Transthoracic Doppler echocardiography to predict optimal tube pulsing window for coronary artery CT angiography

To evaluate the feasibility of transthoracic Doppler echocardiography to determine the optimal pulsing windows for CT coronary angiography to narrow the pulsing windows further, especially in higher heart rate.

Doppler was performed on 135 patients before CT scanning. For Doppler, the intervals with minimal motion were evaluated during both systole and diastole integrating electrocardiogram (ECG) intervals. For CT scanning, the retrospective ECG-gating was applied and the optimal reconstruction intervals were determined. The accuracy of Doppler analysis to predict the optimal reconstruction intervals was tested. The predicted length of pulsing windows was compared between Doppler analysis and traditional prospective ECG-gating protocol (heart rate≦65 bpm, 60-76%; 66-79 bpm, 30-77%; ≧80 bpm, 31-47%).

According to Doppler analysis, the mean length of intervals with minimal motion in systole was 106.4±39.2 ms and 125.2±92.0 ms in diastole. When the intervals with minimal motion during diastole>90 ms, the optimal reconstruction intervals were located at diastole; otherwise, at systole (P<0.001). The optimal reconstruction intervals in 93.8% (132/135) patients could be predicted accurately by Doppler analysis. If the optimal reconstruction intervals predicted by Doppler were applied as the exposure windows, the mean length of pulsing windows should has been 105.2±69.4 ms (range: 26.9-510.3 ms), which was significantly shorter than that of traditional prospective ECG-gating protocol (232.0±120.2 ms, range: 93.2-427.3 ms, P<0.001).

Doppler can help detecting the optimal pulsing windows accurately. Prospective ECG-gating incorporating Doppler analysis may narrow pulsing windows significantly while maintaining image quality.