The manifestations of pulmonary arterial hypertension (PAH) are nonspecific and the course variable, creating a need for reliable parameters to guide clinical decision making. Traditionally, right heart catheterization, transthoracic echocardiogram (TTE), 6-minute walk (6MW), and WHO functional classification have been employed to characterize disease. However, there is increasing evidence that B-type natriuretic peptide (BNP) may be a useful marker for dysfunction of the right ventricle and, as such, may help inform clinical decision making in patients with PAH. To help clarify the role of BNP in PAH, we evaluated the correlation of NT-proBNP with other noninvasive parameters.
We measured 490 plasma NT-proBNP levels from 166 patients with PAH or pulmonary hypertension due to thromboembolic disease and who also had a recent TTE and/or 6MW. Patients with left-sided heart disease or renal insufficiency (serum creatinine > 1.5 mg/dL) were excluded. Descriptive statistics were used to compare NT-proBNP, 6MW, and TTE parameters (including right ventricular systolic pressure (RVSP), right ventricular (RV) size, and right atrial (RA) size).
NT-proBNP levels positively correlated with TTE parameters, including RV size (r = 0.52, p < 0.0001), RA size (r = 0.56, p < 0.0001), and RVSP (r = 0.46, p < 0.0001). NT-proBNP negatively correlated with 6MW distance (r = - 0.41, p < 0.0001). In the TTE subgroup analysis, the highest correlation occurred with NT-proBNP and RV size in patients with PAH associated with connective tissue disease (r = 0.65, p < 0.0001). Patients with idiopathic PAH showed the highest correlation between NT-proBNP and 6MW (r = - 0.50, p < 0.0001). Over 90% of patients with NT-proBNP > 1000pg/mL had moderate or severe RV enlargement by TTE.
NT-proBNP levels correlate with noninvasive parameters of right heart dysfunction and functional capacity in patients with PAH. Highly elevated levels of NT-proBNP are particularly specific for significant RV enlargement.
Our study supports the expanding evidence that NT-proBNP may serve as a surrogate marker in the clinical evaluation and management of PAH.
Charles Hargett, None.