Evaluation of bronchial narrowing in coughing dogs with heart murmurs using computed tomography

Abstract

Background: The origin of cough in dogs with heart murmurs is controversial, because the cough could be primary cardiac (eg, pulmonary edema, bronchi compression by left-sided cardiomegaly) or respiratory (eg, bronchomalacia, other bronchial or bronchiolar disease, interstitial lung disease) in origin.Hypothesis/Objectives: To study the association between left atrium (LA) dilatation and cardiomegaly and bronchial narrowing in coughing dogs with heart murmurs using computed tomography (CT).Animals: Twenty-one client-owned coughing dogs with heart murmurs and 14 historical control dogs.Methods: Dogs with cough and murmur were prospectively recruited over 4 months.Cervical and thoracic radiography, echocardiography, and thoracic CT were performed in enrolled dogs. Control dogs, with no disease on thoracic CT and no records of heart murmur and coughing, were gathered from the institution's computerized database. Degree of bronchial narrowing was assessed using the bronchial-to-aorta (Ao) ratio, measured by 3 radiologists blinded to the clinical findings. After identifying bronchi that were significantly narrowed in dogs with murmur compared to controls, the relationship between degree of narrowing and LA/Ao ratio (measured echocardiographically) and vertebral heart scale (VHS) measured radiographically was studied in dogs with murmur using mixed-effects regression.Result: Significant narrowing was identified for all left-sided bronchi and the right principal, middle, and caudal bronchi in the coughing dogs, compared with controls.Increasing LA size and VHS were significantly inversely associated with diameter for all left-sided and right-sided bronchi indicated above.

Letter regarding “Evaluation of bronchial narrowing in coughing dogs with heart murmurs using computed tomography”

“…As stated above, the classic debate is whether cough in an older, small breed dog with severe left atrial enlargement caused by mitral regurgitation is a result of the enlarged left atrium compressing a normal or a malacic left caudal bronchus, caused by bronchomalacia alone, a consequence of inflammatory airway disease, or a combination of disorders. 2,6,7 Similar to the previous study, 2 the present study 1 found that numerous bronchi were collapsed. No one, however, has previously suggested that cough in these dogs is a result of compression of bronchi other than the left caudal bronchus.…”

“…It is difficult to understand anatomically how a large left atrium could compress bronchi other than the left caudal bronchus, especially those on the right side, which are also commonly collapsed. 1,2,8 Consequently, it seems more logical that the present study provides further evidence that many coughing dogs have widespread bronchomalacia. 8…”

Response to letter regarding “Evaluation of bronchial narrowing in coughing dogs with heart murmurs using computed tomography”

“…Hence, the control group only included dogs without cardiovascular disease that underwent thoracic CT. Table 1 in our article presents demographic information about the dogs of the control group and statistical comparison with the group of dogs with heart disease. 4 …”

“…It is in especially close vicinity to the right principal (RPB), right middle (RB2), and right caudal (RB4) bronchi, which were the bronchi identified as significantly narrowed in dogs with cardiomegaly in our study. 4 Even without using IV contrast injection, the left atrium can be identified on CT, as shown in Figure 1C . In Figure 1C , it can easily be appreciated how an enlarged left atrium can compress both the left‐sided and the right‐sided bronchi.…”

“… Transverse plane CT images of a dog without cardiomegaly at the level of the principal bronchi (A) and caudal bronchi (B), and a dog with cardiomegaly from Lebastard et al study 4 at the level of the principal bronchi (C). The CT images of the dog without cardiomegaly are in soft‐tissue window after IV contrast injection (A, B).…”