Two radiographic methods for assessing left atrial enlargement and cardiac remodeling in dogs with myxomatous mitral valve disease

The vertebral right heart index: A new radiographic method to assess right heart enlargement in dogs

In veterinary medicine, the radiographic assessment of right heart enlargement (RHE) is essentially subjective. The aim of this study was to evaluate the vertebral right heart index (VRHi) as a new quantitative radiographic method to detect RHE in dogs. This was a multicenter, retrospective, observational study, including dogs with RHE and control dogs. All dogs had to have a thoracic radiographic study and a complete echocardiography on the same day. Right heart enlargement was defined as the presence of right atrial enlargement, right ventricular enlargement, and/or hypertrophy based on echocardiography. For the radiographic study, all the radiographic views available for each case were considered for measurement: right lateral (RL), left lateral (LL), ventrodorsal (VD), and dorsoventral (DV). The VRHi was measured using LL, RL, VD, and DV views. A total of 204 dogs were included: 91 dogs with RHE and 113 control dogs. The VRHi (RL), the VRHi (LL), and the VRHi (VD) were significantly greater in dogs with RHE compared with controls (P < .0001). The best diagnostic accuracy was observed for VRHi (LL) (area under the curve [AUC] 0.86, P < .0001; cutoff ≥ 3.5 vertebrae, sensitivity [Se] 71%, specificity [Sp] 89%), followed by VRHi (RL) (AUC 0.85, P < .0001; cutoff ≥ 3.5 vertebrae, Se 68%, Sp 86%) and VRHi (VD) (AUC 0.80, P = .0004; cutoff ≥ 3.0 vertebrae, Se 57%, Sp 95%). In conclusion, the lateral VRHi in LL and RL and the VD VRHi could represent useful radiological tools for the detection of RHE in dogs.

Determination of radiographic vertebral heart score and vertebral left atrial size cutoffs based on echocardiographic left atrial size in dogs with myxomatous mitral valve disease

Progression of myxomatous mitral valve disease (MMVD) in dogs is a common cause of left atrial enlargement. Recently, a classification of left atrial (LA) size based on echocardiographic measurement has been proposed. This study aims to determine the radiographic LA size by reporting the cutoff values of VHS and VLAS for different groups of echocardiographic-measured LA size in dogs with MMVD. This retrospective analytical cross-sectional study included dogs diagnosed with MMVD grouped based on the echocardiographic LA size into normal (LA/Ao < 1.6), mild (1.6-1.89), moderate (1.9-2.2), and severe enlargement (>2.2) and were compared with ACVIM classification. VHS and VLAS were measured on the right lateral radiograph for each dog and cutoff values were calculated. One hundred and three dogs with MMVD were included in the study. A very strong positive correlation was observed between LA/Ao ratio and VHS (rs , 0.823, P < .01) or VLAS (rs , 0.834, P < .01). For VHS, a cutoff of 10.7 v, 11 v, and 11.5 v were established for echocardiographic LA thresholds of 1.6, 1.9, and 2.2 with a sensitivity of 79%, 92%, and 90% and a specificity of 97%, 90.7%, and 78.1%, respectively. For VLAS, a cutoff of 2.5 v, 2.7 v, and 2.9 v were established for echocardiographic LA cutoffs of 1.6, 1.9, and 2.2 with a sensitivity of 73%, 80%, and 83.3% and a specificity of 94%, 92%, and 86.3%, respectively. The results of this study may facilitate clinical decisions based on radiographic examination in dogs with myxomatous mitral valve disease.

Radiographic Left Atrial Size Measurement of Dogs in Different Mitral Valve Disease Stages with Four Different Methods

The left atrial size increases (LAS) in patients with mitral valve disease (MVD) as the disease progresses. The vertebral left atrial size (VLAS), the modified-vertebral left atrial size (M-VLAS), and the radiographic left atrial dimension (RLAD) are methods reported to assess LAS on dogs' radiographs. All these methods transform the LAS into vertebral units. The thoracic inlet (TI) has been used as a reliable reference point to measure the cardiac silhouette of dogs with MVD in different stages. The objective of this study was to assess the clinical utility of measuring a dog LAS on right thoracic X-rays using the TI as a reference and determine whether it could differentiate dogs in different MVD stages. LAS was divided by the TI to obtain the thoracic inlet left atrial score (TILAS). This was a retrospective observational study including 135 apparently healthy dogs performed to assess their LAS with four different methods: VLAS, M-VLAS, RLAD, and TILAS. Thirty-six dogs from the general population were selected and compared to 100 dogs in different MVD stages. The TILAS was significantly different between the control dogs and MVD dogs, increasing with the disease stage: control dogs 0.51 ± 0.08, B1 0.57 ± 0.14, B2 0.75 ± 0.13, and C 0.84 ± 0.18. VLAS, M-VLAS, and RLAD also increased as the disease progressed, as shown in previous studies. The TILAS accuracy to distinguish MVD dogs with cardiac enlargement was comparable to VLAS, M-VLAS, and RLAD (AUC 0.91 vs. 0.93, 0.90, and 0.94 respectively). A TILAS > 0.8 can identify dogs with cardiac enlargement secondary to MVD.

Utility of vertebral left atrial size and vertebral heart size to aid detection of congestive heart failure in dogs with respiratory signs

BACKGROUND

Differentiating cardiogenic vs noncardiogenic causes of respiratory signs can be challenging when echocardiography is unavailable. Radiographic vertebral left atrial size (VLAS) and vertebral heart size (VHS) have been shown to predict echocardiographic left heart size, with VLAS specifically estimating left atrial size.

HYPOTHESIS/OBJECTIVES

Compare the diagnostic accuracy of VLAS and VHS to predict left-sided congestive heart failure (CHF) in dogs presenting with respiratory signs.

ANIMALS

One-hundred fourteen dogs with respiratory signs and radiographic pulmonary abnormalities.

METHODS

Retrospective cross-sectional study. Dogs had to have an echocardiogram and thoracic radiographs obtained within 24 hours. Diagnosis of CHF was confirmed based on the presence of respiratory signs, cardiac disease, LA enlargement, and cardiogenic pulmonary edema.

RESULTS

Fifty-seven dogs had CHF and 57 did not have CHF. Compared to VHS (area under the curve [AUC] 0.85; 95% confidence interval [CI], 0.77-0.91), VLAS was a significantly (P = .03) more accurate predictor of CHF (AUC, 0.92; 95% CI, 0.85-0.96). Optimal cutoff for VLAS was >2.3 vertebrae (sensitivity, 93.0%; specificity, 82.5%). Murmur grade (P = .02) and VLAS (P < .0001) were independently associated with CHF and VHS was not. Increased VHS (54%) was significantly (P = .01) more common than increased VLAS (24%) in dogs without CHF. Results were similar in a subsample of older and smaller dogs.

CONCLUSIONS AND CLINICAL IMPORTANCE

When echocardiography is unavailable, VLAS and murmur grade have clinically utility to aid in differentiating cardiogenic from noncardiogenic respiratory signs. These findings might be especially useful to help rule out CHF in dogs with increased VHS that present with respiratory signs.

The Thoracic Inlet Length as a Reference Point to Radiographically Assess Cardiac Enlargement in Dogs with Myxomatous Mitral Valve Disease

The diagnostic value of the vertebral heart size (VHS) in dogs with mitral valve degeneration (MVD) is compromised when middle thoracic vertebral anomalies are present. The objective of this study was to assess the use of the thoracic inlet heart score (TIHS) to identify left heart enlargement (LHE) secondary to MVD. The cardiac silhouette of 50 clinically healthy dogs and 106 MVD dogs in different stages was assessed on a right lateral chest radiograph. The TIHS and VHS value were calculated for each patient and compared. The TIHS was significantly different between the control dogs and the dogs with MMVD, increasing with disease stage, control 2.91 ± 0.23, Stage B1 2.98 ± 0.36, B2 3.25 ± 0.34, and C 3.53 ± 0.36, p < 0.05. A THIS ≥3.3 showed 69% sensitivity and 81% specificity to identify LHE. The TIHS showed moderate correlation with the VHS, LA/Ao, and LVIDDN 0.59, 0.42, and 0.62, respectively. The intraobserver and interobserver agreement were almost perfect, 0.96, and substantial, 0.73. The TIHS method can be used to identify LHE secondary to MMVD on dogs' thoracic radiographs.

A Novel Standardized Method for Aiding to Determine Left Atrial Enlargement on Lateral Thoracic Radiographs in Dogs

BACKGROUND

Left atrial enlargement indicates severe cardiac disease. Although the gold standard for determining left atrial size is echocardiography, many veterinary practices lack the necessary equipment and expertise. Therefore, thoracic radiography is often used to differentiate cardiogenic pulmonary edema from primary respiratory diseases and to facilitate distinguishing dogs with stage B1 and B2 mitral valve degeneration.

METHODS

The goal was to test a new standardized method for identifying radiographic left atrial enlargement. On a lateral radiograph, a straight line was drawn from the dorsal border of the tracheal bifurcation to the crossing point of the dorsal border of the caudal vena cava and the most cranial crus of the diaphragm. If a part of the left atrium extended this line dorsally, it was considered enlarged. Echocardiographic left atrial to aortic ratio (LA:Ao) was used as a reference. Thirty-nine observers with various levels of experience evaluated 90 radiographs, first subjectively, then applying the new method.

RESULTS

The new method moderately correlated with LA:Ao (r = 0.56-0.66) in all groups. The diagnostic accuracy (72-74%) of the subjective assessment and the new method showed no difference.

CONCLUSIONS

Though the new method was not superior to subjective assessment, it may facilitate learning and subjective interpretation.

Methods of Radiographic Measurements of Heart and Left Atrial Size in Dogs with and without Myxomatous Mitral Valve Disease: Intra- and Interobserver Agreement and Practicability of Different Methods

Dogs suffering from Myxomatous Mitral Valve Disease (MMVD) show a potential heart enlargement, especially in the left atrium, detectable by radiography. Due to digital radiography, different radiographic measurements estimate cardiac size quite uncomplicatedly. The Vertebral Heart Size (VHS), Radiographic Left Atrial Dimension (RLAD), Left Atrial Width (LAWidth), and the Vertebral Left Atrial Size (VLAS) used anatomical landmarks for measuring cardiac size in relation to the vertebral column. This study aimed to compare VHS, RLAD, LAWidth, and VLAS measured in conventional and inverted radiographs by veterinarians with different levels of experience in healthy dogs and dogs with MMVD. The reliability and user-friendliness of these measurements were evaluated, and the staging was compared to the echocardiography staging. A total of 50 unaffected dogs and 150 dogs with MMVD in stages B1, B2, and C were assessed. Three veterinarians with different levels of experience examined 200 conventional radiographs and their corresponding inverted radiographs blinded to the echocardiographic and clinical examination results. Analyses were performed to compare the measurements’ grading and determine anatomical landmarks with measurement difficulties. Additionally, inter- and intraobserver agreement was assessed using intraclass correlation coefficient, and the agreement between radiographic and echocardiographic staging was compared using the kappa coefficient. The VHS, LAWidth, and VLAS were easier to define than the RLAD. The interobserver agreement was almost perfect for VHS (0.962) and good for the other radiographic measurements (RLAD: 0.778, LAWidth: 0.772, VLAS: 0.858). The VHS assigned the most dogs to the correct stage. However, VHS, RLAD, LAWidth, and VLAS presented an almost perfect intraobserver agreement. The dorsal left atrial margin of the RLAD was the most difficult measurement point to identify. The VHS is the most reproducible radiographic method for measuring the canine heart size and shows the highest agreement with echocardiography. An observer-related influence could be detected for RLAD, LAWidth, and VLAS.

Comparison of different radiographic scores with associated echocardiographic measurements and prediction of heart enlargement in dogs with and without myxomatous mitral valve disease

INTRODUCTION

Staging of myxomatous mitral valve disease (MMVD) requires an echocardiographic examination along with thoracic radiographs. The aims of this study were to calculate mean values for radiographic scores vertebral heart size (VHS), left atrial width (LA_Width), radiographic left atrial dimension (RLAD), and vertebral left atrial size (VLAS) in conventional and grayscale inverted images in healthy dogs and dogs with different stages of MMVD, and to find cutoff values for a stage assignment.

ANIMALS

One hundred fifty dogs in different stages of MMVD and 50 unaffected dogs were evaluated.

METHODS

Radiographic scores, echocardiographic left atrium-to-aorta ratio and normalized left ventricular internal dimension at end-diastole, and results of a clinical examination were obtained. Analyses were performed to evaluate the correlation between radiographic scores and echocardiographic values, to determine cutoff values for a radiographic stage assignment, and to compare measurements in conventional and inverted radiographs.

RESULTS

After excluding breed-specific higher VHS, the means of VHS, LA_Width, RLAD, and VLAS were similar in the control group and stage B1. All radiographic scores increased in stages B2 and C. The cutoff values identifying heart enlargement, and therefore differentiating stages B1 and B2, were 11.0 for VHS, 1.8 for LA_Width, 2.0 for RLAD, and 2.3 for VLAS. Besides RLAD, scores were similar in conventional and inverted radiographs.

CONCLUSION

Cutoff values for the different radiographic scores for stage assignment were calculated. Radiographic cardiac scores using either conventional or inverted grayscale could be a tool to differentiate between different stages of MMVD when echocardiography is unavailable.

Vertebral heart size and vertebral left atrial size reference ranges in healthy Maltese dogs

The most common cardiac measurements on thoracic radiography in veterinary medicine are vertebral heart size (VHS) and vertebral left atrial size (VLAS). Previously published studies have demonstrated evidence that reference ranges for these measures vary among different dog breeds, however reference ranges for Maltese breed dogs are currently lacking. We hypothesized that VHS and VLAS in healthy Maltese dogs would not be influenced by sex, age, or bodyweight. This retrospective, reference interval study aimed to describe reference intervals for VHS and VLAS in a sample of clinically healthy Maltese dogs and assess the intra- and interobserver variabilities for VLAS and VHS measurements. A total of 81 clinically healthy Maltese dogs were included, with healthy status being based on a complete cardiologic examination. Thoracic radiography in right lateral recumbency was performed for all dogs. The intra- and interobserver variability assessments of VHS and VLAS were based on measurements independently performed by three observers. The mean VHS was 9.53 ± 0.46 vertebrae (v). The median and interquartile range (IQR) for VLAS was 2 v (IQR, 1.8-2.1v). A statistically significant moderate positive correlation was observed between VHS and VLAS (P < .01, r = 0.416). Both VHS and VLAS showed an almost perfect intraobserver agreement. Interobserver agreement was almost perfect for VHS and substantial for VLAS. Findings supported previous studies recommending the use of breed-specific reference values for VHS and VLAS, and provided background data for future radiographic evaluations of Maltese dogs with clinical signs of cardiac disease.