Biological correlates of QT interval and QT dispersion in 2,265 patients with left ventricular ejection fraction < or =40%.

Increased QT interval and QT dispersion have been associated with increased mortality in a variety of cardiovascular disorders including heart failure. However, the biological correlates of these abnormalities are not clear. QTc and QTd were measured in an automated fashion from digitized electrocardiograms in 2,265 patients with an LV ejection fraction </=40% and were related to clinical, electrocardiographic, and echocardiographic variables. The QTc interval increased with increasing age (P =.0003), heart rate (P <.0001), LV dimensions (P <.0001), left atrial diameter (P <.0001), estimated right atrial pressure (P <.0001), QRS duration (P <.0001), bundle branch blocks (P <.0001) and degree of mitral and tricuspid regurgitation (P <.0001) and decreasing LV ejection fraction (P <.0001) QT dispersion increased with increasing LV isovolumic relaxation time (P =.004) and QTc (P <.0001) and decreased with faster heart rate (P <.0001) and higher right atrial pressure (P =.0007). The biological relationships of QTc and QTd warrant further investigations.