Effects of handrail support on claudication and hemodynamic responses to single-stage and progressive treadmill protocols in peripheral vascular occlusive disease

Because handrail support reduces the energy cost of treadmill walking, claudication and hemodynamic responses of patients with peripheral vascular occlusive disease should also be affected. Furthermore, the reliability of the test results may be reduced unless the same pressure is applied to the handrails over repeated tests. The effect of handrail support on claudication and hemodynamic responses, and on their reliability, were examined during single-stage (2 mph, 12% grade) and progressive (2 mph, 0% grade with 2% increase every 2 minutes) treadmill protocols. Ten patients with stable disease performed both protocols 3 times, separated by 1 week, with and without handrail support. Claudication pain distance and maximal walking distance were greater (p less than 0.05) when handrail support was permitted, and they increased (p less than 0.05) over repeated tests of each protocol. No increase was noted over the tests without support. The responses and reliability of foot transcutaneous oxygen tension, ankle systolic pressure and ankle/brachial systolic pressure index after exercise to maximal tolerable pain were not affected by handrail support. Because claudication distances were altered, it is concluded that handrail support should not be allowed when assessing claudicants, unless balance cannot otherwise be maintained.     

Transluminal atherectomy for occlusive peripheral vascular disease

Sixty-one patients with occlusive peripheral vascular disease were treated with transluminal atherectomy, a catheter-mediated technique for removal of atheroma. The technique was performed using 7Fr, 9Fr or 11Fr atherectomy catheters. Mean percent diameter stenosis was reduced from 71 to 23%, by removal of 831 atheromatous specimens in 949 passes of the cutting element through 136 stenoses in 61 patients. All specimens removed were sent for histopathologic examination to determine the components of the atheroma removed, which differed for specimens removed from original vs restenotic lesions. Percent stenosis was reduced to less than 45% in 118 of 136 stenoses (87%). Complications included 1 thrombus, which resolved after intraarterial infusion of streptokinase and 1 probable distal embolization without sequelae. Three angiographic dissections occurred without impairment of blood flow. There were no instances of acute occlusion, vascular spasm or vessel perforation. Six-month follow-up angiography was performed showing that patients who had a residual stenosis less than 30% after initial atherectomy had a lower restenosis rate (18%) than patients with initial residual stenoses greater than 30% (52%); this result demonstrated the importance of performing more complete atherectomy. Transluminal atherectomy appears to be an effective, predictable and safe method for removing occlusive atheromatous deposits from peripheral arteries.     

Transluminal atherectomy for occlusive peripheral vascular disease

The failure of balloon angioplasty to provide a durable result has led to the development of other methods of catheter-associated interventional therapy. In this study, 112 patients with superficial femoral artery stenosis or occlusion were treated with percutaneous atherectomy. Patients were considered to have a simple lesion if the occluded or stenotic arterial segment was less than 5 cm, and a complex lesion if the length of the occluded segment was greater than 5 cm. All atherectomies were performed in the superficial femoral and popliteal arteries; urokinase thrombolysis was used in conjunction with atherectomy in 16 patients. Atherectomy was considered successful if there was less than 20% residual stenosis determined by arteriography. Initial atherectomy results (30 day patency) were 100% successful in the group with a simple lesion and 93% successful in the group with a complex lesion. At a mean follow-up period of 12 months (range 5 to 24), there was a continued patency rate of 93% and 86%, respectively, in the simple and complex groups. In the patients who had restenosis, all pathologic specimens obtained during the second procedure demonstrated myointimal hyperplasia and organized thrombus. Eight major complications (7.1%) occurred, including one fatal myocardial infarction. The complication rate was 3.5% in the simple group and 8.3% in the complex group. With the exception of the myocardial infarction, all complications were associated with catheter entry site hematomas. Femoropopliteal atherectomy has a high rate of success and low morbidity and mortality for both simple and complex lesions and is a viable and competitive alternative therapy for patients with severe peripheral vascular disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hemodynamic influence of peripheral vascular occlusive disease on abdominal aortic aneurysms.

AIM: Clinical evidence indicates that hemodynamic conditions such as peripheral vascular occlusive disease (PVOD) influence abdominal aortic aneurysm (AAA) disease. METHODS: We retrospectively analyzed 406 operated cases of AAA at our institute over the last 15 years, and compared 39 patients with PVOD to those without, to examine hemodynamic effects and risk factors. Aneurysm size at operation, rupture, shape, expansion rate and several preoperative risk factors were compared. RESULTS: Mean aortic diameter in the AAA with PVOD patients (56.8+/-17.8 mm) showed no significant difference to that in the AAA without PVOD group (60.4+/-14.8 mm). However, the subgroup of AAA with PVOD in whom the aneurysm was found prior to PVOD diagnosis (67.8+/-18.1 mm) (n=19) showed a larger mean AAA diameter compared to the AAA (not followed up until operative indication/prior to operation) without PVOD group (60.4+/-14.8 mm), (n=340), (p=0.04). Smoking was the only preoperative risk factor to show a difference between AAA patients with and without PVOD. The aneurysm expansion rate was determined retrospectively in 13 patients with PVOD who had been followed for at least 1 year by CT scan and 17 patients without PVOD. The rate in the PVOD group was 8.1 mm/year, which was significantly faster than that in PVOD-free patients (4.6 mm/year), (p=0.03). CONCLUSIONS: The findings of a large diameter and fast expansion rate in AAA patients with concomitant PVOD suggest that the hemodynamic effects of PVOD have a great influence on AAA development.     

Percutaneous transluminal atherectomy in the treatment of occlusive peripheral vascular disease

Percutaneous transluminal atherectomy (ATH) can remove the obstructing atheromatous material and may overcome the limitations of balloon angioplasty for the treatment of occlusive peripheral vascular disease. This is the first case reported in China using the Simpson rotational atherectomy device in a patient with total occlusion of left superficial femoral artery. The significant improvement in lumen was achieved by removing a tissue specimen of 14 x 4 x 3 mm3 followed by a balloon angioplasty, which reduced the residual luminal narrowing further from 50% to 20%. No acute complication was found and the patient was discharged from hospital one week after the procedure. Our results suggests that the ATH might be an effective and safe treatment for occlusive peripheral vascular disease.     

Arterial fibrodysplasia: a regional cause of peripheral occlusive vascular disease

The authors studied 17 cases of symptomatic arterial fibrodysplasia involving peripheral arteries without concomitant renovascular hypertension in Iranian males (age range: twenty-two to forty-five years). Affected arteries were most commonly the femoral, iliac, and popliteal, but in 2 cases the axillary and brachial arteries were also affected. Three cases were progressive. Differential diagnosis of arterial fibrodysplasia is discussed. It is concluded that this entity is the most common cause of peripheral occlusive vascular disease in younger Iranian males.     

The relationship between exercise performance and peripheral circulation in patients with peripheral arterial occlusive disease

The exercise performance of patients with peripheral arterial occlusive disease was often impaired. The relationship of exercise performance, daily physical activity, and peripheral circulation was studied. Twenty-five patients with peripheral arterial occlusive disease were recruited; their exercise performance was evaluated with a maximal graded exercise test. A habitual physical activity questionnaire was used to quantify the physical activity level. Measurement of peripheral circulation included the assessment of macrocirculation (ankle-brachial pressure index, calf blood flow by impedance plethysmograph) and microcirculation (cutaneous blood flow, cutaneous temperature, transcutaneous oxygen tension, and cutaneous blood flow responses to iontophoresis). Pearson's product correlation coefficient and multiple linear regression were used in data analysis. Results showed that age, sports index in habitual physical activity questionnaire, and ankle-brachial pressure index were significantly correlated with maximal walking time. Age and sports index were the two major determinants for their exercise performance and accounted for a 61.5% variability.     

Pattern of occlusive peripheral vascular disease in India. (clinicopathological study of 79 cases).

The pattern of peripheral vascular disease in India was studied in 89 patients undergoing amputation for vascular insufficiency. A control group of 26 limbs was studied for aging changes. Clinically, cases were classified into TAO (25), ASO (54) and thrombo-embolic disease (10). Angiographic, macroscopic and microscopic study of dissected vascular tree was done in view of clinical diagnosis. No significant difference was noted in the frequency and extent of involvement of limb arteries in TAO and ASO. Histologically angiitis was noted in 4 cases of TAO and one of ASO but these did not form a distinct clinical group. Primary thrombotic occlusion was seen in 21 cases of TAO and 23 cases of ASO. Atheroma with and without thrombosis was found in 26 cases. In 4 cases the arterial tree was normal. Atheromatous lesions were not seen in control group. In the groups under study they were thought to represent old thrombi rather than degenerative lesions predisposing to thrombosis. In view of these findings it was felt that Buerger's disease was primarily a thrombotic disorder. Angiitis was rare and was probably secondary. The two clinical groups TAO and ASO are not pathologically distinct as very high percentage of the latter showed primary thrombosis. The genesis of thrombosis in two groups however may be different.     

Interval exercise in arterial occlusive disease

During intermittent exercise with periods of six minutes with two minutes pause the fluctuations in arterial and popliteal venous blood of lactate and pyruvate as well as changes in the lactate pyruvate ratio were studied in eleven patients with claudicatio intermittens. Oxygen uptake stabilizes itself within 4-6 min during exercise and VO2 at the end of an exercise period is higher than in the beginning of recovery. The level of arterial lactate does not vary significantly. The highest venous lactate was found in the pause. Significant differences in venous lactate, pyruvate and lactate pyruvate ratio were found between the first and second exercise. It is concluded that during intermittent exercise less glycogen was used and that this glycogen saving effect seems to have been accomplished both by a shift towards more oxidative metabolism and by a greater contribution from other substrates than glycogen.     

Role of hyperhomocystinemia in retinal vascular occlusive disease.

Elevated plasma homocysteine (Hcy) level is considered a risk factor for vascular diseases. In recent years, many scientific reports have suggested that hyperhomocystinemia may be associated with an increased risk of retinal vascular occlusive disease (RVOD). The prevalence of elevation of homocysteine in patients with a recent retinal vascular occlusion was compared to a health control group in this study. Forty-nine consecutive patients (22 M; 27 F) (age 26-85 years, mean 69) with diagnosis of retinal vascular occlusion were compared with 71 healthy controls. These patients underwent laboratory evaluation for plasma fasting total homocysteine, activated protein C resistance, protein C, protein S, antithrombin III, and antiphospholipid and anticardiolipin antibodies. The G20210 prothrombin gene mutation (FII G20210A) and Factor V Leiden mutation (FVL) were evaluated. None of these enrolled subjects had other prothrombic risk factors. The health control group consisted of healthy subjects from the general population, with no history or clinical evidence of retinal vascular disease, recruited during the same 2-year period. High fasting homocystinemia (higher than 15 mumol/L) was detected in 24/49 subjects (48.9%) (P < .0005). There was a high prevalence of hyperhomocystinemia: these data suggest an association between RVOD and high fasting homocystinemia. Elevated homocysteine may be an independent risk factor, and its assessment may be important in the investigation, management, and follow-up of patients with RVOD. Further controlled studies are necessary to clarify the exact role of hyperhomocystinemia in RVOD and to evaluate the appropriate therapeutic approach.     

Abnormal electrocardiographic responses to exercise in patients referred for noninvasive evaluation of occlusive peripheral arterial disease.

Fifty consecutive patients were referred to the noninvasive laboratory for evaluation of suspected peripheral vascular disease. There were 30 men and 20 women aged 27 to 88 years (mean 63). Measurement of cardiovascular risk factors revealed the following distributions: cigarette smoking 90 percent, hypertension 28 percent, diabetes mellitus 22 percent and hyperlipidemia 6 percent. Eight patients had a history of angina pectoris, 7 a prior myocardial infarction, 5 a cerebrovascular accident and 11 prior peripheral arterial revascularizatlon surgery. Evaluation detected 32 patients (64 percent) with occlusive arterial disease of the lower limbs. Lead II of the electrocardiogram was monitored during and 1, 2, 3, 4, and 5 minutes after treadmill exercise with a limiting grade of 10 percent at 2.5 miles/hour. The mean resting and maximal heart rates for the study group were, respectively, 78 and 106 beats/min. The average treadmill speed attained was 1.9 miles/hour at a mean duration of 3.8 minutes. Thirty-seven subjects (74 percent) had normal electrocardiographic responses to exercise. Of 13 patients (26 percent) with an abnormal exercise electrocardiogram, 7 had possible ischemic S-T segment responses. Six subjects manifested frequent premature ventricular complexes during exercise. Four other patients had abnormal S-T segments in the resting electrocardiogram (two had a pattern of left bundle branch block, and two a pattern of left ventricular hypertrophy and strain).A survey of 60 peripheral vascular laboratories in the United States revealed that only 29 percent of the responding 34 centers routinely performed electrocardiographic monitoring during exercise testing. It is concluded that (1) electrocardiographic monitoring during exercise in the peripheral vascular laboratory can provide useful information regarding S-T segment responses, (2) abnormal S-T segment responses in patients with suspected peripheral vascular disease are frequently manifested at low levels of work load, and (3) such routine monitoring should be performed for patient safety.     

Continuous infusion treatment with pentoxifylline in patients with severe peripheral vascular occlusive disease

The effect of continuous i.v. infusion of pentoxifylline, administering 1,200 mg/24 hours through 15 days, was studied in 22 patients (19 m, 3 f) with arteriographically confirmed extensive occlusion in the femoro-popliteal segment, associated with marked intermittent claudication and rest pain of varying severity. The following parameters were used for the verification of the therapeutic response: Flow resistance factor (RF), pressure indices at rest (RPI) and after exercise (PPI) and recovery time (RT) assessed by means of ultrasonic Doppler technique; muscle and skin blood flow at rest and after exercise using 99m Technetium Clearance Technique (TC); toe skin temperature (TST) by electric thermometer; painfree walking distance (WD) assessed on treadmill (horizontal, 4 km/h); rest pain (RP) was assessed by a 4-step-relief-scale. There was an overall good response to treatment, the studied parameters showing the following changes: RF improved in 12/17 patients (= 70%); RT decreased in 14/22 patients (= 63%) RPI and PPI showed no change; TC (muscle) increased after exercise in 17/22 patients (= 77%); TC (skin) increased after exercise in 20/22 patients (= 90%); WD increased on average by 80% (from 115 m to 206 m); TS increased in 16 limbs; RP showed an overall relief. The results of this study indicate that the continuous infusion of pentoxifylline is safe and effective in improving the condition of patients with severe peripheral vascular disease.     

Haemodilution in patients with peripheral arterial occlusive disease.

Haemodilution is an efficient conservative therapy of peripheral arterial occlusive disease. Already a single isovolaemic haemodilution (replacement of 500 ml blood for Haes* 0.5, 10%) increases the pain-free walking distance by 85%. These effects can be maintained by a constant therapy over six weeks and following haemodilution once or twice per month. The haematocrit values should be between 38 and 42%. The haemodilution should be done hyper- or isovolaemically. Not more than 250 ml blood and 500 ml Haes should be infused during one session in order to avoid hypovolaemia. This means an infusion of 250 ml Haes, venesection of 250 ml blood via the same access and then infusion of the remaining 250 ml. The whole procedure should not last more than one hour. Blood pressure, heart rate, lung auscultation and percussion as well as creatinine values has to be controlled during an intensive therapy. If the hydroxyethyl starch concentration exceeds 150 g per week pruritus may occur in singular cases, if the concentration exceeds 700 g per week it is observed in 50% of the cases. Provided the preventive measures are observed haemodilution is an efficient and good therapy which also increases the compliance to practice vascular exercise.     

Haemostatic derangement in advanced peripheral occlusive arterial disease.

BACKGROUND: Dysbalance of the coagulation and fibrinolysis system was suspected to be a further risk factor for the progression of peripheral occlusive arterial disease (POAD). Reports on disturbed platelet function in advanced disease, however, were contradictory. Therefore, we studied haemostasis parameters and platelet function in symptomatic patients with peripheral arterial disease. METHODS: 60 peripheral arterial disease patients hospitalised for invasive diagnostic procedures were included into this comparative study. Patients were clinically stratified according to the criteria for chronic limb ischemia (grade I: n=36; grade II: n=11; grade III: n=13). Plasma fibrinogen, antithrombin III, von Willebrand factor, tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1) prothrombin time, and activated partial thromboplastin time were determined using standard methods. We measured flow cytometrically, the platelet activation marker P-selectin on nonstimulated, ADP- and TRAP-6-stimulated platelets. Angiographic data were assessed using the Bollinger score. RESULTS: Plasma levels of the procoagulant proteins fibrinogen (grade I: 3.7/grade II: 3.9/grade m: 4.0 g/l) and vWF (158/156/178%) increased and of antithrombin III (109/103/102%) and the PAI-1/tPA ratio (5.2/5.0/4.1) decreased with progressive disease. Highest platelet activation levels were observed in the CLI grade II subgroup. A significant correlation of disease severity was seen with the ankle-brachial pressure index (p=0.006; r=0.39) and with the Bollinger score (p=0.002; r=-0.41). CONCLUSIONS: Progressive peripheral obstructive arterial disease was associated with platelet hyper-reactivity, haemostatic dysbalance of pro- and anticoagulant proteins, and a counterregulatory increase of fibrinolytic activity. Therapeutic concepts should include these pathogenetic mechanisms.     

Haptoglobin polymorphism and peripheral arterial occlusive disease.

Haptoglobin (Hp) 2-2 phenotype is a genetic risk factor in coronary atherosclerosis. In this study, haptoglobin phenotypes were determined in 141 patients with peripheral arterial occlusive disease (PAOD) and compared to a reference population (n = 1000). The relative Hp1 allele frequency was decreased among PAOD patients (0.294 vs. 0.403 for the reference population, P < 0.01) due to an overrepresentation of the Hp 2-2 phenotype (50%, odds ratio 1.82 (95% C.I. 1.28-2.60), P < 0.001). This finding was even more pronounced in non-diabetic and in non-smoking PAOD patients (Hp1 allele frequencies: 0.265 and 0.228, respectively). Serum lipids, inflammatory parameters, and blood pressure levels were comparable among the Hp phenotypes, but serum levels of the antioxidant vitamin C were lower in Hp 2-2 patients than in patients with another phenotype (P < 0.05). In PAOD patients with severe atherosclerotic lesions, maximal walking distance of patients carrying a Hp 2-2 phenotype (225-525 m) exceeded that of other Hp phenotypes (50-242 m) (interquartile ranges) (P < 0.05). The findings demonstrate that, despite an increased risk for developing PAOD, the Hp 2-2 phenotype is associated with a longer maximal walking distance which might be attributed to the earlier reported in vitro angiogenic properties of the Hp 2-2 molecule.     

Percutaneous atherectomy of occlusive peripheral vascular disease: stenoses and/or occlusions

Percutaneous atherectomy was performed using the Simpson Atherocath on 131 patients (87 male, 66%) with a mean age of 65 years. Clinical characteristics included evidence of significant coronary disease in 50%, hypertension in 46%, diabetes in 41%, and prior neurologic deficit in 32% of patients. The indication for atherectomy was claudication in 114 (87%) and rest pain, gangrene, or ulcer in 17 patients (13%). Atherectomy was successfully performed in 136/139 stenoses (98%) and in 56/56 occluded vessels with or without prior balloon angioplasty. No serious complications resulting in limb loss or emergency vascular surgery were encountered. Histopathology of retrieved specimens showed that 66% had atheromatous plaque, 45% had tunica media, and 30% had a form of thrombus. Material obtained from an occluded vessel was more likely to have thrombus and tunica media present than that from a stenosis (P less than 0.02 and P less than 0.05, respectively). Early angiographic follow-up (mean time, 17 weeks) showed a relatively low (17%) lesion recurrence rate. Percutaneous atherectomy can be successfully utilized in stenotic and occluded peripheral arteries with good success and no serious complications; stenoses appear to have a low recurrence rate.     

Patterns of oxygen consumption during exercise testing in peripheral vascular disease

Exercise testing on a treadmill was performed in 15 patients with peripheral vascular disease to determine the pattern of oxygen consumption during exercise. A plateau in the oxygen consumption over the final 90 s of exercise was used as a criterion for maximal effort and only 4 out of 15 (27%) obtained a plateau of oxygen consumption compared to 20 out of 26 (77%) normal subjects (chi 2 7.9, p less than 0.005). These findings may account for the limited value of exercise testing in detecting coronary artery disease in patients with peripheral vascular disease.     

Arm exercise testing for coronary artery disease in patients with peripheral vascular disease

We evaluated 74 peripheral vascular disease (PVD) patients (54 men, age 61 +/- 7 years and 17 women, age 63 +/- 7 years) for potential coronary heart disease (CAD) using an arm exercise test (AET) protocol. All patients performed upright two-arm cranking using discontinuous stages of 2 minutes of exercise separated by 2 minutes of rest. Exercise intensity was increased by +100 or 200 kpm (kilopond meters) with each stage. ECG was monitored continuously and blood pressure and 12-lead ECG tracings were obtained at the end of each exercise stage. All patients reached an endpoint of subjective exhaustion. Men achieved 91 +/- 14% of age-predicted heart rate at 597 +/- 167 kpm, while women achieved 86 +/- 14% of age-predicted heart rate at 335 +/- 117 kpm. Ischemic ECG responses (+AET) defined as new or additional ST depression greater than 1.0 mm X 80 ms, occurred in 35 men (65%) and 7 women (42%). Coronary angiography was performed in a subset of 22 patients (15 males and 7 females). CAD (greater than 70% stenosis) was found in 11 of 12 men and 4 of 5 women who showed positive or strongly positive AET responses (overall predictive value for AET = 88%). We conclude that arm exercise stress testing is safely performed in PVD patients who cannot complete treadmill exercise. In this limited series of PVD patients, the predictive value of a +AET response for diagnosis of CAD is similar to established values for treadmill exercise.     

Progressive peripheral arterial occlusive disease and other vascular events during nilotinib therapy in CML

The second generation BCR/ABL kinase inhibitor nilotinib is increasingly used for the treatment of imatinib-resistant chronic myeloid leukemia (CML). So far, nilotinib is considered a well-tolerated drug with little if any side effects, although an increase in the fasting glucose level has been reported. We examined a series of 24 consecutive CML patients treated with nilotinib in our center for the development of non-hematologic adverse events. Three of these 24 CML patients developed a rapidly progressive peripheral arterial occlusive disease (PAOD) during treatment with nilotinib. In all three cases, PAOD required repeated angioplasty and/or multiple surgeries within a few months. No PAOD was known before nilotinib-therapy in these patients, although all three had received imatinib. In two patients, pre-existing risk factors predisposing for PAOD were known, and one of them had developed diabetes mellitus during nilotinib. In the other 21 patients treated with nilotinib in our center, one less severe PAOD, one myocardial infarction, one spinal infarction, one subdural hematoma, and one sudden death of unknown etiology were recorded. In summary, treatment with nilotinib may be associated with an increased risk of vascular adverse events, including PAOD development. In a subgroup of patients, these events are severe or even life-threatening. Although the exact mechanisms remain unknown, we recommend screening for pre-existing PAOD and for vascular risk factors such as diabetes mellitus in all patients before starting nilotinib and in the follow up during nilotinib-therapy.     

Doppler diagnosis in peripheral arterial occlusive disease

PHYSICAL AND TECHNICAL FUNDAMENTALS OF DOPPLER ULTRASONOGRAPHIC METHODS: In addition to units recording both velocity and direction of blood flow, mostly using two ultrasonic frequencies and phase-out technique, there are small non-directional units available which provide useful diagnostic information from the acoustic Doppler signal derived. Doppler ultrasonic techniques utilize two physical phenomena: a) High-frequency ultrasonic energy penetrates biologic tissue and is partially reflected at borders between tissues of differing density. b) If the border area is in motion, due to the Doppler effect, there is a change in the reflected ultrasonic frequency with respect to the frequency emitted. In blood vessels the ultrasonic beam is primarily reflected from the flowing red blood cells where the change in frequency is a function of the velocity of flow (Doppler effect). From the Doppler transducer, the continuously-emitted ultrasonic beam is also received after being reflected. The frequency of the reflected beam is directly proportional to the velocity of the flowing blood. If flow is directed toward the transducer, the frequency of the reflected beam increases and if the flow is away from the transducer, the converse is true. The best Doppler signals can be received when the angle beta of the transducer to the studied vessel is about 45 degrees. The unprocessed Doppler signal represents a frequency spectrum corresponding to the various velocities of the individual lamina of the blood stream from which the prevailing velocity is integrated and registered. The penetration depth is dependent on the frequency emitted. Doppler units are preferred with working frequencies of 8 to 10 MHz and 3 to 5 MHz. With 8 MHz, the maximal depth of penetration is 3.5 cm, with 4 MHz, 8 cm. The lowest detectable velocity is also dependent on the frequency emitted: with 8 MHz, minimum is 3 cm/s. Since flow toward the transducer results in a positive Doppler shift and flow away in a negative shift, with the Doppler signal, the direction of flow can also be determined. The recorded Doppler curves enable a qualitative and, to some degree, quantitative assessment. Phase-out and frequency analysis systems enable differentiation of forward and backward flow components. From separate forward and backward flow curves, the instantaneous summation curve (integrated instantaneous hemotachygram) as well as a trend curve over 5 to 7 seconds can be constructed and the mean flow velocity displayed.