Novel method for assessing myocardial perfusion: visualization and measurement of intramyocardial coronary blood flow in the entire left ventricular wall using contrast enhanced, high frequency Doppler echocardiography

Using a high frequency ultrasonic transducer, intramyocardial coronary blood flow (IM-CBF) can be visualized and evaluated during hemodynamic changes in the anterior wall and septum of the left ventricle (LV). We tested the hypothesis that detection and quantitative measurement of IM-CBF of entire LV segments are feasible using a high frequency ultrasonic transducer in conjunction with intravenous contrast injection in vivo. A 3 - 8 MHz transducer was used to image and measure IM-CBF in 10 anesthetized dogs. We obtained a color Doppler image of IM-CBF in the LV short-axis view after intravenous Levovist injection (25 mg/ml). The IM-CBF velocity was recorded using spectral Doppler in the antero-septal and infero-posterior wall of closed chest dogs and in the entire LV after opening the chest. A significant increase in IM-CBF velocity was observed in all LV regions after adenosine 5'- triphosphate (ATP) administration. After Levovist(TM) injection, the visualization of IM-CBF was improved and the spectral Doppler pattern of coronary flow velocity was clarified compared to baseline. IM-CBF was assessed in the antero-septal region of the LV before and after left anterior descending coronary artery occlusion. A high frequency ultrasonic transducer in conjunction with intravenous contrast injection improved IM-CBF visualization, enabling quantitative evaluation of the intramyocardial coronary circulation in the entire LV after coronary occlusion and hyperemia. This study may represent a step towards noninvasive assessment of myocardial perfusion before and after coronary reperfusion.     

Noninvasive determination of stroke volume with impulse Doppler echocardiography: comparison with the Fick method

Pulsed Doppler echocardiographic studies were performed in 14 patients (eleven with mitral valve disease, two with coronary artery disease, one with aortic and mitral valve replacement) for determination of cardiac output and the results compared with those obtained from simultaneous measurements carried out according to the Fick principle. Determination of cardiac output and stroke volume was achieved with a pulsed Doppler instrument specifically designed in our laboratory (repetition frequency 10 kHz, maximal penetrance 7.7 cm, ultrasonic beam diameter 3 cm at a distance of 5 cm from the transducer). Doppler measurements of the instantaneous blood flow velocity in the ascending aorta were obtained with the transducer in a suprasternal position. Through integration of the mean spatial velocity over an entire cardiac cycle, the distance traversed by the blood during one heart beat was obtained and then multiplied by the echocardiographically-determined cross-section area of the aorta and the heart rate to yield the cardiac output. There was a statistically-significant linear correlation between the cardiac output determined by Doppler (CO-D) and Fick (CO-F): CO-D = 0.92 CO-F X 0.48, r = 0.85, n = 14. The mean values for the two methods were 3.89 and 3.68 1/min, respectively. The correlation between the two methods improved if only those patients with sinus rhythm were taken into consideration (CO-D = 1.05 CO-F - 0.21, r = 0.93, n = 11). The results show that the pulsed Doppler method used enables accurate determination of cardiac output. The method can be carried out in all patients without aortic stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Simultaneous Doppler blood velocity measurements from aorta and radial artery in normal human subjects

We used two independent, pulsed, range-gated, ultrasonic, Doppler blood velocity meters to record blood velocities in the aorta and a peripheral artery in 32 normal subjects aged 8 to 62 years. Aortic signals were obtained from an unfocussed transducer in the suprasternal notch using a 2.25 MHz instrument. Simultaneous tracings were obtained from the radial or posterior tibial artery using an 8 MHz instrument. The audio Doppler signals were subjected to spectral analysis and mean velocity was calculated at 5 ms intervals during 11 successive heart beats at each site. The increase in mean velocity at the start of systole in the aorta followed a linear pattern for the first 45 ms of ejection in two thirds of the beats, irrespective of the age or size of the subject. A similar linear velocity increase in early systole was seen in the peripheral arterial signals after a delay due to the time taken for the flow wave to pass to the periphery. Thus the constant acceleration seen in aortic blood velocity tracings is transmitted to peripheral arteries in an attenuated and delayed but undistorted form.     

Evaluation of coronary flow velocity and coronary flow reserve before and after coronary angioplasty using transthoracic Doppler echocardiography and Doppler guide wire

Evaluation of left anterior descending coronary (LAD) blood flow before and after coronary angioplasty was carried out non-invasively by ultrasonic Doppler echocardiography with a newly developed digital, high-frequency, high-resolution transthoracic ultrasonic Doppler flowmeter and a 7.5 MHz probe. The results were compared with those obtained using an intracoronary Doppler guide wire. Sixteen patients, 12 males and 4 females (mean age 57 +/- 14 years) with old myocardial infarction (8 patients) and angina pectoris (8 patients) were studied. Coronary flow reserve was compared following intravenous administration of adenosine triphosphate in 12 patients. The LAD blood flow was detected in 15 of 16 patients. There was a significant increase in the diastolic peak velocity from 22.2 +/- 10.6 to 29.4 +/- 14.6 cm/sec (mean +/- SD) and the coronary flow reserve from 1.8 +/- 0.3 to 2.8 +/- 0.6 (mean +/- SD). There was a good correlation between the data obtained using transthoracic flow measurement and intracoronary flow measurement (r = 0.61, p < 0.05). LAD blood flow can be easily detected parasternally using a digital, high frequency, high-resolution ultrasonic Doppler flowmeter. This method may be applicable for judging the efficacy of coronary angioplasty by measuring coronary flow reserve and for observing the clinical course of the patient non-invasively.     

Studies in vitro of the relationship between ultrasound and laser Doppler velocimetry and applicability to the simplified Bernoulli relationship

While there has been wide general acceptance of Doppler methods that use the simplified Bernoulii relationship to estimate pressure gradients across stenotic orifices, there is still ongoing controversy related to potential sources of error in the method. In this study we tested accuracy o ultrasound Doppler measurements of flow velocity when compared with the gold standard of laser light Doppler anemometry in a pulsatile flow model of pulmonic stenosis in vitro. We tested two commercially available Doppler systems and examined steered and nonsteered, parallel and off-axis and angle-corrected velocity determinations using continuous-wave and high-pulse repetition frequency (HPRF) methods. We also examined the potential range of error in the simplified Bernoulli method. One hundred and twenty individual flow states were examined with three stenotic valve orifices (3.0, 1.0, and 0.5 cm2 flow area) to measure velocities up to 620 cn/sec. A very high correlation coefficient was obtained for the comparison of laser Doppler anemometric and ultrasound velocity recordings by the nonsteered continuous-wave technique (r= .99, SEE = 17.9 cn/sec), but there was a tendency for underestimation of higher velocities when the transducer was positioned at 30 degrees and the ultrasound beam was steered so as to be parallel to the visualized flow jet (r = .98, SEE = 29.6 cn/sec). The HPRF ultrasound Doppler technique was also highly accurate in this optimized setting for measuring velocities (r = .99, SEE = 17 cm/sec), but also slightly underestimated the highest velocities. Our results also verified the accuracy of the simplified Bernoulli equation for converting instantaneous velocity measurements to estimated peak instantaneous gradient (r = .97, SEE = 8.4 mm Hg).     

Transcutaneous aortovelography: reproducibility in adults and children.

Transcutaneous aortovelography (TAV), a new ultrasonic technique for measuring instantaneous mainstream blood velocity in the aorta, is described. The technique uses the Doppler shift principle. The highest local blood velocity within the aortic arch can be recorded from a transducer placed in the suprasternal notch. Inspection of the systolic complexes recorded allows measurement of peak velocity, systolic complex area (proportional to ejected stroke volume), mean (time averaged) blood velocity and initial systolic acceleration. Formal analysis of variance was performed on measurements made by the five observers on 11 healthy adults and by 2 observers on 10 healthy children. Coefficients of variation of from 4 to 8% were found of all variables other than acceleration where the variation was up to 16%. Peak velocities in adults ranged from 97 to 130 cm/sec and were higher in children.     

Signal processing in 2 dimensional Doppler echocardiography

Blood flow recordings made by 2 dimensional Doppler echocardiography can sometimes be understood more easily than conventional Doppler recordings, because of the anatomical 2 dimensional presentation. In contrast, signal processing has become more complicated and requires more explanation. In 2 dimensional Doppler echocardiography the analog ultrasonic signal received by the transducer is converted into an audible signal, which next is digitized and analyzed for its mean frequency and variance. Data collection and processing require application of multigating and high speed frequency analysis, generally based upon autocorrelation. Some artifacts may be perceived, such as color reversal due to aliasing, deceptively colored tissue surfaces due to beam motion, and wall motion ghost signals due to multiple reflections. Color flow imaging is appropriate for a rapid scan of the heart cavities to detect and roughly evaluate flow abnormalities. Quantification is still accomplished by switching to conventional Doppler mode.     

Doppler color flow image size: dependence on instrument settings

Doppler color flow imaging provides important qualitative information about the location and spatial distribution of intracardiac blood flow. However, the effect of instrument-related variables on the size of color Doppler images requires further definition. Flow of a silicone particle solution was established in a tube or cylinder and scanned as color gain, pulse repetition frequency, depth, and transducer frequency were varied. The diameter of Doppler color flow images were measured during constant laminar or disturbed flow parallel to the ultrasound beam and during laminar flow perpendicular to the ultrasound beam. The diameter of color Doppler images of laminar flow perpendicular and parallel to the beam varied directly with color gain. Diameter varied inversely with transducer frequency for laminar flow parallel to the transducer and inversely with pulse repetition frequency for laminar flow perpendicular to the transducer. The diameter of laminar flow parallel to the transducer varied directly with the depth of the flow area below the transducer. The size of the color flow dropout of laminar flow exactly perpendicular to the ultrasound beam varied directly with transducer frequency and inversely with gain. During disturbed flow parallel to the transducer, the diameter of the image varied directly with gain and inversely with transducer frequency and pulse repetition frequency. Instrument settings have a significant impact on the size of color Doppler images. Understanding the effects of changes in these variables is important for reliable diagnostic use of Doppler color flow imaging.     

Real-time observation of blood flow velocity profiles in the right ventricular inflow tract by a newly-developed instantaneous B-mode and multi-channel Doppler echocardiography

We observed the blood flow profile in the right ventricular inflow tract through the tricuspid valve using the newly-developed equipment which images by instantaneous B-mode and multi-channel Doppler echocardiography. The Doppler system had 64 sampling gates in an ultrasonic beam within a depth of 13 cm. A cursor line was set at an angle of 45 degrees to the tricuspid annulus on two-dimensional echocardiography in a parasternal long-axis view of the right atrium and right ventricle. The blood flow velocity was displayed on the vertical line on the left-side of the CRT image. All Doppler-shifted frequencies of the 64 channels were analyzed using a fast Fourier transform formula by a built-in processor. The Doppler-shifted frequency was displayed at 30 frames per sec. The study subjects consisted of 20 children without cardiac anomalies. Their ages ranged from 2 to 18 years. A typical blood velocity profile at the tricuspid valve ring during the rapid filling phase had an "M" shape, i.e., the velocity was greater at both margins than in the central portion, followed by a flat profile. A small retrograde flow was observed behind the posterior tricuspid leaflet at this time. The flow velocity decreased in mid-diastole, then increased again during the atrial contraction period, with either flat or parabolic profile. During inspiration, the velocity was greater and the shape of the flow profile throughout diastole tended to be flat. In systole, a slow antegrade flow was observed in the tricuspid valve ring area, and its flow profile was parabolic.(ABSTRACT TRUNCATED AT 250 WORDS)     

An ultrasound system for combined cardiac imaging and Doppler blood flow measurement in man

An ultrasound instrument has been developed that combines a real-time cross-sectional imaging system and a spectrum analyzer-based Doppler velocimeter. This combination allows the Doppler sample volume to be superimposed on the cross-sectional image of the heart so that the sample volume can be located accurately. The same 2.2 MHz transducer utilized for cross-sectional imaging is stopped mechanically and quickly switched to transmit and receive the Doppler ultrasound signal. Preliminary experience in 20 young and adult normal subjects indicates that it is possible to place the Doppler sample volume in the proximal main pulmonary artery at a point where the sound beam and blood flow stream are parallel. Measurement of the distance from transducer to the sample volume and the peak blood flow velocities in the main pulmonary artery of normal subjects indicates that these quantities are within the measurement capabilities of the system. The ultimate goal of this device is to make measurements of volume blood flow in man noninvasively.     

Pulsed Doppler: determination of diameter, blood flow velocity, and volumic flow of brachial artery in man

A pulsed Doppler velocimeter suitable for the determination of blood flow velocity and volumic flow in peripheral arteries is described. The apparatus has two main characteristics: an adjustable range-gated time system and a double transducer probe. The error in the determination of the angle between the ultrasound beam and flow of blood with this apparatus was less than 2%, and overestimation of the arterial diameter due to the sample volume size did not exceed 0.035 +/- 0.015 cm. The apparatus was used to determine diameter, blood flow velocity and volumic flow of the brachial artery of 22 healthy men. The values were respectively 0.440 +/- 0.010 cm, 9.15 +/- 1.01 cm.s-1 and 85 +/- 10 cm3.min-1. Administration of intravenous nitroglycerin significantly increased the arterial diameter (p less than 0.001) without any significant change in volumic flow. The described pulsed Doppler velocimeter provides an accurate noninvasive method for determining volumic flow in peripheral arteries in clinical investigation and cardiovascular pharmacology.     

Transcutaneous Doppler ultrasound measurement of superior mesenteric artery blood flow in man.

A duplex scanner which consists of a real time two dimensional scanner and a pulsed Doppler flowmeter was used to measure superior mesenteric blood flow in 70 healthy subjects. By processing the Doppler shift signals, the instantaneous average Doppler shift frequency and then the instantaneous average velocity of the flow rate were calculated. Both diameter of the vessel and angle between vessel and beam were measured from real time imaging. The mean (+/- standard error of the mean) of the superior mesenteric blood flow was 517 +/- 19 ml/min. There was neither significant difference in flow between sexes, nor correlation between flow and age (r = 0.042). The mean of coefficients of variability were 6.8% over the short term, and 8.2% in long term studies.     

A simplified method to measure coronary blood flow velocity in patients: validation and application of a Judkins-style Doppler-tipped angiographic catheter

To facilitate more rapid and safe measurement of coronary flow velocity reserve in patients, we developed a Judkins-style angiographic catheter tipped with a 20 MHz Doppler crystal. In 19 patients without coronary artery disease, resting and hyperemic (10 mg intracoronary papaverine) mean and phasic coronary flow velocity signals were measured with the Judkins-style and 2.5F intracoronary Doppler catheters at identical coronary loci. Mean coronary flow velocity at rest was similar (14 +/- 8, 10 +/- 7 cm/sec, p = ns), but was higher during hyperemia for the Judkins-Doppler (41 +/- 8 versus 32 +/- 14 cm/sec, p less than 0.05). Coronary flow velocity reserve, calculated as the ratio of mean velocity at rest to mean velocity following papaverine, was 3.3 +/- 1.4 and 3.7 +/- 1.2 units (p = ns) for the Judkins and intracoronary Doppler techniques, respectively (r = 0.801, p less than 0.001). The Judkins-style Doppler catheter technique permits flow velocity and coronary flow velocity reserve measurements that correlate strongly with those of the intracoronary catheter technique, facilitating safe, quick, and accurate assessment of coronary physiology.     

Intracardiac flow vector measurement by simultaneous dual-frequency two-beam pulsed Doppler echocardiography

Conventional single-beam pulsed Doppler echocardiography has certain limitations in quantitatively measuring the intracardiac blood flow, because the Doppler incident-angle to the flow stream is uncertain. In the present study, the absolute velocity and direction of the intracardiac blood flow, i.e., flow vector, were measured using our newly-developed dual-frequency two-beam pulsed Doppler echocardiography. This instrument has two transducers with center frequencies of 3.5 MHz (main-beam) and 2.2 MHz (sub-beam) which are linked by two arms. Three potentiometers are set up by the three joints to sense the relative angles. Two velocity components at the intersection of the main- and sub-Doppler beams were measured simultaneously with different directional approaches. The flow vector was calculated manually from the two velocity components. The study population consisted of 18 healthy subjects ranging in age from 23 to 39 years. The left ventricular (LV) inflow vector was measured at the center of the mitral annulus, and the ejection flow vector was measured at the levels of the tip (E1) and the mid-portion (E2) of the anterior mitral leaflet in the LV outflow tract. The results were as follows: 1. The LV rapid inflow (R) was directed slight posteriorly towards the cardiac apex, and its average maximal velocity was 78 +/- 15 cm/sec (mean +/- SD). The LV inflow due to the atrial contraction was directed even more posteriorly than was the R, and its average maximum velocity was 43 +/- 10 cm/sec. 2. The LV ejection flows at E1 and E2 were directed slightly posteriorly rather than parallel to the interventricular septum, and the maximum velocity at E1 and E2 was 53 +/- 20 m/sec and 85 +/- 23 cm/sec, respectively. In conclusion, the dual-frequency two-beam pulsed Doppler technique allows quantitative measurement of the intracardiac blood flow dynamics regardless of the Doppler incident-angle to the flow stream.     

Energy Analysis of Flow Induced Harmonic Motion in Blood Vessel Walls

Energy is transferred between the flowing blood and the vessel walls during pulsatile blood flow (a normal pulse cycle) resulting in storage and dissipation of elastic energy. This allows the elastic and muscular arteries to act as an auxiliary pump to propel the blood fluid forward during systole and maintain a basal blood pressure during diastole. The pulsatile flow pattern caused by the contraction of the left ventricle sets up a state of harmonic motion in the blood vessel walls throughout the arterial vasculature. In this paper, we report on a kinetic energy analysis of pressure and flow velocity waveforms, which characterize energy transfer between the blood and the blood vessel walls at different frequencies of pulsatile flow and pressure. Porcine carotid arteries were tested under simulated physiologic pulsatile flow and pressure conditions in a model water bath system and compared to measurements in vivo on human carotid arteries. Fluid and wall pressures were monitored on the porcine vessels in situ using an absolute differential pressure transducer (fluid) and by a low-pressure volumetric balloon transducer (wall), respectively. A continuous-wave Doppler ultrasonic transducer monitored flow velocity and measurements were made both in vitro and in vivo at frequencies of 1.2 Hz (72 cycles per minute) and 2.1 Hz (125 cycles per minute) for comparison purposes. The areas under the pressure versus time and flow velocity versus time curves were used to calculate the relative change in work and kinetic energies. The calculations of the ratios of the relaxation slopes versus the impact slopes showed that the vessel wall absorbed more energy at the frequency of 1.2 Hz than at the 2.1 Hz frequency. The results of these calculations indicate that energy of the pulse pressure at rest pulse rates is absorbed and dissipated in the vessel wall and the surrounding extracellular matrix. At higher pulse rates and pressures, the vessel wall becomes increasingly elastic, and therefore, transmits or reflects most of the energy of the pressure pulse back to the blood fluid. As the vessel wall becomes less compliant with aging or disease, the energy absorbing and dissipating properties of the arterial wall at rest pulse rate diminish.     

The initial clinical evaluation of a transesophageal system with pulsed Doppler, continuous wave Doppler, and color flow imaging based on an annular array technology

The application of transesophageal echocardiography (TEE) offers access to a great deal of important clinical information regarding cardiovascular anatomy and physiology. Two applications which have not been reported and would appear to be of interest are continuous wave Doppler capabilities and the implementation of higher frequency transducers. A TEE system designed at the Institute of Biomedical Engineering in Trondheim, which is based on an annular array technology, offers these capabilities. We evaluated this instrument in the clinical setting in a series of 30 patients to test the probe function in terms of the tissue and flow imaging quality with a 7.5 MHz carrier frequency, and to report on the implementation of a continuous wave Doppler modality in a TEE probe. We found that the annular array method permitted the use of high frequency probes for tissue and flow imaging which resulted in excellent image resolution, and that shifting the carrier frequency of the transducer to a lower frequency permitted the optimization of the Doppler sensitivity. The continuous wave Doppler was used to measure abnormal blood flow velocities in excess of 5.0m/s, and was particularly useful in the operating room as velocity measurements could be obtained without compromising the sterile field. The results of our evaluation indicate that high imaging frequencies and continuous wave Doppler can be applied by an annular array TEE transducer.     

Effects of amyl nitrite on phasic aortocoronary bypass graft blood velocity in man.

With the use of a Doppler flowmeter catheter, phasic instantaneous aortocoronary saphenous vein bypass graft blood velocity was continuously measured during the inhalation of amyl nitrite in 20 closed-chest conscious subjects. Administration of amyl nitrite augmented peak diastolic and systolic graft blood velocity within 10 seconds and maximal blood velocities were recorded between 8 and 60 seconds after inhalation. Control mean (+/- 1 S.D.) bypass graft blood velocity was 25 +/- 10 cm. per second and after amyl nitrite 46 +/- 14 cm. per second, resulting in an average 84 per cent rise of blood velocity. It is concluded that amyl nitrite increases aortocoronary bypass graft blood velocity, suggesting a possible enhancement of blood flow to the distal native circulation in patients so operated upon.     

Doppler-echocardiographic determination of the degree of severity of mitral stenosis

The assessment of severity of mitral stenosis is generally based on the mitral valve orifice area as calculated by the Gorlin formula from the invasively-measured pressure gradient and flow across the valve. As an additional reference for evaluating severity, the hemodynamically-determined pressure half-time has been suggested; that is, the time required for the peak gradient across the stenotic valve to drop to one-half of its original value. Since the pressure gradient and the velocity of flow in the region of the stenosis are related to each other as described in the Bernoulli equation and, since the velocity of flow can be analyzed with Doppler echocardiography, the possibility is afforded for noninvasive determination of both the pressure gradient and the pressure half-time. From the Doppler echocardiographically determined pressure half-time, the mitral valve orifice area can be calculated. This study, in a relatively large population of patients with mitral stenosis, was undertaken to compare the pressure half-times obtained from Doppler echocardiography with the valve orifice areas derived from hemodynamic measurement, to analyze the relationship between the two latter parameters and to evaluate the relevance of the newly-developed method. In Doppler echocardiography, the frequency shift of emitted sound reflected from moving blood cells is measured. The velocity of blood flow is proportional to the frequency shift delta f.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical usefulness of intravenous albunex for the Doppler assessment of aortic stenosis

Optimal Doppler recordings of stenotic aortic flow are not always easy to obtain. Therefore, the present study investigated how useful intravenous Albunex injections were for improving the Doppler assessment of pressure gradients for aortic stenosis in 20 consecutive patients who underwent Doppler and left-heart catheterization studies within a 1-week period. Continuous-wave Doppler echocardiography was performed using both a 2.5 MHz duplex and a 1.9MHz independent transducer before and after Albunex injections. The maximum and mean pressure gradients were calculated from the highest Doppler velocity tracings using the simplified Bernoulli equation. Pullback catheterization pressure tracings from the left ventricle to the ascending aorta were superimposed for determination of the maximum instantaneous and mean pressure gradients. The Doppler-derived peak and mean pressure gradients showed significant underestimation compared with the catheterization gradients (23+/-17 mmHg and 11+/-7 mmHg, respectively). However, this underestimation disappeared with Albunex injection (-2+/-7 mmHg and -1+/-4mmHg, respectively). Although the Doppler-derived instantaneous and mean pressure gradients correlated well with the catheterization gradients (r=0.909 and r=0.879, respectively), they became much closer with Albunex (r=0.987 and r=0.963, respectively). The improvements in the Doppler-derived peak pressure gradients were significant from an apical window (n=12, 84-120mmHg, p<0.001). but less so from non-apical windows (n=8, 84-91 mmHg, p=0.0146). Accordingly, Albunex is most useful for Doppler recordings of stenotic aortic flow available from the apical window, but not less so from other acoustic windows.     

Doppler techniques for lower extremity arterial diagnosis

Doppler ultrasonic methods are based on a frequency shift incurred in the reflected sound from moving objects, for example, red blood cells. According to the desired depth of penetration, ultrasonic frequencies between 2 and 10 MHz are used. Continuous-wave Doppler detects all blood flow through the path of the ultrasound beam and pulsed-wave Doppler ultrasound permits detection of flow at specific sites in the arterial lumen. Through measurement of the systolic blood pressure, the extent of hemodynamically-significant arterial occlusive disease can be assessed. With the use of the ankle-arm index, which is normally greater than 1.0, compensation is enabled for variations in systemic pressure. Localization of the occlusive lesion can be obtained by measuring the systolic pressure at various levels in the limb. Normally, the ratio of high-thigh to brachial artery systolic pressure is greater than 1.2 and the difference in systolic pressure between any two adjacent levels in the leg should be less than 20 mm Hg. Measurement of toe pressure may be helpful when the ankle pressure is falsely elevated due to arterial calcification; in normal limbs, the systolic toe pressure is about 80 to 90% of the brachial systolic pressure. The use of small cuffs on large limbs can result in spuriously high pressure and medial calcification in the arterial wall can also lead to falsely high pressures. Treadmill exercise testing with determination of the immediate drop in ankle systolic pressure and the time for recovery to resting pressure is valuable to confirm or rule out intermittent claudication as the cause of leg pain and to detect severe multiple level arterial disease.(ABSTRACT TRUNCATED AT 250 WORDS)