Closed transventricular dilation resulted in an immediate 83% decrease in the peak systolic pressure gradient from a preoperative mean of 97 +/- 22 mm Hg to a mean of 14 +/- 15 mm Hg. However, systolic pressure gradients measured by direct catheterization at month 3 (77 +/- 26 mm Hg), and by Doppler echocardiography at week 6 to month 9 (85 +/- 32 mm Hg) were not significantly different from preoperative values, which suggested recurrence of the aortic stenosis. Closed transventricular dilation should not be considered a definitive treatment for discrete subvalvular aortic stenosis in dogs, but may be useful in young dogs with critical aortic stenosis as a bridge to more definitive surgery.     

Echocardiographic parameters in 14 healthy English Bull Terriers

OBJECTIVE: To determine the range of various cardiac parameters using echocardiography in apparently normal, healthy English Bull Terriers. DESIGN: Fourteen English Bull Terriers were selected for study. Cardiac auscultation of the parents of these dogs was normal. Echocardiographic examination of one parent of each animal showed: no mitral or aortic valve abnormalities; no myocardial lesions; no two dimensional evidence of fixed or dynamic left ventricular outflow tract obstruction; and no systolic aortic or left ventricular outflow tract turbulence on colour flow Doppler examination. The 14 selected dogs did not have arrhythmias or murmurs, and on echocardiographic examination had similar findings to their parents. Systolic blood pressure was measured in all dogs and they had no clinical evidence of Bull Terrier polycystic kidney disease or Bull Terrier hereditary nephritis. PROCEDURE: All dogs were auscultated and subjected to a sequential global echocardiographic assessment of the heart, including two dimensional long and short axis, and colour flow Doppler interrogation of the mitral and aortic valves. Dimensional measurements, including those from the left atrium, aortic annulus and left ventricle, were taken from a right parasternal window, and derived values such as fractional shortening, stroke volume and left atrial to aortic annulus ratio were calculated. Peak systolic aortic velocity was measured from the left parasternal window using two dimensional-guided pulsed wave Doppler with angle correction. Systolic blood pressure was measured using a Doppler monitor. The absence of Bull Terrier polycystic kidney disease was determined using renal ultrasonography, and of Bull Terrier hereditary nephritis using urinary protein to creatinine ratio. RESULTS: These 14 dogs had greater left ventricular wall thickness and smaller aortic root diameters than those reported as normal for other breeds of comparable body size. Left atrial dimensions were also larger, however this may have been due to the "maximising" method of measurement. These apparently normal English Bull Terriers also had higher aortic velocities than those reported for other breeds, possibly due to a smaller aortic root diameter or other anatomic substrate of the left ventricular outflow tract, lower systemic vascular resistance, or breed-specific "normal" left ventricular hypertrophy. While these dogs were selected to be as close to normal as possible, the breed may have a particular anatomy that produces abnormal left ventricular echocardiographic parameters. CONCLUSION: These echocardiographic parameters may be used to diagnose left ventricular outflow tract obstruction and left ventricular hypertrophy, and inaccurate diagnoses may result if breed-specific values are not used.     

Surgical correction of subaortic stenosis via right ventriculotomy and septal resection in a dog

After 2 years of medical management with a beta-adrenoreceptor blocking agent, a 30-month-old castrated male Golden Retriever with subaortic stenosis was treated surgically because of progression of its condition. In an attempt to achieve complete relief of the left ventricular outflow obstruction, a modified Konno procedure consisting of right ventriculotomy and septal myectomy from the infundibular portion of the right ventricle was performed; this combination of procedures allowed wide resection of the septal portion of the left ventricular outflow obstruction. Two years after surgery, the mass of the dog's left ventricle had decreased and the peak calculated pressure gradient across the aortic valve had decreased to 40 mm Hg, compared with a preoperative value of 240 mm Hg; at that evaluation, the dog had gained weight and was able to play normally. It is suggested that use of this modified approach to the outflow tract may have a positive effect on long-term survival time in dogs with subaortic stenosis.     

Surgical correction of subvalvular aortic stenosis using cardiopulmonary bypass in a dog

A three-month-old male Golden Retriever had symptoms including exercise intolerance, dyspnea and syncope and was diagnosed with subvalvular aortic stenosis. Cardiac catheterization revealed a left ventricular-aortic systolic pressure gradient of 90 mm Hg. Surgical correction of the condition was achieved using cardiopulmonary bypass. The subvalvular fibrous lesion was resected through an aortotomy. The stenosis was dilated from 8.5 mm to 12.0 mm in diameter. Postoperatively the dog was asymptomatic. Seven months after surgery, the pressure gradient decreased to 44 mm Hg. However, after another three months, the dog died suddenly without any premonitory signs. Postmortem examination revealed that pathologic changes caused by increased left ventricular pressure overload were not severe.     

Mitral Stenosis in 15 Dogs

Mitral stenosis was diagnosed in 15 young to middle-aged dogs. There were 5 Newfoundlands and 4 bull terriers affected, suggesting a breed predisposition for this disorder. Clinical signs included cough, dyspnea, exercise intolerance, and syncope. Soft left apical diastolic murmurs were heard only in 4 dogs, whereas 8 dogs had systolic murmurs characteristic of mitral regurgitation. Left atrial enlargement was the most prominent radiographic feature. Left-sided congestive heart failure was detected by radiographs in 11 dogs within 1 year of diagnosis. Electrocardiographic abnormalities varied among dogs and included atrial and ventricular enlargement, as well as atrial and ventricular arrhythmias. Abnormalities on M-mode and two-dimensional echocardiograms included abnormal diastolic motion of the mitral valve characterized by decreased leaflet separation, valve doming, concordant motion of the parietal mitral valve leaflet, and a decreased E-to-F slope. Increased mitral valve inflow velocities and prolonged pressure half-times were detected by Doppler echocardiography. Cardiac catheterization, performed in 8 dogs, documented a diastolic pressure gradient between the left atrial, pulmonary capillary wedge, or pulmonary artery diastolic pressures and the left ventricular diastolic pressure. Necropsy showed mitral stenosis caused by thickened, fused mitral valve leaflets in 5 dogs and a supramitral ring in another dog. The outcome in affected dogs was poor; 9 of 15 dogs were euthanatized or died by 2 1/2 years of age.     

Surgical correction of ventricular septal defect with aortic regurgitation in a dog

An 8-month-old entire Miniature Dachshund, weighing 4.2 kg, was presented for examination following delvelopment of a cough. Ventricular septal defect had been diagnosed tentatively in its infancy on the basis of a cardiac murmur detected by auscultation and echocardiography. Echocardiography using a B mode right parasternal long-axis view showed a defect at the atrioventricular junction and a thickened cusp of the aortic valve prolapsing into the defect. Colour-flow Doppler showed shunt blood flow across the defect at the level of the atrioventricular junction, from left to right. The sinus of Valsalva was dilated, with turbulent blood flow. Aortic regurgitation was also observed. Cardiac catheterisation studies confirmed the diagnosis of a supracristal ventricular septal defect with aortic regurgitation. Despite medication with digoxin, enalapril and aminophylin, started from the first admission, left ventricular internal dimensions gradually increased, and fractional shortening of the left ventricle gradually decreased. Surgery, with the aid of extracorporeal circulation, to close the ventricular septal defect, was performed 1 year after the initial examination. The aortic valve was left untreated. Postoperatively, the systolic murmur disappeared. Shunt flow from the left to the right ventricle was no longer observed on echocardiography, however there was still a small amount of aortic regurgitation during diastole visualised with colour-flow Doppler echocardiography. The prolapse of the cusp of the aortic valve on B-mode echocardiography was no longer observed and thickening of the cusp had not progressed. Left ventricular function measurement using M mode echocardiography showed a reduced left ventricular volume overload with reduced left ventricular internal dimensions and increased fractional shortening. The cough was relieved and no follow-up medication was scheduled. Early surgical closure of the ventricular septal defect improved the patient's condition and controlled prolapse and thickening of the aortic valve.     

Perioperative management of calves undergoing implantation of a left ventricular assist device

OBJECTIVE: To describe perioperative management of calves that underwent left lateral thoracotomy, aortic cross-clamping, partial left heart bypass and implantation of a left ventricular assist device. SAMPLE POPULATION: A total of 43 healthy castrated male calves, weighing 121 +/- 24 kg. RESULTS: Diazepam (mean +/- SD, 0.26 +/- 0.07 mg/kg), ketamine (5.9 +/- 2.17 mg/kg) and isoflurane were used in the anesthetic management of calves undergoing implantation of a left ventricular assist device in the descending thoracic aorta. Other adjunctive agents administered were fentanyl (11 +/- 5.4 microg/kg), lidocaine (4.9 +/- 3.19 mg/kg), bupivacaine (0.75%) and butorphanol (0.49 +/- 0.13 mg/kg). None of the calves regurgitated at induction or during intubation. A tube was used to drain the rumen and prevent bloat during the procedure. Partial left heart bypass was used to perfuse the caudal half of the body during the period of aortic cross clamp and device implantation. Initial mean systemic blood pressure was 96 +/- 25 mm Hg, and pressures measured in the auricular artery increased during aortic cross-clamping and bypass. Vasoconstrictor therapy was required to treat caudal arterial hypotension during the procedure in 9 calves. Mean systemic arterial pressures returned to baseline values by the end of the anesthetic period. Initial mean pulmonary arterial pressures (PAP) were 22 +/- 3 mm Hg. A significant but transient increase in pulmonary arterial pressure occurred after both heparin and protamine administration. CONCLUSIONS: The described anesthetic protocol was effective for thoracotomy and implantation of an intra-aortic left ventricular assist device in normal calves. Partial left ventricular bypass was a useful adjunct during the period of aortic cross clamp. The doses of heparin and protamine administered were effective. Responsibility to monitor oxygenation of the cranial half of the animal continues during the bypass period as hypoxemia due to pulmonary dysfunction will not be detected by the perfusionist.     

Hemodynamic effects of butorphanol in desflurane-anesthetized dogs

ObjectiveTo evaluate the effects of butorphanol on cardiopulmonary parameters in dogs anesthetized with desflurane and breathing spontaneously.Study designProspective, randomized experimental trial.AnimalsTwenty dogs weighing 12 ± 3 kg.MethodsAnimals were distributed into two groups: a control group (CG) and butorphanol group (BG). Propofol was used for induction and anesthesia was maintained with desflurane (10%). Forty minutes after induction, the dogs in the CG received sodium chloride 0.9% (0.05 mL kg^?1 IM), and dogs in the BG received butorphanol (0.4 mg kg^?1 IM). The first measurements of body temperature (BT), heart rate (HR), arterial pressures (AP), cardiac output (CO), cardiac index (CI), central venous pressure (CVP), stroke volume index (SVI), pulmonary arterial occlusion pressure (PAOP), mean pulmonary arterial pressure (mPAP), left ventricular stroke work (LVSW), systemic (SVR) and pulmonary (PVR) vascular resistances, respiratory rate (f_R), and arterial oxygen (PaO₂) and carbon dioxide (PaCO₂) partial pressures were taken immediately before the administration of butorphanol or sodium chloride solution (T0) and then at 15-minute intervals (T15–T75).ResultsIn the BG, HR, AP, mPAP and SVR decreased significantly from T15 to T75 compared to baseline. f_R was lower at T30 than at T0 in the BG. AP and f_R were significantly lower than in the CG from T15 to T75. PVR was lower in the BG than in the CG at T30, while PaCO₂ was higher compared with T0 from T30 to T75 in the BG and significantly higher than in the CG at T30 to T75.Conclusions and clinical relevanceAt the studied dose, butorphanol caused hypotension and decreased ventilation during desflurane anesthesia in dogs. The hypotension (from 86 ± 10 to 64 ± 10 mmHg) is clinically relevant, despite the maintenance of cardiac index.     

Transthoracic echocardiography in Estrela Mountain dogs: reference values for the breed

Of 100 Estrela Mountain dogs, 74 were examined to obtain echocardiographic reference values for the breed. The influence of bodyweight, age and sex on different echocardiographic parameters was studied using either analysis of variance or regression analysis. Statistically significant differences were found between sex and heart rate as well as interventricular septal thickness at end-systole and left ventricular internal dimension at end-diastole. A statistically significant linear correlation was also found between several parameters and (1) age (mean arterial pressure, left ventricular internal dimension at end-systole, fractional shortening, circularity index in systole, aortic valve velocity time integral, pulmonic valve velocity time integral and mitral valve E wave peak velocity), (2) weight (left ventricular posterior wall thickness at end-diastole and end-systole, end-diastolic volume index, left atrium diameter, aortic valve peak velocity and mitral valve E wave deceleration time), (3) sex and age (left ventricle end-diastolic volume), and (4) sex and weight (aortic root diameter and pulmonic valve peak velocity). Reference values for the breed are presented, as well as dispersion graphics for selected parameters, based on a regression equation.     

Balloon Dilation of Congenital Subaortic Stenosis in the Dog

Balloon dilation during cardiac catheterization was evaluated for the treatment of congenital subaortic stenosis (SAS) in nine dogs. Under general anesthesia, bilateral cardiac catheterization was performed through the right jugular vein and carotid artery. Thermodilution cardiac output, and left ventricular and aortic root pressures and angiograms were obtained before and after balloon dilation. Balloons measuring 18–20 mm in diameter and 30–40 mm in length were positioned across the stenosis and three inflations 4–5 minutes apart were performed. There was no significant change in cardiac output, aortic pressure, or degree of aortic regurgitation after balloon dilation. For the entire group balloon dilation resulted in significant decreases in left ventricular systolic pressure (-61.2 ± 37.2 mm Hg [mean change ± SD], range -14 to -123), mean systolic pressure gradient (-39.6 ± 24.4 mm Hg, range –8.4 to -72.2), and peak systolic pressure gradient (-64.3 ± 46.5 mm Hg, range –17 to –143). Calculated left ventricular outflow cross-sectional area increased significantly (+.4 ± .5 cm², range –.06 to + 1.30). Clinical signs improved in the five symptomatic dogs. Individual hemodynamic responses varied widely, but the magnitude of improvement correlated with the severity of obstruction. Three dogs showed a decrease of 60% or greater (≥100 mm Hg), and six dogs showed a decrease of 25–50% (17–71 mm Hg) in peak systolic gradient after balloon dilation. Complications were frequent but most were transient and manageable. These preliminary results suggest that balloon dilation can acutely decrease outflow resistance in dogs with SAS and may be effective therapy for some affected dogs.     

Effects of enalapril in cats with pressure overload-induced left ventricular hypertrophy

In order to evaluate the effect of enalapril on haemodynamics and renal function in a pressure overload model, we prepared eight feline models of left ventricular hypertrophy (LVH) by banding of the aortic arch. The LVH cats were assigned to the placebo group or the enalapril group (0.5 mg/kg, PO, sid) 3 months following surgery, and each received its respective drug for 4 weeks. Each week, blood pressure, angiotensin converting enzyme (ACE) activity in blood, and creatinine clearance were measured, and complete blood count (CBC), biochemical examination of the blood, echocardiography, and chest radiography were carried out. The interventricular septum thickness (IVSd, IVSs), fractional shortening (FS), and ejection fraction (EF) increased significantly in the LVH cats following surgery (P<0.05). There was no significant difference between the placebo group and the enalapril group with respect to general physical parameters, CBC, biochemical parameters and renal function. In the enalapril group, systolic arterial pressure, mean arterial pressure, and ACE activity in blood decreased significantly following administration (P<0.05). In addition, the left ventricular free wall thickness in diastole and IVSd decreased significantly following administration (P<0.05). These results suggest that, in a pressure overload model, enalapril (0.5 mg/kg, sid) inhibits cardiac hypertrophy, reduces blood pressure, and does not adversely affect renal function.     

Short-term effects of ecadotril in dogs with induced congestive heart failure

OBJECTIVE: To evaluate short-term hemodynamic effects of ecadotril in a model of congestive heart failure in dogs. ANIMALS: 6 conscious adult male dogs. PROCEDURES: Instruments were placed in dogs to measure left ventricular, aortic, and atrial blood pressures. Heart failure was induced by repeated coronary embolization with latex microspheres. Four times, and in random order, dogs were given vehicle or active drug (3, 10, or 30 mg/kg of body weight) orally. Hemodynamic variables, urine flow, and urinary electrolyte excretion were measured before and 30, 90, and 150 minutes, and 10 and 21 hours after drug administration. RESULTS: Changes in urine flow, heart rate, mean arterial pressure, or peak positive and negative rate of change in ventricular pressure were not apparent. Urinary sodium excretion significantly increased in response to the low and high doses of ecadotril but not in response to the 10 mg/kg dose. Left ventricular end diastolic pressure (LVEDP) consistently decreased in dose- and time-dependent manner. Maximal group-averaged reductions in LVEDP were 5.2, 8.1, and 10 mm Hg for the low, middle, and high doses, respectively. The magnitude of the decrease in LVEDP was not related to cumulative change in urine flow. CONCLUSIONS AND CLINICAL RELEVANCE: Orally administered ecadotril reduced left ventricular filling pressures in these dogs by a mechanism that does not require a substantial diuretic effect. Ecadotril may be effective for alleviating clinical signs in dogs with left-sided heart failure and may be particularly beneficial for use in dogs that are refractory to traditional diuretic therapy.     

Pulmonary function in dogs with mitral valve regurgitation

Mitral valve regurgitation was created in 2 groups of dogs. Groups were selected on absence (group 1) or presence (group 2) of clinical signs of congestive left ventricular failure. Group-2 dogs, in which mean left atrial pressures were greater than 30 mm of Hg, had increases in heart rate, pulmonary arterial mean pressure, left atrial diameter, and left ventricular diastolic diameter. These changes were associated with decreased arterial O2 tension, decreased static and dynamic compliance, reduced lung volumes, and increased pulmonary resistance. Group-1 dogs, in which mean left atrial pressure was less than 30 mm of Hg, had moderate changes in hemodynamics, but no changes in pulmonary function, except during exercise when arterial O2 tension decreased.     

Evaluation of techniques and outcomes of mitral valve repair in dogs

OBJECTIVE: To describe surgical techniques for and assess outcome of treatment of mitral regurgitation in dogs. DESIGN: Uncontrolled prospective study. ANIMALS: 18 dogs with naturally occurring mitral regurgitation. PROCEDURE: All dogs weighed > 5 kg (11 lb) and had severe mitral regurgitation, congestive heart failure (CHF), and no serious noncardiac disease. Left ventricular volume indices, left atrial size, and degree of mitral regurgitation were determined echocardiographically before and after surgery. Repair techniques included circumferential annuloplasty, placement of artificial chordae, chordal fenestration and papillary muscle splitting, and edge-to-edge repair. Factors predictive for surgery survival and resolution of CHF were determined. RESULTS: 12 dogs survived surgery. Factors predictive for surgery survival included weight > 10 kg (22 lb) and CHF of less than 6 months' duration. In 9 dogs, CHF resolved for a median period of 1 year (range, 4 months to 3 years) after surgery. One dog had stable CHF at 12 months. One dog died as a result of progressive CHF; another was euthanatized for a noncardiac reason. Left ventricular diastolic volume index was 226.9 +/- 117.7 cm3/m2 before surgery and 134.9 +/- 70.4 cm3/m2 at 6 months after surgery (n = 10). Factors predictive for resolution of CHF included left ventricular diastolic volume index < 250 cm3/m2 and systolic volume index < 70 cm3/m2. CONCLUSION AND CLINICAL RELEVANCE: Mitral valve repair may resolve CHF in dogs with severe mitral regurgitation, particularly in dogs that weigh > 10 kg and are treated within 6 months of the onset of CHF.