Fetal cardiac function: Feasibility in obtaining the right modified myocardial performance index in a single Doppler waveform.

OBJECTIVE

We aimed to assess the feasibility of assessing the fetal right Myocardial Performance Index (RMPI) using single waveform and to compare absolute values with dual technique.

METHODS

We studied 145 morphologically normal appropriately grown fetuses at 16-28 weeks' gestation with local Ethics Committee approval using fixed machine settings: Doppler sweep velocity at 15 cm/s; angle of insonation <15; wall motion filter 300 Hz. Doppler gate was 3 mm, increased to 4-5 mm if needed. RMPI was obtained twice in the same fetus; using 'dual-image' and 'single-image' techniques. Dual images were acquired as previously described. Single images were taken from the tip or just below the tricuspid valve towards the ventricular septum in the apical four-chamber view. RMPI was calculated using two-value (a-b/b) or three-value (ICT+IRT/ET) formulae where 'a', 'b' or (ET) represent the isovolumetric and ejection times, and ICT and IRT represent the isovolumetric contraction and relaxation times.

RESULTS

Dual image was accessible in 100% of fetuses. Single-image acquisition was 100%, 92.3% and 76.5% at 16-24, 24-27, and 27-28 weeks respectively (95.2% overall). Doppler gate increased in 23 cases (16.6%); 8/17 (47%) at 27-28 weeks' gestation. Mean and standard deviation for 'dual image' and 'single image' were: RMPI 0.46 ± 0.09 and 0.49 ± 0.07; 'a' 249.06 ± 11.50 and 249.11 ± 11.93; 'b' 170.85 ± 8.95 and 167.62 ± 8.39.

CONCLUSIONS

Single-image acquisition RMPI is highly feasible from 16 to 26 weeks gestation. Difference in mean values may represent overestimation of ejection time in the 'dual-image' technique.