Non-invasive diagnostic and functional evaluation of cardiac involvement in patients with systemic sclerosis

Elevated serum brain natriuretic peptide (BNP) released from myocytes of ventricles upon stretch have been found in patients with isolated right ventricular (RV) pressure overload. However, limited data suggest that serum BNP may be elevated in systemic sclerosis (SSc) patients, especially with RV dysfunction. We assessed serum N-terminal proBNP (NT-proBNP) in SSc and evaluated whether it reflects the severity of RV overload. We prospectively studied 51 consecutive patients (47F, mean age 53.3 +/- 15.2 years) with SSc (mean disease duration 9 +/- 12.4 years). The control group formed 31 healthy subjects (27F, mean age 52.6 +/- 12.1 years). NT-proBNP level, 6-minute walking test (6MWT), and transthoracic echocardiography (TTE) for the assessment of RV overload were performed. Serum NT-proBNP exceeded the reference value of 125 pg/mL in 31 (61%) SSc patients. The mean serum log NT-proBNP concentration in SSc was higher than in controls (2.138 +/- 0.527 vs. 1.634 +/- 0.420 pg/mL, p<0.001). 13 (25%) SSc patients have tricuspid regurgitation peak gradient (TRPG) exceeding 31 mmHg reflecting pulmonary arterial hypertension (PAH). The SSc presented other echocardiographic signs of RV overload. Mean 6MWT distance was shorter in SSc than in controls (528 +/- 100 vs. 617 +/- 80 m, p<0.001). NT-proBNP level correlated positively with TRPG, RV diameter, RV Tei index and negatively with 6MWT distance. ROC analysis identified >115 pg/ml as the best NT-proBNP threshold predicting PAH for SSc patients (sensitivity 92%, specificity 44%). Results of our study suggest that NT-proBNP measurement is a useful screening method for PAH in SSc patients. Since elevated plasma NT-proBNP level reflects the degree of right ventricular overload and limitation of exercise capacity, abnormal NT-proBNP levels should imply further evaluation including echocardiography.