A group of clinician-researchers with expertise in the field of cardiovascular and pulmonary diseases propose in a commentary that guidelines for the diagnosis of pulmonary hypertension (PH) should be changed to include patients who may be at risk of developing the disease.
The researchers contend that a broader definition of PH to include patients presenting mean pulmonary artery pressure (mPAP) values of 19 mmHg or higher — instead of the current guideline of 25 mmHg or higher — will promote early patient care and potentially reduce mortality rates associated with the disease.
In 1975 the World Health Organization (WHO) provided the first standardized hemodynamics-based classification of PH, setting mPAP values equal or higher than 25 mm Hg as a criteria for PH. However, this system was established arbitrarily with no formal clinical evaluation of the changes associated with different mPAP ranges. Despite the controversy, the WHO classification prevailed and has remained unchanged for 42 years.
More recently clinicians and researchers have initiated a quest to change this classification.
In a first attempt, definition of normative mPAP values from healthy populations was suggested. However, this approach raised ethical concerns, since mPAP evaluation requires invasive testing methods.
A retrospective study that collected data from 1,182 healthy individuals revealed that, on average, mPAP was 14 mmHg, with an upper limit of 19-20 mmHg. However, the prognostic relevance of such limit values is still poorly understood.
Use of echocardiography to measure the activity of the heart’s valves in combination with additional evaluation of the heart features has been proposed as a surrogate method to screen and stratify at-risk patients. Yet, these methods do not provide an accurate evaluation of pulmonary artery pressure.
“Overall, an accurate and contemporary definition of pulmonary hypertension is dependent on the prognosis associated with the mPAP level,” the researchers wrote.
Several studies have provided evidence that mPAP values close to normal also can be associated with long-term increased risk and mortality. Researchers at Vanderbilt University have shown that patients with borderline pulmonary hypertension (mPAP between 19 and 24 mmHg) had poorer prognosis compared to those with lower pulmonary arterial pressure.
In addition, “mPAP [values] of 19–24 mmHg independently predicts diminished exercise capacity and other important endpoints of pulmonary hypertension in patients with scleroderma, as well as in numerous other at-risk subgroups,” the researchers wrote.
The researchers believe the extensive clinical data collected has provided sufficient information on the range of pulmonary artery pressure that should be considered abnormal, all converging to a mPAP of about 19 mmHg.
“We acknowledge that true threshold effects are uncommon in human disease and that future studies might further widen the mPAP continuum corresponding to clinical risk to even lower levels,” the team wrote.
Overall, the researchers believe the current standard definition of PH excludes many individuals at risk, who could be included by adjusting the diagnostic mPAP standard to 19 mmHg or higher.
“In changing this definition, we would acknowledge the pathological implications of an mPAP of 19–24 mmHg and appropriately increase awareness, clinical monitoring, and efforts to modify risk factors for these previously undiagnosed patients,” the researchers concluded.