COR PULMONALE AND PULMONARY HYPERTENSION

Cor=heart, pulmonale=lungs. Cor pulmonale is dysfunction of the right side of the heart due to disease of the respiratory system. Confused? You can go to the website at http://www.americanheart.org/Heart_and_Stroke_A_Z_Guide/hworks.html

Pulmonary hypertension, that is high blood pressure in the pulmonary artery, causes right heart dysfunction. Usually pressures in the pulmonary artery are low, normal being about 25systolic, 10 diastolic, measured in millimeters (mm) of Mercury (Hg) pressure. Recall that your systemic arterial blood pressure measured in your arm is about 120/80 mm Hg! The blood vessels in the lung are not very muscular and do not cause much resistance to the flow of the low oxygenated blood. High blood pressure in the lungs (Pulmonary Artery Hypertension) can occur by at least four different ways.

1. A decrease in the volume of the blood vessels, so that fewer blood vessels carry more blood. This can occur with blood clots clogging the arteries (Pulmonary Emboli) and Emphysema with destruction of the capillaries at the alveolar level.

2. Constriction of the blood vessels (vasoconstriction) due to hypoxia. Hypoxia is low oxygen level in the alveoli. Hypoxia can occur when one travels up a mountain, gaining altitude but decreasing in oxygen, in neuromuscular diseases such as kyphoscoliosis, polio, sleep apnea and COPD. These all prevent deep breaths with subsequent supplying the alveoli with fresh air. This is an oversimplification of the disease processes!

3. Increased pressure beyond the blood vessels, like a dam on a river. This occurs with failure of the left ventricle in its ability to pump blood forward efficiently due to coronary artery disease, or with disease of the mitral or aortic valve, when they either prevent blood from moving forward by being narrowed or are leaky and allow blood to flow back into the lungs.

4. Thick blood, making the heart work harder to push molasses rather than water. Blood can become thicker by having too many red blood cells (polycythemia), having deformed red blood cells like in sickle cell disease, or having abnormal proteins like in cryogobulinemia.

In most patients with COPD, decreased oxygen in the alveoli is due to the lung disease. The hypoxia is the cause of constriction of the small pulmonary artery blood vessels, the pulmonary arterioles. The narrowed blood vessels cause the right ventricle to have to squeeze harder to get blood to the alveoli and to the left side of the heart. This increased squeeze is reflected in higher blood pressure in the right atrium, right ventricle and pulmonary artery. The right side of the heart is a puny muscle; recall that it normally has to produce pressures of only 25 mm Hg, whereas the left side has to generate pressures of 120 mm Hg. In order to generate the higher pressure the right heart chambers initially dilate (enlargement), and later the muscle gets thicker and bigger (hypertrophy). For a while this accommodation of the right heart works, and in some people the process is reversible with increased oxygenation of the alveoli. This is what happens when the mountain climber descends the mountain. If the alveolar hypoxia persists, the constriction of the blood vessels may become permanent. As the right heart chambers dilate the tricuspid valve begins to leak making the system less efficient in pushing blood forward.

Hypoxia also affects the kidney. The kidney produces a hormone, erythropoietin (EPO), which stimulates the bone marrow to produce more red blood cells to carry oxygen around more efficiently. If the body produces too many red blood cells (polycythemia) these act to thicken the blood and can produce Pulmonary Hypertension all by itself! Hypoxia in the kidney interferes with the ability of the body to rid itself of excess salt and water, increasing the volume of fluid in the body, which shows up as a swollen liver and/or swelling (edema) of the lower legs.

Right heart failure is diagnosed clinically by noting that the legs or the liver are swollen on physical exam. Confirmation of the diagnosis can be made by looking at the Electrocardiogram (EKG), doing a special sound wave test (the Echocardiogram), or actually measuring the pressures in the right heart by way of right heart catherization. The causes of right heart failure are sought by doing a history and physical exam, checking blood tests, checking the arterial blood gas tensions (ABG's), pulmonary function tests and ventilation-perfusion scans. The specific tests performed will depend on the history and clinical findings.

Therapy of Pulmonary Hypertension and Right Heart Failure is directed toward getting more oxygen in to the alveoli and reversing the process that produced the pulmonary hypertension. So if we are dealing with chronic mountain sickness, the individual is transported to a lower altitude. If we are dealing with sleep apnea, one could try ventilatory assist devises such as CPAP or BiPAP. If one is dealing with neuromuscular disease, one may try CPAP or a cuirass ventilator (a portable iron lung). If COPD is the cause, one uses oxygen, bronchodilators and corticosteroids. If the process is not reversible one uses salt or sodium restriction, diuretics with careful follow-up of the blood sodium, potassium, chloride, blood urea nitrogen. If the red blood count (Hematocrit) is above 55, removal of blood may be helpful.

This is a long article, relating that failure of the heart due to respiratory disease (Cor Pulmonale) is secondary to high blood pressure in the pulmonary artery circuit. Low oxygen levels in the alveoli are the most common cause in individuals with COPD. The process is important to detect and treat, as it may be reversible in its early stages. It is treatable in the later stages.

Dr. Ron