Objective: We sought to determine whether a prolonged QRS-interval duration is associated with decreased left ventricular (LV) systolic function.
Background: The 12-lead electrocardiogram (ECG) is a routine test for suspected cardiac disease. Although several scoring systems have been devised to estimate LV systolic function, no studies have examined the direct relationship between QRS duration alone and LV systolic function.
Methods: We analyzed the standard 12-lead surface ECG of 270 consecutive patients, referred for radionuclide ventriculography. Patients (n = 44) with bundle branch blocks, atrial flutter or fibrillation, pacemaker rhythm, recent myocardial infarction or bypass surgery, and patients on antiarrhythmic drugs were excluded. In the remaining patients (n = 226), we correlated the QRS duration on standard resting ECG, and the resting LV ejection fraction (EF), end-systolic and end-diastolic counts (ESC and EDC, respectively; LV volume indices), as obtained by radionuclide angiography. We used a multivariate analysis to identify independent predictors of reduced ventricular function entering QRS duration, the previously described R-wave score and clinical variables in our model.
Results: The QRS duration in the abnormal EF group was significantly longer than in the normal EF group (0.102 vs. 0.091 s, p < 0.0001). A QRS duration >0.10 s was highly specific (83.6%), but modestly sensitive (43.8%), for the prediction of abnormal EF. Furthermore, an abnormal EF was predicted with incrementally increased specificity (83.6% to 99.3%) and a corresponding decrease in sensitivity (43.8% to 13.8%) for each 0.01-s increase in the definition of prolonged QRS (from >0.10 to >0.12 s). Accordingly, the positive likelihood ratio for the prediction of decreased LV function was increased from 2.67 to 19.7 as the definition of prolonged QRS duration was increased from >0.10 to >0.12 s. In the multivariate analysis, a prolonged QRS duration and a low R-wave score were the only independent predictors of decreased LV systolic function.
Conclusions: Prolonged QRS duration (>0.10 s) obtained from a standard resting 12-lead ECG is a specific, but relatively insensitive indicator of decreased LV systolic function. Further prolongation of the QRS had a higher specificity for decreased LV EF and a higher positive likelihood ratio for predicting abnormal LV EF.