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Pulmonary arterial hypertension (PAH) is a chronic disease of the
pulmonary vasculature characterized by progressive narrowing of the
pulmonary arteries, which in turn leads to increased pulmonary vascular
resistance, right heart failure, and death.1 There has been a
significant improvement in the available medical therapeutic options in
this field that have impacted the short-term survival and morbidity in
these patients.2 However, the median survival post-diagnosis stays limited at 7 years.3 Physicians' ability to predict PAH disease progression allows them to
determine the patient's prognosis, identify treatment goals, and monitor
his or her response to therapy.4 If widely adopted, risk
prediction can enhance the consistency of treatment approaches and
improve the timeliness of referral for lung transplantation. This allows
for an optimal, directed care that ultimately reduces morbidity and
improves mortality in patients with PAH.
IMPORTANT FACTORS FOR RISK STRATIFICATION
Like our patients with PAH, risk stratification should have a
multifaceted approach that includes both objective and subjective
variables that ultimately create an overall risk profile. These
parameters should be statistically validated and evidence based. The
following factors have been cited in literature in their implications
for patient outcomes:
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Demographics. Within PAH,
there are certain subtypes of patients that have a worse prognosis.
These include age (>60 years), male gender, systemic connective
tissue disease, and the bone morphogenetic protein receptor II mutation.5-8
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Functional Class and Capacity.
Functional class is an easily accessible risk parameter that can be
obtained at every clinic visit. This self-reporting system of symptoms
is a subjective but consistent and effective clinical tool, representing
the continuum of disease. Patients who have a lower functional class (I
or II) at baseline have a more favorable prognosis than those who are
functional class III or IV. Although changes in 6-minute walk distance
have not been shown to predict survival, improvement or deterioration of
functional capacity is considered vital to decisions to initiate,
maintain, or escalate therapy. A threshold of 440 meters is suggestive
of a distinction between high-and low-risk patients in pulmonary
hypertension guidelines.6,8 Reduced exercise capacity noted
on exercise testing also indicates a worse prognosis. Syncope,
considered a marker of class IV symptoms, has additional prognostic
relevance in PAH.
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Laboratory testing.
Plasma brain natriuretic peptide (BNP) is secreted by the left and right
ventricles when the cardiac muscle is under stress and is considered an
independent predictor of mortality in patients with PAH.9 The degree of right ventricular dysfunction in patients with PAH
correlates with increasing levels of BNP. A recently published
evaluation of BNP demonstrated that an optimal BNP threshold of 340
pg/mL strongly predicts 5-year survival in patients with PAH (hazard
ratio 3.6; 95% confidence interval, 3.0-4.2; p < 0.001).10 Additionally, elevated levels of creatinine, total bilirubin, uric
acid, and troponin, along with decreased albumin and serum sodium, are
all markers of worse outcomes in patients with PAH.4
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Imaging. An
echocardiogram is a vital imaging tool in screening for pulmonary
hypertension and assessing the right ventricular size and function in
patients with PAH. A tricuspid annular plane systolic excursion of
<1.8 cm, right atrial size >18 cm2, and the presence of pericardial effusion are all known to suggest high-risk patients.1 Cardiac magnetic resonance imaging is gaining ground in assessing these
parameters due to better image quality, especially in reference to
assessment of right ventricular size, morphology, and function.
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Hemodynamics. A right
heart catheterization is vital for accurate diagnosis in PAH as well as
providing prognostic information. Known prognostic parameters include
high right atrial pressure (>14 mmHg), pulmonary vascular resistance
(>5 WU), venous oxygen saturation <60%, and low cardiac index (<2 L/min/m2).8
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Hospitalizations. All-cause hospitalization,
especially related to PAH events, within 6 months is associated with an
increased risk of mortality and recurrent hospitalizations.10
TOOLS FOR RISK STRATIFICATION
There are various risk calculators that are available to risk
stratify patients with PAH that all focus on different aspects of the
disease process. The primary aim of these assessments is to project
patient trajectory based on available information, allowing for informed
and individualized decision-making. Ideally, these tools should be
multifaceted, applicable along the continuum of disease, easy to use,
and validated. Analysis of the Registry to Evaluate Early and Long-term
PAH Disease Management data produced a versatile risk calculator based
on over 2,500 PAH registry patients who were newly and previously
diagnosed with PAH (Table 1).6,10 Similarly, the European PAH
registries (French Pulmonary Arterial Hypertension Network registry,
Spanish Registry Of Pulmonary Arterial Hypertension, Swedish Pulmonary
Arterial Hypertension Registry, and Comparative, Prospective Registry of
Newly Initiated Therapies for Pulmonary Hypertension) have developed
algorithms to stratify patients as low, intermediate, or high risk of
death and are represented in the 2015 European Society of Cardiology and
European Respiratory Society pulmonary hypertension guidelines (Table
2).8,11,12 These registries and evaluations of clinical trial
sets have provided important insights into the importance of both
modifiable (e.g., 6-minute walk distance, functional class, and BNP) and
nonmodifiable (e.g., age, gender, and PAH etiology) risk factors that
predict survival.
TAKE-HOME POINTS
When managing patients with PAH, risk assessment should play a vital
role in the care delivered to the patient. To accurately prognosticate
and provide evidence-based treatment plans to the patient should be of
utmost importance. The various risk calculators, such as that from the
Registry to Evaluate Early and Long-term PAH Disease Management, have
been validated and are effective at providing the patient and physician
with valuable information to predict mortality and prognosis and
ultimately provide appropriate treatment.
REFERENCES
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1. McLaughlin VV, Shah SJ, Souza R, Humbert M. Management of pulmonary arterial hypertension. J Am Coll Cardiol 2015;65:1976-97.
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2. Kanwar MK, Thenappan T, Vachiéry JL. Update in treatment options in pulmonary hypertension. J Heart Lung Transplant 2016;35:695-703.
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3. McLaughlin V. Managing pulmonary arterial hypertension and
optimizing treatment options: prognosis of pulmonary artery
hypertension. Am J Cardiol 2013;111(8 Suppl):10C-5C.
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4. Benza RL, Lohmueller LC, Kraisangka J, Kanwar M. Risk
Assessment in Pulmonary Arterial Hypertension Patients: The Long and
Short of it. Advances in Pulmonary Hypertension 2018;16:125-35.
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5. Humbert M, Sitbon O, Chaouat A, et al. Survival in patients
with idiopathic, familial, and anorexigen-associated pulmonary arterial
hypertension in the modern management era. Circulation 2010;122:156-63.
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6. Benza RL, Miller DP, Gomberg-Maitland M, et al. Predicting
survival in pulmonary arterial hypertension: insights from the Registry
to Evaluate Early and Long-Term Pulmonary Arterial Hypertension Disease
Management (REVEAL). Circulation 2010;122:164-72.
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7. Evans JD, Girerd B, Montani D, et al. BMPR2 mutations and
survival in pulmonary arterial hypertension: an individual participant
data meta-analysis. Lancet Respir Med 2016;4:129-37.
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8. Galiè N, Humbert M, Vachiery JL, et al. 2015 ESC/ERS Guidelines
for the diagnosis and treatment of pulmonary hypertension: The Joint
Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of
the European Society of Cardiology (ESC) and the European Respiratory
Society (ERS): Endorsed by: Association for European Paediatric and
Congenital Cardiology (AEPC), International Society for Heart and Lung
Transplantation (ISHLT). Eur Heart J 2016;37:67-119.
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9. Nagaya N, Nishikimi T, Okano Y, et al. Plasma brain natriuretic
peptide levels increase in proportion to the extent of right
ventricular dysfunction in pulmonary hypertension. J Am Coll Cardiol 1998;31:202-8.
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10. Benza RL, Elliott CG, Farber HW, et al. Updated Risk Score
Calculator for Patients with Pulmonary Arterial Hypertension (PAH) in
the Registry to Evaluate Early and Long-Term PAH Disease Management
(REVEAL). Am J Respir Crit Care Med 2017;195:A6899-A.
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11. Boucly A, Weatherald J, Savale L, et al. Risk assessment,
prognosis and guideline implementation in pulmonary arterial
hypertension. Eur Respir J 2017;50:1700889.
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12. Hoeper MM, Kramer T, Pan Z, et al. Mortality in pulmonary
arterial hypertension: prediction by the 2015 European pulmonary
hypertension guidelines risk stratification model. Eur Respir J 2017;50:1700740.
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13. Benza RL, Gomberg-Maitland M, Miller DP, et al. The REVEAL
Registry risk score calculator in patients newly diagnosed with
pulmonary arterial hypertension. Chest 2012;141:354-62.