The accuracy of the diagnosis of renal artery stenosis using noninvasive echo-Doppler velocimetry was compared with that of angiography in 40 renal arteries. The duplex-Doppler signals were detected through the muscle of the back (the translumbar approach). Renal artery stenosis was diagnosed by three objectively defined Doppler parameters, the acceleration index (AI), the acceleration time (AT), and the acceleration time ratio (ATR). The normal range obtained on 11 control subjects was defined as AI greater than or equal to 3.78, AT less than or equal to 0.07 s, and ATR less than or equal to 1.35. High technological success (98%) was obtained using the translumbar approach. In comparison with angiography (cases of significant stenosis), the accuracy of the echo-Doppler method using the criteria of the AI was 95%, the sensitivity was 100%, and the specificity was 93%. This noninvasive method may be one of the most accurate screening methods for diagnosing significant renal artery stenosis.

Efficacy of echo-Doppler examination for the evaluation of renovascular disease.

Currently, there is no agreement as to the best method for quantifying Doppler ultrasound recordings from peripheral arteries in order to detect occlusive disease. The four methods assessed in this study are: the pulsatility index, height-width index, path length index, and a Laplace transform function index. Recordings of the Doppler ultrasound spectral waveforms from the common femoral artery of 232 limbs were digitized to obtain the maximum velocity waveforms. This data was analyzed and the various indices were computed and then compared with the arteriographic grades. The effect of distal disease was also examined. The diagnostic accuracy of each index was determined from receiver operating characteristics curves. We concluded that all four indices were capable of detecting significant aortoiliac disease with approximately equal diagnostic accuracy of 90-95% but that pulsatility index had the advantages of simplicity and ease of calculation.

Comparative study of four methods for quantifying Doppler ultrasound waveforms from the femoral artery.

The renal blood flow velocity characteristics in 8 normal controls, 19 essential hypertensive patients and 8 hypertensive patients with renovascular disease were evaluated using echo-Doppler velocimetry. Two different approaches for ultrasonic detection of the renal artery, the translumbar and the transabdominal approach, were used. Renal Doppler sonograms were analyzed by measuring the acceleration index and the peak-systolic frequency/end-diastolic frequency (S/D) ratio. Renovascular patients who required surgery were examined before and after angioplasty. Doppler signals could be detected in all 35 subjects by using the translumbar approach. The acceleration index of the affected renal arteries significantly correlated to the percent stenosis of the renal artery determined by angiography. The acceleration index in the affected renal artery was improved by surgical treatment. The S/D ratio in essential hypertensives was significantly higher than that in the normal controls. There was a significant inverse correlation between the S/D ratio and creatinine clearance. Echo-Doppler velocimetry is considered to be useful in the diagnosis of renovascular disease and also in the evaluation of abnormalities of renal vascular resistance in hypertensive patients.

Echo-Doppler velocimeter in the diagnosis of hypertensive patients: the renal artery Doppler technique

Human umbilical hemodynamics was investigated in 27 pregnant patients with gestational ages from 29 to 43 weeks using a pulsed Doppler flowmeter. The signals were analyzed by Fast Fourier Transform using a minicomputer. Coherent averaging of the signals, along with the computation of maximum velocity, mean velocity and the first moment of Fourier spectra about the zero frequency axis were performed. Hemodynamic indices were measured utilizing a comprehensive feature characterization technique of the blood flow velocity waveform. It was observed that coherent averaging reduced spectral variance thus relatively simplifying the analyses. The Pulsatility Index based on the first moment of the Fourier spectra indicated a higher umbilical flow change during the fetal cardiac cycle, than that predicted by the peak velocity Pulsatility Index. We also observed a high Pulsatility Index in association with three cases of oligohydramnios indicating the possibility of an elevated placental circulatory impedance. Variation in the peak velocity up to 20% was also noted with fetal breathing movements. Further studies are necessary to determine the clinical relevance of these findings.

Doppler evaluation of fetal hemodynamics

One hundred and seventy-five aortofemoral segments were studied in order to determine the role of CW Doppler ultrasound combined with real-time spectral analysis in the assessment of aortoiliac disease. The pulsatility index (PI), determined from the maximum velocity waveform, was compared to the systolic pressure difference between the aorta and common-femoral artery as measured at the time of angiography. Receiver operating characteristic curves were constructed and the optimum sensitivities and specificities measured. Results show that if a PI(max) of 5.5 is taken as the threshold level, then the PI is 95% sensitive and specific in detecting hemodynamically significant aortoiliac disease that corresponds to a resting aortofemoral pressure difference of 10 mm Hg or greater. We also carefully examine those technical aspects of Doppler recording and analysis that influence the accuracy of PI measurements

Relationship between Doppler pulsatility index and direct femoral pressure measurements in the diagnosis of aortoiliac occlusive disease.

The common femoral to popliteal segments of 123 patients with radiologically confirmed arterial disease have been compared with those of 43 volunteers apparently free from disease. The comparisons have been based upon parameters derived from Doppler-shifted, continuous wave ultrasound. Simultaneous recordings of the Doppler signal were made from over the common femoral artery and the popliteal artery; these were analyzed subsequently to reveal variations of maximum frequency with time. Fifteen parameters were obtained from each segment. Of these the Pulsatility Index (P.I.) the Damping Factor(Δ), the pulse wave transit time(TT) the rise time ratio(RTR) from each segment were examined in detail. The Doppler results from the patient groups were compared also with the findings from arteriography. On the basis of these comparisons it was found that the RTR was simpler to measure than other more commonly used parameters such as Pulsatility Index and at least as sensitive for the differentiation between severe arterial disease and the mildly affected or normal state. However, none of these parameters was sufficiently sensitive to distinguish between mild to moderate disease and normal.

V.A. Cannon

Papers

Quantitative assessment of the common femoral to popliteal arterial segment using continuous wave Doppler ultrasound