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|Classification and external resources|
|Classification and external resources|
Cor pulmonale (Latin cor, heart + New Latin pulmōnāle, of the lungs), also known as pulmonary heart disease, is enlargement and failure of the right ventricle of the heart as a response to increased vascular resistance or high blood pressure in the lungs (pulmonary hypertension).
Chronic cor pulmonale usually results in right ventricular hypertrophy (RVH), whereas acute cor pulmonale usually results in dilatation. Hypertrophy is an adaptive response to a long-term increase in pressure. Individual muscle cells grow larger (in thickness) and change to drive the increased contractile force required to move the blood against greater resistance. Dilatation is a stretching (in length) of the ventricle in response to acute increased pressure, such as when caused by a pulmonary embolism or ARDS (acute respiratory distress syndrome).
To be classified as cor pulmonale, the cause must originate in the pulmonary circulation system. Two major causes are vascular changes as a result of tissue damage (e.g. disease, hypoxic injury, chemical agents, etc.), and chronic hypoxic pulmonary vasoconstriction. RVH due to a systemic defect is not classified as cor pulmonale.
If left untreated, cor pulmonale can lead to death.
The heart and lungs are intricately related. Whenever the heart is affected by disease, the lungs will follow and vice versa. Pulmonary heart disease is by definition a condition when the lungs cause the heart to fail.
The heart has two pumping chambers. The left ventricle pumps blood throughout the body. The right ventricle pumps blood to the lungs where it is oxygenated and returned to the left heart for distribution. In normal circumstances, the right heart pumps blood into the lungs without any resistance. The lungs usually have minimal pressure and the right heart easily pumps blood through.
However with certain lung diseases chronically present, like emphysema and chronic bronchitis (chronic obstructive pulmonary disease - COPD) or pulmonary hypertension, the blood vessels of the lungs are significantly reduced in number (due to lung tissue destruction) and/or chronically constricted (due to poor alveolar ventilation in the case of COPD). The right ventricle is no longer able to push blood into the lungs effectively, and the chronic overload eventually causes it to fail.
The symptoms of pulmonary heart disease depend on the stage of the disorder. In the early stages, one may have no symptoms but as pulmonary heart disease progresses, most individuals will develop the symptoms like:
Blood backs up into the systemic venous system, including the hepatic vein. Chronic congestion in the centrilobular region of the liver leads to hypoxia and fatty changes of more peripheral hepatocytes, leading to what is known as nutmeg liver.
In many cases, the diagnosis of pulmonary heart disease is not easy as both the lung and heart disease can produce similar symptoms. Most patients undergo an electrocardiogram, chest X ray, echocardiogram, CT scan of the chest and a cardiac catheterization. During a cardiac catheterization, a small flexible tube is inserted from the groin and under x ray guidance images of the heart are obtained. Moreover the technique allows measurement of pressures in the lung and heart which provide a clue to the diagnosis.
There are several mechanisms leading to pulmonary hypertension and cor pulmonale:
While not all lung diseases can be prevented one can reduce the risk of lung disease. This means avoiding or discontinuing smoking. Patients with end stage emphysema or chronic obstructive lung disease always end up with right heart failure. When working in environments where there are chemicals, wear masks to prevent inhalation of dust particles.
Elimination of the cause is the most important intervention. Smoking must be stopped, exposure to dust, flames, household smoke and to cold weather is avoided. If there is evidence of respiratory infection, it should be treated with appropriate antibiotics after culture and sensitivity. Diuretics for RVF, In pulmonary embolism, thrombolysis (enzymatic dissolution of the blood clot) is advocated by some authorities if there is dysfunction of the right ventricle, and is otherwise treated with anticoagulants. In COPD, long-term oxygen therapy may improve cor pulmonale.
Cor pulmonale may lead to congestive heart failure (CHF), with worsening of respiration due to pulmonary edema, swelling of the legs due to peripheral edema and painful congestive hepatomegaly (enlargement of the liver due to tissue damage as explained in the Complications section. This situation requires diuretics (to decrease strain on the heart), sometimes nitrates (to improve blood flow), phosphodiesterase inhibitors such as sildenafil or tadalafil and occasionally inotropes (to improve heart contractility). CHF is a negative prognostic indicator in cor pulmonale.
Oxygen is often required to resolve the shortness of breath. Plus, oxygen to the lungs also helps relax the blood vessels and eases right heart failure. Oxygen is given at the rate of 2 litres per minute. Excess oxygen can be harmful to patients because hypoxia is the main stimulus to respiration. If such hypoxia is suddenly corrected by overflow of oxygen, such stimulus to the respiratory center is suddenly withdrawn and respiratory arrest occurs. When wheezing is present, majority of the patients require bronchodilators. A variety of drugs have been developed to relax the blood vessels in the lung. Calcium channel blockers are used but only work in a few cases. Other novel medications that need to be inhaled or given intravenously include prostacyclin derivatives.
Cases of COPD with chronic cor pulmonale present with secondary polycythemia, if severe it may increase the blood viscosity and contribute to pulmonary hypertension. If hematocrit(PCV) is above 60%, then it is better to reduce the red blood cell count by phlebotomies.
Mucolytic agents like bromhexine and carbocisteine help bring out excessive bronchial secretions more easily by coughing.
When medical therapy fails, one may require a transplant. However, since the lungs are damaged, both the heart and lungs needs to be transplanted. With a shortage of donors this therapy is only done 10-15 times a year in North America.
Each year there are about 20,000 deaths and close to 280,000 hospital admissions among individuals who have pulmonary heart disease. The majority of individuals affected by pulmonary heart disease are women less than 65 years of age. Infants who are born with congenital heart disorders (esp. holes in the heart like a VSD) are prone to pulmonary artery disease. While pulmonary heart disease is serious, it is much less common than coronary artery disease.