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Radiographic cardiac size in cats and dogs with heartworm disease compared with reference values using the vertebral
Annette Litster1, Clarke Atkins, Rick Atwell
1School of Veterinary Science, University of Queensland, St. Lucia, Qld. 4072, Australia.
Insights
Heartworm infection in cats and dogs commonly causes an enlarged heart silhouette on radiographs. The vertebral heart scale (VHS) and other measurements can help monitor heartworm disease progression.
Area of Science:
- Veterinary Radiology
- Cardiology
- Parasitology
Background:
- The vertebral heart scale (VHS) is an established method for objectively assessing cardiac size relative to body size in animals.
- Heartworm disease, caused by Dirofilaria immitis, is a serious parasitic infection affecting the cardiovascular system of dogs and cats.
Purpose of the Study:
- To evaluate the utility of the vertebral heart scale (VHS) method in quantifying cardiac and major vessel size in heartworm-infected cats and dogs.
- To compare these measurements against established reference values to identify radiographic changes associated with heartworm disease.
Main Methods:
- Thoracic radiographs were obtained from 28 heartworm-infected cats and 25 heartworm-infected dogs.
- Standardized measurements of the cardiac silhouette (using VHS), caudal vena cava diameter, and pulmonary or caudal lobar artery width were performed on lateral and ventrodorsal/dorsoventral radiographs.
Main Results:
- Heartworm-infected cats and dogs exhibited significantly larger mean VHS values compared to reference values on lateral radiographs.
- A significant positive correlation was observed between caudal vena cava diameter and VHS in both infected species.
- The ratio of the right pulmonary artery (cats) or right caudal lobar artery (dogs) width to the width of the 9th rib was elevated in infected animals compared to reference values.
Conclusions:
- The vertebral heart scale (VHS) method is a valuable tool for detecting cardiac enlargement in heartworm-infected cats and dogs.
- Measurements of the caudal vena cava and pulmonary/caudal lobar artery provide additional objective data for monitoring disease progression and staging therapy in heartworm disease.
Objectives:
To measure the size of the heart, caudal vena cava and right pulmonary artery (cats) or right caudal lobar artery (dogs) using the vertebral scale method in heartworm-infected cats and dogs and compare the results with reference values.
Background:
The vertebral heart scale (VHS) method is an objective measure of heart size relative to body size.
Animals:
Thoracic radiographs from heartworm-infected cats (n=28) and dogs (n=25).
Materials And Methods:
Standardized measurements using a previously published method were made using lateral, dorsoventral and/or ventrodorsal thoracic radiographs.
Results:
On lateral radiographs, the mean VHS for the heartworm-infected group was significantly larger than the reference value for both cats and dogs (cats p=0.009, dogs p<0.001). On lateral radiographs of both infected cats and dogs, there was a significant correlation between mean diameter of the caudal vena cava and VHS (cats p=0.002, r=0.59; dogs p=0.012, r=0.53). The mean ratio of the width of the right pulmonary artery (cats) or right caudal lobar artery (dogs) to the width of rib 9 was higher than reference values for each species.
Conclusions:
Heartworm-infected cats and dogs often have an enlarged cardiac silhouette on thoracic radiographs. The VHS method, measurement of the caudal vena cava expressed in vertebral lengths, and the calculation of the ratio of the right pulmonary or caudal lobar artery width to rib 9 width are all useful tools to monitor the natural history of the disease and aid in staging for therapy of heartworm disease.
