Ventricular systolic dysfunction in dogs diagnosed with hypoadrenocorticism.

In human patients with hypoadrenocorticism, a secondary dilated cardiomyopathy is noted that has been reported to resolve with replacement steroid therapy. A similar secondary dilated cardiomyopathy in dogs with hypoadrenocorticism has not been previously described. We present three dogs concurrently diagnosed with hypoadrenocorticism and ventricular dilation with systolic dysfunction. Two dogs were presented with clinical signs consistent with biventricular congestive heart failure and a third dog was presented with signs of acute hypoadrenocorticism without congestive heart failure. All dogs recovered to normal cardiac size and function with therapy. Hypoadrenocorticism should be considered as a differential diagnosis in dogs that present with ventricular dilation and systolic dysfunction if there are other indicators in the clinical and laboratory testing. Additionally, a thorough cardiac evaluation should be recommended for dogs that are found to have a heart murmur at the time of diagnosis of hypoadrenocorticism.

Usefulness of dyssynchrony indices based on two-dimensional speckle tracking echocardiography in a canine model of left bundle branch block.

INTRODUCTION: Determine the usefulness of dyssynchrony indices derived from two-dimensional speckle tracking echocardiography for the detection of mechanical dyssynchrony in a canine model of left bundle branch block. ANIMALS: Ten healthy beagles. MATERIALS AND METHODS: Segmental, time-radial strain curves were obtained using two-dimensional speckle tracking echocardiography. The maximum difference and standard deviation of the time to peak radial strain for six predefined segments (MaxD-TpSR and 6SD-TpSR) were calculated, together with the left ventricular dyssynchrony by radial strain (DysSR), before and after ablation of the left bundle branch block. Receiver operating characteristic curve analysis was performed using dogs after ablation as positive controls. RESULTS: After ablation, all dogs showed multiple peaks in at least one segment on the time-radial strain curve, while all dyssynchrony indices increased significantly (MaxD-TpSR from 16.25 ± 16.04 [mean ± standard deviation] to 44.4 ± 26.18 ms, 6SD-TpSR from 7.59 ± 7.40 to 19.62 ± 11.91 ms, and DysSR from 4.20 ± 2.12 to 10.87± 2.92%, p<0.05). In receiver operating characteristic curve analysis, the areas under the curve for MaxD-TpSR, 6SD-TpSR, and DysSR were 0.825, 0.800, and 0.980, respectively. CONCLUSIONS: Left ventricular dyssynchrony by radial strain can detect mechanical dyssynchrony with higher sensitivity and specificity than dyssynchrony indices, based on the time to peak radial strain.

Deformação miocárdica radial por meio do speckle tracking bidimensional em suínos com hipertensão pulmonar induzida e tratados com angiotensina-(1-7) / Evaluation of myocardial radial deformation by bidimensional speckle tracking in pigs with pulmonary hypertension treated with angiotensin- (1-7)

A hipertensão arterial pulmonar (HAP) é uma doença complexa, caracterizada por disfunção endotelial, que resulta em remodelamento vascular pulmonar e elevação da pressão arterial pulmonar, com consequente insuficiência cardíaca direita. O speckle tracking bidimensional (2D-STE) é uma das mais recentes ferramentas da ecocardiografia, o qual tem sido empregado para avaliação mais precoce da função ventricular e do efeito da HAP sobre a função dos ventrículos esquerdo e direito. O objetivo deste estudo foi avaliar a deformação (St e StR) miocárdica radial do VE em modelo experimental de suínos com HAP induzida e tratados com angiotensina-(1-7), a fim de verificar as possibilidades desse novo fármaco nas respostas clínica e hemodinâmica, pois apresenta efeitos anti-inflamatório e vasodilatador, bem como ações antiproliferativas no sistema cardiovascular. Neste estudo, foi possível observar que os animais tratados com Ang-(1-7) apresentaram St e StR radiais maiores que o grupo placebo aos 60 dias de experimento, demonstrando uma melhora na função sistólica do miocárdio pelo aumento da deformação miocárdica (16,06±7,50 - placebo; 25,14±14,91 - Ang-(1-7)) e StR (1,28±0,51 - placebo; 1,51±0,58 - Ang-(1-7)). Essa melhora na função sistólica pode ser atribuída aos efeitos do fármaco, que reduziram também o desenvolvimento da hipertensão pulmonar. Diante dos resultados, acredita-se que a Ang-(1-7) possa ser um medicamento promissor para tratamento da HAP.(AU)

Pulmonary arterial hypertension (PAH) is a complex disease characterized by endothelial dysfunction resulting in pulmonary vascular remodeling, increased pulmonary arterial pressure, with subsequent right heart failure. The two-dimensional speckle tracking (2D-STE) is one of the newer tools used for early assessment of ventricular function. The aim of this study was to evaluate the radial myocardial deformation (St and StR) of LV in experimental pigs with induced PAH and treated with Ang- (1-7), checking the possibilities of this new drug in clinical and hemodynamic response, since it has anti-inflammatory effects and antiproliferative actions on the cardiovascular system. In this study we observed that animals treated with Ang (1-7) had radial St and StR higher than the placebo group at 60 days of the experiment demonstrating an improvement in systolic function of the myocardium by increased myocardial deformation (16.06±7.50 - placebo; 25.14±14.91 - Ang (1-7)) and StR (1.28±0.51 - placebo; 1.51±0.58 - Ang (1-7)). This improvement in systolic function can be attributed to drug effects while also reducing the development of pulmonary hypertension. Based on the results it is believed that Ang (1-7) may be a promising drug for the treatment of PAH.(AU)

Estudio tractográfico de la anatomía helicoidal del miocardio ventricular mediante resonancia magnética por tensor de difusión / Helical structure of the cardiac ventricular anatomy assessed by diffusion tensor magnetic resonance imaging with multiresolution tractography

Introducción y objetivos. La integración de la anatomía y la función del miocardio ventricular es fundamental para una completa comprensión de la fisiología cardiaca, lo que podría revelar conocimientos clave para futuros estudios experimentales y procedimientos clínicos. Se han propuesto varios modelos conceptuales de la organización de las fibras miocárdicas, pero la dificultad para automatizar y analizar objetivamente una estructura anatómica tan compleja ha impedido que se llegue a un acuerdo. El objetivo de nuestro estudio es analizar objetivamente la arquitectura de las fibras miocárdicas mediante métodos avanzados de procesamiento gráfico por computadora aplicados a imágenes de resonancia magnética por tensor de difusión. Métodos. Se han realizado reconstrucciones tractográficas automatizadas de datos de imágenes de resonancia magnética por tensor de difusión sin segmentar de corazones provenientes de la base de datos pública de la Johns Hopkins University. Las reconstrucciones a máxima resolución se han construido con 200 semillas y se componen de perfiles calculados sobre el volumen de vectores propios primarios obtenidos del tensor de difusión. También aportamos una nueva técnica de visualización multiescalar para obtener tractografías simplificadas. Esta metodología permite mantener las principales propiedades geométricas de las fibras y descifrar las principales propiedades de la organización arquitectónica del miocardio. Resultados. En el análisis de las tractografías de todo el espectro multiescalar, encontramos una correlación exacta en los detalles de bajo nivel, así como de la conceptualización abstracta de la disposición helicoidal continua de las fibras miocárdicas que conforman la arquitectura ventricular. Conclusiones. El análisis objetivo de la arquitectura miocárdica mediante un método automatizado que incluye el miocardio completo y utiliza diferentes niveles de complejidad tridimensional revela una organización de las fibras en forma de estructura helicoidal continua que conforma ambos ventrículos. Estos datos concuerdan con el modelo de banda ventricular miocárdica descrita por F. Torrent-Guasp (AU)

Introduction and objectives. Deeper understanding of the myocardial structure linking the morphology and function of the heart would unravel crucial knowledge for medical and surgical clinical procedures and studies. Several conceptual models of myocardial fiber organization have been proposed but the lack of an automatic and objective methodology prevented an agreement. We sought to deepen this knowledge through advanced computer graphical representations of the myocardial fiber architecture by diffusion tensor magnetic resonance imaging. Methods. We performed automatic tractography reconstruction of unsegmented diffusion tensor magnetic resonance imaging datasets of canine heart from the public database of the Johns Hopkins University. Full-scale tractographies have been built with 200 seeds and are composed by streamlines computed on the vector field of primary eigenvectors at the diffusion tensor volumes. We also introduced a novel multiscale visualization technique in order to obtain a simplified tractography. This methodology retains the main geometric features of the fiber tracts, making it easier to decipher the main properties of the architectural organization of the heart. Results. Output analysis of our tractographic representations showed exact correlation with low-level details of myocardial architecture, but also with the more abstract conceptualization of a continuous helical ventricular myocardial fiber array. Conclusions. Objective analysis of myocardial architecture by an automated method, including the entire myocardium and using several 3-dimensional levels of complexity, reveals a continuous helical myocardial fiber arrangement of both right and left ventricles, supporting the anatomical model of the helical ventricular myocardial band described by F. Torrent-Guasp (AU)

Effect of oral administration of pimobendan in cats with heart failure.

OBJECTIVE: To determine the effect of PO administration of pimobendan on clinical and echocardiographic variables and survival time in cats with heart failure characterized by ventricular systolic dysfunction. DESIGN: Retrospective cohort study. ANIMALS: 27 client-owned cats (16 male and 11 female) with heart failure, treated with pimobendan (mean ± SD dosage, 0.26 ± 0.08 mg/kg [0.118 ± 0.036 mg/lb], PO, q 12 h). PROCEDURES: Information on medical history, laboratory results, diagnostic imaging findings, treatments received, and survival time were obtained from medical records of cats that received pimobendan because of cardiac disease. When possible, additional follow-up information was obtained through telephone interviews with referring veterinarians and owners. RESULTS: The mean ± SD age of all 27 cats was 8.9 ± 5.2 years. All cats had received several cardiac medications. Types of heart disease represented included unclassified cardiomyopathy (CM; n = 11 [41%]), dilated CM (8 [30%]), arrhythmogenic right ventricular CM (4 [15%]), congenital heart disease (3 [11 %]), and hypertrophic CM with regional hypokinesis (1 [4%]). All cats had ventricular systolic dysfunction. One cat with systolic anterior motion of the mitral valve became severely hypotensive after initial administration of pimobendan and was excluded from the survival analysis. Median survival time was 167 days (95% confidence interval, 32 to 339 days). CONCLUSIONS AND CLINICAL RELEVANCE: Pimobendan appeared to be well tolerated in cats with heart failure characterized by ventricular systolic dysfunction of various etiologies. Cats with systolic anterior motion of the mitral valve may develop systemic hypotension when treated with pimobendan. Additional studies are needed to establish dosages for pimobendan and its effects before it can be recommended for treatment of cats with CHF.

Surgical management of combined hydrocephalus, syringohydromyelia, and ventricular cyst in a dog.

Combined hydrocephalus, syringohydromyelia, and a ventricular cyst were found by magnetic resonance imaging in a 7-month-old, male miniature dachshund with gait abnormalities and altered mentation. Clinical signs did not improve with prednisone therapy. Ventriculoperitoneal shunting improved the clinical signs and anatomical abnormalities. Repeated operations were needed to replace the ventricular drainage tube at 3 and 31 months after the first surgery. The animal died suddenly with severe tonic-clonic, generalized seizures 3 weeks after the third operation. Ventriculoperitoneal shunting may be a viable treatment for syringohydromyelia associated with hydrocephalus.

Ventricular dyssynchrony as a cause of structural disease in the heart of Dorper sheep.

Ventricular dyssynchrony is a disturbance of the normal, organized electromechanical coupling of the two ventricles. This condition has many causes, such as left bundle branch block, ventricular preexcitation, right ventricular pacing and right ventricular premature ventricular complexes (PVCs). Ventricular dyssynchrony has many adverse haemodynamic effects on the left ventricle and we wanted to know whether these adverse haemodynamic effects might have any structural consequences on the left ventricles of such hearts. Six healthy Dorper wethers were subjected to numerous right ventricular PVCs to induce ventricular dyssynchrony in order to determine whether any structural consequences will occur in the left ventricles of these hearts. Myocarditis in the musculature of the left ventricles of all six these hearts was seen.

Correlation of QT dispersion with indices used to evaluate the severity of familial ventricular arrhythmias in Boxers.

OBJECTIVE: To measure QT interval duration and QT dispersion in Boxers and to determine whether QT variables correlate with indices of disease severity in Boxers with familial ventricular arrhythmias, including the number of ventricular premature complexes per day, arrhythmia grade, and fractional shortening. ANIMALS: 25 Boxers were evaluated by ECG and echocardiography. PROCEDURE: The QT interval duration was measured from 12-lead ECG and corrected for heart rate (QTc), using Fridericia's formula. The QT and QTc were calculated for each lead, from which QT and QTc dispersion were determined. Echocardiography and 24-hour ambulatory ECG were performed to evaluate for familial ventricular arrhythmias. Total number of ventricular premature complexes, arrhythmia grade, and fractional shortening were determined and used as indices of disease severity. RESULTS: There was no correlation between any QT variable and total number of ventricular premature complexes, arrhythmia grade, or fractional shortening. No difference between QT dispersion and QTc dispersion was identified, and correction for heart rate did not affect the results. CONCLUSIONS AND CLINICAL RELEVANCE: QT interval duration and dispersion did not correlate with indices of disease severity for familial ventricular arrhythmias. Heart rate correction of the QT interval did not appear to be necessary for QT dispersion calculation in this group of dogs. QT dispersion does not appear to be a useful noninvasive diagnostic tool in the evaluation of familial ventricular arrhythmias of Boxers. Identification of affected individuals at risk for sudden death remains a challenge in the management of this disease.

Congestive heart failure associated with myxomatous degeneration of the left atrioventricular valve in a parakeet.

Congestive heart failure was diagnosed in a 27-year-old Indian ringneck parakeet with exercise-induced dyspnea. A grade IV/VI holosystolic murmur that radiated to the right sternal area was auscultated over the left side of the sternum. Radiography revealed progressive cardiomegaly, hepatomegaly, pulmonary edema, and accumulation of fluid within the coelomic cavity. Echocardiography revealed biatrial enlargement and enlargement of the right ventricle. Doppler recording revealed high velocity left and right atrioventricular valve regurgitation. Treatment with digoxin and furosemide alleviated clinical signs for approximately 10 months. Gross postmortem examination revealed cardiac enlargement and eccentric hypertrophy of both ventricles on cross-section. Pulmonary congestion and edema, hepatomegaly, hepatic congestion, and ascites were also evident. Histologic examination of the heart revealed myxomatous degeneration of the left atrioventricular valve, muscular hypertrophy of the right atrioventricular valve, and biventricular chronic myofiber degeneration and necrosis.

Comparison of in-hospital versus 24-hour ambulatory electrocardiography for detection of ventricular premature complexes in mature Boxers.

OBJECTIVE: To evaluate the use of in-hospital electrocardiography (ECG) for detection of ventricular premature complexes (VPC), compared with 24-hour ambulatory ECG. DESIGN: Original study. ANIMALS: 188 Boxers > 9 months old; 31 had a history of syncope, and 157 were healthy (no history of syncope). PROCEDURE: In-hospital ECG was performed on all Boxers for at least 2 minutes. Within 7 days after the in-hospital ECG was completed, 24-hour ambulatory ECG was performed. RESULTS: The specificity of in-hospital ECG was 100% for the detection of at least 50 VPC in a 24-hour period in dogs with syncope and 93% in healthy dogs. In-hospital ECG had poor sensitivity, although sensitivity increased as the number of VPC per 24 hours increased. CONCLUSIONS AND CLINICAL RELEVANCE: Use of in-hospital ECG is highly specific for detection of at least 50 VPC during a 24-hour period. However, in-hospital ECG is insensitive, and a lack of VPC does not suggest that the dog does not have a substantial number of VPC during that same period. The use of in-hospital ECG appears to be inadequate for screening purposes and therapeutic evaluations in mature Boxers with ventricular arrhythmic disease.

Results of ambulatory electrocardiography in overtly healthy Doberman Pinschers with echocardiographic abnormalities.

OBJECTIVE: To identify, by means of 24-hour ambulatory electrocardiography, electrocardiographic abnormalities in overtly healthy Doberman Pinschers in which results of echocardiography were abnormal. DESIGN: Clinical case series. ANIMALS: 56 (35 male, 21 female) overtly healthy Doberman Pinschers with echocardiographic evidence of cardiomyopathy on initial examination that subsequently died of cardiomyopathy. PROCEDURE: Twenty-four-hour ambulatory electrocardiographic (Holter) recordings obtained at the time of initial examination were reviewed. For all dogs, scan quality was > 90%. RESULTS: Initial Holter recordings of all 56 dogs contained ventricular premature contractions (VPC). Thirty-six (65%) dogs had > 1,000 VPC/24 h, 17 (31%) had > 5,000 VPC/24 h, and 11 (19%) had > 10,000 VPC/24 h. Fifty-four (96%) dogs had couplets of VPC, 37 (66%) had triplets of VPC, and 36 (64%) had episodes of nonsustained (< 30 seconds) ventricular tachycardia. Number of VPC/24 h during the initial Holter recordings was positively correlated with numbers of couplets and triplets of VPC and number of ventricular escape beats and negatively correlated with left ventricular fractional shortening. Twenty-eight dogs died suddenly prior to the putative onset of congestive heart failure. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that along with echocardiography, 24-hour ambulatory electrocardiography can be used to help identify overtly healthy Doberman Pinschers with cardiomyopathy.

Baroreflex sensitivity predicts the induction of ventricular arrhythmias by cesium chloride in rabbits.

Previous studies have shown that the autonomic nervous system plays an important role in the genesis of ventricular tachycardia (VT) in patients with long QT syndrome, and in cesium chloride (Cs)-induced VT in animals. The present study investigated whether baroreflex sensitivity predicts the induction of VT by Cs in the rabbit in vivo. Monophasic action potentials (MAPs) of the left ventricular endocardium were recorded simultaneously with the surface ECG in 27 rabbits. Rabbits were divided into 4 groups based on the Cs-induced ventricular arrhythmias: (1) no ventricular premature contractions (No-VPC group), (2) single or paired VPC (VPC group), (3) monomorphic VT (MVT group), and (4) polymorphic VT (PVT group). Baroreflex sensitivity was significantly lower in the MVT and PVT groups than in the No-VPC and VPC groups. The plasma norepinephrine concentration before Cs injection was significantly higher in the MVT group than in the other 3 groups, and the norepinephrine concentration after Cs injection was significantly higher in the MVT and PVT groups than in the No-VPC and VPC groups. Baroreflex sensitivity was negatively correlated with the norepinephrine concentration before Cs injection. These results suggest that autonomic nervous system dysfunction, as defined by reduced baroreflex sensitivity, and elevated plasma norepinephrine concentrations predict increased susceptibility to Cs-induced VT.

Malignant ventricular dysrhythmia in broiler chickens dying of sudden death syndrome.

A flock of broiler chickens was monitored intensively for overt signs indicative of sudden death. Electrocardiographic tracing of terminal cardiac activity was obtained from six broilers succumbing to sudden death syndrome and from six control chickens which were killed by cervical dislocation. Normal sinus rhythm, heart rate and electrocardiogram (ECG) pattern with P, QRS, and T deflections were observed for two to three minutes in the control chickens. The ECG tracing from birds dying of sudden death syndrome showed no identifiable P, QRS, or T waveforms. Initial more regular oscillatory waves resembling ventricular flutter, changed to irregular, undulating waves characteristic of ventricular fibrillation. A straight line, indicating cessation of heart activity, appeared within four to six minutes of the onset of clinical signs. It was concluded that the sudden death syndrome is associated with an acute cardiovascular failure caused by a lethal cardiac dysrhythmia, ventricular fibrillation.