The Prognostic Value of QRS Complex Duration and Left Ventricular Mechanical Dyssynchrony in Systolic Heart Failure

Backgrounds: Recently it was reported that left ventricular(LV) mechanical dyssynchrony increased the risk of developing heart failure(HF) and was likely to be related to poor outcomes in HF patients. However, the relationship between QRS complex and Phase SD of rest 99mTc surrogated as left ventricular mechanical dyssynchrony and the correlation with the prognosis of HF patients has not been elucidated. Methods: Following the measurement of QRS complex of Electrocardiography and Phase SD, consecutive 829 patients with congestive HF with reduced left ventricular ejection fraction less than 50% were divided into 3 groups: group 1, overall; group 2, QRS complex>120 msec; group 3, QRScomplex>150 msec. Patients were followed up during 37 months with primary end points of lethal cardiac events. Results: Patients(n = 211)with cardiac event had wider QRS complex and greater Phase SD were selected by univariate analysis, but only greater Phase SD was selected by multivariate analysis in group1. In both group 2 and group 3 multivariate analysis identified NYHA functional class, hemoglobin level, left atrial diameter, septal E/e and Phase SD as significant prognostic variables independently of cardiac functional parameters. ROC analyses, however, revealed different Phase SD thresholds for identifying high-risk HF patients as follows; 36 for group1,37 for group2 and 41 for group3. Conclusions: LV mechanical dyssynchrony can identify high-risk HF patients. LV dyssynchrony as Phase SD more than 37 and 41 independently predict cardiac mortality risk in HF patients with reduced left ventricular ejection fraction with QRS complex more than 120 msec and 150 msec, respectively.