評估犬隻呼吸道與慢性心臟疾病相關性之研究

Abstract

呼吸系統與左右心之間複雜的交互作用，可能導致心肺疾病有較高合併發生的機率。在呼吸系統疾病下造成心臟功能與結構改變的致病機轉可能來自於肺循環血流動力學的改變與血管床重塑，另外慢性炎症反應和缺氧也可能是誘發的原因之一。左右心間高度的依存關係來自於共同擁有的心室間隔、心包囊與結構上交錯的肌纖維，而這樣密切的交互作用在右心與左心衰竭的關係上可能扮演重要的角色。本論文包含兩個部分，第一項研究包含了五十四隻無心肺症狀的健康犬隻與一百三十三隻按照紐約心臟協會分級系統修正版 (modified New York heart association functional classification) 分組的退化性二尖瓣疾病犬，透過統計胸腔放射線數位影像上從氣管到支氣管共六個部位的氣管徑與入胸處寬度比例與左右主要之氣管交叉處的夾角在不同心衰竭分級犬隻上的差異去了解氣管與支氣管塌陷和退化性二尖瓣疾病的關係。結果顯示氣管塌陷與退化性二尖瓣疾病的發生並無直接相關性，也無法證明氣管塌陷是心衰竭的危險因子之一，而氣管與支氣管僅在心臟解剖學相關位置受到壓迫，且壓迫程度與心衰竭程度相關。第二項研究中使用心臟超音波測量四十隻健康無心肺症狀犬隻與其他分別因呼吸道疾病、犬心絲蟲病與退化性二尖瓣心臟病而提升肺動脈壓力的一百六十九隻病犬，以超音波測得右心參數來評估不同病因導致的肺高壓對於右心功能之影響。結果顯示不同病因導致的肺高壓可能會造成不同程度的右心塑形，其中以心絲蟲與呼吸道疾病導致之肺動脈高壓對肺動脈與右心結構上的影響程度較為顯著。而在這三種造成肺動脈高壓的疾病間，左右心交互作用的差異可能來自於心絲蟲，呼吸道疾病以及退化性二尖瓣疾病間左右心狀態與壓力上的不同。

The complex interactions among respiratory system, right and left heart may lead to the high comorbidity between the cardiorespiratory diseases. The hemodynamic alteration and vascular bed remodeling of the pulmonary circulation, systemic inflammation and hypoxia are the possible pathogenesis of cardiac functional and structural changes in respiratory system disorders. Ventricular interdependence mediated through interventricular septum, pericardium sac and transmitted myofibers may play an important role in the relationship of right and left heart failure. The ratio of tracheobronchial diameters to thoracic inlet distance and the angle of tracheal bifurcation on thoracic radiographs were estimated to investigate the relationship between chronic degenerative mitral valvular disease (CDMD) and tracheobronchial collapse in 54 clinically healthy small breed dogs and 79 dogs with CDMD at different conditions of modified New York heart association functional classification. The result indicated that narrowing of trachea and bronchus in dogs with CDMD developed where the anatomical regions directly contacted with the heart and the degree of tracheobronchial compression was associated with severity of CDMD. However, the study failed to identify that trachea collapse is one of the risk factors for development CDMD and left heart failure. In the second study, the echocardiographic right indices were measured in 40 clinically healthy dogs and 169 dogs with different causes of elevated pulmonary artery pressure. The result presented that right heart indices were affected differently by chronic respiratory disorders, heartworm disease and moderate to severe CDMD; chronic respiratory disorders and heartworm disease had significant effect on the deformation of the pulmonary vascular and right ventricle. The different ventricular interdependence among the three causes of elevated pulmonary artery pressure might be attributed to the interaction between the dilated right ventricle and the different conditions of left ventricle.