以斑點追蹤心臟超音波技術於心絲蟲患犬之臨床應用

Abstract

犬心絲蟲症是藉由蚊蟲叮咬而感染心絲蟲(Dirofilaria immitis)所導致，成蟲寄生於犬隻的肺動脈，干擾患犬之血液循環及造成肺部病變，嚴重可能導致肺高壓。在近幾年的研究中發現，心絲蟲的感染能夠直接引起心肌損傷，包含干擾心肌液體的平衡、重塑心肌間質中的細胞外基質。已知心肌間質的水腫會造成心臟的收縮及舒張功能不全，間質中細胞外膠原纖維的量減少、排列改變也會導致心肌無法正常收縮與舒張。在人醫中發現，長期肺高壓造成心輸出減少的主要原因是由於右心擴張導致的左心室變形、中膈逆理性移動及左心舒張灌流異常。此論文包含兩個部份，以新式的二維斑點追蹤超音波技術分別評估心絲蟲患犬及因呼吸道或心臟問題引起輕微肺高壓之患犬的左心室心肌功能。整體而言，大部分患犬的斑點追蹤超音波結果都顯示較正常犬來的低，並且有半數以上的數值達到統計差異(P < 0.05)。相對來說，傳統上用來評估心臟收縮與舒張功能的超音波數值在所有犬隻都是正常且沒有差異的。因此此研究結果顯示，心絲蟲與輕微肺高壓患犬的左心室心肌功能均有受損，而新式斑點追蹤超音波能作為一個敏感性高的診斷工具。

Canine heartworm disease (HWD) is caused by the parasite Dirofilaria immitis. Presence of adult worms in pulmonary arteries may cause pulmonary hypertension (PH), induce myocardial fluid imbalance and remodeling of interstitial extracellular matrix (ECM) of myocardium. Interstitial edema formation in the myocardium may lead to systolic and diastolic dysfunction and remodeling of ECM may be associated with processes of both myocardial contraction and relaxation. Left ventricular (LV) deformation, paradoxical ventricular septal motion and abnormal LV diastolic filling are supposed as major pathophysiologic mechanisms for impaired cardiac output in chronic PH. We investigated the change of LV myocardial function in dogs affected with HWD and mild PH using two-dimensional speckle tracking echocardiography (2D STE), respectively. Most of the longitudinal and circumferential strains and strain rates decreased in dogs with HWD and mild PH compared to normal controls, and more than 50% of variables achieved statistically significant (P < 0.05) despite both systolic and diastolic performance of LV were normal when evaluated using parameters derived from the conventional echocardiography. Results of this study indicated that STE provided a sensitive method of detecting left ventricular myocardial dysfunction of dogs with HWD and mild PH.