Can detect the left ventricular contraction performance from pep using ecg r wave?

The onset of ventricular depolarization defines the start of the pre-ejection period (PEP), which is commonly used as an index of myocardial contractility. Although the fiducial point for this onset has traditionally been the onset of the Q wave of the electrocardiogram (qPEP), the Q wave is not visible in some patients. Therefore, other measurement points have also been used in the literature, including the peak of the R wave (rPEP). However, there has been little systematic examination of measurement issues associated with the selection of the fiducial point for ventricular activation.