QT dispersion in patients with rheumatic mitral stenosis and its relation with echocardiographic findings and serum NT-proBNP levels

OBJECTIVES
We evaluated the value of QT interval dispersion in patients with rheumatic mitral stenosis (MS) in association with echocardiographic parameters and serum N-terminal pro brain natriuretic peptide (NT-proBNP) levels.

STUDY DESIGN
The study consisted of 46 patients (39 women, 7 men; mean age 46.9±9.7 years) with moderate-to-severe rheumatic MS. All patients underwent echocardiographic examination. Blood samples for NT-proBNP were collected immediately after ECG recording. QT interval and QRS complex were measured manually on standard 12-lead surface ECGs. Electrocardiographic and echocardiographic findings and serum NT-proBNP levels were compared with those of a control group consisting of 30 healthy subjects (26 women, 4 men; mean age 46.1±7.3 years).

RESULTS
Compared to controls, serum NT-proBNP levels were significantly higher in MS patients (284.6±206.5 vs. 70.2±9.3 pg/ml, p<0.001). The mean QT interval, QTc interval, and QT dispersion were significantly prolonged in MS patients compared to controls (378±25 vs. 349±21, 420±22 vs. 401±19, and 61±21 vs. 38±15 msec, respectively; p<0.005). QT and QTc dispersions were negatively correlated with mitral valve area (QT: r=-0.311, p=0.03; QTc: r=-0.327, p=0.02), and positively correlated with serum NT-proBNP level (QT: r=0.583, p<0.001; QTc: r=0.637, p<0.001). QTc dispersion was also an independent predictor of serum NT-proBNP level in regression analysis (β=0.330, p=0.03).

CONCLUSION
Our results indicate that QT dispersion is related to the echocardiographic degree of rheumatic mitral valve disease and serum NT-proBNP levels in rheumatic MS. Being a noninvasive, easy, and inexpensive method, QT dispersion may be used as a complementary tool to the clinical and echocardiographic evaluation of patients with rheumatic MS.