Introduction
Pulmonary arterial hypertension (PAH) is a disease resulting from restricted blood flow through the pulmonary artery resulting in increased pulmonary resistance and ultimately right heart failure. The diagnosis of PAH is based on exclusion of multiple diseases and factors. Based on an initial set of symptoms in a patient, the health care professional will build an increasing “index of suspicion” based on isolation of physiological and morphological criteria that underlie the clinical definition of pulmonary hypertension.
Based on WHO Guidelines, pulmonary arterial hypertension (PAH, Group 1) differs from pulmonary hypertension (PH, Groups 2-5) in that Group 1 involves direct vascular muscle cell proliferation and vasoconstriction of the pulmonary arteries. The process of patient work-up will depend on the suspected etiology of the pulmonary hypertension (Figure 1).
Adapted from McLaughlin VV, et al. JACC 2009;53:1573-1619.
“Typical” PAH Patient Presentation
• PAH patients are more often female.
• Patients often experience a delay in diagnosis.
• Patients frequently exhibit dyspnea upon exertion (shortness of breath) that worsens over time.
• Patients may have lower extremity edema.
• Upon initial physical exam and history, patients may not exhibit “remarkable” signs.
In this patient case example, the only characteristic that might suggest a pulmonary vascular issue is the elevated, estimated pulmonary arterial systolic pressure (PASP), which at 50 mmHg is higher than normal.
Figure 3 depicts the frequency of the typical signs and symptoms of PAH.
Adapted from Elliott EG, et al. Chest 2007;132(suppl 4):631S.
Overview of the Diagnostic Process
The 2009 Expert Consensus panel on pulmonary hypertension has produced general guidelines for the diagnosis of pulmonary hypertension. As noted in this document, the suspicion of PH may arise in various ways. As a result, the sequence of tests may vary but the diagnosis of PAH requires that certain diagnostic data support the diagnosis of pulmonary hypertension.
Certain pivotal tests are essential to creating the diagnosis of any form of pulmonary hypertension, regardless of any underlying disease etiology (as might be found in WHO Groups 2-5). Pivotal testing often indicates the need for secondary tests, which help confirm or refute the existence of underlying conditions that may contribute to pulmonary hypertension.
The 2009 JACC/AHA Pulmonary Hypertension diagnostic algorithm is provided in Figure 4.
Adapted from McLaughlin VV, et al. JACC 2009;53:1573-1619.
While many of the pivotal tests lead the health care provider towards an ultimate diagnosis of PAH, it is only the use of right heart catheterization (RHC) which can confirm the diagnosis.
Health care providers less familiar with pulmonary hypertension as a disease state may be less familiar with the diagnostic workup and treatment options. In these cases, it is important to strongly consider referring the patient to a pulmonary hypertension specialty center for evaluation.
Considering the Pivotal Tests
In subsequent pages, we will examine in more detail the majority of the pivotal tests used to diagnose pulmonary hypertension. Again, the principal focus will be on PAH (Group I patients) and specifically, we will look closer at the following diagnostic procedures:
• Laboratory Tests
• Electrocardiogram
• Chest X-Ray
• cMRI
• Echocardiogram
• Pulmonary Function Testing
• Functional Testing: 6-Minute Walk Test
• Right Heart Catheterization
The goal of these pages will be to highlight not only the test procedures, but the key data which can be derived from the tests as they lead to increasing the “index of suspicion” and ultimately the PAH diagnosis.
References
1. Elliott EG, et al. Chest 2007;132(suppl 4):631S.
2. McLaughlin VV, et al. JACC 2009;53:1573-1619.
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