Ventricle Of Dog Research Articles

Effect of Skull Type on the Relative Size of Cerebral Cortex and Lateral Ventricles in Dogs.

Volume measurements of the brain are of interest in the diagnosis of brain pathology. This is particularly so in the investigation hydrocephalus and canine cognitive dysfunction (CCD), both of which result in thinning of the cerebral cortex and enlarged ventricles. Volume assessment can be made using computed tomography or more usually magnetic resonance imaging (MRI). There is, however, some uncertainty in the interpretation of such volume data due to the great variation in skull size and shape seen in dog. In this retrospective study, we examined normal MRI images from 63 dogs <6 years of age. We used a continuous variable, the cranial index (CrI) to indicate skull shape and compared it with MRI volume measurements derived using Cavalieri’s principle. We found a negative correlation between CrI and the ratio of cortical to ventricular volume. Breeds with a high CrI (large laterolateral compared to rostrocaudal cranial cavity dimension) had a smaller ratio of cortical to ventricular volume (low C:V ratio) than breeds with lower CrI skull types. It is important to consider this effect of skull shape on the relative volume estimates of the cerebral cortex and ventricles when trying to establish if pathology is present.

Repolarization of Heart Ventricles in Dogs during Recovery after Antiorthostatic Hypokinesia.

Repolarization properties of ventricular myocardium were studied in anesthetized adult dogs of both sexes subjected to antiorthostatic hypokinesia (head-down tilt at 45° and 60° to the horizontal) and during recovery period (horizontal position for 15 min). The time of repolarization of ventricular myocardium during recovery surpassed the initial value, which represents an adaptive response of the heart to antiorthostasis.

Seroprevalence of circulating Angiostrongylus vasorum antigen and parasite-specific antibodies in dogs from Portugal

Angiostrongylus vasorum is a nematode that lives in the pulmonary arteries and right cardiac ventricle of domestic dogs and wild canids. It is increasingly being reported in several European countries and North America. This parasite induces inflammatory verminous pneumonia, causing severe respiratory disease in dogs. In some instances, coagulopathies, neurological signs and even death may occur. Scant data are available regarding the occurrence of A. vasorum in Portugal. Therefore, sera of 906 shelter dogs from North to South mainland Portugal were collected. ELISAs to detect A. vasorum circulating antigen and specific antibodies against this parasite were performed. A total of six dogs [0.66 %, 95 % confidence intervals (CI) 0.24–1.43] were positive for both A. vasorum antigen and antibody detection, indicating an active infection, and 12 dogs (1.32 %, CI 0.68–2.30) were A. vasorum antibody-positive only. Regions with antigen- and antibody-positive animals overlapped and were distributed over nearly all sampled areas in the country. This is the first large-scale ELISA-based serological survey for A. vasorum in dogs from Portugal. The endemic occurrence of A. vasorum in dogs from different geographical areas of Portugal is therefore confirmed.

Acetylation mediates Cx43 reduction caused by electrical stimulation

Communication between cardiomyocytes depends upon gap junctions (GJ). Previous studies have demonstrated that electrical stimulation induces GJ remodeling and modifies histone acetylase (HAT) and deacetylase (HDAC) activities, although these two results have not been linked. The aim of this work was to establish whether electrical stimulation modulates GJ-mediated cardiac cell–cell communication by acetylation-dependent mechanisms. Field stimulation of HL-1 cardiomyocytes at 0.5Hz for 24h significantly reduced connexin43 (Cx43) expression and cell–cell communication. HDAC activity was down-regulated whereas HAT activity was not modified resulting in increased acetylation of Cx43. Consistent with a post-translational mechanism, we did not observe a reduction in Cx43 mRNA in electrically stimulated cells, while the proteasomal inhibitor MG132 maintained Cx43 expression. Further, the treatment of paced cells with the HAT inhibitor Anacardic Acid maintained both the levels of Cx43 and cell–cell communication. Finally, we observed increased acetylation of Cx43 in the left ventricles of dogs subjected to chronic tachypacing as a model of abnormal ventricular activation.In conclusion, our findings suggest that altered electrical activity can regulate cardiomyocyte communication by influencing the acetylation status of Cx43.

Magnetic resonance imaging signs of high intraventricular pressure--comparison of findings in dogs with clinically relevant internal hydrocephalus and asymptomatic dogs with ventriculomegaly.

BackgroundMagnetic resonance imaging (MRI) findings of canine brains with enlarged ventricles in asymptomatic dogs were compared to those in dogs with clinically relevant internal hydrocephalus, in order to determine the imaging findings indicative of a relevant increase in intraventricular pressure. Discrimination between clinically relevant hydrocephalus and ventriculomegaly based on MRI findings has not been established yet and is anything but trivial because of the wide variation in ventricular size in different dog breeds and individuals. The MRI scans of the brains of 67 dogs of various breeds, skull conformation and weight were reviewed retrospectively. Based on clinical and imaging findings, the dogs were divided into three groups: a normal group (n = 20), a group with clinically silent ventriculomegaly (n = 25) and a group with severe clinically relevant internal hydrocephalus (n = 22). In addition to the ventricle/brain-index, a number of potential subjective signs of increased intraventricular pressure were recorded and compared between the groups.ResultsThe ventricle/brain-index was significantly higher in dogs with relevant hydrocephalus (p < 0.001) and a threshold value of 0.6 was specified as a discriminator between internal hydrocephalus and ventriculomegaly. Other MR imaging findings associated with clinically relevant hydrocephalus were an elevation of the corpus callosum (p < 0.01), dorsoventral flattening of the interthalamic adhesion (p < 0.0001), periventricular edema (p < 0.0001), dilation of the olfactory recesses (p < 0.0001), thinning of the cortical sulci (p < 0.0001) and/or the subarachnoid space (p < 0.0027) and disruption of the internal capsule adjacent to the caudate nucleus (p < 0.0001).ConclusionA combination of the abovementioned criteria may support a diagnosis of hydrocephalus that requires treatment.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-015-0479-5) contains supplementary material, which is available to authorized users.

Combined Serological Detection of Circulating Angiostrongylus vasorum Antigen and Parasite-specific Antibodies in Dogs from Hungary.

The occurrence of the nematode Angiostrongylus vasorum, also known as the French heartworm, is increasingly being reported from various European countries. The adults of this parasite species live in the pulmonary arteries and right cardiac ventricle of wild canids and domestic dogs. Larval stages and eggs in the lungs induce inflammatory verminous pneumonia, causing severe respiratory disease in dogs. Furthermore, haematological and neurological signs and even death may occur. In Hungary, A. vasorum has been identified in red foxes, golden jackals and in two dogs and some slugs. In this first large-scale survey, 1247 sera from pet dogs were collected and tested by an ELISA for the detection of circulating antigen of A. vasorum and by a separate ELISA to detect specific antibodies against the parasite. A total of 1.36% (n = 17, 95 % confidence intervals, CI: 0.80 - 2.17 %) of the animals were positive in both ELISAs, while 1.76 % (n = 22, CI: 1.11 - 2.66 %) of the tested dogs were antigen-positive only and 2.73 % (n = 34, CI: 1.90 - 3.79 %) were positive for specific antibodies only. Regions with antigen- and antibody-positive animals overlapped and were distributed over nearly the whole sampled areas of the country. A considerable number of cases was observed in Budapest and also in the southern part of the country bordering Croatia, while in the most eastern part bordering Ukraine no positive samples were detected. These results confirm the endemic occurrence of A. vasorum in dogs originating from different parts of Hungary and the significant advantages of A. vasorum serology in epidemiological studies.

Tissue Doppler and strain imaging of left ventricle in Beagle dogs with iatrogenic hypercortisolism.

Changes in radial and longitudinal left ventricular (LV) function were investigated in beagles with iatrogenic hypercortisolism. A total of 11 normal dogs were used, and 2 mg/kg prednisone was administered per oral q12 h for 28 days to 7 out of 11 dogs to induce iatrogenic hypercortisolism. Body weight, blood pressure, conventional echocardiography and tissue Doppler imaging (TDI) of normal and iatrogenic hypercortisolism groups were conducted. The myocardial wall velocity of the LV was measured using color TDI and myocardial deformation was determined by the strain and strain rate. Conventional echocardiography revealed that the diastolic LV free wall and interventricular septum in the hypercortisolism group were thickened relative to those in the normal group. The peak early diastolic myocardial velocity and early to late diastolic myocardial velocity ratio of TDI in the hypercortisolism group were significantly lower than those in the normal group. The strain values in the hypercortisolism group were significantly lower than those in the normal group, particularly for longitudinal wall motion. The lower values of myocardium from TDI and strain imaging could be used to investigate subclinical LV systolic and diastolic dysfunction in dogs with the iatrogenic hypercortisolism.

Abstract 13799: Electrical Pacing Inhibits Gap Junction-Mediated Cardiac Cell -Cell Communication by Promoting Cx43-Acetylation

Background: Communication among cardiomyocytes depends upon Gap Junction (GJ) protein expression and conductance. Previous studies demonstrated that electrical stimulation can induce GJ remodeling and evidences from neurons also indicate that electrical pacing modifies Lysine acetylase (KAT) and deacetylases (KDAC) activities. Objectives: Aim of the present work was to establish whether electrical stimulation modulates GJ-mediated cardiac cell-cell communication by acetylation dependent mechanisms. Methods and Results: Neonatal rat cardiomyocytes (NRCM; n=3) and in HL-1 atrial cells (n=20) were exposed to electrical field stimulation for 24 hours (Ionoptix C-Pace®; 0.5 Hz, 20 V, 0.5 msec pulses). Connexin 43 (Cx43) expression decreased almost 50% in NRCM and 40 % in HL-1; in contrast Cx40 and Cx45 expression was unchanged. Further, confocal microscopy revealed that electrical stimulation induced Cx43 accumulation in the cytoplasm of HL-1 cells. Electrical stimulation significatly down-regulated KDAC activity up to the 30% (n=3), whereas KAT activity was not modified; the net effect was a general increase of cell protein acetylation, confirmed by western blot analysis. Specifically, the pacing-dependent acetylation of Cx43 was proven by immunoprecipitation assay (n=5). Interestingly, our model mimicked the action of the KDAC pan-inhibitors TSA and SAHA on Cx43 expression and intracellular distribution, although we did not observe Cx43 mRNA significant reduction in electrically stimulated cells. In agreement, MG132 proteasome inhibitor (10 μM) restored Cx43 expression level. Finally, also the treatment of paced cells with the KAT inhibitor Anacardic Acid (0.5 μM) was able to rescue Cx43 level (n=4). Intriguingly, preliminary results also indicate lateralization and increased acetylation of Cx43 in the left ventricles of dogs with pacing-induced dilated cardiomyopathy (n=2). Conclusions: In vitro electrical stimulation of cardiac cells promotes Cx43 acetylation, which results in Cx43 down-modulation and intracellular relocalization. These findings suggest that electrical activity-dependent increase in acetylation may represent a novel mechanism for the regulation of cardiomyocyte communication.

Potential role of potassium currents in the repolarization reserve: the importance of cardiac repolarization reserve in safety pharmacology

E-mail: jost.norbert@gmail.com Cardiac repolarization is a delicate process and the determinants of repolarization in various species are poorly understood. This study compared the contribution of IK1, IKr and IKs to cardiac repolarization in canine and human ventricular preparations by applying conventional microelectrode, whole cell patch-clamp and molecular biological techniques. Pharmacological inhibition of IKr evokes modest prolongation of repolarization in the dog ventricle, while it largely lengthens it in the human. These results suggest that in human, in addition to its known effect to establish the resting membrane potential, IK1 is contributing only to the repolarization reserve, while in the dog, IK1 also plays a role to secure the normal repolarization. Therefore, the smaller IK1 in human comparing to the dog makes the ventricle more susceptible to repolarization lengthening in the human than in the dog. This should be taken into consideration when pharmacological results from the dog studies are extrapolated to the human, i.e. the effect on repolarization of drugs potentially blocking IKr/HERG channels can be underestimated in the human based on experiments performed in the dog. We conclude that humans show much greater repolarizationdelaying effects of IKr-block than dogs, because of lower repolarization-reserve contributions from IK1 and IKs. These results are relevant to understanding species-specific determinants of repolarization and emphasize the limitations of animal models for the human disease.

Serum cardiac troponin I concentrations in clinically normal and Dirofilaria immitis infected Korean Jindo dogs

Abstract : This study was conducted to determine the serum cardiac troponin I (cTnI) concentrations in clinically normal(uninfected) Korean Jindo dogs and those infected with Dirofilaria (D.) immitis. Forty Korean Jindo dogs (22 females,18 males) were obtained from two kennels in the Boryeong area of Chungnam Province and the Daejeon area, Korea.Significantly higher cTnI concentrations were observed in D. immitis-infected dogs than clinically normal dogs. cTnItesting in addition to thoracic radiography, echocardiography, and electrocardiography shows promise as an additionalmethod for diagnosis of heartworm infection.Keywords : cardiac troponin I, Dirofilaria immitis, Korean Jindo dog Dirofilaria (D.) immitis resides in the pulmonary arteries,right ventricle, and right atrium of infected dogs, cats, ferretsand wild canids in temperate, tropic and subtropic zones [4].Canine heartworm disease can be manifested by thromboem-bolism, pulmonary hypertension, right-sided congestive heartfailure, and ascites. Korea is in the temperate zone and is oneof the enzootic regions of D. immitis [7, 8]. The prevalenceof heartworm disease in Korean dogs was estimated to be28.3% in a survey conducted from 1994 to 1995 that used anantigen test [3]. Using a similar antigen test, a recent surveyof several Korean provinces, conducted from 2001 to 2002,revealed an increase in the prevalence of heartworm infec-tion to 40.0% [7]. However, a recent report showed thatnumbers of cases of canine heartworm disease diagnosedfrom 2007 to 2008 had decreased, although the risk of expo-sure to this nematode in the breeding farms is still high [8].Injury to the sarcomere leads to the detachment of cardiactroponin I (cTnI) from actin, and the subsequent disruption ofthe cell membrane allows leakage of cTnI into the generalcirculation [5]. A high level of cTnI in serum or plasma isconsidered to be a very sensitive and specific indicator ofmyocardial cell damage and necrosis [5]. An elevated cTnIconcentration is associated with poor long-term outcomesand is an independent predictor of mortality [2]. The objec-tive of this study was to determine serum cTnI concentrationin Korean Jindo dogs clinically normal and uninfected orinfected with D. immitis. Forty Korean Jindo dogs (22 females, 18 males; weight,17~23 kg) were obtained from 2 kennels in the Boryeongarea of Chungnam Province and the Daejeon area, Korea.The ages of the dogs ranged from 1 to 12 years (median; 4.1years). They underwent physical examinations, and evalua-tions of serum biochemistries and cTnI concentrations. Thedogs were divided into 2 groups. Twenty dogs were assignedto the clinically normal group and 20 dogs were assigned tothe D. immitis-infected group. None of the D. immitis-infected dogs had laboratory abnormalities or clinical signssuch as exercise intolerance, dyspnea, cough, ascites and car-diac murmurs. To these dogs were therefore classified withmild canine heartworm disease severity [5]. The dogs werefasted for 12 hours prior to blood collection. Blood sampleswere collected through cephalic venipuncture, and each sam-ple was allowed to clot at room temperature for 30 min, andthen centrifuged at 1,500 × g for 5 min. Aliquots of serumwere frozen in plastic tubes at −80

Interoperable executive library for the simulation of biomedical processes

We present an Interoperable Executive Library (IEL) built to run, in parallel, a collection of multi-component tasks focusing on simulating complex biomedical phenomena of the heart. The IEL is a light-weight software integrator designed for managing the distribution of data and memory, coordinates communication among parallel processes, and directs execution of a set of loosely coupled numerical and physics tasks or modules. The dynamical process of the heart uses computing modules of electrical generation, physiological signal propagation, mechanics deformation, and fluid flow transportation. The cardiac electro-physiology is represented by a reaction–diffusion equations using the Beeler–Reuter model. The contracting motion of the heart is described by the continuum mechanical equilibrium equations. At the end of a heart beat, the fluid flow pattern inside the ventricle is computed by solving the incompressible Navier–Stokes equations. The finite element method is used to solve these loosely coupled sets of equations. Simulations are performed on two simplified heart models as well as a dog ventricle. The functionality and performance of the IEL framework on a distributed computing system are demonstrated and shown.

Long-Duration Ventricular Fibrillation Exhibits 2 Distinct Organized States

Previous studies showed that endocardial activation during long-duration ventricular fibrillation (VF) exhibits organized activity. We identified and quantified the different types of organized activity. Two 64-electrode basket catheters were inserted, respectively, into the left ventricle and right ventricle of dogs to record endocardial activation from the endocardium during 7 minutes of VF (controls, n=6). The study was repeated with the K(ATP) channel opener pinacidil (n=6) and the calcium channel blocker flunarizine (n=6). After 2 minutes of VF without drugs, 2 highly organized left ventricular endocardial activation patterns were observed: (1) ventricular electric synchrony pattern, in which endocardial activation arose focally and either had a propagation sequence similar to sinus rhythm or arose near papillary muscles, and (2) stable pattern, in which activation was regular and repeatable, sometimes forming a stable re-entrant circuit around the left ventricular apex. Between 3 and 7 minutes of VF, the percent of time ventricular electric synchrony was present was control=25%, flunarizine=24% (P=0.44), and pinacidil=0.1% (P<0.001) and the percent of time stable pattern was present was control=71%, flunarizine=48% (P<0.001), and pinacidil=56% (P<0.001). The remainder of the time, nonstable re-entrant activation with little repeatability was present. After 3 minutes, VF exhibits 2 highly organized endocardial activation patterns 96% of the time, one potentially arising focally in the Purkinje system that was prevented with a K(ATP) channel opener but not a calcium channel blocker and the other potentially arising from a stable re-entrant circuit near the apical left ventricular endocardium.

“Compensated hyperosmolarity” of cerebrospinal fluid and the development of hydrocephalus

Acute osmolar loading of cerebrospinal fluid within one lateral ventricle of dogs was examined as a cause of water extraction from the bloodstream and an increase in intracranial pressure. We have shown that a certain amount of 3H2O from the bloodstream enters osmotically loaded cerebrospinal fluid significantly faster, hence causing a significant increase in intracranial pressure. The noted phenomenon in which intracranial pressure still significantly increases, but in which the hyperosmolarity of the cerebrospinal fluid is no longer present, was named “compensated hyperosmolarity”. In the case of the sub-chronic application of hyperosmolar solutions into cat ventricles, we observed an increase in cerebrospinal fluid volume and a more pronounced development of hydrocephalus in the area of application, but without significant increase in intracranial pressure and without blockage of cerebrospinal fluid pathways. These results support the newly proposed hypothesis of cerebrospinal fluid hydrodynamics and the ability to develop new strategies for the treatment of cerebrospinal fluid-related diseases.

Volume overload induces differential spatiotemporal regulation of myocardial soluble guanylyl cyclase in eccentric hypertrophy and heart failure

Nitric oxide activation of soluble guanylyl cyclase (sGC) blunts the cardiac stress response, including cardiomyocyte hypertrophy. In the concentric hypertrophied heart, oxidation and re-localization of myocardial sGC diminish cyclase activity, thus aggravating depressed nitric oxide–cyclic guanosine monophosphate (NO–cGMP) signaling in the pressure-overloaded failing heart. Here, we hypothesized that volume-overload differentially disrupts myocardial sGC activity during early compensated and late decompensated stages of eccentric hypertrophy. To this end, we studied the expression, redox state, subcellular localization, and activity of sGC in the left ventricle of dogs subjected to chordal rupture-induced mitral regurgitation (MR). Unoperated dogs were used as Controls. Animals were studied at 4weeks and 12months post chordal rupture, corresponding with early (4wkMR) and late stages (12moMR) of eccentric hypertrophy. We found that the sGC heterodimer subunits relocalized away from caveolae-enriched lipid raft microdomains at different stages; sGCβ1 at 4wkMR, followed by sGCα1 at 12moMR. Moreover, expression of both sGC subunits fell at 12moMR. Using the heme-dependent NO donor DEA/NO and NO-/heme-independent sGC activator BAY 60-2770, we determined the redox state and inducible activity of sGC in the myocardium, within caveolae and non-lipid raft microdomains. sGC was oxidized in non-lipid raft microdomains at 4wkMR and 12moMR. While overall DEA/NO-responsiveness remained intact in MR hearts, DEA/NO responsiveness of sGC in non-lipid raft microdomains was depressed at 12moMR. Caveolae-localization protected sGC against oxidation. Further studies revealed that these modifications of sGC were also reflected in caveolae-localized cGMP-dependent protein kinase (PKG) and MAPK signaling. In MR hearts, PKG-mediated phosphorylation of vasodilator-stimulated phosphoprotein (VASP) disappeared from caveolae whereas caveolae-localization of phosphorylated ERK5 increased. These findings show that differential oxidation, re-localization, and expression of sGC subunits distinguish eccentric from concentric hypertrophy as well as compensated from decompensated heart failure.

An Assessment of Left Ventricular Systolic Function with the Use of a Continuous Doppler Imaging in Dogs with Spontaneous Mitral Regurgitation. A Preliminary Study

Abstract The aim of this study was to evaluate systolic function of left ventricle in dogs with spontaneous mitral regurgitation by estimating the rate of pressure rise in the left ventricle (dP/dt). Ninety-three dogs of different breed and sex, with chronic degenerative valvular disease were examined. All dogs had echocardiography examination with dP/dt estimation assessed from mitral regurgitant jet using continuous Doppler-echocardiography. The dogs were divided into four classes of heart failure according to NYHA class. Results: dogs in NYHA I dP/dt = 2,142 ±1,309, SF=33.6±10.5, EF=66.58± 14; NYHA II dP/dt = 3,062 ±1,798, SF=42 ±10, EF=76.5 ±11.5; NYHA III dP/dt = 3,483 ±2,136, SF=44.2 ±21, EF=75.7 ±13; NYHA IV dP/dt = 4,496 ±1,797, SF=40.6 ±6, EF=70.4 ±16. Dogs with chronic cardiac insufficiency and mitral insufficiency due to chronic degenerative valvular disease had no echocardiograhic evidence of left ventricular systolic dysfunction assessed from mitral regurgitant jet dP/dt.

About half of the late sodium current in cardiac myocytes from dog ventricle is due to non-cardiac-type Na+ channels

Voltage gated sodium channels (NaVs) are essential to propagate neuronal and cardiac electrical impulses. While the cardiac Na+ current (INa) is often all attributed to the cardiac isoform, NaV1.5, some evidence suggests that other Na+ channel isoforms are also expressed in the heart ventricle. One way to distinguish Na+ channels is by their sensitivity to tetrodotoxin (TTX); various “non-cardiac-type” Na+ channels are relatively sensitive to TTX (denoted tNaV channels) compared to NaV1.5 channels. tNaV channels have been detected in hearts with various pathological conditions such as hypertrophy, infarction and ischemia, where they might enhance the late Na+ current (INaL) thereby prolonging the action potential under such conditions (resulting in a prolonged QT interval on the EKG). The principal aim of this article is to evaluate the extent to which non-cardiac isotypes contribute to INaL under normal physiological conditions. INaL was measured in acutely dissociated dog cardiomyocytes using the patch-clamp technique. Our results indicate that 44% on average of the late INa current is due to non-cardiac NaVs. Previous studies indicated that the overexpression of non-cardiac NaV channels is responsible for the prolonged duration of the cardiac action potential (and, thereby, a prolonged QT interval) under pathophysiological conditions associated with various heart diseases. Our finding indicates that non-cardiac NaV channels are strong contributors to INaL under physiological conditions thereby suggesting that these channels are also major determinants of the duration of the cardiac action potential even in healthy hearts. Interestingly, these results may explain the observations of cardiac arrhythmias associated with prolonged QT intervals in people with inherited neuronal and musculoskeletal diseases involving mutations that enhance the current from non-cardiac-type NaVs, a connection which apparently was never made before.

A Fully Coupled Model for Electromechanics of the Heart

We present a fully coupled electromechanical model of the heart. The model integrates cardiac electrophysiology and cardiac mechanics through excitation-induced contraction and deformation-induced current. Numerical schemes based on finite element were implemented in a supercomputer. Numerical examples were presented using a thin cardiac tissue and a dog ventricle with realistic geometry. Performance of the parallel simulation scheme was studied. The model provides a useful tool to understand cardiovascular dynamics.

Leptin Expression in Dogs with Cardiac Disease and Congestive Heart Failure

Leptin belongs to the group of adipokines and has recently attracted attention because of its effects on the cardiovascular system. Increased leptin concentrations are reported in obese dogs but its role in cardiac disease (CD) is not known. Therefore, we investigated leptin expression in blood samples from dogs with congestive heart failure (CHF), and from myocardial samples of dogs with CDs. Leptin mRNA was analyzed from blood samples of 8 dogs presented for cardiac screening in which no abnormalities were detected and 8 dogs in CHF. In addition, myocardial samples (interventricular septum, right and left atria, and ventricles) of 10 dogs with no cardiac abnormalities (controls), 7 dogs with acquired and 3 dogs with congenital CDs were investigated using real-time polymerase chain reaction (PCR). Dogs with CHF had significantly higher blood concentrations of leptin mRNA than dogs without CD (P = .013). Myocardial leptin expression was significantly increased in acquired (P = .035) and decreased in congenital CD (P = .016) in comparison to controls. Dogs in heart failure stage D showed higher myocardial leptin concentrations than dogs in stage C3 and B (P = .031). Differences according to myocardial region (P < .05) were detected and higher leptin concentrations were present in the atria in comparison to the ventricles in dogs with CD (P = .005). Comparing male and female dogs with CD revealed higher leptin concentrations in female dogs (P = .001). These results indicate leptin mRNA concentrations vary with CD, severity of CD, myocardial region, and possibly sex. Therefore, leptin might play a role in canine CD.

Contractile Strength during Variable Heart Duration Is Species and Preload Dependent

We investigate the effect of beat-to-beat variability on cardiac contractility. Cardiac trabeculae were isolated from the right ventricle of rabbits and beagle dogs and stimulated to isometrically contract, alternating between fixed steady state versus variable interbeat intervals. Trabeculae were stimulated at physiologically relevant frequencies for each species (dog 1 and 4 Hz; rabbit 2 and 4 Hz) intercalating fixed periods with 40% variability. A subset of the trabeculae (at 90% of optimal length) was stretched prior to stimulation between 5 and 13% and stimulated at the same frequencies with a fixed versus 40% variation. Fixed rate response at the same base frequency was measured before and after each variable period and the average force reported. In canine preparations no change in force was observed as a result of the imposed variability in beat-to-beat duration. In the rabbit, we observed a nonsignificant decrease in force between fixed and variable pacing at both 2 and 4 Hz (n = 8) when 40% variability was introduced. When a 5% and 13% stretch was applied, the correlation coefficient sharply increased, indicating a more prominent impact of the prebeat duration on the following cycle with higher preload.

E0662 Evaluation of the whole and regional myocardial function of left ventricle in dogs with congestive heart failure induced by fast right ventricular pacing

ObjectiveUse the Doppler and strain rate imaging (SRI) to evaluate the systolic and diastolic function of the whole and regional ventricular myocardial in congestive heart failure dog models induced by...