Global longitudinal cardiac strain and strain rate for assessment of fetal cardiac function: novel experience with velocity vector imaging.

Background: Cardiac strain and strain rate are new methods to quantitate fetal cardiac function. Doppler-based techniques are regional measurements limited by angle of insonation. Newer feature-tracking algorithms permit angle independent measurements from two-dimensional datasets. This report describes the novel measurement of global strain, strain rate, and velocity using Velocity Vector Imaging (VVI) in a group of fetuses with and without heart disease.

Methods: Global and segmental longitudinal measurements were performed on the right and left ventricles in 33 normal fetuses and 15 fetuses with heart disease. Segmental measurements were compared to global measurements. Clinical outcome data were recorded for fetuses with heart disease.

Results: Forty-eight fetuses were evaluated with VVI. Cardiac strain and strain rate in normal fetuses were similar to normal adult values, but lower than pediatric values (LV strain = -17.7%, strain rate -2.4/sec; RV strain = -18.0%, strain rate -1.9/sec). No difference was present between segmental and global measurements of cardiac strain and strain rate, although basal and apical velocities were significantly different from global velocities for both right and left ventricles. In fetuses with heart disease, lower global cardiac strain appeared to correlate with clinical status, although there was no correlation with visual estimates of cardiac function or outcome.

Conclusion: Measurement of global longitudinal cardiac strain and strain rate is possible in fetuses using VVI. Segmental measurements are not significantly different from global measurements; global measurements may be a useful tool to quantitate fetal cardiac function.