Background: Rheumatic heart disease is a common reason for cardiovascular morbidity and mortality. Plasma levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) are known to rise in patients with MS, but the role of this compound as a non-invasive marker of left atrial (LA) dysfunction is yet to be established. The study aim was to correlate levels of NT-proBNP in patients with rheumatic mitral stenosis (MS), with echocardiographic parameters of LA function including tissue Doppler-derived strain/strain rate (S/Sr) indices, hemodynamic parameters of LA function, before and after percutaneous balloon mitral valvotomy (PBMV) for a follow up of one year.
Methods: The study included 51 patients with severe MS and 10 age- and gender-matched controls. All patients and subjects underwent detailed clinical and echocardiographic evaluation (including LA S/Sr indices) prior to PBMV and at 12 h, one month and one year after PBMV. Venous blood samples were withdrawn to monitor NT-proBNP levels during the same period. LA functions were assessed echocardiographically, using conventional parameters, while S/Sr indices were calculated at mid-LA segments (septal, lateral, anterior and inferior) during ventricular systole, and at early and late diastole. The LA appendage contraction velocity was calculated using transesophageal echocardiography (TEE) and correlated with NT-proBNP levels. The cardiac output (CO) was calculated invasively. The pulmonary capillary wedge pressure (PCWP), pulmonary artery pressure (PAP) and other parameters were correlated with NT-proBNP levels before and after PBMV.
Results: The mean NT-proBNP level before PBMV was 761.76 ± 213.6 pg/ml, and was 425 pg/ml, 300 pg/ml and 50 pg/ml at one day, one month and one year, respectively (p <0.01). The S/Sr indices at each mid-LA segment (septal, lateral, anterior, and inferior) during ventricular systole (LAs), at early (LAe) and late diastole (LAa) were each significantly lower in patients than in controls (p <0.001). The S/Sr values were improved significantly (p <0.05) in most segments at one day and at one month after PBMV, but after one year the values were increased by >50%, in relation to the NT-proBNP level. There were significant falls in mean PAP and PCWP and a rise in CO, each of which correlated significantly with NTproBNP levels.
Conclusions: NT-proBNP levels correlated significantly with LA dysfunction, and can predict improvements in LA function following PBMV in rheumatic MS for up to one year. Tissue Doppler-derived S/Sr indices may be used to detect fine variations over and above conventional echocardiography, and this may be clinically valuable in the prognosis of MS patients.