Background Radiography is useful to determine left atrial (LA) size when echocardiography is not available. Recently, the authors have described Radiographic Left Atrial Dimension (RLAD) as a new radiographic measurement to assess LA size. The objective of this study was to assess the clinical usefulness of 2 new radiographic measurements to detect and quantify left atrial enlargement (LAE) compared to RLAD and using left atrium to aortic root (LA/Ao) ratio as gold standard. These new measurements, bronchus-to-spine (Br-Spine) and RLAD-to-spine (RLAD-Spine) may be more precise in cases were LA boundaries are not well defined. Fifty dogs, 25 with and 25 without LAE were recruited. Reference LA/Ao ratio was assessed by 2D echocardiography and LAE was considered if LA/Ao > 1.6. Br-spine was measured as a straight vertical line from the main stem bronchus to the ventral border of the vertebra situated immediately dorsal to the heart base. RLAD-Spine was measured from RLAD endpoint perpendicularly to spine. The correlation of RLAD, Br-Spine and RLAD-Spine methods with LA/Ao and their sensitivity and specificity for detecting LAE were calculated. Receiver Operating Characteristic (ROC) curves were used to estimate the optimal cut-off for each method. Results Correlations between Br-Spine, RLAD-Spine, RLAD and LA/Ao ratio were - 0.66, - 0.76 and 0.89 respectively (P < 0.001). Sensitivity at the optimal cut-off values for detecting LAE were 32.0, 64.0 and 96.0%, respectively. Specificity was 96.0% in all cases. Conclusion Br-Spine and RLAD-Spine were less sensitive radiographic measurements than RLAD in detecting LAE in dogs. Both Br-Spine and RLAD-Spine may not be good alternatives to RLAD.

中文翻译：

---

心脏到脊柱测量以检测二尖瓣关闭不全狗的左心房扩大。

背景 当超声心动图不可用时，X 线摄影可用于确定左心房 (LA) 大小。最近，作者将放射学左心房尺寸 (RLAD) 描述为评估 LA 大小的新放射学测量方法。本研究的目的是评估与 RLAD 相比并使用左心房与主动脉根部 (LA/Ao) 比率作为金标准的 2 种新放射学测量方法在检测和量化左心房扩大 (LAE) 方面的临床实用性。这些新的测量值，支气管到脊柱 (Br-Spine) 和 RLAD 到脊柱 (RLAD-Spine) 在 LA 边界未明确定义的情况下可能更精确。招募了 50 只狗，其中 25 只患有 LAE，25 只没有 LAE。参考 LA/Ao 比率通过 2D 超声心动图评估，如果 LA/Ao > 1.6 则考虑 LAE。Br-脊柱测量为从主干支气管到紧邻心脏基底背侧的椎骨腹侧边缘的垂直直线。RLAD-Spine 从 RLAD 端点垂直于脊柱测量。计算了 RLAD、Br-Spine 和 RLAD-Spine 方法与 LA/Ao 的相关性及其检测 LAE 的敏感性和特异性。接受者操作特征 (ROC) 曲线用于估计每种方法的最佳截止值。结果Br-Spine、RLAD-Spine、RLAD和LA/Ao比值的相关性分别为-0.66、-0.76和0.89（P < 0.001）。检测 LAE 的最佳截止值的灵敏度分别为 32.0、64.0 和 96.0%。所有病例的特异性为 96.0%。结论 Br-Spine 和 RLAD-Spine 在检测犬 LAE 方面的放射照相测量灵敏度低于 RLAD。Br-Spine 和 RLAD-Spine 都可能不是 RLAD 的良好替代品。