Increased intracranial resistance as reflected by low end diastolic velocity, high resistance index, and increased diameter of extracranial carotid arteries has better power than extracranial carotid atherosclerosis in predicting ischemic stroke in Chinese of Taiwan
Background: Peak systolic velocity (PSV) has been considered a good index of detecting high degree stenosis (>50%) of carotid arteries and has been used in combination with stenosis percentage to identify high risk individual for ischemic stroke (IS). Fewer studies focused on other parameters such as end diastolic velocity (EDV), flow volume (FV), resistance index (RI), and diameter (DIA). We aimed to compare the predictive power of various Duplex ultrasonography indices on ischemic stroke in Chinese. Methods: We conducted a case-control study on 251 first-ever IS patients (age≥40) and 242 age and sex matched outpatient controls. Duplex indices of spectral analysis and image were obtained. Percentage of stenosis, plaque score (PS), PSV, EDV, RI, DIA, and FV of right carotid arteries were included the analysis. Results: Parameters of common carotid artery (CCA) were used due to its stronger predictive power of IS risk than those of internal and external CA. Higher sensitivity and specificity for IS were demonstrated for each of EDV, RI and DIA than PS, stenosis percentage, PSV, and FV. Factor analysis extracted two factors out of 5 best indices, which were intracranial resistance factor (composed of EDV, RI, and DIA) and carotid atherosclerosis factor ( PS and stenosis percentage). Significantly high age-and-sex-adjusted odds ratios for IS appeared on those subjects with low EDV (OR=4.93, p=0.0001), high RI (OR=3.26, p=0.0001), large DIA (OR=2.82, p=0.0001), or positive PS (OR=2.51, p=0.0001). Higher odds ratios (OR=10.16, p=0.0000) were occurred in those subjects with low EDV, high RI, and large DIA combined. Conclusion: An intracranial resistance component may be described by low EDV, high RI, and large DIA. We found strong associations of IS risk with EDV, RI, and DIA separately or combined. This association was much stronger than that of PS or that of stenosis percentage, indicating the significance of intracranial resistance in the pathogenesis of ischemic stroke in Chinese.