ECHOCARDIOGRAPHIC ASSESSMENT OF 537 DOGS WITH MITRAL VALVE PROLAPSE AND LEAFLET INVOLVEMENT

In this work we investigated which mitral valve leaflet was most often involved in mitral valve prolapse with degenerative mitral valve disease and whether there was an association with breed, age, gender, or weight. Five hundred and thirty-seven dogs with mitral valve prolapse-degenerative mitral valve disease were assessed; the cross-breed dog was the most represented breed (248 dogs, 46.2%). Mitral valve prolapse was more common in male dogs, and the average age was 11.3±2.8 years. Prolapse of the anterior leaflet was present in 48.4% of dogs, prolapse of the the posterior leaflet in 7.1%, and bileaflet prolapse was present in 44.5%; this distribution is different than that typically found in humans. There was a significant correlation between severity of mitral regurgitation and severity of mitral valve prolapse or ISACHC class, and between severity of mitral valve prolapse and ISACHC class. There was no relationship between the particular affected leaflet(s) and severity of mitral regurgitation, severity of mitral valve prolapse, or ISACHC class. Our findings suggest that the susceptibility to the mitral valve prolapse-degenerative mitral valve disease is not confined to a specific breeds and that the specific leaflet prolapsing is different in dogs compared with humans.     

MEASUREMENTS OF THE PULMONARY VASCULATURE ON THORACIC RADIOGRAPHS IN HEALTHY DOGS COMPARED TO DOGS WITH MITRAL REGURGITATION

This study reassessed the previously reported radiographic method of comparing pulmonary vessels versus rib diameter for differentiating healthy dogs and dogs with mitral regurgitation. The width of the right cranial pulmonary artery and vein at the fourth rib level, right caudal pulmonary artery and vein at the ninth rib level, and the diameters of the fourth rib and ninth rib were measured in prospectively recruited healthy dogs (n = 40) and retrospectively recruited dogs with mitral regurgitation (n = 58). In healthy dogs, the pulmonary arteries and accompanying veins were similar in size. The cranial lobar vessels were smaller than the fourth rib. However, 67.5% of right caudal pulmonary artery diameters and 65% of vein diameters were larger than the ninth rib in healthy dogs. The right caudal pulmonary vein diameter in dogs with mitral regurgitation, particularly those within moderate and severe grades, was significantly larger than that in healthy dogs (P < 0.001). The comparative method used to detect enlargement of the right caudal pulmonary vein relative to the accompanying pulmonary artery had the highest sensitivity (80.2%) and specificity (82.5%) for predicting mitral regurgitation. A cut‐off of 1.22 when applying the ninth rib criterion had better specificity (73%) than the most used value ≤ 1 (89.7% sensitivity and 63.8% specificity), although it has less sensitivity (73%). We recommend using the accompanying pulmonary artery and 1.22 × the diameter of the ninth rib as a radiographic criterion for assessing the size of the right caudal pulmonary vein and differentiating healthy dogs from those with mitral regurgitation.     

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

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

RADIOGRAPHIC FINDINGS IN DOGS WITH SPONTANEOUS PULMONARY THROMBOSIS OR EMBOLISM

Thoracic radiographs of 21 dogs with necropsy-confirmed pulmonary thrombosis or embolism (PTE) were reviewed. Two major lung patterns were seen: (1) regional oligemia, giving the impression of a hyperlucent zone; (2) alveolar pulmonary infiltrate, indicating hemorrhage or infarction. Hemorrhage and infarction could not be differentiated radiographically. Other common findings were attenuation or loss of visualization of a lobar artery or lobar vein and pleural effusion, particularly with infarction and cardiac disease. PTE was often associated with renal disease (glomerulonephritis, amyloidosis), septic processes, pancreatitis, systemic venous or right heart thrombosis, cardiac insufficiency, and hypercorticism.     

OBSERVER VARIATION IN THE TWO-DIMENSIONAL ECHOCARDIOGRAPHIC EVALUATION OF MITRAL VALVE PROLAPSE IN DOGS

In this study, the observer variation and the influence of observer experience in diagnosing mitral valve prolapse in dogs was assessed by having three observers with different degrees of echocardiographic experience (10 years, 4 years, and no prior experience) analyze 303 mitral valve video recordings from 253 dogs, both with and without mitral regurgitation. To assess intraobserver variation, 16 recordings were analyzed twice, and 34 dogs were scanned twice at intervals of a few days. By consensus, 90 dogs had no mitral valve prolapse, 130 had mild and 33 had severe mitral valve prolapse. Intraobserver repeatabilities ranged from 88% to 100% and interobserver repeatabilities from 70% to 78%. In 79% to 94% of the dogs that were scanned twice, the observers diagnosed both recordings identically. All repeatabilities were reduced by approximately 10% when mitral valve prolapse was graded into mild and severe. The three observers differed significantly in diagnosing mitral valve prolapse when compared with each other in pairs (all p-values < 0.01). The unexperienced observer had the highest and most unsystematic occurrence of false diagnoses. It is possible that the interobserver repeatabilities would have been lower had each sonographer obtained his own echocardiograms. We conclude, that mitral valve prolapse in dogs can be diagnosed using two-dimensional echocardiography with the same degree of observer variation as reported in human studies, and that education and training of staff is mandatory to ensure proper ultrasonographic evaluation.     

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.     

PULMONARY VENOUS FLOW CHARACTERISTICS AS ASSESSED BY TRANSTHORACIC PULSED DOPPLER ECHOCARDIOGRAPHY IN NORMAL DOGS

Transthoracic Doppler echocardiography was used to evaluate the technique of measuring and normal patterns of pulmonary venous flow in fourteen normal dogs. Polyphasic pulmonary venous flow profiles were obtained in all dogs, consisting of one (S) or two (S_E and S_L) systolic forward flow waves, one early diastolic forward flow wave (D), one reverse flow wave (R) related to atrial contraction, and one reverse flow wave (R₂) observed after cessation of systolic flow. Pulmonary venous flow was laminar in 9 dogs (65%). Maximal flow velocity during systole (0.39 ± 0.14 m/sec) was significantly lower (P < 0.01) than in early diastole (0.56 ± 0.14 m/sec). During late diastole peak flow velocity was 0.20 ± 0.08 m/sec and maximum R₂ velocity was 0.17 ± 0.05 m/sec. Duration of mitral A-wave was significantly greater (P < 0.05) than R-wave duration in all dogs (0.075 ± 0.10 vs 0.058 ± 0.012 sec). These results can be used for comparison with patterns found in disease states.     

COLLATERAL PULMONARY CIRCULATION IN DOGS EXPERIMENTALLY INFECTED WITH DIROFILARIA IMMITIS: ITS ANGIOGRAPHIC EVALUATION*

Collateral pulmonary circulation was evaluated angiographically 11 months after experimental infection of dogs with either 25 or 100 infective larvae of Dirofilaria immitis. In both groups, collateral pulmonary circulation developed from bronchial arteries and esophageal branches of the left gastric artery. Of the four dogs receiving 25 larvae, one had no detectable collateral circulation, one developed collateral pulmonary circulation from the bronchial arteries only, and two had collateral pulmonary circulation from the bronchial arteries and esophageal branches of the left gastric artery. Of the three dogs receiving 100 larvae, all had collateral pulmonary circulation from the bronchial arteries and the esophageal branches of the left gastric artery. Bronchial artery collateral pulmonary circulation was more extensive in the 100-larvae dogs than in the 25-larvae dogs. Collateral pulmonary circulation from the left gastric artery esophageal branches was similar in both dog groups. Angiographically detectable collateral pulmonary circulation developed within the first year of heaertworm infection. In some respects, the extent of collateral pulmonary circulation development was related to the severity of heartworm infection.     

DOPPLER ULTRASOUND OF THE PROSTATE IN NORMAL DOGS AND IN DOGS WITH CHRONIC LYMPHOCYTIC-LYMPHOPLASMOCYTIC PROSTATITIS

The prostate gland of 11 normal dogs and five dogs with histological confirmed chronic lymphocytic or lymphoplasmocytic prostatitis were imaged with grey-scale and Doppler ultrasound. Three vessel types (prostatic artery, capsular artery and parenchymal artery) were identified with color Doppler and the resistive index and maximum and minimum velocities were measured with pulsed wave Doppler. No differences between normal dogs and dogs with prostatitis was identified in either grey-scale ultrasound or in any Doppler parameters measured. Regardless of histologic diagnosis, acepromazine (0.05 mg/kg IV) caused a significant decrease in capsular artery maximum and minimum velocities and prostatic artery resistive index. This study establishes normal Doppler ultrasound parameters for the intact male canine prostate gland. Additional studies are necessary to further evaluate the clinical utility of Doppler ultrasound in canine prostatic diseases.     

RADIOGRAPHIC APPEARANCE OF CONFIRMED PULMONARY LYMPHOMA IN CATS AND DOGS

Herein we describe the thoracic radiographic appearance of confirmed pulmonary lymphoma. Patients with thoracic radiographs and cytologically or histologically confirmed pulmonary lymphoma were sought by contacting American College of Veterinary Radiology members. Seven cats and 16 dogs met the inclusion criteria, ranging in age from 4 to 15 years. Method of diagnosis was via ultrasound‐guided cytology (four), surgical biopsy (two), ultrasound‐guided biopsy (one), and necropsy (16). Radiographic findings varied but ranged from normal (one) to alveolar (six) and/or unstructured interstitial infiltrates (11), nodules and/or masses (eight), and bronchial infiltrates (four). Additional thoracic radiographic findings included pleural effusion and lymphadenopathy. The results of this evaluation indicate a wide variability in thoracic radiographic abnormalities in cats and dogs with pulmonary lymphoma.     

COMPARISON OF DOPPLER-DERIVED PEAK AORTIC VELOCITIES OBTAINED FROM SUBCOSTAL AND APICAL TRANSDUCER SITES IN HEALTHY DOGS

The accuracy of Doppler-derived blood flow velocity depends on the angle of incidence between the ultrasound beam and the direction of flow. In dogs with subaortic stenosis, it is known that the subcostal transducer site provides higher left ventricular ejection velocities than does the apical site. Left ventricular ejection velocities obtained from the subcostal site in healthy dogs have not been reported; accordingly, we examined healthy, random-source dogs to test the hypothesis that aortic velocities obtained from the subcostal and apical transducer sites differ. In 38 unsedated dogs, high-pulsed repetition frequency (HPRF) and continuous-wave (CW) Doppler studies of the proximal aorta and left ventricular outflow tract were performed using two-dimensional echocardiographic guidance. The effects of Doppler modality, transducer site, and their interaction on peak aortic velocity were tested through the use of analysis of variance. P values less than 0.05 were considered to indicate significance. The mean (+/-SE) peak aortic velocities were as follows: subcostal site (HPRF) = 1.44 +/- 0.03; apical site (HPRF) = 1.39 +/- 0.03; subcostal site (CW) = 1.48 +/- 0.03; apical site (CW) = 1.39 +/- 0.03. Aortic velocities obtained from the subcostal site were significantly greater than those obtained from the cardiac apex (P = 0.0001). Lower and upper limits of 95% reference intervals for aortic velocities by method of measurement and transducer location are proposed. In a population of healthy dogs, peak aortic velocities obtained from the subcostal site exceeded those obtained from the cardiac apex but did so only to a marginal degree.     

COMPARISON OF THE RESISTIVE INDEX TO CLINICAL PARAMETERS IN DOGS WITH RENAL DISEASE

The resistive index (RI) is a measurement of arteriole vascular resistance and is obtained by pulsed-wave Doppler interrogation. The diagnostic potential of the renal resistive index (RI) was retrospectively investigated in 142 kidneys from 81 dogs. The resistive index of each kidney was compared to clinical laboratory parameters, clinical diagnoses, and sonographic findings. The mean renal resistive index (RI) for 22 normal kidneys was 0.61 (standard deviation = 0.06). An elevation in the mean renal RI (>0.70) was found for the clinical diagnoses of acute renal failure and congenital dysplasia. When a RI of greater than 0.70 was considered abnormal, the sensitivity and specificity of the RI in determining normal vs, abnormal kidneys were 38% and 96% respectively.     

PULMONARY MINERALIZATION IN FOUR DOGS WITH CUSHING'S SYNDROME

The clinical and imaging features of four dogs with Cushing's syndrome and pulmonary mineralization are reviewed. Three dogs presented with a primary complaint of respiratory distress/dyspnea. Three dogs had pituitary dependent Cushing's syndrome, while the remaining one dog had iatrogenic Cushing's syndrome. Each dog had clinical features typical for Cushing's syndrome. Two of the dogs were euthanized due to progressive hypoxemia. In each dog, the serum calcium, phosphorous, blood urea nitrogen and creatinine were normal.
A generalized increase in unstructured interstitial pulmonary opacity with diffuse mineralization was noted on thoracic radiographs of all dogs. In one dog, an ill-defined nodular interstitial pattern of mineralization was present. Delayed bone phase scintigraphy using ^99mTechnetium methylene diphosphonate documented generalized pulmonary uptake in two dogs. ^99mTechnetium labeled microaggregated albumin lung perfusion scans were normal in these two dogs. ^99mTc-MDP scintigraphy can provide useful information in diagnosing pulmonary mineralization in Cushingoid dogs.     

DIAGNOSTIC VALUE OF COMPUTED TOMOGRAPHY IN DOGS WITH CHRONIC NASAL DISEASE

Computed tomographic (CT) studies of 80 dogs with chronic nasal disease (nasal neoplasia (n = 19), nasal aspergillosis (n = 46), nonspecific rhinitis (n = 11), and foreign body rhinitis (n = 4)) were reviewed retrospectively by two independent observers. Each observer filled out a custom-designed list to record his or her interpretation of the CT signs and selected a diagnosis. Accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for the diagnosis of each disease. The agreement between observers was evaluated. The CT signs corresponded to those previously described in the literature. CT had an accuracy greater than 90% for each observer in all disease processes. The sensitivity, specificity, PPV, and NPV were greater than 80% in all dogs with the exception of the PPV of foreign body rhinitis (80% for observer A and 44% for observer B). There was a substantial, to almost perfect, agreement between the two observers regarding the CT signs and diagnosis. This study indicates a high accuracy of CT for diagnosis of dogs with chronic nasal disease. The differentiation between nasal aspergillosis restricted to the nasal passages and foreign body rhinitis may be difficult when the foreign body is not visible.     

DIASTOLIC MITRAL REGURGITATION DETECTED BY PULSED WAVE DOPPLER ECHOCARDIOGRAPHY AND COLOR FLOW DOPPLER MAPPING IN FIVE DOGS AND TWO CATS WITH SECOND- AND THIRD-DEGREE ATRIOVENTRICULAR BLOCK

M-mode echocardiography, color flow Doppler mapping, and pulsed wave Doppler echocardiography were used to characterize diastolic mitral regurgitation in five dogs and two cats with second- and third-degree atrioventricular block. Incomplete closure and partial reopening of the mitral valve following nonconducted P-waves were demonstrated by m-mode echocardiography. Low velocity reflux of blood into the left atrium after nonconducted P-waves was imaged by color-flow Doppler mapping and spectral Doppler echocardiography. Late diastolic mitral regurgitation was not observed in clinically normal control dogs or cats, but a low velocity, mid-diastolic flow reversal was detected in the dogs. This probably represented normal physiologic intravalvular flow. Diastolic mitral regurgitation is a common echocardiographic finding, in dogs and cats with, second- and third-degree atrioventricular block.     

TRANSESOPHAGEAL ECHOCARDIOGRAPHY OF THE LEFT VENTRICULAR OUTFLOW TRACT, AORTIC VALVE AND ASCENDING AORTA IN BOXER DOGS WITH HEART MURMURS

The study was aimed at evaluating the anatomy of the left ventricular outflow tract, aortic valve, and ascending aorta by means of multiplane transesophageal echocardiography in Boxer dogs with left basilar heart murmurs and at comparing two-dimensional (2D) transthoracic to transesophageal echocardiography for the diagnosis of subaortic stenosis in this breed. Twenty-eight Boxers were included in the study and allocated to four groups according to physical and routine transthoracic 2D and Doppler echocardiography findings: group A--dogs with low grade (I-II/VI) heart murmurs without overt evidence of aortic stenosis (14 dogs); group B--dogs with type 1 subaortic stenosis (seven dogs); group C--dogs with type 2 subaortic stenosis (five dogs); group D--dogs with type 3 subaortic stenosis (two dogs). Anatomic lesions were not discovered by transesophageal echocardiography in dogs belonging to group A. Transesophageal imaging confirmed the type of subaortic stenosis, as graded by transthoracic echocardiography, in diseased animals (groups BCD). Morphologic information obtained by transesophageal echocardiography in Boxer dogs was similar to that obtained by transthoracic echocardiography.     

A RETROSPECTIVE EVALUATION OF THE RADIOGRAPHIC EVIDENCE OF PULMONARY METASTATIC DISEASE ON INITIAL PRESENTATION IN THE DOG

Thoracic radiographs of 346 dogs, diagnosed as having primary neoplasms, were reviewed for radiographic changes associated with pulmonary metastatic disease at the time of initial presentation. Dogs having radiographic changes of single or multiple interstitial nodular opacities, in the absence of concurrent intrathoracic disease, were considered to have pulmonary metastatic disease. The frequency of metastasis associated with each histologic tumor type was compared by chi-squared analysis. Dogs having primary thyroid carcinomas and transitional cell carcinomas demonstrated the greatest frequency of radiographic changes, 62.5% and 26% respectively. In dogs having a variety of other neoplasms, including nasal adenocarcinomas and cutaneous neoplasms, thoracic radiography proved useful in delineating intercurrent disease and staging, as well as the extent of neoplastic involvement. These results indicate early radiographic evaluation of the thorax should be performed on all dogs with confirmed or suspected primary neoplasms.     

COMPUTED TOMOGRAPHY BRONCHIAL LUMEN TO PULMONARY ARTERY DIAMETER RATIO IN DOGS WITHOUT CLINICAL PULMONARY DISEASE

Bronchiectasis is diagnosed in humans using multiple computed tomography (CT) criteria, the most important being dilatation of the bronchi. The most widely used criterion for detection of bronchial dilatation is a bronchial lumen to pulmonary artery diameter (bronchoarterial [BA]) ratio >1.0. No studies have been performed to determine the BA ratio in normal dogs. Thoracic CT images of 24 dogs without clinical pulmonary disease were reviewed. The BA ratio of the lobar bronchi of the left cranial (cranial and caudal parts), right cranial, right middle, left caudal, and right caudal lung lobes was measured. The mean of the mean BA ratio for all dogs was 1.45±0.21 (99% confidence interval [CI]=1.34–1.56). The mean of the mean BA ratio as determined by lung lobe was 1.45±0.04 (99% CI=1.41–1.49). The range of individual BA ratios was 0.8–2.0. There was no significant difference in mean BA ratios as a function of lung lobe ( P =0.60). The BA ratio in these clinically normal dogs was consistent and may be a useful tool in evaluating for bronchiectasis on CT images. BA ratios >2.0 were not identified in this population, suggesting a threshold to differentiate normal from abnormal bronchi.     

COMPUTED TOMOGRAPHY ANGIOGRAPHY FOR EVALUATION OF PULMONARY EMBOLISM IN AN EXPERIMENTAL MODEL AND HEARTWORM INFESTED DOGS

This study was performed to characterize pulmonary embolism with computed tomography pulmonary angiography in experimental pulmonary embolism and heartworm infected dogs. In the experimental group, there were pulmonary changes after pulmonary embolism induction as follows: hypoattenuating round filling defects in pulmonary arteries, arterial dilations with straight and abrupt cut‐off appearances in the pulmonary embolism regions, pulmonary infarctions, a cavity formation and spontaneous pneumothorax, and emboli migration. In the heartworm‐infected group, three out of eight dogs developed pulmonary embolism, especially in the right caudal arteries. Arterial dilations with typical tortuosity were also identified, mainly in the right caudal arteries in five dogs. Computed tomography pulmonary angiography can be an important imaging modality in the diagnosis of pulmonary embolism and the evaluation of pulmonary arterial and parenchymal changes in dogs.     

RESULTS OF MYELOGRAPHY IN SEVEN DOGS WITH MYELOMALACIA

Myelomalacia is a hemorrhagic infarction of the spinal cord that can occur as a sequel to acute spinal cord injury. Myelomalacia may be focal or diffuse; the diffuse form is typically associated with cranial migration of neurologic signs ("ascending syndrome") and is often fatal. In a retrospective study of seven affected dogs, diffuse myelomalacia was associated with intervertebral disc extrusion in five dogs, focal myelomalacia was associated with fibrocartilagenous embolus in one dog, and had no apparent cause in one dog. The myelographic signs included a variable degree of contrast medium infiltration into the spinal cord in six dogs (86%) and/or spinal cord swelling in six dogs (86%). In one dog with focal myelomalacia, the only myelographic sign was spinal cord swelling.