The relationship between echocardiographic parameters and plasma N-terminal pro-brain natriuretic peptide levels in patients with dilated cardiomyopathy

The myocardial performance index (MPI), defined as the sum of isovolumic contraction and relaxation times divided by ejection time, and N-terminal pro-brain natriuretic peptide (NTproBNP) have been utilised to express global left ventricular (LV) function. The ratio between early diastolic transmitral velocity (E, using pulsed Doppler) and early mitral annular diastolic velocity (Ea, using tissue Doppler imaging) has been proposed as the best Doppler predictor for evaluating LV filling pressures in a variety of cardiac diseases. Purpose: To assess the relationship between echocardiographic parameters (conventional echocardiography and Tissue Doppler imaging) and NTproBNP in patients with dilated cardiomyopathy (DCM) in sinus rhythm. Methods: Conventional echocardiography and tissue Doppler imaging were performed in 50 consecutive patients (age 63±13 years) with DCM, in sinus rhythm, concomitent with NTproBNP determination. Patients with inadequate echocardiographic images, paced rhythm, mitral prosthesis, severe mitral annular calcification or renal failure were not included. Ea and Sa (peak systolic mitral annular velocity during ejection) were determined at the lateral site of mitral annulus. MPI (using conventional echocardiography) and E/Ea were calculated. Results: The simple regression analysis demonstrated the strongest statistically significant linear correlation between MPI and NTproBNP (r=0.70, p<0.001). Significant correlations were also found between NTproBNP and E/Ea (r=0.59, p<0.001), pulmonary artery systolic pressure (r=0.54, p<0.001), Sa (r=-0.46, p=0.001) and E (r=0.41, p=0.003). There were no correlations between NTproBNP and Ea, LV ejection fraction, left atrial surface, left atrial volume and mitral E deceleration time. The area under the receiver-operating characteristic curve (ROC) for prediction of NTproBNP level >900 pg/ml was maximal for MPI (AUC=0.76, p<0.001), followed by E/Ea (AUC=0.71, p<0.001). The optimal MPI cut-off for prediction of NTproBNP level >900 pg/ml was 0.77 (84% sensitivity and 82% specificity). Conclusions: Of all parameters investigated, MPI had the strongest correlation with NTproBNP in patients with DCM in sinus rhythm, and can be a simple and accurate predictor of the plasma NTproBNP levels.