acknowledged that despite numerous studies, the predictive value of f-QRS in the 12-lead ECG in patients after acute coronary syndrome is controversial. Research carried out in large groups of patients provides conflicting results, therefore, there is a need to carry out a number of meta-analysis in order to draw the right conclusions.
In the present study, we meant to detect whether the f-QRS presence has any role in the prediction of poor outcomes in patients with acute coronary syndrome. During the study, we have found that it is not the mere presence of f-QRS that affect the outcomes, but its location and the number of fragmented leads that matter.
In our study, f-QRS presented in 46 out of 84 patients (54.8%) with acute coronary syndrome. These 2 groups did not present any significant difference regarding general demographic characteristics and the most important risk factors of coronary heart disease. These results matched those in  by Bekler and associates. On examination of the patients enrolled in the study, measurement of SBP and HR as vital signs showed no significant difference between both groups.
 compared HR between patients with acute coronary syndrome according to the occurrence of f-QRS using Holter, average of HR between both groups was not statistically significant (P value was 0.33).
There was no significant relation between both main groups regarding positive cardiac bio-markers(P = 0.534), in the study conducted by , P value of elevated CPK and troponin I between f-QRS group and non f-QRS group was 0.39 and 0.60 respectively.
We assessed the Killip class between both groups with more focus on Killip IV which represents cardiogenic shock. There were no significant differences between them,  defined heart failure as a Killip class ˃ 1, there was no significant difference between the three groups of the study (persistent f-QRS, transient f-QRS and non f-QRS) as regards Killip class ˃ 1.
The updated GRACE risk score was higher in group (A) with no significant difference between both groups (P = 0.899). However,  succeeded to find a higher and significant GRACE score in group with f-QRS than non f-QRS group, this dissimilarity in both studies results is believed to be due to different patients populations as they excluded STEMI and UA from their study, our study included all variants of acute coronary syndrome.
In the term of in-hospital death, there was not any significant difference between the both groups (P = > 0.99). In NSTEMI, there was no significant difference between f-QRS group and non f-QRS regarding mortality in the study conducted by . From the above information, we can find that presence of f-QRS in ECG of patients with ACS does not add any significant prognostic value (Table 1), but the impact of number or location of fragmented leads has great value as seen next.
Receiver operator characteristic (ROC) analysis showed that greater than 3fragmented QRS was the optimum cutoff value for number of f-QRS leads in predicting in-hospital mortality (Fig. 2), these findings are almost in agreement with the study conducted by  where it concluded that the presence of ≥ 3 f-QRS leads is independently connected with cardiac mortality or hospitalization for heart failure in 170 patients with past MI .Thereby, we divided the cases group into 2 subgroups according to the numbers of f-QRS leads. Subgroup (A1) included patients with more than 3 f-QRS leads and subgroup (A2) included patients with 3 or less f-QRS leads. Moreover, the case group was also divided according to the location of f-QRS into three groups (anterior, lateral, and inferior). Subgroup (A1) showed a significant difference in the term of SBP and HR readings on admission where it showed lower and higher values respectively than subgroup (A2) (Tables 2 and 3). Anterior f-QRS was also associated with significant higher HR and lower SBP than non-anterior f-QRS (Table 4). Number of f-QRS was not significantly related to Killip IV and both subgroups did not show any significant difference (P = 0.114). Only anterior f-QRS when compared to non-anterior f-QRS showed the significant difference (P = 0.030). Patients in the subgroup (A1) had a higher and significant updated GRACE risk score than subgroup (A2). Furthermore, anterior location of f-QRS had statistically significant higher updated GRACE risk score (P = 0.033) than non-anterior f-QRS.
Finally, in terms of in-hospital death, subgroup (A1) showed a significantly higher incidence of in-hospital death in relation to subgroup (A2) (P = 0.015) ., in their research on the value of the number of fragmented QRS leads in the prediction of in-hospital mortality in acute STEMI patients treated with primary PCI. They concluded that the number of f-QRS leads was significantly higher among patients with in-hospital mortality.
Anterior f-QRS location was associated significantly with in-hospital death. Terho and colleagues concluded in , that f-QRS in lateral leads in patients with confirmed cardiac diseases was associated with higher risk of all-cause death, it is worth noting that they considered lateral leads territory on ECG was (I, aVL, V4 to V6) while in our study we considered lateral f-QRS territory only in ( I, aVL, and V6) and anterior leads ( V1 to V5) as [10, 15] have done. Based on the above analysis, our explanation to the non-significant result between the two major groups is thought to be due to that f-QRS in 2 and 3 leads presented in 39% and 26% of the fragmented group respectively.
Study limitations include the relatively small sample, retrospective with less precisive and available data, no inclusion of f-QRS in aVR, V3r, and V4r leads, no study of arrhythmia, re-infarction or long term mortality, and finally, the low pass filter that is optimally used in order to detect f-QRS is 100-150 Hz, it may be masked when using filter with a lower setting.