PULMONARY HYPERTENSION

Pulmonary hypertension is considered present when the mean PA pressure is greater than 25 mm Hg at rest or 30 mm Hg during exercise.

Etiology and Classification

• Secondary pulmonary hypertension is present when there is a identifiable cause with hemodynamic sequelae leading to pulmonary hypertension. Disease of the left heart, pulmonary embolism, chronic hypoxemia and left to right shunts are common etiologies.
• Primary pulmonary hypertension is obviously idiopathic. However, it is often associated with cirrhosis , AIDS and can be familial.

Pathogenesis
Elevated pressure, through endothelial cell dysfunction, produces structural changes in the pulmonary vasculature. These changes ultimately decrease pulmonary blood flow and stress the heart to the point of failure. Based on etiology, pulmonary hypertension is divided into two categories.

• Primary (idiopathic): The cause is unknown.
• Secondary: The hypertension is secondary to a variety of conditions which increase pulmonary blood flow or increase resistance to blood flow. Example: Interstitial fibrosis.

Pathology
The changes involve large and small pulmonary blood vessels and range from mild to severe. The major changes includeatherosclerosis, striking medial hypertrophy and intimal fibrosis of small arteries and arterioles, and plexogenic arteriopathy. Refer to Figure 15-7 in your textbook.

Pathophysiology 

Dyspnea and fatigue eventually give way to irreversible respiratory insufficiency,

 cyanosis and cor pulmonale

Clinical Features

• Primary pulmonary hypertension often occurs in young females. Dyspnea on exertion, fatigue, syncope, dizziness, edema and angina occur during the course of illness.
• Loud pulmonary component of the second heart sound, pulmonary ejection click, RV lift, S4 gallop, syst murmur of tricuspid regurgitation and a diastolic murmur of pulmonary regurgitation can be recognized. Findings are subtle and the diagnosis is often missed.
• Complex testing is often required to establish the presence of pulmonary hypertension and to rule out secondary causes.

Therapy

• Prognosis is poor and five year survival is between 22-33%.
• See cor pulmonale for therapeutic measures for secondary pulmonary hypertension.
• Anticoagulation, Calcium channel blocks, Nitric oxide and Prostacyclin are current therapeutic options.
• Anticoagulation has to given indefinitely.
• 20-35 % of patients respond to vasodilators acutely and benefit from their use.
• Infusion of prostacycline, continuously and chronically, improves hemodynamics, symptoms and survival. This requires implantation of a permanent central venous catheter, use of an external portable infusion pump and comprehensively trained support staff.
• Lung transplant is an option for patients refractory to medical management.