Electrocardiographic patterns of ventricular pre-excitation in dogs with right-sided accessory pathways.

INTRODUCTION: The aim of the study was to describe the electrocardiographic features of ventricular pre-excitation (VPE) patterns characterized by the presence of delta (δ) wave, short P-δQRS interval, wide δQRS complexes in dogs with right-sided accessory pathways. ANIMALS, MATERIALS AND METHODS: Twenty-six dogs with a confirmed accessory pathways (AP) via electrophysiological mapping were included. All dogs underwent a complete physical examination, 12-lead ECG, thoracic radiography, echocardiographic examination and electrophysiologic mapping. The AP were located in the following regions: right anterior, right posteroseptal, right posterior. The following parameters were determined: P-δQRS interval, δQRS duration, δQRS axis, δQRS morphology, δ-wave polarity, Q-wave, R-wave, R'-wave, S-wave amplitude, and R/S ratio. RESULTS: In lead II, the median δQRS complex duration was 82.4 (IQR 7.2) and the median P-δQRS interval duration was 54.6 (IQR 4.2) msec. The median δQRS complex axis in the frontal plane was: + 68° (IQR 52.5) for right anterior APs, - 24 ° (IQR 24) for right postero-septal APs, - 43.5 ° (IQR 27.25) for right posterior APs (P = 0.007). In lead II, the polarity of the δ wave was positive in 5/5 right anterior APs and negative in 7/11 postero-septal APs and 8/10 in right posterior APs. In precordial leads of all dogs, R/S was ≤ 1 in V1 and > 1 in all leads from V2 to V6. CONCLUSION: Surface electrocardiogram can be used to distinguish right anterior APs from right posterior and right postero-septal ahead of an invasive electrophysiological study.

Retrospective evaluation of hypertrophic cardiomyopathy in 68 dogs.

BACKGROUND: There is a lack of clinical data on hypertrophic cardiomyopathy (HCM) in dogs. HYPOTHESIS/OBJECTIVES: To investigate signalment, clinical signs, diagnostic findings, and survival in dogs with HCM. ANIMALS: Sixty-eight client-owned dogs. METHODS: Retrospective multicenter study. Medical records were searched between 2003 and 2015. The diagnosis of left ventricular (LV) hypertrophy was made by echocardiographic examination. RESULTS: Three hundred and forty-five dogs with LV hypertrophy were identified, of which 277 were excluded. The remaining 68 dogs were 0.3 to 14 years old and predominantly <10 kg (85%), and without a sex predilection. Twenty-four % were Shih Tzu and 24% terrier breeds. Most (80%) had a systolic heart murmur. Owner-determined exercise intolerance (37%) and syncope (18%) were most commonly reported signs. The majority (84%) of dogs had symmetrical LV hypertrophy, whereas asymmetrical septal and LV free wall hypertrophy was observed in 9% and 6% of dogs, respectively. Isolated basal interventricular septal hypertrophy was not observed. Commonly recorded were systolic anterior motion of the mitral valve (60%) and LV diastolic dysfunction (89% of dogs where diastolic function was evaluated). Six dogs died unexpectedly, and 3 developed congestive heart failure. Known survival times were between 1 day and 114 months after diagnosis. CONCLUSIONS AND CLINICAL IMPORTANCE: Hypertrophic cardiomyopathy in dogs should be considered as a differential diagnosis if LV hypertrophy is identified. Small breed dogs are overrepresented, and it is uncommon for dogs with HCM to develop CHF although sudden death can occur.

Cardiac Disease of Raptors.

Cardiac disease, in its various presentations, is being recognized as a common raptor health problem. Evidence suggests that the prevalence of cardiac disease varies between captive and wild bird of prey populations, probably because of differences in activity levels and diet. However, a wide variety of cardiovascular diseases have been reported to affect raptor species (captive and free living), including atherosclerosis, pathogenic arrhythmias, infectious cardiomyopathies, and endocarditis. Diagnostic testing used to identify cardiac abnormalities include radiographic imaging, electrocardiogram, echocardiogram, and computed tomography angiograms. Information pertaining to therapeutic treatment for raptor cardiac disease patients is inadequate or has not been investigated. This review of cardiac disease will provide current information regarding cardiac diseases that are diagnosed in birds of prey, diagnostic testing, and treatment options.

Immunofluorescent Localization of Plakoglobin Is Altered in Endomyocardial Biopsy Samples from Dogs with Clinically Relevant Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC).

Diagnosing the early stages of canine Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) is complicated by day-to-day arrhythmia variability, and absence of reliable, transthoracic echocardiographic features. Definitive diagnosis requires histopathologic identification of transmural fibrofatty replacement of the right ventricle. Reduction of immunofluorescent signal for plakoglobin (PG) at the intercalated disc (ID) is reported in ARVC-affected humans and boxers. Our objective was to determine whether reduced immunofluorescent signal for PG in endomyocardial biopsy samples (EMBs) correspond with a histopathologic diagnosis of ARVC. Here, 49 dogs were evaluated: 43 with advanced cardiac disease and 6 non-clinical boxers with mild to moderate ventricular arrhythmia (VA) burden. EMBs were obtained from all dogs; samples were prepared with antibodies recognizing cadherin (PC) and PG and evaluated with confocal microscopy. Investigators were blinded to breed and clinical status. ARVC was histopathologically diagnosed in 8 out of 49 dogs. Of these, three out of eight had clinical signs consistent with ARVC (two boxers, one English bulldog) and reduced PG signal at ID; five out of eight were non-clinical boxers with moderate VA and no reduction in PG. A total of 41 out of 49 dogs were histopathologically diagnosed with non-ARVC cardiac disease; 1 out of 41 showed reduction of PG at ID, while 40 out of 41 had no PG reduction. These results suggest that EMB PG signal is reduced in dogs with advanced ARVC, but not in the occult phase of the disease. Additionally, presence of PG at ID supports a diagnosis of non-ARVC cardiac disease in dogs with clinical signs. These results may offer an additional test that helps differentiate advanced ARVC from other myocardial diseases.

Optimizing single-chamber pacing in dogs Part 1: Rate determinations, rate interventions and hysteresis.

Determining ideal pacing rates to meet physiological needs and optimizing programming to prevent unnecessary right ventricular pacing in dogs requires an understanding of heart rate profiles and applicable pacing technology. The heart rate and rhythm of the dog is complex necessitating investigation of rate requirements of activity and circadian influences. Overlaying this information are a multiplicity of other factors such as age, breed, temperament, cardiovascular disease and underlining rhythm disorders that contribute to the difficulty in making general conclusions. However, all such information permits better implementation of programming options with the goal of better outcomes. In this review (Part 1 of a two-part review) instantaneous heart rate, rolling average heart rate, simple average heart rate, heart rate tachograms, RR interval tachograms (2D, 3D and dynamic), and Poincaré plots (2D, 3D and dynamic) are discussed as they apply to decisions in the determination and examination of pacing rates for dogs programmed in the VVI pacing mode (Ventricular paced, Ventricular sensed, Inhibited pacing). The applicable pacing operations available for three pacemaker companies are reviewed (Abbott, Biotronik/Dextronix, and Medtronic). The programmable options considered include: slowest pacing rate without additional features to extend the pacing interval, sleep/rest rate preferences, hysteresis to lengthen pacing interval following intrinsic beats, and intermittent increases in pacing following abrupt loss of intrinsic rhythm. Recommendations are suggested for follow-up of individual dogs with examination of pacing statistics and Holter monitoring.

Optimizing single-chamber pacing in dogs. Part 2: Rate adaptive pacing.

Proper programming of pacemakers for dogs in the rate adaptive mode requires an understanding of the rate requirements for each individual and the interplay of programmable features. The specific advantages and disadvantages of the rate adaptive mode should be considered on a case by case basis. Fundamentally, two components are linked in the implementation of rate adaptive pacing: (1) sensing the need for a change in rate and (2) responding with the appropriate alteration in pacing rate. The programming interaction of these two components are interdependent and affected by the rates programmed. These features may be adjusted manually or automatically. In this review (Part 2 of a two-part review) the considerations required to program each aspect that optimizes the pacing rate profile are reviewed. These include the lower rate, upper sensor rate, activities of daily life rate, sensor threshold, acceleration and deceleration, slope, activities of daily life zone, exertion zone, automatic versus manual adjustments and closed loop stimulation. The programming features of pacemakers manufactured by three companies are summarized (Abbott, formerly St. Jude; Biotronik/Dextronix; Medtronic). Means of assessing the success of pacemaker programing is examined through examples of pacemaker data, Holter analysis, Poincaré plots and tachograms. Finally, the questions and considerations for rate adaptive pacing in dogs that demand investigation are proposed.

Resolution of caval syndrome during initial hemodynamic stabilization in dogs with heartworm disease.

OBJECTIVE: To report on the spontaneous resolution of caval syndrome in 5 dogs selected for their response to medical stabilization prior to scheduled heartworm extraction. SERIES SUMMARY: Five dogs with heartworm caval syndrome were treated with sildenafil, fluid, and supplemental oxygen therapy. Moreover, 4 of 5 dogs were also administered pimobendan to achieve hemodynamic stabilization in preparation for percutaneous heartworm extraction. Spontaneous heartworm migration back into the pulmonary arteries was detected from 2 h to 5 days after treatment initiation. UNIQUE INFORMATION PROVIDED: Unanticipated spontaneous resolution of caval syndrome was documented in a low number of dogs after initiation of a patient stabilization protocol aiming at improving right ventricular hemodynamics and reducing pulmonary artery pressure prior to scheduled heartworm extraction. At this time, it is unknown if intervention to improve the hemodynamic status of the animal prior to heartworm extraction improves procedure outcome, and which factors contributed to the migration of the heartworms back into the pulmonary arteries in these selected cases. Therefore, this approach cannot be recommended in place of current recommendations for treatment of caval syndrome.

Beat-to-Beat Patterning of Sinus Rhythm Reveals Non-linear Rhythm in the Dog Compared to the Human.

The human and dog have sinus arrhythmia; however, the beat-to-beat interval changes were hypothesized to be different. Geometric analyses (R-R interval tachograms, dynamic Poincaré plots) to examine rate changes on a beat-to-beat basis were analyzed along with time and frequency domain heart rate variability from 40 human and 130 canine 24-h electrocardiographic recordings. Humans had bell-shaped beat-interval distributions, narrow interval bands across time with continuous interval change and linear changes in rate. In contrast, dogs had skewed non-singular beat distributions, wide interval bands {despite faster average heart rate of dogs [mean (range); 81 (64-119)] bpm compared to humans [74.5 (59-103) p = 0.005]} with regions displaying a paucity of intervals (zone of avoidance) and linear plus non-linear rate changes. In the dog, dynamic Poincaré plots showed linear rate changes as intervals prolonged until a point of divergence from the line of identity at a mean interval of 598.5 (95% CI: 583.5-613.5) ms (bifurcation interval). The dog had bimodal beat distribution during sleep with slower rates and greater variability than during active hours that showed singular interval distributions, higher rates and less variability. During sleep, Poincaré plots of the dog had clustered or branched patterns of intervals. A slower rate supported greater parasympathetic modulation with a branched compared to the clustered distribution. Treatment with atropine eliminated the non-linear patterns, while hydromorphone shifted the bifurcated branching and beat clustering to longer intervals. These results demonstrate the unique non-linear nature of beat-to-beat variability in the dog compared to humans with increases in interval duration (decrease heart rate). These results provoke the possibility that changes are linear with a dominant sympathetic modulation and non-linear with a dominant parasympathetic modulation. The abrupt bifurcation, zone of avoidance and beat-to-beat patterning are concordant with other studies demonstrating the development of exit block from the sinus node with parasympathetic modulation influencing not only the oscillation of the pacing cells, but conduction to the atria. Studies are required to associate the in vivo sinus node beat patterns identified in this study to the mapping of sinus impulse origin and exit from the sinus node.

Atrial Fibrillation: Current Therapies.

A rate control, or a rhythm control, strategy can be applied to the management of atrial fibrillation. Rate control of atrial fibrillation consists of decreasing the ventricular response rate by limiting the number of supraventricular impulses that can travel through the atrioventricular node. The goal of decreasing heart rate in dogs with atrial fibrillation is usually achieved with a combination of the calcium channel blocker diltiazem and digoxin. Rhythm control of atrial fibrillation encompasses pharmacologic and nonpharmacologic methods to terminate the arrhythmia and restore sinus rhythm. Transthoracic synchronized electrical cardioversion is commonly used to stop atrial fibrillation.

COMPUTED TOMOGRAPHIC MEASUREMENT OF THE MAIN PULMONARY ARTERY TO AORTIC DIAMETER RATIO IN HEALTHY DOGS: A COMPARISON TO ECHOCARDIOGRAPHICALLY DERIVED RATIOS.

Indicators of pulmonary hypertension in dogs examined with thoracic computed tomography (CT) are not well established in the veterinary literature. In humans, the main pulmonary artery to aortic diameter ratio (MPA:Ao) measured via CT, has been shown to be more sensitive than echocardiographic variables for predicting presence and severity of pulmonary hypertension, in some cases. In veterinary literature, the MPA:Ao has been determined echocardiographically to have an upper limit of about 1:1. Measurement of this ratio has not been described in dogs using CT. The objectives of this cross-sectional, prospective study were to compare echocardiographic measurement of MPA:Ao with that obtained via CT, determine if measurement of MPA:Ao via CT is repeatable and reproducible, and determine the effect of respiration and contrast administration on the measurement of MPA:Ao via CT. Ten healthy dogs without pulmonary hypertension were anesthetized to undergo thoracic CT using three protocols and echocardiography. The MPA:Ao was measured three times by three observers for each of the three CT protocols and compared to echocardiographic measurements. The mean MPA:Ao measured among all observers and CT protocols was 1.108 ± 0.152 (SD). The effect of CT scan protocol on MPA:Ao significantly differed among the three methods (P = 0.0014), where expiratory scans had lower MPA:Ao than inspiratory scans. The ratio measured on inspiratory CT scans consistently overestimated MPA:Ao when compared to echocardiography (bias = 0.226). Findings did not support the echocardiographically derived upper limit of MPA:Ao as an upper limit for determination of main pulmonary arterial enlargement on CT.

Fungal myocarditis and pericardial effusion secondary to Inonotus tropicalis (phylum Basidiomycota) in a dog.

Fungal disease is a rare cause of pericardial effusion in dogs. This report describes the first case of fungal pericardial effusion and myocarditis secondary to the fungal organism Inonotus tropicalis. A 9-year-old female spayed French bulldog with a multi-year history of treatment with glucocorticoids for management of atopy was presented for exercise intolerance, ascites and weight loss. Physical examination and thoracic imaging revealed enlarged peripheral and cranial mediastinal lymph nodes, left ventricular thickening and cardiac tamponade secondary to pericardial effusion. Fine needle aspiration of the cranial mediastinal lymph node showed pyogranulomatous inflammation with short, thin and poorly septated hyphae. Culture of the aspirate yielded a fungal isolate identified as Inonotus tropicalis based on morphologic features and rRNA gene sequencing. Postmortem examination showed myocardial thickening with multifocal to coalescing, firm, white, ill-defined nodules. Histology confirmed the presence of disseminated fungal infection with extensive myocardial involvement. Inonotus tropicalis is an opportunistic poroid wood-decaying basidiomycete. Infection in this dog was likely the result of chronic immunosuppressive therapy.

Effects of intramuscular sedation with alfaxalone and butorphanol on echocardiographic measurements in healthy cats.

OBJECTIVES: The aim of the study was to evaluate the effects of intramuscular (IM) injections of alfaxalone combined with butorphanol on echocardiographic (ECG) measurements in cats. METHODS: Client-owned adult domestic shorthair cats younger than 5 years of age were recruited. All cats that were considered healthy on the basis of physical examination, blood work, urinalysis, blood pressure measurement and baseline ECG underwent a second ECG under sedation. Cats were sedated with two separate IM injections of butorphanol at 0.2 mg/kg and alfaxalone at 2 mg/kg. ECG variables were analysed using a linear mixed model, and sedation scores were analysed using an ordinal mixed logistic model. The significance level was set at α = 0.05 and adjusted at α = 0.0017 for multiple comparisons of the ECG measurements. RESULTS: Ten healthy cats were included. Sedation was uneventful, and recovery was smooth and quick for all cats. The mean duration of lateral recumbency was 36.3 ± 4.37 mins. Reduction in heart rate following sedation approached statistical significance (P = 0.002). The thickness of the interventricular septum, the thickness of the left ventricular free wall, and the left ventricular internal dimensions in diastole and systole were not affected by the sedation. The changes in left atrium/aortic ratio and shortening fraction were statistically significant. Although the peak velocity of early diastolic transmitral flow (E) and late diastolic transmitral flow (A), the peak early diastolic (Ea) mitral valve annulus velocity, and the peak late diastolic (Aa) mitral valve annulus velocity changed after sedation, the ratios E/A, E/Ea and Ea/Aa were not significantly different after sedation. CONCLUSIONS AND RELEVANCE: IM injections of alfaxalone and butorphanol induced rapid, deep and short-lasting sedation. The mean differences after sedation were not clinically significant for most echocardiographic measurements.

Establishment of macrocyclic lactone resistant Dirofilaria immitis isolates in experimentally infected laboratory dogs.

BACKGROUND: Strains of Dirofilaria immitis suspected of lack of efficacy (LOE) to macrocyclic lactone (ML) preventive drugs have been increasingly reported in dogs by practicing veterinarians since 2005 in the Lower Mississippi Delta region. If proven, and not controlled in the early stages, the emergence of ML drug resistance threatens to become a widespread problem in the US that may limit the effectiveness of current preventive drug treatment methods. METHODS: To validate practice reports, a statewide survey of Louisiana veterinarians was done to define the extent of the problem and identify focal 'hotspots' of reported ML LOEs using Geographic Information Systems (GIS) methods. The present study then utilized microfilariae (Mf) from two canine field cases from different state locations that fit criteria for a high index of suspicion of LOE against heartworms by ML drugs. Blood containing Mf from the canine field cases was used to infect and produce L3 in Aedes aegypti for experimental infection of two groups of dogs, each of which contained two laboratory dogs, one treated with prophylactic ivermectin (12 µg/kg) monthly for 6 months at twice the label dose (6 µg/kg), and one untreated control. RESULTS: Both treated and untreated dogs from Group I and Group II developed patent D. immitis infections by 218 DPI and 189 DPI, respectively, as evidenced by a positive occult heartworm antigen test and microfilaremia by the Knott's test. Mf counts gradually increased post-patency in test and control dogs. Infective larvae raised from microfilariae from the treated Group I dog were used to successfully establish a second generation isolate, confirming heritability of resistance in the face of a monthly ivermectin challenge dose of 24 µg/kg, given monthly for 3 months. CONCLUSIONS: These experimental infection studies provide in vivo evidence of the existence of ML drug resistance in dogs infected by D. immitis L3 from suspect field LOE cases in the Lower Mississippi Delta. Results encourage further work on mechanisms underlying the emergence of ML resistance in D. immitis and development of evidence-based resistance management strategies for heartworm preventives in order to extend the useful life of current drugs.

Atrial septal pacing in small dogs: a pilot study.

OBJECTIVE: To determine the feasibility of atrial septal pacing via a delivery catheter-guided small non-retracting helix pacing lead. ANIMALS: Six healthy beagles (8.3-12.9 kg). METHODS: Using single plane fluoroscopic guidance, Medtronic(®) 3830 SelectSecure leads were connected to the atrial septum via Medtronic® Attain Select® II standard 90 Left Heart delivery catheter. Pacing threshold and lead impedance were measured at implantation. The Wenckebach point was tested via atrial pacing up to 220 paced pulses per minute (ppm). Thoracic radiographs were performed following implantation to identify the lead position, and repeated at 24 h, 1 month, and 3 months post-operatively. RESULTS: Macro-lead dislodgement occurred in two dogs at 24 h and in three dogs at one-month post-implantation. Lead impedance, measured at the time of implantation, ranged from 583 to 1421 Ω. The Wenckebach point was >220 ppm in four of the six dogs. The remaining two dogs had Wenckebach points of 120 and 190 ppm. CONCLUSIONS: This pilot study suggests the selected implantation technique and lead system were inadequate for secure placement in the atrial septum of these dogs. The possible reasons for inadequate stability include unsuitable lead design for this location, inadequate lead slack at the time of implantation and inadequate seating of the lead as evidenced by low impedance at the time of implantation. Other implantation techniques and/or pacing leads should be investigated to determine the optimal way of pacing the atria in small breed dogs that are prone to sinus node dysfunction.

Outcome of a heartworm treatment protocol in dogs presenting to Louisiana State University from 2008 to 2011: 50 cases.

Since 2008, the American Heartworm Society has recommended using a three-dose melarsomine protocol (a single intramuscular injection of melarsomine dihydrochloride at 2.5mg/kg, followed approximately 1 month later with two doses administered 24h apart) for all heartworm-positive dogs, with doxycycline given at 10mg/kg twice daily for 4 weeks prior to administration of melarsomine. To report the efficacy and side effects of this standard heartworm treatment protocol in 50 dogs presenting to our hospital from 2008 to 2011, information on the history, clinical, laboratory, and diagnostic imaging findings and treatment was obtained from medical records. When possible, additional follow-up information was obtained through telephone interviews with referring veterinarians and owners. Twenty-six dogs (52%) experienced minor complications, such as injection site reactions, gastrointestinal signs (vomiting, diarrhea, inappetance), and behavioral changes (lethargy, depression) during or after heartworm treatment. Twenty-seven dogs (54%) experienced respiratory signs (coughing, dyspnea) and heart failure attributed to progressive heartworm disease and worm death. Seven dogs (14%) died within the treatment period. Owners frequently reported behavioral changes, such as depression and lethargy, suspected to be secondary to pain. Fifty percent of owners surveyed indicated that, prior to the diagnosis, they either were not currently administering heartworm preventative, or they had recently adopted the dog from a shelter that did not administer preventatives. After treatment, 100% were administering heartworm preventatives to their pet. Eighteen dogs (36%) received a heartworm antigen test 6 months after adulticide therapy, 12 of which tested negative and six tested positive. Four of the dogs with a positive test at 6 months had negative tests 1 month later with no additional treatment. Adverse effects were common with the recommended protocol, but the majority of these were mild. Dogs in Class 1 (i.e., heartworm positive but otherwise largely lacking clinical evidence of disease) did not experience any major adverse effects or death.

Comparison of cardiac output determined by an ultrasound velocity dilution cardiac output method and by the lithium dilution cardiac output method in juvenile horses with experimentally induced hypovolemia.

OBJECTIVE: To assess the accuracy of an ultrasound velocity dilution cardiac output (UDCO) method, compared with that of the lithium dilution cardiac output (LiDCO) method, for determination of cardiac output (CO) in juvenile horses with experimentally induced hypovolemia. ANIMALS: 12 anesthetized 2- to 6-month-old horses. PROCEDURES: For each anesthetized horse, CO was determined by the LiDCO and UDCO methods prior to any intervention (baseline state), after withdrawal of approximately 40% of the horse's blood volume (low CO state), after maintenance of hypovolemia and infusion of norepinephrine until mean arterial blood pressure was equal to baseline value (high CO state), and after further infusion of norepinephrine and back-transfusion of withdrawn blood (posttransfusion state). For each of the 4 hemodynamic situations, CO and calculated cardiac index (CI) values were obtained by each method in duplicate (8 pairs of measurements/horse); mean values for each horse and overall mean values across all horses were calculated. Agreement between CI determined by each method (96 paired values) was assessed by Bland-Altman analysis. RESULTS: For the UDCO method-derived CI measurements among the 12 horses, mean ± SD bias was -4 ± 11.3 mL/kg/min (95% limits of agreement, -26.1 to 18.2 mL/kg/min) and mean relative bias was -10.4 ± 21.5% (95% limits of agreement, -52.6% to 31.8%). CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that, compared with the LiDCO method, the UDCO method has acceptable clinical usefulness for determination of CO in foals.

Transthoracic lung ultrasound in normal dogs and dogs with cardiogenic pulmonary edema: a pilot study.

Pulmonary edema is the most common complication of left-sided heart failure in dogs and early detection is important for effective clinical management. In people, pulmonary edema is commonly diagnosed based on transthoracic ultrasonography and detection of B line artifacts (vertical, narrow-based, well-defined hyperechoic rays arising from the pleural surface). The purpose of this study was to determine whether B line artifacts could also be useful diagnostic predictors for cardiogenic pulmonary edema in dogs. Thirty-one normal dogs and nine dogs with cardiogenic pulmonary edema were prospectively recruited. For each dog, presence or absence of cardiogenic pulmonary edema was based on physical examination, heartworm testing, thoracic radiographs, and echocardiography. A single observer performed transthoracic ultrasonography in all dogs and recorded video clips and still images for each of four quadrants in each hemithorax. Distribution, sonographic characteristics, and number of B lines per thoracic quadrant were determined and compared between groups. B lines were detected in 31% of normal dogs (mean 0.9 ± 0.3 SD per dog) and 100% of dogs with cardiogenic pulmonary edema (mean 6.2 ± 3.8 SD per dog). Artifacts were more numerous and widely distributed in dogs with congestive heart failure (P < 0.0001). In severe cases, B lines increased in number and became confluent. The locations of B line artifacts appeared consistent with locations of edema on radiographs. Findings from the current study supported the use of thoracic ultrasonography and detection of B lines as techniques for diagnosing cardiogenic pulmonary edema in dogs.

Shunting between the CVC and both the azygos vein and thoracic duct in a dog with CTD.

A 5 mo old female rottweiler was referred for evaluation of a suspected congenital heart disease. Clinical signs included anorexia, exercise intolerance, and severe loss of body condition. Clinical examination revealed dyspnea, pale mucous membranes, and weak femoral pulses. Pleural and abdominal effusions and iron deficiency anemia were identified. A distended intrathoracic caudal vena cava (CVC) visible on thoracic radiographs suggested that the modified transudate abdominal effusion was the result of improper venous return to the right side of the heart. Cor triatriatum dexter (CTD) was diagnosed via echocardiography but did not explain all the anomalies detected during a contrast echocardiography. Abnormal communications between the CVC and azygos vein and the CVC and thoracic duct were subsequently identified by abdominal ultrasonography and angiography. Medical management with diuretics, iron supplements, and surgical treatment of CTD resulted in normalization of the respiratory rate, the exercise intolerance, and the anemia. To the authors' knowledge, this is the first reported case of CTD associated with shunts between the CTV and both the azygos vein and thoracic duct in dogs. This report emphasizes the importance of presurgical assessment of concurrent thoracic and abdominal congenital vascular abnormalities.