Impact of Second Harmonic Imaging on the Determination of the Global and Regional Left Ventricular Function by 2D Echocardiography: a Comparison with MIBI Gated SPECT

AIMS: To evaluate the impact of second harmonic (SH) compared to fundamental mode (FM) imaging on the echocardiographic determination of ejection fraction (EF) and wall motion score index (WMSI), using MIBI gated SPECT as an independent reference. METHODS: Sixty-two consecutive patients underwent an echocardiography study and a MIBI gated SPECT over 24 hours. EF was estimated visually (estimated-E) and was calculated with the Simpson biplane method (Tracing-T), for both FM and SH. WMSI was determined by two independent echo-readers blinded to the nuclear imaging results. The same segmentation and scoring system was used for WMSI determined by MIBI gated SPECT. RESULTS: The percentages of unscored segments because of suboptimal endocardial border detection were 19.5% (FM) and 9.0% (SH). The correlation coefficients (r) between SPECT-EF and echo-EF were: FM (E)=0.705, FM (T)=0.546, SH (E)=0.771, SH (T)=0.743. Agreement between SPECT-EF and echo-EF was acceptable for both imaging modalities (mean of the difference +/- 2 S.D.): -2.8 +/- 18.5 (FM) and -3.5 +/- 16.4 (SH). Correlation coefficients (r) between WMSI calculated by SPECT and by echo were 0.715 (FM) and 0.789 (SH). Agreement between SPECT-WMSI and echo-WMSI was good for all imaging modes but better with SH compared to FM: 0.12 +/- 0.91 (FM), 0.10 +/- 0.77 (SH). The interobserver correlation coefficients (r) for the WMSI were 0.939 (FM) and 0.996 (SH). The agreement between the two observers was better for SH compared to FM. The systematic differences (mean differences) were 0.21 (FM) and -0.01 (SH), and the random differences between both observers (2 S.D.) decreased from 1.55 (FM) to 0.29 (SH). CONCLUSIONS: The use of SH echocardiography decreases the number of unscored segments. This results in an important gain in correlation and agreement for EF determination between echo and SPECT, and in a considerable decline of the interobserver variability for the echo-determined WMSI. WMSI determined by MIBI gated SPECT correlated closely with the SH WMSI, and agreement between both methods was excellent.