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Pulmonary Hypertension

Abstract

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Expert OpinionJan 31, 2019

JOURNAL:Am J Cardiol. Article Link

Risk Stratification in PAH

Karlee K Hoffman, MD; Sir Raymond L. Benza, MD, FACC; Manreet Kanwar, MBBS, FACC Keywords: Arrhythmias and Clinical EP; Heart Failure and Cardiomyopathies; Noninvasive Imaging; Pericardial Disease; Prevention; Pulmonary Hypertension and Venous Thromboembolism; Atrial Fibrillation/Supraventricular Arrhythmias; Acute Heart Failure; Heart Failure and Cardiac Biomarkers; Pulmonary Hypertension; Echocardiography/Ultrasound; Magnetic Resonance Imaging; Hypertension

FULL TEXT

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:

  • 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
  • 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.
  • 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
  • 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.
  • 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
  • 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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