Clinical usefulness of the common carotid artery blood flow velocity ratio as measured by an ultrasonic quantitative flow measurement system: evaluation with respect to prevalence of ischemic heart disease.

The present study evaluated the clinical usefulness of the measurement of common carotid artery blood flow velocity by an ultrasonic quantitative flow measurement system (QFM), and its correlation with the prevalence of ischemic heart disease (IHD). The subjects in this study included 287 patients (149 men and 138 women; mean age, 67.6+/-11.0 years) being treated as outpatients. Bilateral common carotid artery blood flow velocity was measured using a QFM-1100 (Hayashi Denki Co., Ltd.). The "high to low velocity ratio" (H/L ratio) was calculated by dividing the higher value by the lower value of the velocity of the common carotid artery. In 43 of 287 patients, we used an SSA-270 ACE (Toshiba Co., Ltd) to determine the presence of plaque and measure intimal-medial thickness (IMT) in the common carotid arteries. The mean H/L ratio was 1.45, with a median value of 1.25. The patients were stratified into subgroups based on H/L ratios from 1.0 and above in 0.1 increments in order to compare the prevalence rates of IHD. The prevalence rates in groups with H/L ratios of 1.3 and greater were significantly higher than those in the group with H/L ratios less than 1.3. In logistic regression analysis, the unadjusted H/L ratio was an independent risk factor for IHD at ratios from greater than 1.1 to greater than 1.6. The age-adjusted H/L ratio was an independent risk factor for IHD at ratios from greater than 1.1 to greater than 1.4. IMT was significantly higher in patients with a H/L ratio of 1.4 or greater versus patients with a ratio less than 1.4 (1.154+/-0.417 mm vs. 0.421+/-0.425 mm; p<0.05). The prevalence of carotid artery plaque was also significantly higher in patients with a H/L ratio of 1.4 or greater versus patients with a ratio of less than 1.4 (76.5% vs. 38.5%; p<0.03). Therefore, determination of the carotid artery H/L ratio by means of QFM may be clinically useful in screening patients for coronary artery lesions.