Dispersion of ventricular repolarization: Temporal and spatial

Table 1 Physiological meaning and cut-off values of electrocardiogram -indices of ventricular repolarization

Repolarization heterogeneity aspect	T-wave index	Cut-off values (arrhythmogenesis)
Maximal end of repolarization/maximal APD values	QT	450 ms (males), 460 ms (females)[119]
Maximal end of repolarization/maximal APD values in conditions of QRS widening	JTend
The proportion between the minimal and the maximal APD	Tpeak-Tend/QT	0.22[122]; 0.23[123]; 0.31[114]
	T-wave symmetry	≤ 1.7[98]
The global repolarization dispersion	Tpeak-Tend	≥ 103.3 ± 17.4 ms[86,87]; ≥ 142 ms[114]
	T-wave amplitude and T-wave area, calculated on the basis of T-vector or Root Mean Square ECG
	Ventricular gradient, or QRS-T integral
Local differences in repolarization dispersion	Tpeak-Tend dispersion	35 ms[113]; 42 ms[114]
	Lead-to-lead differences in Tpeak and Tend instants between adjacent leads
Local differences in the end of repolarization times	QT dispersion	39 ms[114]; 93 ms[124]
Early repolarization (plateau phase)	JTpeak
The difference in the spatial sequence of depolarization and repolarization	Spatial QRS-T angle	135°[89,94-99]
The general direction of repolarization sequence	T-vector projection onto the heart ventricles
	T-loop complexity
The relative magnitudes of apicobasal, anterior-posterior and left-to-right repolarization gradients	Ratio between X, Y, Z components of T-vector
The location or the areas of the shortest and the longest APD	T-vector projection onto the heart ventricles
Electrical instability of ventricular myocardium at cellular level	Macrovolt and microvolt T-wave alternans
	Beat-to-beat T-vector variability

APD: Action potential duration; ECG: Electrocardiogram.