Pulmonary hypertension

• What is Pulmonary Hypertension
• Statistics on Pulmonary Hypertension
• Risk Factors for Pulmonary Hypertension
• Progression of Pulmonary Hypertension
• Symptoms of Pulmonary Hypertension
• Clinical Examination of Pulmonary Hypertension
• How is Pulmonary Hypertension Diagnosed?
• Prognosis of Pulmonary Hypertension
• How is Pulmonary Hypertension Treated?
• Pulmonary Hypertension References

What is Pulmonary Hypertension

Pulmonary hypertension means high blood pressure in the lung blood vessels. It is not a disease itself, but rather a final common pathway for many different diseases. Pulmonary arterial hypertension is classified as pulmonary artery pressures higher than 30mmHg. It may affect the arteries or veins of the lungs. Pulmonary arteries take blood from the right side of the heart to the pulmonary capillaries; pulmonary veins transport the oxygenated blood from the capillaries to the left side of the heart. The disease discussed below is pulmonary arterial hypertension. Pulmonary venous hypertension, usually arising due to left heart disease, is discussed under ‘pulmonary oedema’, though in chronic form it eventually causes pulmonary arterial hypertension.

Statistics on Pulmonary Hypertension

Primary pulmonary hypertension (ie. no obvious cause) is a rare disease. It is found in 0.1-0.2% of all patients at autopsy, but many are asymptomatic until late in the process.

Secondary pulmonary hypertension, however, is much more common that that – since it frequently complicates almost any form of chronic lung disease.

Risk Factors for Pulmonary Hypertension

Many diseases may cause pulmonary hypertension. These include:

• Diseases of the lung blood vessels themselves (pulmonary embolisms),
• Any chronic lung disease (especially COPD),
• Musculoskeletal disorders (myasthenia gravis),
• Left heart disorders (left ventricular failure, mitral stenosis),
• Morbid obesity,
• Obstructive sleep apnoea;

When none of these causes are present, “primary pulmonary hypertension” is diagnosed. It is a diagnosis of exclusion.

Progression of Pulmonary Hypertension

As mentioned above, pulmonary hypertension is a final common pathway for many different diseases. Thus, the early natural history of the pulmonary hypertension is disease such as pulmonary embolism or chronic lung disease. These diseases cause injury to the lung endothelial cells. These are the cells lining the blood vessels.

Endothelial damage causes a range of local effects, mediated by the release of enzymes and chemicals from these cells. These changes result in constriction of pulmonary blood vessels. In some cases, spasm of muscle layers inside blood vessels is also a factor; this means that treatment with vasodilator medication may be useful.

In the early stages of disease, these changes may only occur during exacerbations of underlying lung disease, for example, acute exacerbation of COPD. Eventually, however, pulmonary hypertension becomes severe and persistant. The strain on the right ventricle of the heart causes its function to decline, leading to right heart failure.

Lack of oxygen, caused by underlying lung disease, and abnormal blood flow through the lungs, further impairs the function of the right ventricle, and eventually leads to left ventricular failure, as well.

How is Pulmonary Hypertension Diagnosed?

• Chest x-ray: changes both due to the previous lung disease, as well as the pulmonary hypertension may be seen;
• ECG may show abnormalities of the right atrium and ventricle.

Prognosis of Pulmonary Hypertension

The onset of pulmonary hypertension on the background of any other disease has a poor prognosis, because it is usually progressive, and eventually leads to right heart failure (cor pulmonale). Only 1/5 of patients on average are alive within 2-5 years of onset.

How is Pulmonary Hypertension Treated?

Treatment depends on the underlying cause of pulmonary hypertension. For example, effective treatment of COPD is important in patients with pulmonary hypertension secondary to this disease. Treatment directed at pulmonary hypertension itself may include the following:

• Diuretics (such as hydrochlorothiazine) may be needed to treat fluid build up due to right heart failure.
• Vasodilators (such as verapamil) may improve symptoms by dilating pulmonary arteries (see Natural History)
• Anticoagulation by warfarin is given in cases of primary pulmonary hypertension, because the possibility of recurrent pulmonary embolism as an underlying cause can seldom be completely excluded.

Heart and lung transplantation is sometimes recommended for young patients with primary, or secondary hypertension due to disease such as cystic fibrosis. Recent progress in medical therapies has diminished the role of transplantation in the management of PPH during the past decade. Drug therapy is not effective in some patients, responses to therapy are not sustained over time in others, and drug side effects eventually limit the benefits of treatment in a few more.

Lung transplantation is therefore ultimately the only alternative for patients whose PPH is severe and cannot be managed medically. The outcome of lung and heart-lung transplantation for PHH has been good but sobering. Functional recovery has been excellent, but long-term survival results have been limited by the high prevalence of chronic allograft rejection.

Pulmonary Hypertension References

1. Budev MM. Arroliga AC. Jennings CA. Diagnosis and evaluation of pulmonary hypertension.Cleveland Clinic Journal of Medicine. 70 Suppl 1:S9-17, 2003 Apr.
2. Cotran RS, Kumar V, Collins T. Robbins Pathological Basis of Disease Sixth Ed. WB Saunders Company 1999. pp704-706.
3. Galie N. Manes A. Branzi A.The new clinical trials on pharmacological treatment in pulmonary arterial hypertension. European Respiratory Journal. 20(4):1037-49, 2002 Oct.
4. Kumar P, Clark M. Clinical Medicine. Fourth Ed. WB Saunders, 1998. pp.719-723.
5. Talley NJ, O’Connor S. Clinical examination. Third Ed. MacClennan & Petty, 1996. p 70-71
6. Trulock EP.Lung transplantation for primary pulmonary hypertension. Clinics in Chest Medicine. 22(3):583-93, 2001 Sep.