While high blood pressure or hypertension is the elevated blood pressure in the arteries, pulmonary hypertension is unusually high blood pressure in the blood vessels leading to, and passing through the lungs of the dog. In this condition, blood pressure in the arteries leading from the heart to the lungs is higher than normal ranges.
In dogs, pulmonary hypertension is always secondary to some other underlying condition. A number of causes can be responsible for pulmonary hypertension such as vasoconstriction — narrowing or constriction of the arteries or capillaries of the lungs, pulmonary artery blockage, high pressure within the left atrium (left-sided top chamber of the heart) with resultant increase in blood pressure in the capillaries of the lungs, or excessive blood flow in the arteries of the lungs.
Blood enters the heart through two large veins known as superior and inferior vana cavas. This oxygen-poor blood is emptied into right atrium which contracts and the blood is pumped into right ventricle through tricuspid valve. Once the right ventricle is filled with blood, the tricuspid valve closes to prevent backward flow of blood into right atrium. Contraction of right ventricle causes blood to leave the heart through the pulmonic valve and move into the pulmonary artery and to the lungs where it is oxygenated. From lungs, the oxygenated blood is returned to left atrium through pulmonary vein. As the left atrium contracts, the blood moves through mitral valve into left ventricle. Once left ventricle is full, the mitral valve closes to prevent backward flow of the blood. Contraction of left ventricle sends oxygenated blood into the aorta and to the rest of the body.
Pulmonary hypertension is a potentially dangerous condition as it can alter the shape and performance of the heart. Right ventricle may become enlarged while left ventricle may fills abnormally. As less oxygen reaches the body, signs such as exercise intolerance and bluish skin may become evident. Increased pressure in the right heart can cause pooling of blood in the body. Tricuspid valve may not function normally and backward flow of blood from right ventricle into right atrium may occur, eventually leading to right-sided congestive heart failure.
Common signs and symptoms associated with pulmonary hypertension include
Bluish-purplish tinged skin
Coughing or vomiting up blood