Assessment of left ventricular systolic function by velocity vector imaging

OBJECTIVES: To study the usefulness of a novel echocardiographic technique, velocity vector imaging (VVI) in the measurement of left ventricular ejection fraction (LVEF). BACKGROUND: Ejection fraction measured by echocardiography forms the cornerstone in the assessment of LV systolic function. Errors in measurement of EF by routine two-dimensional echocardiography (2D ECHO) limit its utility. The VVI is a new technology which uses speckle tracking and other algorithms to track the endocardial border. This may help in more accurate assessment of EF. METHODS: Global and regional LVEF was measured in 49 patients using VVI, 2D ECHO and radionuclide-gated single photon emission computed tomography (SPECT). Results were categorised as normal, mild, moderate, or severe LV systolic dysfunction based on American Society of ECHO classification. The results were analysed by appropriate statistical tests for correlations. RESULTS: The mean EF was 35 ± 12.08% by VVI, 54.2 ± 19.51% by SPECT (P< 0.001 vs VVI) and 50.3 ± 8.92% by 2D ECHO (P < 0.001 vs VVI). There was weak linear positive correlation between EF measured by VVI and the other modalities (Pearson's correlation coefficient 0.577 for SPECT and 0.573 for 2D; P=0.01). The VVI systematically underestimated the EF compared to SPECT. Greater number of patients had moderate or severe LV systolic dysfunction by VVI (37; 74.5%) than by SPECT (17; 34.7%; P=0.037). We derived a correction factor to calculate SPECT EF from VVI EF as follows: EF (SPECT) = EF (VVI) × 0.9 + 21 or approximately VVI (EF) + 20. CONCLUSION: Measurement of EF by VVI is feasible. The VVI underestimated the EF when compared to nuclear-gated SPECT in this study. The accuracy of this technology and the need for a correction factor needs to be assessed in future studies.