الفهرس 
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Abstract
It is well known that isolated LBBB provokes a slight decrease in global left ventricular contractility mainly due to decreased regional ejection fraction of the septum (154,155).
On the other hand, complete LBBB represents a common electrocardiographic finding among patients with congestive heart failure and it has been suggested to contribute to left ventricular pump dysfunction, dysynchronizing conduction and mechanical activity(156,157).
Even though LBBB morphology with QRSd > 120 msec. is included in the current recommendations for biventricular pacing in CHF patients, several studies have shown that the mechanical improvement after electrical resynchronization does not closely relate to QRSd (15,16).
Therefore, several investigators claim that surface ECG is not sensitive enough to detect the electromechanical delay that leads to ventricular dysynchronization (17, 18).
QRS dispersion (QRSD), measured as the difference between maximal and minimal QRSd on the 12-lead surface ECG, has been recently proposed to be associated with increased mortality in CHF patients (19).
Thus, the aim of this prospective study was to investigate whether QRSD is related to LV systolic dysfunction in patients with complete LBBB.
The population of the study included 40 consecutive patients with complete LBBB excluding patients with acute coronary syndromes, patients with atrial fibrillation and patients suffering from decompensated CHF NYHA class III & IV.
Full history and Clinical examination were done to complete accurate diagnosis and to exclude unwanted patients.
Calculation of mean QRS duration and QRS dispersion was done to each patient using 12- lead surface ECG recorded at velocity of 50 mm/sec.
Echocardiography examination was done to all patients. LV systolic function was determined by left ventricular ejection fraction (LVEF) calculated using left ventricular end-diastolic volume (LVEDV) and left ventricular end-systolic volume (LVESV) obtained by modified Simpson method or disk summation method.
Data were collected in a table and the following statistical relations were done:
Relation between each of QRS dispersion and mean QRS duration to many clinical characteristics of the patients as; Age, Sex, diabetes mellitus, Hypertension, Ischemic heart disease.
Relation between each of QRS dispersion and mean QRS duration to the intake of many drugs used in management of CHF as beta blockers, diuretics, angiotensin converting enzyme inhibitors, digoxin.
Relation between each of QRS dispersion and mean QRS duration to LV systolic function.
The following results were obtained:
1- QRS dispersion and LV systolic function had strong negative correlation with high statistical significance and the value was higher than that between mean QRS duration and LV systolic function.
2- Some of the patients’ clinical characteristics were independent correlates that may affect QRS dispersion and these correlations had variable statistical significances.
3- Patients taking drugs used in the treatment of CHF as beta blockers, ACE inhibitors, digoxin and diuretics had increased QRSD.
from these results we concluded the following:
1- QRS dispersion can simply be obtained from 12-lead surface ECG.
2- Both mean QRS duration and QRS dispersion were related to LV systolic function.
3- QRS dispersion was more accurate than mean QRS duration as an index of LV systolic function.
4- The more QRS dispersion values, the worse LV systolic function in patients with complete LBBB.