The fractionated QRS complex for cardiovascular risk assessm
The QRS complex recorded at the thoracic surface is the electrocardiographic (ECG) manifestation of the ventricular depolarization process. During sinus rhythm, the normal QRS complex is a mono-, bi-, or triphasic signal. The presence of additional usually small deflections define this QRS complex as fractionated or fragmented. The clinical significance of ventricular fractionated signals during sinus rhythm originates from mapping studies during surgical or electrophysiological procedures in patients with ventricular tachycardia (VT). Endocardially obtained electrograms during sinus rhythm usually show biphasic signals during ventricular activation in normal areas. In abnormal areas, however, electrograms are characterized by multiple low-amplitude deflections during the simultaneously recorded QRS complex in the surface ECG, and often also after QRS offset as late activity. Since these abnormal areas appeared to be the site of VT origin and its ablation is a curative procedure, intracardiac fractionation appeared to be associated with cardiac disease. The substrate for intracardiac fractionation is anisotropic activation pathways, slow conduction, and load mismatch, due to impaired excitation, cardiomyocyte disconnection, and altered tissue architecture by fibrotic alteration.