Cardiology Service, William R. Pritchard Veterinary Medical Teaching Hospital, University of California Davis, School of Veterinary Medicine, Davis, California, USA.
J Vet Intern Med. 2012 Mar-Apr;26(2):312-9. doi: 10.1111/j.1939-1676.2012.00887.x. Epub 2012 Feb 15.
Cough in the geriatric small breed dog with myxomatous mitral valve degeneration (MMVD), a large left atrium, and absence of heart failure often is attributed to compression of the left mainstem bronchus by the left atrium. Studies investigating this syndrome are lacking in dogs.
Airway collapse is independent of left atrial enlargement.
A total of 16 dogs presenting with chronic cough in the absence of congestive heart failure. Group 1 dogs (n = 10) had moderate-to-severe left atrial enlargement based on an echocardiographically calculated left atrial:aortic surface area [LA:Ao(a)] > 6. Group 2 dogs (n = 6) had no to mild left atrial enlargement [LA:Ao(a) ≤ 6].
Dogs were prospectively evaluated. CBC, biochemistry, urinalysis, cervical and thoracic radiographs, fluoroscopy, echocardiography, and bronchoscopy were performed. Bronchoscopic abnormalities were compared between groups using Fisher's Exact Test. P < .05 was considered significant.
Fluoroscopy identified airway collapse in both groups. Bronchoscopic evidence of airway collapse >50% was observed in multiple bronchi with no difference between groups. All dogs had inflammation on airway cytology with respiratory infection in 1 dog in group 2. Left atrial size was interpreted radiographically as enlarged in 9 of 10 group 1 dog and in 2 of 6 group 2 dogs. VHS was above normal in both groups of dogs regardless of echocardiographic evidence of cardiomegaly.
Results failed to identify an association between left atrial enlargement and airway collapse in dogs with MMVD, but did suggest that airway inflammation is common in dogs with airway collapse.
患有黏液样心肌变性（MMVD）、左心房增大且无心力衰竭的老年小型犬出现咳嗽，通常归因于左心房对左主支气管的压迫。目前缺乏对该综合征进行研究的犬类资料。
气道塌陷与左心房增大无关。
共 16 只表现出慢性咳嗽但无充血性心力衰竭的犬。第 1 组犬（n=10）的左心房超声计算面积（LA:Ao(a)）大于 6，提示左心房中度至重度增大。第 2 组犬（n=6）左心房无增大或轻度增大（LA:Ao(a)≤6）。
前瞻性评估所有犬。进行了全血细胞计数、生化检查、尿液分析、颈椎和胸部 X 线摄影、透视、超声心动图和支气管镜检查。使用 Fisher 精确检验比较两组之间的支气管镜异常。P<.05 为差异有统计学意义。
透视发现两组均存在气道塌陷。两组均观察到多个支气管的气道塌陷程度>50%，但两组间无差异。所有犬的气道细胞学均有炎症，其中 1 只第 2 组犬存在呼吸道感染。根据 X 线摄影结果，10 只第 1 组犬中的 9 只和 6 只第 2 组犬中的 2 只被认为左心房增大。两组犬的 VHS 均高于正常水平，而不管超声心动图是否有心脏增大的证据。
结果未能确定 MMVD 犬左心房增大与气道塌陷之间的关联，但确实表明气道炎症在气道塌陷犬中很常见。
