DECREASE OF ELECTRICAL CARDIAC SYSTOLE

At present, we know the pathologies EKG of short PQ and its variants; We also know (2000-03) the pattern called EKG short QT Syndrome.(7,8.)
But what is not described in today is the mixed pattern, the pattern EKG of short PQ and QT on the same layout EKG.
The vast majority of authors, they regard as limit values of the QTc interval (Bazett) between 0.46 seconds (maximum value) and 0.35 seconds (minimum value). (1,2,3.)
Both a prolonged QT interval and decreased QT interval dispersion (QTD) have been proposed as surface EKG markers of vulnerability to ventricular arrhythmias and potential predictors of mortality. (4).
The QT interval, in its basic form, is a seemingly simple concept. Defined as the interval from the beginning of the QRS complex to the end of the T wave on a surface EKG, the QT interval represents the period of global ventricular depolarization and subsequent repolarization. Prolongation of the QT interval due to inherited ion channel abnormalities or due to drugs or metabolic abnormalities has been associated with an increased incidence of ventricular arrhythmias. In addition, experimental studies have demonstrated that regional differences in repolarization facilitate reentry and the development of ventricular arrhythmias. Heterogeneous ventricular repolarization was recognized from surface EKGs as early as 1934. Over a decade ago, the difference between the longest and shortest QT intervals on a standard 12-lead EKG (QT dispersion) was forwarded as a simply measured marker for vulnerability to ventricular arrhythmias and risk for sudden cardiac death. A number of publications followed, and currently there are > 1.000 articles in the literature on QT dispersion. However, the exact physiologic mechanism and true clinical utility of QT dispersion have been the subject of intense debate over the past several years.
In general, interobserver and intraobserver variability of QT dispersion measurements can be as much as 30 to 40%.
Recent studies suggest that using a specific combination of "quasiorthogonal" leads (aVF, V1, and V4; I, aVF, V2, and V4) may provide sufficient QT dispersion data for analysis. Other authors (including us) consider V4-V5-V6 as the derivations with better predictive value (they are looking directly at left ventricle). (3,4,5.)
However, at this time no standardized method for acquiring QT dispersion exists.