One of the most serious progressive disorders, primarily affecting young women, is pulmonary artery hypertension, or PAH. PAH results from increased and sustained high blood pressure in the pulmonary artery, which increase the strain on the heart to transport blood to the lungs. PAH is primary, with no known cause, or secondary to underlying diseases in origin. A test using adenosine, a vasodilator, can yield positive results by decreasing arterial resistance and lowering blood pressure, thereby improving health status.
Adenosine Function
Adenosine is a fast acting, vasodilating, calcium channel blocker proven useful in testing the response of the pulmonary artery to vasodilation effects. Subsequent use of calcium channel blockers is possible with a good response. With adenosine's effects having a short duration of action, it must be given rapidly by intravenous access but is generally well-tolerated. Some people do experience side effects including transient flushing, acute chest pain and possible worsening of right heart function. The results of the test determine the value of calcium channel blocker use for therapy or the need to seek other methods.
Pulmonary Circulation
A unique feature of the pulmonary circulatory system is that oxygen concentration within the vessels is reversed. Normally, arteries carry oxygenated blood throughout your body while veins carry deoxygenated blood back to the right side of the heart and then the lungs. In the pulmonary circulatory system, the high pressure arterial blood is deoxygenated when it leaves the right side of the heart via the pulmonary arteries, traveling to the lungs to be oxygenated. Return of oxygenated blood to the left side of the heart occurs via the low pressure pulmonary veins. Increased pulmonary artery pressure can result from heredity, chronic lung diseases and heart disorders leading to PAH.
Symptoms
Shortness of breath, which might or might not reflect a specific underlying heart or lung disorder, is typically the first symptom of pulmonary artery hypertension. Dizziness and fainting, chest pain or discomfort, an enlarged abdomen and fatigue also are symptoms. Physical signs noted on a medical exam include a left parasternal lift, enhanced second heart sound reflecting a pulmonary component, and tricuspid valve reflux. Fluid retention, cold extremities and a bluish skin color, called cyanosis, also are symptomatic of pulmonary artery hypertension.
Diagnostics and Treatment
Cardiac catheterization, the diagnostic test for PAH, provides access to the pulmonary artery to assess pressures and enable a trial of adenosine to evaluate the reaction of the right pulmonary artery during the procedure. Treatment begins with supplemental oxygen, which decreases pulmonary pressures and helps alleviate symptoms, especially when used at night. Diuretics relieve fluid retention and oral anticoagulants help prevent blood clotting. Calcium channel blockers show varied results, but can be effective if adenosine testing is positive. Lung transplant is an option but carries a high mortality rate.
References
- Drugs.com: Adenosine Side Effects
- "RT For Decision Makers In Respiratory Care"; Advances in the Classification and Treatments of Pulmonary Hypertension; Paul Nuccio; October 2007
- "Journal of the American College of Cardiology"; Comparison of the Effects of Adenosine and Nifedipine in Pulmonary Hypertension; B. J. Schrader, et al.; 1992
- "Current Medical Diagnosis & Treatment"; Stephen J. McPhee and Maxine A. Papadakis; 2008
- "Nursing Drug Handbook": 2007
