久保田 義則^{1, 2}

Yoshinori KUBOTA^{1, 2}

¹松尾クリニック, ²北播磨総合医療センター中央検査室

¹Matsuo Clinic, ²Department of Clinical Laboratory, Kita-Harima Medical Center

キーワード : TVF, below-knee artery, R-P time

下肢動脈狭窄に対する新しい血流波形評価法-TVF；transit time of vessel flow．下腿領域動脈の超音波検査は細く見づらい血管が対象であり，実施困難な検査部位の代表である．TVFは下腿領域動脈の潅流状態を評価するための指標であり，通常検査の中で計測されている血流波形から算出できる利点がある．過去の保存データからも再計算が可能である．TVFの算出には生理的変動の影響が含まれるため，計測時には安静状態での情報収集が重要である．正確な時間測定を使用する診断方法であるため，3つの波形を表示できる最大掃引速度に設定する．TVFの参考正常値は30ms以下であり，スクリーニング検査として行った場合，治療対象外の血管として評価できる．TVFの算出には心電図記録が必須で，膝窩動脈と足関節部位の後脛骨動脈および前脛骨動脈における3拍以上の血流波形が必要である．治療後の経過観察では血行動態的な評価を行う方法として，画像診断と併せて評価に用いる．TVFの算出のために計測されるR-P時間に関しても，様々な使い方が試行されている．これら指標に対する検討は，現在のところ十分に行われてはいないが，血管機能や血行動態を解析する方法として今後の研究が待たれる．

A new evaluation method of blood flow waveforms for lower limb arterial stenosis is proposed. The below-knee arteries are narrow and hard to see, making ultrasound examinations of them difficult. Transit time of vessel flow (TVF), an index for evaluating the perfusion state of the below-knee arteries, has an advantage in that it can be calculated from the blood flow waveform, which is usually measured during a standard examination. It is possible to recalculate it from past stored data. Since the calculation of TVF is affected by physiological fluctuation, it is important to acquire data in the stationary state at the time of measurement. Because it is a diagnostic method that uses precise time measurement, the ultrasound unit is set to the maximum sweep speed that can display three waveforms. The normal reference value of TVF is 30 ms or less, and it can be used to evaluate arteries that do not require treatment when it is performed as a screening test. For calculation of TVF, electrocardiogram recording is essential, and blood flow waveforms of three beats or more in the popliteal artery and the ankle artery are necessary. For follow-up study after treatment, it is used for evaluation in conjunction with image diagnosis as a method for performing hemodynamic evaluation. Various applications have also been tried with respect to the R-P time measured for the calculation of TVF. Although studies on these indices have been limited to date, further research on TVF as a method for analyzing vascular function and hemodynamics is expected.