Correlation of QT Dispersion With Myocardial Perfusion in Patients With ST Elevation Myocardial Infarction Treated by Primary Per Cutaneous Coronary Intervention

Worldwide, coronary artery disease (CAD) is the most frequent cause of death. Over seven million people every year die from CAD, accounting for 12.8% of all deaths. Every sixth man and every seventh woman in Europe die from myocardial infarction. The in-hospital mortality of STEMI patients in the national registries of the European society of cardiology (ESC) countries varies between 6% and 14%.

ST elevation myocardial infarction (STEMI) generally results from intraluminal thrombus formation and occlusion of a ruptured or an unstable plaque .

The main goal of therapy in STEMI is to restore microvascular flow and sustain the myocardial perfusion .

Reperfusion therapy for acute myocardial infarction (AMI) is aimed at achieving prompt restoration of myocardial perfusion to maximize preservation of the electrical and mechanical integrity of the jeopardized myocardium. Percutaneous coronary intervention (PCI) has increased the rate of successful recanalization of infarct-related arteries (IRAs) to >90% .

A variety of markers including ECG and coronary angiography have been utilized to assess myocardial reperfusion .

The prolongation of QRS duration,evaluated by a standard 12-lead ECG, is a marker of ventricular dysfunction and has been associated with a poor prognosis in STEMI .

QT-interval parameters are potentially proposed as available non-invasive markers for assessing the ventricular homogeneity as well as for predicting electrical instability ,QT interval (QTI) is defined as the longest interval from the beginning of the QRS complex to the end of the T-wave; QT dispersion (QTd) is defined as the difference between the longest and shortest QTI, and reflects electrical activity of the ventricles . .

The prolongation of the latter parameter is a main predictor for fatal arrhythmia in patients with myocardial infarction (MI) .

The measurement of QTI and QTd parameters are dependent on heart rate and can be corrected by the QT correction formulas, which are termed the corrected QTI (QTc) and QTd (QTcd) .

Myocardial blush grade (MBG) is validated measurement of myocardial perfusion . The MBG is used to assess the washout of myocardial blush during angiography. Grade 0 is defined as the failure of the contrast to enter the microvasculature. In grade 1 cases, contrast enters slowly, but fails to exit the microvasculature. Grade 2 defines delayed entry and exit from the microvasculature. Finally, grade 3 indicates normal entry and exit from the microvasculature .

ECG is a necessary, simple, rapid and non invasive tool for the diagnosis of myocardial infarction and evaluation of myocardial reperfusion that still to be investigated . QT dispersion is a crude and approximate measure of a general abnormality of repolarization; it reflects inhomogeneity of ventricular repolarization . This measurement is an attempt to distinguish between myocardium that is homogeneous from myocardium that displays inhomogeneity, which is accompanied by increased dispersion of the ventricular recovery times and prolongation of repolarization