Pulmonary hypertension is a condition where the blood pressure in the lungs is increased. It is not specifically a disease but is a condition which accompanies many other diseases or syndromes. These diseases have various causes. In order to understand the mechanisms that increase blood pressure within the lungs, it is important to understand the basic anatomy of the heart and lungs, and their accompanying blood vessels.
Anatomy of the heart and lungs
The lungs are a sponge-like organ that are attached to the heart by blood vessels. The heart has four chambers that are divided by thick walls of muscle. There are two atria and two ventricles. The superior and inferior vena cava are veins that enter the right atrium bringing de-oxygenated blood from the body. This blood passes into the right ventricle from where it is pumped into the pulmonary arteries that lead to the lungs where the blood will be oxygenated. This means that the blood releases carbon dioxide which is breathed out of the lungs and exchanges it for oxygen. The newly oxygenated blood then travels by the pulmonary veins back to the heart, to the left atrium. From there the blood travels to the left ventricle and continues into the large artery called the aorta. The aorta then branches off and delivers blood to the body.
The origin of pulmonary hypertension
Pulmonary hypertension is caused by an increase in blood pressure in the blood vessels of the lungs. This increases the strain on the right side of the heart, which pumps blood across the lungs to the left side of the heart. The result is that the right side of the heart pumps less blood to the lungs and less blood reaches the left side of the heart, which pumps oxygenated blood to the whole body. This creates the symptoms which will be discussed below.
Types of pulmonary hypertension
By definition, pulmonary hypertension is present when the mean blood pressure in the lungs is higher than 25 mmHg. In order to calculate the mean blood pressure, one must know the systolic and diastolic blood pressures. Pulmonary hypertension is classified according to the condition that caused it. In the case of Idiopathic pulmonary hypertension, the cause is not known. Others conditions are termed secondary and occur in connection with other diseases of the lungs, heart or thoracic wall.
Primary pulmonary hypertension
As already stated, it is not known what causes primary or idiopathic pulmonary hypertension. This condition often occurs in young individuals. It is linked with changes in the walls of the pulmonary blood vessels that cause their narrowing. This leads to increased pressure in the arteries of the lungs. It is exhibited by breathing problems and signs of heart failure.
Secondary pulmonary hypertension
This type of pulmonary hypertension is much more common and occurs in connection with heart disease and chronic lung diseases. Secondary pulmonary hypertension also occurs in patients with pulmonary embolisms and heart defects.
Pulmonary hypertension and left-sided heart disease
Left-sided heart disease is connected with gradual heart deterioration and the difficulty of the heart to fulfill its proper function. The pressure in the left atrium gradually increases and is propagated into the pulmonary blood vessels. It can be caused by the narrowing of the mitral valve (between the left atrium and left ventricle) or heart failure. These are the most common causes of pulmonary hypertension.
Pulmonary hypertension and lung disease
This is the second most common cause of pulmonary hypertension. It is often a primary disease of the lungs such as pulomonary fibrosis, chronic obstructive pulmonary disease or sarcoidosis. The presence of pulmonary hypertension in these conditions is a negative prognostic factor.
Chronic thromboembolic pulmonary hypertension
Pulmonary hypertension can occur often a pulmonary embolism that was not properly treated. Pulmonary embolism is caused by blood coagulum that obstructs the pulmonary artery or its branches. If the blood coagulum is not removed than it can stick to the blood vessel and so create a narrowing.
Symptoms of pulmonary hypertension
Unfortunately, there are no symptoms which are specific only to pulmonary hypertension. Therefore, these symptoms are called non-specific. This is the reason that pulmonary hypertension can be easily mistaken for other diseases and therefore not diagnosed properly. Pulmonary hypertension presents with fatigue and weakness, shortness of breath, fainting spells, chest pains during exhertion and/or inactivity, nail clubbing and hoarseness.
Diagnosis of pulmonary hypertension
As previously discussed, it is difficult to diagnose pulmonary hypertension based only on symptoms. Therefore, other methods must be utilized. It is possible to use chest X-ray, where there will be an enlargement of the right side of the heart. An electrocardiogram (ECG) can also be used. It records the electrical activity of the heart and will show signs of right heart enlargement. Another method is the echocardiography (ECHO). The ECHO is an ultrasound diagnostic method that allows visualization of the heart; its size and valves. Another useful method is spirometry which investigates the functioning of the lungs. The definitive diagnostic tool is the right-sided cardiac cathetrization. In this method, a catheter is threaded into the right side of the heart from the femoral artery. It is then pushed into the pulmonary artery where the pulmonary pressure can be measured.
Treatment of pulmonary hypertension
The treatment of pulmonary hypertension is targeted towards treating the primary cause of the condition. Medications that decrease blood coagulation are used, for example warfarin. Also, medications that relax the blood vessel wall are effective, but only in 5 % of patients. Therefore, medications that restrict the narrowing of blood vessels are more often used. It is also important to support the heart muscle. In severe cases, patients may be indicated for lung transplantation.