Adjusting N-Terminal Pro-Brain Type Natriuretic Peptide Levels for Ventricular Mass Improves Prediction of Right Atrial Pressure and Cardiac Index in Patients with Pulmonary Arterial Hypertension

Abstract

Purpose Elevated N-Terminal Pro-Brain Type Natriuretic Peptide (NT-ProBNP) levels correlate with filling pressures and prognosis in patients with pulmonary arterial hypertension (PAH). Since NT-ProBNP is predominantly produced by the ventricular myocardium in response to wall stress, we hypothesized that adjusting NT-ProBNP for left and right ventricular mass index would improve prediction of right atrial pressure (RAP) and cardiac index in PAH patients. Methods and Materials We reviewed our cardiac MRI (CMRI) and clinical databases to identify PAH patients who had CMRI, catheterization and NT-ProBNP levels obtained. Left and right ventricular mass was measured by CMRI and indexed for body surface area. NT-ProBNP levels and NT-ProBNP levels adjusted for left and right ventricular mass index were correlated to invasive RAP, PAP, RVEF and end diastolic volume index (RVEDVI). Results 46 PAH patients (57±15yrs, 80% female) were included. Invasive hemodynamics revealed mean PAP 43±12 mmHg, mean RAP 9±6 mmHg, and cardiac index 2.83±0.69 L/min/m2. RVEF was 41±15% and NT-ProBNP levels were 1830±2455 pg/ml. Unadjusted NT-ProBNP correlated relatively poorly with RAP (r=0.25, P=0.103), mean PAP (r=0.148, P=0.336) and cardiac index (r=-0.18, P=0.239). However, NT-ProBNP adjusted for ventricular mass correlated better with both RAP (r=0.46, P=0.004) and cardiac index (r=-0.46, P=0.003) and was a marginally better predictor of PAP (r=0.22, P=0.18). Both NT-ProBNP levels and adjusted NT-ProBNP correlated significantly with RVEF (r=-0.55, P Conclusions Adjusting NT-ProBNP for left and right ventricular mass index improved prediction of invasive RAP and cardiac index in patients with PAH versus ‘raw’ NT-ProBNP levels alone. Future studies are warranted to determine whether adjusted NT-ProBNP may be a better predictor of outcomes in PAH patients.