References
Pulmonary hypertension in dogs: an overview
Abstract
Pulmonary hypertension is a complex syndrome that can be caused by congenital or acquired disease. Congenital conditions include cardiac shunts, such as ventricular septal defect and patent ductus arteriosus. Acquired diseases that eventually lead to pulmonary hypertension include cardiac, systemic and pulmonary pathologies, for example late stage myxomatous mitral valve disease and interstitial lung disease such as idiopathic pulmonary fibrosis. It can be a challenge to identify pulmonary hypertension because the diagnostic process usually requires advanced imaging tools, such as echocardiography, and a good understanding of the animal's history. Pulmonary hypertension can have a profound effect on a dog's quality of life and can lead to severe respiratory distress and damage to the cardiovascular system. Therefore pulmonary hypertension needs to be identified and addressed promptly. Pulmonary hypertension can be reversible in the early stages, but it is generally not reversible when chronic changes to the pulmonary vasculature have occurred. The article reviews the definition of pulmonary hypertension and its pathophysiology, its diagnosis and treatment in canine patients, and discusses the most common congenital and acquired causes.
Pulmonary hypertension is defined as an abnormal increase in pressure within the pulmonary artery. The gold standard method of diagnosing pulmonary hypertension is directly assessing pulmonary arterial pressure (PAP), obtained by right heart catheterisation. According to the human literature, pulmonary hypertension can be diagnosed if mean PAP is ≥25 mmHg at rest (Hoeper et al, 2013). Increased PAP is an abnormal haemodynamic state that can be associated with numerous, diverse disorders which in human patients include diseases such as congenital systemic-to-pulmonary shunts, idiopathic pulmonary fibrosis, chronic thromboembolism or chronic lung disease (Simonneau et al, 2019).
The systemic circulation consists of veins, venules, arteries, arterioles and capillaries, and is a high-pressure system. There is a significant pressure difference between the arterial and venous systems. The inlet is the aorta with high blood pressure of approximately 98–120 mmHg and the outlet is the venae cavae, with pressure of approximately 2–6 mmHg for a typical dog at rest. The pressure difference between the arterial and venous systems is a direct cause of blood flow (Klein et al, 2007).
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