Pulmonary Hypertension

00:01 Most patients can be treated with either anticoagulation or for very large PEs, thrombolysis and anticoagulation.

00:02 Pulmonary hypertension. So the other common pulmonary circulation problem, as well as PEs, is pulmonary hypertension, and what this means is a raised pulmonary artery pressure, above 25 millimeters of mercury, at rest, above 30 millimeters of mercury during exercise.

00:17 Now this is incredibly common as a complication of hypoxic lung disease, in which case it is called cor pulmonale or left-sided heart disease. But in those circumstances, it's not often treated as a specific issue. There are also a range of causes of pulmonary hypertension independent of lung disease and left-sided cardiac disease, and we'll discuss those in a bit more detail later. With pulmonary hypertension, the cause of the pulmonary hypertension in cor pulmonale is the hypoxia itself. So the standard reaction of a pulmonary artery to hypoxia is vasoconstriction, and that's to ensure ventilation perfusion matching occurs, but in somebody who is very severely affected by lung disease with widespread hypoxia, that physiological response that normally occurs upon recirculation, vasoconstriction in response to a hypoxia becomes a pathological problem as the vasoconstriction increases the pressure in pulmonary artery circulation, and eventually leads to right-sided failure, and that's called cor pulmonale. In addition, patients with left-sided cardiac problems, that will have raised the pressure in the pulmonary veins, and then that will raise the pressure in the pulmonary capillaries, and then in the pulmonary arteries as a sort of backpressure issued from the left-sided cardiac disease, and that occurs with left-sided cardiac myopathies, cardiac failure, and valvular disease. Emphysema specifically causes lung destruction and as it destroys the lung that will also destroy aspects of the pulmonary circulation, leading to pulmonary hypertension, and then the pulmonary arteries can be blocked independent of any issue of the lungs or cardiac problems, and this most commonly occurs in the description, in what I described earlier which is multiple small pulmonary emboli. But in addition, there are a bunch of diseases where you get endothelial abnormalities of the pulmonary circulation leading to pulmonary artery hypertension due to loss of the pulmonary artery circulation.

02:30 And those are the sort of primary pulmonary hypertensive diseases.

02:32 So we're going to list the causes of pulmonary hypertension. This top category are the rarer causes, and these are the ones that I just described where you get primary problems of the pulmonary artery circulation, and that's divided into idiopathic, which tends to be young ladies, the reason for that is not clear, can be due to toxins (aminorex, fenfluramine, rapeseed oil) have all been associated with pulmonary hypertension, it is frequently associated with connective tissue diseases such as systemic sclerosis, chronic HIV infection has a late complication of pulmonary hypertension, and sarcoidosis occasionally also causes pulmonary hypertension. That category is the rarer causes. Now the secondary causes are the common causes, the chronic hypoxic lung disease, causing cor pulmonale, and the most common cause of that will be COPD. Congestive cardiac failure, mitral valve disease, as we've already mentioned.

03:32 But there are other causes of chronic hypoxic lung disease that may end up causing secondary pulmonary hypertension, such as obesity hypoventilation, chest wall restrictive disease, interstitial lung disease. And then there is direct occlusion of the pulmonary circulation which is characterized, well the most common cause of that would be chronic thrombo-embolic disease with multiple small PEs knocking off individual small arterials which, over time leads to pulmonary hypertension.

03:58 A similar situation can occur in sickle-cell disease and in patients infected with schistosomiasis, although both of those are relatively rare compared to chronic thrombo-embolic disease.