First recognized as a separate disease in the early 20th century, pulmonary hypertension is now known to occur in both genders, at any age.
Normal pulmonary artery pressure is much lower than arterial blood pressure. Pulmonary hypertension is high blood pressure in the lung arteries. It occurs as a result of thickening of all three layers of the small pulmonary artery branches throughout the lungs, especially the muscular layer.
Patients often mistake shortness of breath, or dyspnea, for something other than a disease, like thinking endurance is decreased because of too much time spent at work, or they may think, "I'm short of breath because I stopped going to the gym."
Pulmonary hypertension has many different causes and may be easily overlooked because the symptoms are the same as for many heart diseases. We try to maintain a high index of suspicion for the disease because effective treatments exist.
It can be categorized into one of four primary groups.
■ Many patients who suffer from World Health Organization Group 1 Pulmonary Arterial Hypertension, or Group 1 PAH, harbor a gene mutation placing them at high risk for developing the disease. It appears that the presence of the mutation alone is not sufficient to result in the disease; rather, some external trigger is required to set it off. Hence, this form is known as idiopathic pulmonary arterial hypertension, or iPAH.
Treatment for iPAH includes oral drugs, inhaled medications, or drugs continuously infused subcutaneously, like an insulin pump in diabetes, or through a permanent indwelling intravenous line. A noninvasive test called an echocardiogram can suggest the diagnosis, and it is confirmed by a cardiac catheterization procedure called right heart catheterization, in which the pulmonary artery pressure is directly measured.
■ In the WHO Group 2 category of hypertension, patients suffer from forms of pulmonary hypertension that are secondary to other disease processes, including those leading to malfunction of the left ventricle. Since the left ventricle is downstream of the lungs, any disease significantly affecting left ventricular filling pressure has the potential to lead to secondary pulmonary hypertension. For example, a combination of essential ("regular") hypertension and obesity can lead to malfunction of the left ventricle in diastole, the filling half of the cardiac cycle, leading to secondary pulmonary hypertension.
■ Diseases that affect the lungs or cause low oxygen levels can also result in secondary pulmonary hypertension, WHO Group 3.
■ Other causes not to be overlooked are multiple long-term blood clots in the lung arteries, called chronicthromboembolic pulmonary hypertension, or WHO Group 4, and miscellaneous causes (Group 5), including sarcoidosis.
Effective treatment is available for all types of pulmonary hypertension. The sooner the diagnosis, particularly for WHO Group 1, the better the outcome.
Dr. David C Booth directs Pulmonary Hypertension Services at the UK HealthCare Gill Heart Institute and is in the Interventional Cardiology group.