Clinicians Beware: Not All Pulmonary Hypertension is Created Equal

Doppler echocardiography has made the measurement of systolic pulmonary arterial (PA) pressure easy and commonplace. Its use has revealed the prevalence of elevated PA pressure in a wide variety of diagnoses and conditions that is more extensive than anyone could have predicted 20 years ago. At the same time, revolutionary developments in the management of idiopathic pulmonary arterial hypertension (PAH) (formerly known as primary pulmonary hypertension), have heightened the quest to find and treat pulmonary hypertension (PH), especially because most persons afflicted with this rapidly fatal disease are otherwise healthy young women. In addition, PA hypertension complicating other systemic diseases such as scleroderma, lupus, HIV, and congenital heart disease begs for improvement in management because survival is associated with the presence of PH in these disorders. Because of the success in improving quality of life and survival in idiopathic PAH, a sense of pressure to treat all PH has developed in the medical community, even when the PH is modest or a secondary phenomenon. The immense cost of PH therapies, and the lack of documented efficacy in many secondary causes, should make clinicians skeptical about the desirability of therapy, and points to the need for further clinical trials and newer drugs.

The Consensus Document in this issue of Circulation was composed by a group consisting of some of the best clinical investigators in the field of PH. In addition to being comprehensive and factual, the document contains practical wisdom, especially in the last sections on evaluation and management of nonidiopathic PH. I would only highlight a few areas that have been observed to be confusing, misunderstood, or ignored in referrals to PH centers and that this consensus statement helps to clarify. The first is that the pulmonary artery pressure estimated by Doppler echocardiography is systolic pressure, not mean pressure. The tendency is to assume or report this pressure as if it is mean pressure and act accordingly. In fact, mean PA pressure is only approximately 60% of systolic pressure. A systolic pressure of 40 mmHg corresponds to a mean PA pressure of about 24 mm Hg, which is at the upper end of normal or borderline hypertensive. Second, Doppler flow interpretation can both under- and overestimate PA systolic pressure significantly, due to a variety of possible problems, including technical error. Thus, chronic management decisions should never be made simply on a Doppler estimation of PA pressure. If PH is suspected, the diagnostic algorithms outlined in this Consensus Document should be followed, and careful consideration is necessary to get the diagnosis right.

Reaching the right diagnosis also relies on a methodical and complete cardiac catheterization. This means attention to the physiology of the right heart. Oxygen saturation should be measured in the inferior vena cava, superior vena cava, right atrium, right ventricle, and pulmonary artery so as not to miss step-ups suggesting intracardiac shunts or anomalous venous return. Failure to do so may result in missing the diagnosis of congenital heart disease and may result in wrong therapies. Accurate pulmonary artery wedge pressure is crucial to make a correct diagnosis and is sometimes difficult to measure in PH. Difficulty with wedging usually results in an overestimation of the wedge. It is important to struggle to find the correct wedge pressure by wedging several sites and by paying attention to respiratory variation and signs of mitral valve dysfunction. An accurate wedge is also crucial to detect left ventricular systolic or diastolic dysfunction in patients with PH because therapeutic options are different from idiopathic PAH. Cardiologists should be prepared to do left heart catheterization simultaneously with right heart measurements when the wedge pressure is confusing or if constrictive pericarditis, restrictive cardiomyopathy, or valvular disease is suspected. Estimation of cardiac output is needed to assess right ventricular function and correlate it with functional class. Once PH is severe and chronic, the functional status and survival of patients is more closely related to right ventricular performance than to absolute PA pressure. Finally, a full work-up including lung perfusion scan to discover or exclude chronic pulmonary thromboembolic PH is needed, because this form of PH can be reversed with surgical pulmonary thromboendarterectomy.

Thus, the problem is to get the right diagnosis, or rather, to get the diagnosis right, at the outset, so that appropriate treatment options can be considered and implemented. Entering the complicated treatment algorithm is daunting enough, but putting the wrong patient in treatment is costly and potentially dangerous. Many patients referred to PH centers have diastolic dysfunction, sometimes related to hypertension, obesity, and glucose intolerance. These patients pose a special diagnostic challenge because they may have PH out of proportion to elevations in the wedge pressure. In some cases, a volume challenge during catheterization may be useful, and an accurate wedge pressure measurement is essential. Successful management of these patients, as outlined in this Consensus Document, is likely to depend on afterload reduction, diuresis, and weight control. Other conditions associated with PH, such as scleroderma, interstitial lung disease, pulmonary veno-occlusive disease, and many others, have their own medical approaches and need to be ascertained and managed individually.

This Consensus Document contains not only an encyclopedic summary of what is known about diagnosis and treatment of PH, but also the collective wisdom gained by the frontline experience of physicians who have been dedicated to fighting PH. It is a must read for those interested in entering the field, and a wonderful resource for doctors who have patients with indications that they may have PH.