Table 1. Comparison of echocardiographic assessment methods to quantify left ventricular dyssynchrony.

Method	Dyssynchrony indices	Advantages	Limitations
M-mode	Septal to posterior wall motion delay.	Wide availability. Simple method. No specialized software required.	Inability to differentiate passive motion from active contraction. Myocardial infarction or scar involving septum or posterior wall. Measurement variability.
Tissue Doppler velocity	Septal-to-lateral wall delay. Maximal delay of time-to-peak velocity. Yu index.	Wide availability. High temporal resolution.	Doppler angle dependency. Inability to differentiate passive motion from active contraction. Measurement variability.
Two-dimensional speckle tracking strain	Anteroseptal to posterior delay. SD of time to peak strain. Radial discoordination index. Strain delay index. Septal rebound stretch.	Angle independency. Ability to differentiate passive motion from active contraction. High signal to noise ratio.	Through plane motion. Relatively low frame rate. Analysis affected by image quality. Measurement variability.
Three-dimensional echocardiography	Systolic dyssynchrony index.	Angle independency. Simultaneous assessments of volumes and systolic function.	Low temporal resolution. Low spatial resolution.
Three-dimensional speckle tracking strain	SD of time-to-peak area strain. SD of time-to-peak minimal endocardial surface area. Area-tracking based strain dyssynchrony index.	Automated analysis. Ability to quantify area strain. Simultaneous assessments of volumes, systolic function, regional strain and torsion.	Low temporal resolution. Limited clinical experience. Need for careful image acquisition. Specialized software required.
Cardiac magnetic resonance imaging	Circumferential uniformity ratio estimate.	High spatial resolution. High reproducibility. Ability to quantify scar.	Time-consuming image acquisition. Relatively limited clinical experience. Incompatibility with implanted pacemaker. Specialized software required.
Radionuclide imaging	Phase SD. Histogram bandwidth.	Automated analysis. High reproducibility. Ability to assess scar location.	Low temporal and spatial resolution. Limited clinical experience. Limited availability of analysis software.

SD, standard deviation.