Aims: We directly compared TomTec and QLAB software packages for the three-dimensional echocardiographic (3DE) assessment of left ventricular (LV) dyssynchrony including their ability to predict response to cardiac resynchronization therapy (CRT) in patients with ischaemic and non-ischaemic cardiomyopathy.
Methods and results: A total of 140 heart failure patients with the LVEF ≤35% and 60 healthy volunteers underwent 3DE. A subgroup of 60 patients underwent CRT and were evaluated before and 6-12 months after implantation. The systolic dyssynchrony index (SDI) was derived from the dispersion of time to minimum regional volume for all 16 LV segments and measured with both software packages and compared using Pearson's correlation and Bland-Altman analysis. Measurements of SDI were significantly higher using TomTec compared with QLAB in both patients (10.9 ± 3.8 vs. 9.7 ± 3.9, P < 0.001) and healthy volunteers (4.1 ± 0.8 vs. 2.4 ± 1, P < 0.001), with large biases and wide limits of agreement. A moderate correlation (r = 0.65, P < 0.001) was observed between both software packages in patients while their inter-observer and intra-observer reliability were good. Of the 60 patients undergoing CRT, reverse remodelling as a measure of response was observed in 41 patients (68%). The optimal SDI cut-off value to predict response to CRT was higher for TomTec than for QLAB (8.8 vs.7.3%, P < 0.001) and demonstrated better sensitivity and specificity (93 and 61%, respectively) compared with QLAB (88 and 33%, respectively). Response prediction in patients with non-ischaemic cardiomyopathy was excellent with a sensitivity and specificity of 95 and 100% for TomTec and 70 and 83% for QLAB using similar cut-off values of 9.1 and 9.2%, respectively.
Conclusion: Different 3DE software packages for the assessment of mechanical dyssynchrony should not be used interchangeably until better software standardization is achieved. Dyssynchrony assessment with 3DE for the prediction of response to CRT seems particularly useful in patients with non-ischaemic cardiomyopathy.
Keywords: Cardiac resynchronization therapy; Dyssynchrony; Software packages; Three-dimensional echocardiography.