BACKGROUND The fragmented QRS complex (FQRS) was found to be associated to malignant ventricular arrhythmias and sudden death in patients with hypertrophic cardiomyopathy and other entities. There is scant data available correlating the presence of FQRS with QT interval prolongation in patients with ischemic heart disease (IHD). METHODS A descriptive, retrospective, cross-sectional study was performed in 123 patients with IHD to analyze and correlate the presence of FQRS with QT interval prolongation in the conventional 12-leads electrocardiogram in patients with documented chronic IHD. RESULTS There were 62% male patients. The mean age was 63.8±12.6 years. Thirty six (44%) patients had fragmented QRS (64% men and 36% women). The duration of QT and QTc, the mean values were 413±59ms, and 463±67ms, respectively. Of the 36 patients with FQRS, 23 patients have prolongation of the QTc interval, and 13 patients did not present it. Of the 45 patients without FQRS, 21 of them have prolongation of the QTc interval, and 24 patients did not have it. These data resulted in a sensitivity of 52% with a moderate SnNout, a specificity of 65% with moderate SpPin, a positive predictive accuracy of 64%, a negative predictive accuracy of 53%. These data resulted in a prevalence of 54%. CONCLUSIONS the presence of FQRS in the ECG has a moderate sensitivity and specificity, as well as, moderate negative and positive predictive value of the existence of QT interval prolongation in patients with ischemic heart disease.