Table 1.

Main diagnostic techniques used in dyssynchrony.

Diagnostic Technique		Method	Cut-Off	Advantages	Disadvantages
1. ECG		QRS duration	≥150 msec		Insufficient for distinguishing between right- or left-sided conduction abnormalities and inter- versus intraventricular dyssynchrony
2. ECO	Opposing wall delay	TDI color peak velocity—4 chambers, PLAX	≥65 msec	Rapid, can be analyzed offline	Requires TDI color equipment; susceptible by passive tethering motion
	Maximum wall delay	same	≥100 msec	Complete detection of longitudinal dyssynchrony	Requires TDI color equipment; susceptible by passive tethering motion
	Yu index	TDI color (apical 2/4 chamber, PLAX)	≥33 msec	Same	Requires TDI color equipment; susceptible by passive tethering motion; time-consuming
	Delay in initiation of systolic velocity	Same	≥100 msec	Widely available	Not possible offline; affected by passive tethering motion; difficulty in acquiring
	Delay in longitudinal contraction	TDI strain (apical view)	-	Less affected by passive tethering motion	Specialized equipment, demanding technique
	Septal–posterior wall delay	M mode parasternal LV view	≥130 msec	Rapid, widely available	More affected by passive motion or tethering; akinesis provides difficulty
		Radial strain—parasternal mid-LV view—speckle tracking	≥130 msec	Speckle tracking may be applied; less affected by passive motion/tethering	Specialized equipment; assessing only radial dynamics
	Mechanical delay	Routine pulsed Doppler (RVOT/LVOT views)	≥40 msec	Widely available; advanced technique; highly reproducible	Affected by LV and RV function
	Longitudinal shortening as percentage GLS	Speckle tracking, apical view of LV	−9%	Waveforms can illustrate contraction delay and temporal dispersion in multiple myocardial segments; higher reproducibility	Errors in triggering, definition of region of interest; depends on preload, afterload, and heart rate; interobserver and intra-observer variability
	Myocardial wall shortening from inward movement of overall endocardial circumference GCS	Speckle tracking; mid-papillary LV short-axis view	−9%	Unchanged in patients with severe aortic stenosis; does not discriminate the contractility of different LV wall layers	Learning skills slower; lower reproducibility
	Transmural strain GRS	Speckle tracking; mid-papillary LV short-axis view		Unchanged in patients with severe aortic stenosis; does not discriminate the contractility of different LV wall layers