Measurement Conditions of End-Diastolic Ratio of Common Carotid Arteries Alter Diagnostic Ability for Large Artery Intracranial Occlusive Disease

Background End-diastolic ratio, calculated by the side-to-side ratio of end-diastolic flow velocities of the common carotid arteries, is an indicator for large artery intracranial occlusive disease. However, the diagnostic ability of end-diastolic ratios derived from different measurement conditions is unclear. Methods End-diastolic ratios were measured twice by single carotid duplex ultrasonography. End-diastolic ratio_1st was calculated from separate end-diastolic flow velocities measured during routine assessment. End-diastolic ratio_2nd was calculated almost simultaneously without head rotation. For each end-diastolic ratio, the measurement conditions and prediction ability for occlusions of the internal carotid artery or proximal portion of the middle cerebral artery using an established cutoff of 1.4 or greater were compared. Results Two hundred thirty-three patients (147 men, median 67 years) were registered, with available intracranial artery information in 158 patients (67.8%) and occlusions detected in 7 patients (4.4%). End-diastolic ratio_1st was significantly higher than end-diastolic ratio_2nd (median 1.21 versus 1.08, P <.001). Compared with end-diastolic ratio_1st, end-diastolic ratio_2nd had a significantly shorter time interval (median 709 versus 28 seconds, P <.001) and smaller pulse rate difference (1.54 ± 5.10 versus.25 ± 4.63 beats per minute, P =.004). To predict occlusions, the sensitivity, specificity, and overall accuracy for end-diastolic ratio_1st of 1.4 or greater were 85.7%, 70.9%, and 71.5%, respectively, and for end-diastolic ratio_2nd of 1.4 or greater were 85.7%, 98.0%, and 97.5%, respectively. End-diastolic ratio_2nd had better specificity and overall accuracy than end-diastolic ratio_1st (P <.001). Conclusions End-diastolic ratio varies with measurement conditions. Combined end-diastolic flow velocities measurement may improve diagnostic ability for large artery intracranial occlusive disease.