Optimizing left atrial appendage imaging: the diagnostic value of left lateral decubitus cardiac CT angiography

By
Zihao Wang
ChenJing Wu
Yi Mang
Zhuang Zhuang
Xinshi Huang
Zhenzhang Wang
June 5, 2026
0 min

Frontiers In Cardiovascular Medicine

Overview

This study evaluates the diagnostic efficacy of single-phase left lateral decubitus (LLD) cardiac CT angiography (CCTA) compared to conventional biphasic supine (BS) CCTA. The LLD approach significantly improves contrast filling in the left atrial appendage (LAA) while reducing radiation exposure by approximately 50%.

Background

Atrial fibrillation is a prevalent arrhythmia linked to a high risk of thromboembolic events, with the left atrial appendage being a common site for thrombus formation. Current imaging techniques, particularly transesophageal echocardiography (TEE), are semi-invasive and operator-dependent, prompting the need for reliable non-invasive alternatives like CCTA. Optimizing CCTA protocols to enhance diagnostic accuracy while minimizing radiation exposure is crucial for improving patient safety and outcomes.

Data Highlights

Parameter	Biphasic Supine (BS)	Left Lateral Decubitus (LLD)
Contrast Agent Filling (HU)	70.3	444.8
Early Filling Defect Rate	28%	8.8%
Sensitivity	-	100%
Specificity	-	0.94
Mean Effective Dose (mSv)	7.84	3.89

Key Findings

The LLD position significantly improved contrast filling in the LAA apex (median 444.8 HU vs. 70.3 HU, p < 0.001).
Early filling defect rate decreased from 28% in the BS group to 8.8% in the LLD group (p < 0.001).
LLD-CCTA demonstrated a sensitivity of 100% and specificity of 0.94.
The mean effective radiation dose was reduced from 7.84 mSv to 3.89 mSv (p < 0.001).
Diagnostic performance of LLD-CCTA was not statistically inferior to the biphasic protocol (p = 0.35).

Clinical Implications

The findings suggest that LLD-CCTA can be a viable alternative to BS-CCTA for assessing LAA thrombus, offering similar diagnostic accuracy with reduced radiation exposure. This may enhance patient safety and streamline imaging workflows in clinical practice.

Conclusion

Single-phase LLD-CCTA effectively maintains diagnostic accuracy while significantly lowering radiation exposure, warranting further validation for routine clinical use.