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Abstract
Congestive heart failure (CHF) is a common condition affecting remarkable number of population and high annual expenditures. Despite B- blockers, sprinolactons, angiotensine-converting enzyme inhibitors, the prognosis is poor. Many methods to assess and evaluate the degree of heart failure has been established either invasive and non invasive. Previous studies indicated that a normal 12-lead ECG is associated with normal LV function in 92% to 95% of cases , but it is claimed that surface ECG is not sensitive enough to detect the electromechanical delay that leads to electromechanical desynochrnization .Left bundle branch block (LBBB) is a common finding in patients with heart failure. The presence of complete LBBB in these patients has been proposed to be a factor that negatively affects left ventricular systolic function and an independent predictor of mortality . The pretence of wide QRS duration in those with LBBB may lead to asynchrony of (LV) contraction that may reflect the need of resynchronization therapy. Recently the interlead dispersion Of QRS interval (QRSD)and QRS duration (QRSd) have been suggested to be associated with increased mortality in CHF patients . QT dispersion is considered an important marker of risk for incidence of ventricular arrhythmias QT and QRS dispersion were both independent predictors of non-sudden cardiac death.
This study aimed to evaluate the relative predictive value of interlead dispersion of QRS interval ( QRSD ) and QRS duration (QRSd) in relation to systolic functional status of left ventricle in patients with left bundle branch block. The study population included sixty persons and was divided according to the presence of normal (?50%) (n=30) or abnormal (<50%) (n=30) resting left ventricular ejection fraction (LVEF).
All subjects of study were subjected to the following:Full history taking
• Full clinical examination .Chest radiography .Surface 12-lead resting electro-cardiogram with measurement of QRS duration , QRS dispersion, QT duration and dispersion
• Echocardiography with assessment of left ventricular systolic dysfunction..
The results of the present study showed that age in group (I) was ranged from 50 to 64 years and in group (II) it was ranged from 41 to 59 years and statistical analysis showed significant difference between both groups.
The results of this study found highly statistically significant difference between intake of some drugs (e.g. diuretics, digoxin and B blockers) in relation to LVEF; so those patients who were taking these drugs have significantly lower EF than those who did not take it. In the present study we assessed the relationship between QRS duration and dispersion in resting 12 lead ECG and resting LVEF we also assessed the relationship between QT duration and dispersion and its relationship with resting LVEF in patients with LBBB, and the results showed significant difference between both groups as regard QRS dispersion, and QRS duration and correlation between both LVEF and QRS dispersion showed highly significant negative correlation . As regards cut off value of QRS duration from which we can expect the LVEF whether preserved or depressed it was 160 msec that can predict LV systolic with sensitivity of 70%, specificity 66.7%, positive prediction 67.7% and negative prediction 69.0%, As regards cut off value of QRS dispersion that may predict the LVEF whether preserved or depressed, it was 45 msec with sensitivity of 83.6%, specificity 66.7%, positive prediction 71.4% and negative prediction 80.0% As regards logistic regression analysis of different ECG parameters, showed that QRS dispersion is the most significant predictor for evaluation of LV systolic function so LVEF exhibits a stronger correlation with QRSD than QRSd.here was significant difference as regard QT duration between both groups of the study ,also QT duration and dispersion showed significant negative correlation with LVEF