Cor pulmonale - Right-sided Heart Failure

What is Cor pulmonale?

Cor pulmonale is a common type of heart disease produced by the dysfunctional response to pulmonary arterial hypertension, leading to hypertrophy and/or dilatation of the right ventricle. The diseases which affect the structure and/or the function of the lungs stimulate this condition, ultimately leading to the failure of the right heart. Amongst the various causes behind Cor pulmonale, chronic obstructive pulmonary disease (COPD) ranks first. This is followed by idiopathic pulmonary fibrosis and obesity–hypoventilation syndrome. The underlying pathological mechanism leading to the hypertrophy of the right ventricle during cor pulmonale is always pulmonary hypertension (PH). This PH is indicated by the presence of a resting mean pulmonary artery pressure (PAP) > 20 mm Hg.

Due to its close association with COPD, its prevalence has been detected to be high. However, an exact estimation of cor pulmonale in COPD is relatively complicated, because of the difficulty in performing large scale right heart catheterization (insertion of a catheter into the pulmonary artery through the right side of the heart to measure the pressures in hearts and lungs) in patients at risk.

What causes Cor pulmonale?

  • Diseases like COPD, which limit the airflow, cause chronic bronchial obstruction. This deficiency of oxygen or chronic hypoxia leads to pulmonary arteriolar constriction. The physiological mechanism which maintains the airflow starts showing excessive action to compensate the oxygen deficiency. This leads to an increased pulmonary arterial pressure (PAP). Some other factors which increase the PAP include respiratory acidosis and chronic hypercapnoea, as these diseases stimulate pulmonary vasoconstriction.
  • Some diseases which disrupt the pulmonary vascular bed like emphysema, pulmonary emboli, and pulmonary fibrosis and those which increase the blood viscosity like sickle-cell disease, polycythemia, also lead to a raise in mean PAP.
  • Restrictive lung diseases, like kyphoscoliosis, idiopathic pulmonary fibrosis, and pneumoconiosis, restrict the pulmonary volumes from extrinsic or parenchymatous origin. These diseases are also considered to be the leading cause of Cor pulmonale. Pickwickian syndrome, alternatively known as obesity–hypoventilation syndrome, leads to respiratory insufficiency of “central” origin and is a relatively frequent cause of cor pulmonale. This disease is associated with pronounced gas exchange abnormalities and poor ventilatory drive.

Symptoms of Cor pulmonale

  • Some common symptoms shown due to pulmonary hypertension include difficulty in breathing during exertion (dyspnea), shortness of breath and faster heart-beat during activity, fatigue and lethargy.
  • The patient looses consciousness for a small span of time followed by a period of activity (known as syncope in medical terms) as the brain receives insufficient supply of the blood.
  • Sometimes, the heart beats so fast that the patient can feel his heart pounding.
  • Initially, these symptoms are only observed when the patient is exerting himself but gradually, these symptoms start appearing even while taking rest or with mild activity.
  • Some other symptoms generally observed include, swelling of the feet or ankles, cough and persistent wheeze.

Diagnosis of Cor pulmonale in COPD

The clinical signs observed during cor pulmonale are not sensitive and specific. They are generally observed during the advanced stages of the disease, that is, after the development of pulmonary hypertension. Even though swelling in the ankle region indicates RHF (right heart failure), it is a non-specific symptom and can arise due to other causes also. A murmur of tricuspid regurgitation (backflow of the blood due to defective tricuspid valve) is noticed in advanced stages in patients with respiratory disorders. This murmuring sound indicates right ventricular dilatation. But, as it is noticed in advanced stages, preventive steps cannot be taken.

Hence the clinical assessment methods generally used are:

  • Electrocardiography (ECG) – A non- invasive diagnostic technique used to measure pulmonary hypertension is ECG. A normal ECG is not specific and is unable to rule out presence of pulmonary hypertension in COPD patients. However, continuous wave doppler echocardiography and pulsed wave doppler echocardiography have been found to be more effective in detection.
  • MRI – Images obtained from contrast MRI give a very good picture of the right ventricular structure and function.
  • Right heart catheterization – It is a gold standard test used to measure PAPs.
  • Brain natriuretic peptide (BNP) – It is a cardiac hormone synthesized by the ventricles and gets released into blood circulation, when heart is subjected to tension. Measuring the plasma levels of this hormone is an accurate diagnostic test.

Treatment of Cor pulmonale

Treatment of this disease is targeted towards increasing the patient’s capacity to tolerate exercises and improve the oxygen levels of the arterial blood. This is achieved mainly by using diuretics which reduce right ventricular dilatation, hence improving its contractility. Pulmonary vasodialators, like nitric oxide and long term oxygen therapy, not only improve the chances of survival but also prevent progression of PH. Lung volume reduction surgery (LVRS) is performed for the better distribution of pulmonary blood flow and ventilationperfusion matching.

Can we prevent Cor pulmonale?

The chances of Cor pulmonale can be reduced by avoiding habits like cigarette smoking. Intake of proper diet low in sodium, cholesterol, saturated fats and rich in potassium is very essential for these patients. As the heart failure drugs deplete the magnesium reserves, foods rich in magnesium like soybeans, oatmeal, nuts, seeds and wheat germ should be consumed. Plenty of fresh fruits, vegetables and dietary fibers should be included in diet.

My sources of information

Shujaat A, Minkin R, and Eden E. 2007. Pulmonary hypertension and chronic cor pulmonale in COPD. Int J Chron Obstruct Pulmon Dis. 2(3): 273–282.

Weitzenblum Emmanuel. 2003. CHRONIC COR PULMONALE. Heart. 89(2): 225–230.

http://www.nlm.nih.gov/medlineplus/ency/article/000129.htm

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