Thoracic Radiographic Assessment of Cats With Hypertrophic Cardiomyopathy

Amara H. Estrada, DVM, DACVIM (Cardiology), University of Florida

ArticleLast Updated December 20233 min read
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In the Literature

Kim S, Lee D, Park S, Suh GH, Choi J. Radiographic findings of cardiopulmonary structures can predict hypertrophic cardiomyopathy and congestive heart failure in cats. Am J Vet Res. 2023;84(9):ajvr.23.01.0017. doi:10.2460/ajvr.23.01.0017

The Research …

Hypertrophic cardiomyopathy (HCM) is difficult to diagnose without echocardiography, particularly early in the disease when left atrial enlargement is minimal. This can present a challenge when determining next steps (eg, benign neglect with recheck in 6-12 months) for cats with heart murmurs. Establishing objective criteria with thoracic radiography to predict likelihood of hemodynamically or clinically significant disease would therefore be valuable.

The goal of this study was to use established radiographic objective measurements (ie, vertebral heart scale, vertebral left atrial size) in combination with measurement of the degree of pulmonary arterial or venous dilation to predict HCM and congestive heart failure (CHF) in cats. Thoracic radiographs of cats (35 healthy cats, 22 cats with HCM, 21 cats with HCM and CHF) with concurrent echocardiography were retrospectively evaluated.

Results demonstrated that cats with HCM had dilation of the caudal pulmonary arteries compared with healthy cats. In addition, cats with HCM and CHF had dilated caudal pulmonary veins compared with cats with HCM alone. The authors proposed a cutoff value of 5.35 mm for the upper limit of normal for caudal pulmonary vein measurement (ie, SD-CdPV [distal side of the summated shadow made by the caudal lobar pulmonary vein with the rib]).

… The Takeaways

Key pearls to put into practice:

  • Clinical utility of measuring the caudal pulmonary veins is limited. In this study, measurement of the caudal pulmonary veins was only possible in a small subset of cats with HCM due to vessel summation with adjacent structures (eg, caudal vena cava, vertebral body, lung infiltrates). A caudal pulmonary vein diameter of >5.35 mm may improve confidence in the diagnosis of heart disease but cannot be relied on alone for diagnosis or used to rule heart disease in or out.

  • Radiography cannot replace the diagnostic utility of directly assessing left atrial size and degree of left ventricular hypertrophy via echocardiography; however, measuring the pulmonary vasculature as described in this study may improve confidence in diagnosing heart disease in severe cases or ruling out hemodynamically or clinically important disease in patients with mild cardiac changes.

  • When used in combination with focused ultrasound assessment of left atrial size, measuring vertebral heart scale, vertebral left atrial size, and pulmonary vasculature on radiographs may increase confidence in diagnosing and treating patients.