A Study to Assess NT-proBNP Levels in Constrictive Pericarditis and Restrictive Cardiomyopathy: Diagnostic and Prognostic Implications

Abstract

Background: Differentiating constrictive pericarditis (CP) from restrictive cardiomyopathy (RCM) remains one of the most challenging diagnostic dilemmas in cardiology. Both conditions share overlapping haemodynamic and echocardiographic features, yet their management strategies and prognoses differ fundamentally. N-terminal pro-B-type natriuretic peptide (NT-proBNP), a biomarker of ventricular wall stress, may offer a non-invasive means to distinguish between these conditions and assess disease severity.

Objectives: To measure and compare NT-proBNP levels in patients with confirmed CP, confirmed RCM, and matched healthy controls; to evaluate NT-proBNP as a discriminatory biomarker between CP and RCM; and to correlate NT-proBNP with echocardiographic, haemodynamic, and functional parameters.

Methods: This prospective, case-control study enrolled 90 participants: 30 with confirmed CP, 30 with biopsy-proven RCM, and 30 healthy age- and sex-matched controls. Serum NT-proBNP was measured by electrochemiluminescence immunoassay (ECLIA). Comprehensive echocardiography, cardiac catheterisation (where indicated), and cardiac MRI were performed. Statistical analyses included Mann-Whitney U test, Pearson correlation, ROC curve analysis, and binary logistic regression.

Results: Median NT-proBNP was 138 pg/mL (IQR 112–174) in controls, 2710 pg/mL (IQR 2150–3380) in CP, and 4050 pg/mL (IQR 3480–4820) in RCM (p < 0.001 for all comparisons). NT-proBNP was significantly higher in RCM than CP (p < 0.001). AUC was 0.91 (CP vs controls) and 0.88 (RCM vs controls). At cut-off 3500 pg/mL for RCM vs CP: sensitivity 83.3%, specificity 80.0%. NT-proBNP correlated with NYHA class (r = 0.74 in CP; r = 0.81 in RCM), E/e’ ratio (r = 0.68), and invasive filling pressures (r = 0.72; all p < 0.001). NT-proBNP ≥ 3500 pg/mL independently predicted RCM over CP (OR 6.2; 95% CI 2.4–15.8; p < 0.001).

Conclusions: NT-proBNP is markedly elevated in both CP and RCM, but substantially higher in RCM. It correlates with functional status and haemodynamic severity. NT-proBNP ≥ 3500 pg/mL may serve as a useful adjunct biomarker for differentiating RCM from CP, warranting validation in larger prospective cohorts.