a frequency spectrum analyser to provide cerebral blood velocity waveforms. The pulsatility index (PI), A/B ratio, and rise and fall slope of the waveforms were calculated. The results indicated that cerebrovascular resistance was raised appreciably on day 1 of life compared with later in the first week. In 18 of 25 infants (72 %) there was no continuous carotid blood flow in the first hours of life. We suggest that the human cerebral circulation adapts to the process of birth in a similar fashion to that of animal models.

Background. An audit of 100 proximal (above knee) deep vein thromboses (DVT) was carried out to document the dynamic status of the condition during the first year.Methods. Duplex ultrasound was used to diagnose the presence of an acute deep vein thrombosis in a consecutive series of patients. Follow-up bilateral ultrasound scans were performed at one week, one month, six months and at one year and clot retraction, lysis or extension were recorded. The patients' treatment regime and symptoms were also recorded at each follow-up examination.Results. There were 100 proximal DVT's from 89 patients (11 bilateral thromboses). The patient population included those with a previous history of DVT or in the end stages of a major illness and those with reversible risk factors. The mortality rate over the one-year period was 14%, most of the deaths occurring in the first month. The majority of deaths occurred as a result of an underlying primary disease (e.g. cancer) and 3% died from a pulmonary embolism. All patients were treated initially with either intravenous (IV) heparin or subcutaneous low molecular weight (SCLMW) heparin. Following heparin all patients were treated with warfarin. The duration of anticoagulant therapy varied with most physicians treating the patient for six months. Symptomatic and asymptomatic events (pulmonary emboli, extension of thrombi, new DVT's) were recorded in the follow-up period especially in the initial and late phase.Conclusions. The audit concluded that the diagnosis and treatment of DVT continues to be a major clinical problem with uncertainty as to the type and length of treatment required. The mobility of the patient was not considered in the choice of initial heparin treatment. Anticoagulants were generally continued for a period of up to six months regardless of the patient's risk factors. Little consideration was given to asymptomatic events with physicians still depending on unreliable clinical symptoms to determine if recurrences had occurred. Generally, no consideration was given to the long-term consequences of a post-thrombotic limb at the initial stage of treatment of a DVT.

INTRODUCTION:The subsequent course of residual abnormalities after an acute deep vein thrombosis (DVT) can vary within individual venous segments. To investigate the pattern of response within the individual venous segment, we used sequential duplex scanning to determine whether certain segments are more likely to recanalize or remain occluded.METHODS:The anatomic segments involved in 63 above-knee DVTs were examined with duplex scanning at 1 week, 1 month, 6 months, and 1 year after the acute event. The segments under investigation were the external iliac vein (EIV), common femoral vein (CFV), superficial femoral vein (SFV), and popliteal vein (PV). Reflux studies were performed at each follow-up examination. During the follow-up period the segments were examined to see whether they were occluded, partially recanalized, or totally recanalized and the development of reflux was noted.RESULTS:Most DVTs were multisegmental with a total number of 171 sites involved. Initially, a greater number of segments were occluded (71%) than partially thrombosed (29%). The occluded segments were predominantly in the SFV and PV. At 1 year the thrombi had fully resolved in 60% of the venous segments, 27% remained partially recanalized, and 13% were occluded. The venous segments that resolved within the first 6 months had a higher rate of valvular competence than those that resolved from 6 months to 1 year. The SFV and PV had a higher incidence of valvular incompetence than the EIV and CFV. All venous segments that were partially recanalized at 1 year were found to have significant reflux. The SFV had the highest incidence of total occlusion at the end of 1 year (36%). Many of the occluded SFVs had established collateral pathways that displayed no evidence of reflux.CONCLUSION:The lower extremity venous segments differ in respect to their tendencies to partially or fully recanalize or remain occluded. All partially recanalized segments displayed reflux. Fully resolved segments that recanalized within the first 6 months were more likely to have competent valves than those that recanalized after 6 months. In the presence of an occluded SFV, collateral pathways establish rapidly. No reflux was found in these collaterals.

PURPOSE This study was designed to determine whether patients having underlying venous disease in their contralateral limbs indicates a more severe long-term clinical outcome in the ipsilateral limb after a deep vein thrombosis (DVT) and to determine what other factors may influence the long-term outcome. METHODS An acute DVT was initially diagnosed by means of duplex ultrasound scanning. Follow-up clinical examinations and bilateral duplex reflux studies were performed for a mean period as long as 3 years. The patients were divided into two groups: group I, those with no history of a contralateral DVT, and group II, those with a history of a contralateral DVT. The patients were classified at their final examination according to the Clinical, Etiology, Anatomic, Pathophysiologic (CEAP) classification, and the ipsilateral and contralateral limbs were compared. Predisposing factors were compared with the final clinical outcome. RESULTS Sixty-three patients were monitored in a mean follow-up period of 3 years. There was a significant difference in the incidence of symptoms between the ipsilateral limbs (P <.01) and the contralateral limbs (P <.001) for both groups. There was no significant difference between the incidence of superficial reflux between the ipsilateral and contralateral limbs, but the deep venous system and perforator veins were involved more often in the ipsilateral limbs. In group I, only six patients (10%) had no evidence of venous dysfunction (CEAP = 0) in their ipsilateral or contralateral limbs at the time of the final examination, and all patients had reversible risk factors. Of patients who had a mild clinical outcome (CEAP score, 1 to 3), 64% had a healthy contralateral limb, and the remaining 36% had mild to moderate disease. Eighty percent of patients with the most severe clinical outcome (CEAP > 3) had mild to moderate venous disease in their contralateral limb and had nonreversible risk factors. CONCLUSION There are a significant number of patients with an acute DVT who had an underlying venous disease in the uninvolved contralateral limb. An ipsilateral post-thrombotic limb is more likely to develop in patients with primary venous reflux after an acute DVT. The level of venous dysfunction in the contralateral limb is an indication of the severity of disease developing in the ipsilateral limb. The initial risk factors of the patients have an influence on the final clinical outcome.

BACKGROUND In vitro studies have shown that as the organisation of a thrombus progresses its ultrasound appearance becomes more echogenic. When diagnosing a deep vein thrombosis (DVT) using duplex ultrasound, an estimation of the degree of organisation of the thrombus is made by assessing its echogenicity. This method is purely subjective and has many pitfalls. METHODS A study was performed on 100 proximal DVTs from 89 patients diagnosed by duplex ultrasound. These images were transferred to a computer and standardised using, the adobe Photoshop. The thrombus in the image frame was outlined and the grey scale median (GSM) calculated. The grey scale median which is a measure of the echogenicity of the thrombus (indicating the degree of organisation), varied considerably from patient to patient. RESULTS The results show that the level of organisation of a thrombus on initial diagnosis is unrelated to the clinical signs or duration of symptoms of the patient. This has further implications when considering a therapy regimen based on the duration of symptoms (e.g. thrombolysis). Additionally, the age of the patient, predisposing factors and bulk of the thrombus appear to be unrelated to the value of the grey scale median at the initial visit. The initial grey scale median values were then compared to those at a one week's follow-up examination. Those with a low initial value of the grey scale median were found to increase, indicating further organisation, as expected. However, patients with higher initial grey scale median values were found to fluctuate, some increasing and some decreasing. The increase the grey scale median was due to a more homogenous appearance across the thrombus as the organisation process became more established. A decrease in grey scale median indicated areas of lysis occurring within the thrombus. CONCLUSIONS Measuring the value of the grey scale median is a quantitative way of assessing the degree of organisation of a deep vein thrombosis. This can be used to asses the suitability of patients for various treatment regimen. It is also a useful means of assessing the long-term implications of different therapies and could aid in determining the long-term outcome for the patient.

Background The use of standardised computerised ultrasound images is an objective and quantitative method of determining the echogenicity of thrombus. This method had been applied to study the natural history of 100 acute thrombi over a period of one year to. determine if early changes in echogenicity could indicate whether the thrombus would lyse, partially recanalise or remain occlusive. Methods. A consecutive series of 100 above knee deep vein thromboses (DVT's) were analysed over a period of one year. The presence of a DVT was initially diagnosed by duplex scanning and the patients underwent follow-up scans at one week, one month, six months and at one year. A grey scale image of the thrombus was transferred to a computer at each examination and its grey scale median (GSM) was measured. The mean GSM's were calculated for each examination and compared. At one year the patients were divided into groups according to their final outcome (i.e. lysis, recanalisation or occlusion) and the mean GSM values from each group were compared. Results. There were 100 proximal DVT's from 89 patients. At one year 14% of the patients had died and 23% were lost to follow-up. The mean GSM values increased over the one year period from 25.87+/-18.33 to a final value of 64+/-25.52 at one year. A total of 21 thrombi had fully resolved but there was no significant difference in their GSM values before resolution when compared to the other patients. Twenty-four patients had partially recanalised thrombi and 18 remained totally occluded. There was no significant difference in mean GSM values between these two groups until after six months when the permanently occluded venous segments had higher GSM values than those which partially recanalised. Conclusions. Measurement of GSM is an objective method of determining the degree of organisation of a thrombus and describes the subjective changes of individual thrombi. However, the organisation of a thrombus is a dynamic pro cess and mean GSM values did not reflect these changes. Early changes in GSM could not predict the final outcome of the thrombus i.e. lysis, recanalisation or occlusion.

When diagnosing a deep vein thrombosis (DVT) using duplex ultrasound, an estimation of the degree of organisation of the thrombus is made by assessing its echogenicity appearance. This method is purely subjective and has many pitfalls. Computer analysis can standardise the image and measure the grey scale median (GSM). The GSM is a measure of the overall echogenicity of the thrombus (indicating the degree of organisation). On initial diagnosis no relationship was found between the level of organisation and the duration of clinical symptoms, the size of the thrombus or to the age of the patient. The initial GSM values were then compared to the values at one week follow-up examination. The changes at one week were indicated by a higher GSM if the thrombus became more organised or by a lower GSM is lysis was occurring.

Calf veins are one of the most common sites for deep vein thrombosis (DVT) but the management of patients with calf vein thrombosis differs. Many centres consider pharmacological treatment unnecessary and elect not to examine the calf veins with duplex ultrasound. Others advocate monitoring the thrombus with serial venous duplex scanning and commence treatment if there is evidence of propagation. In this laboratory duplex scanning of the calf veins is routinely carried out as part of the diagnostic procedure for DVT. A study was carried out where 50 patients with isolated calf vein thrombosis were followed over a one year period to determine the long term outcome in the calf veins. Note was made of the choice of treatment. A high percentage (85%) were treated with heparin/warfarin and only 15% received no pharmacological treatment. There was a propagation rate of 15%, one of which resulted in a fatal pulmonary embolus (PE). The DVT recurrence rate was 14% within the year. No long term effects such as valvular damage were noted during the follow-up period. The results suggest the need for better guidelines for the diagnosis and treatment of isolated calf vein thrombosis. Future studies with larger groups of patients need to be carried out to determine the significance of the recurrence rate and the long term effects. Duplex scanning enhances the diagnosis of calf vein thrombosis and should be used for closer observation of potential thrombus propagation.

BACKGROUND:The late sequelae of an acute deep vein thrombosis (DVT) are difficult to predict. There are many retrospective studies which suggest that the post-phlebitic syndrome is associated with the development of valvular incompetence but these have lead to little understanding of the changes involved in the venous system following an acute thrombotic event. Duplex ultrasound imaging is an useful method to study changes in the venous system because it can locate a thrombus, assess the changes which occur over time and monitor the development of recanalization and reflux of blood flow.METHODS:In this study, 50 patients were followed by serial duplex ultrasound examination to determine if a more accurate prediction of patients at risk could be found. Rapid thrombolysis and extent of the thrombosis are both factors which influence the return of the vein to normal function.RESULTS:Complete thrombolysis within a short period of time occurred in 24% of patients resulting in preserved valvular function. After one year there were 34% with early post-phlebitic symptoms. All of these patients had veins which recanalized slowly and developed valvular incompetence with reflux. Veins remained occluded in 14% of patients and of these 8% had competent collateral channels. This appeared to be a better outcome because none of these patients had developed symptoms after one year. Recurrent DVT's occurred in 8% within the year. Of these, 4% presented with symptoms and 4% were without symptoms but thrombus was found by ultrasound examination.CONCLUSIONS:Serial duplex examination leads to better understanding of the natural history of an acute DVT. This may have clinical implications and lead to better management of acute DVT thereby reducing the long term risks of the post phlebitic limb.

The role of the surface characteristics of carotid artery lesions in the long-term prognosis of cerebrovascular disease has not been established. 184 patients who presented with symptoms of hemispheric TIA or retinal ischemia, and had ipsilateral carotid artery atheromatous disease, were clinically followed 5-8 years (mean 6.3 years) after initial presentation. Based on the findings of the initial duplex ultrasound examination, a comparison was made between those patients who suffered a vascular event in the follow-up period and those who remained alive and without subsequent vascular symptoms. The only significant difference found between the groups was the distribution of the lesion surface characteristics (p<0.01). The degree of stenosis caused by the lesion or the size of the low-ecbo pool within the lesion were not found to be significantly associated with subsequent clinical events. The results of this study emphasise the importance of the ultrasound evaluation of the carotid lesion surface characteristics, and their inclusion in the criteria for decisions on patient treatment.

Loss of pressure across a stenosis depends on the geometry of that obstruction, but flow only depends on geometry when both perfusion pressure and peripheral resistance are constant. As cerebrovascular resistance is generally low then flow over a stenosis will be dominated by stenotic resistance. A relatively modest reduction in systolic perfusion pressure will produce a large increase in stenotic resistance. Evaluation of a 'haemodynamically significant' or 'critical' or 'dynamic' stenosis should include consideration of variations in cardiac function and blood pressure as well as local vascular dynamics. Examination of the ultrasound image characteristics of the arterial lesion gives additional structural information of the contents and surface of the lesion and any movement relative to the vessel wall. This may give guidance in separating clinically stable from unstable lesions, and also in following progression or regression of disease. The physical forces which are applied to some lesions may cause the release of material from the substance of the lesion into the arterial lumen or cause damage resulting in progression of the lesion itself.

Subcutaneous arteriovenous fistulae are constructed regularly for haemodialysis in uraemia. However there is little available data on fistula blood flow patterns. Twenty-eight radio-cephalic fistulae constructed for 18 patients were examined over a 3-month-period using range gated pulsed Doppler ultrasound. Contralateral arms were also examined. The parameters measured were mean arterial and venous diameter, mean volume flow and mean velocity flow. The values obtained from successful and failed fistulae were compared. There was no statistical difference between either arterial or venous diameter in the two groups. Mean velocity flow and mean volume flow in the successful group however did differ significantly from those that failed. Unless the values obtained at 48 h are significantly higher than the contralateral arm, then the fistula seems unlikely to succeed. It would also seem that a simple Doppler flow meter which gives reliable mean velocity flow values is sufficient for these investigations and may even be used preoperatively, resulting in fewer re-operations.

This chapter describes a study for the Doppler spectral analysis of cerebral blood flow in preterm infants and the relationship to intraventricular hemorrhage (IVH). IVH continues to be a major cause of mortality and morbidity in preterm infants. The study group comprised 25 normal preterm infants without significant respiratory, cardiovascular, or neurological problems and 32 infants who developed IVH. The healthy infants had a mean gestational age of 32.0 weeks and a mean birth weight of 1740 g, while the infants in whom IVH occurred had a mean gestational age of 29.3 weeks and a mean birth weight of 1300 g. Analysis of the pulsatility index (PI) of the common carotid artery showed a lower value prior to the occurrence of IVH with the PI also being reduced at the time of hemorrhage. Subsequent to the development of IVH, the PI did not differ significantly from the healthy preterm infants. The blood flow velocity waveforms of the anterior cerebral artery demonstrated no difference in the PI before IVH was diagnosed and the control values. It is found that when IVH occurred, however, the PI was significantly reduced.

A Doppler technique has been used in three separate studies to measure the changes induced by increasing infusion rates of isoprenaline on blood velocity, blood flow and diameters in the femoral and posterior tibial arteries of normal volunteers and to investigate the effects of various B-adrenoceptor antagonists on these changes. Heart rate and blood pressures were also recorded. Isoprenaline produced the expected changes in heart rates and blood pressures in the volunteers and changes induced in these responses by the B-adrenoceptor antagonist were as seen by previous workers. The only expected finding was that systolic blood pressure at the ankle was decreased compared to that in the arm which was increased. Isoprenaline produced reproducible dose-dependant increases in blood velocity, blood flow and diameters in the femoral artery, but little or no effects in the posterior tibial artery. These differences may reflect the difference in distribution of these arteries, the femoral to large muscular beds and the posterior tibial artery essentially to skin vascular beds. The different effects of the B-adrenoceptor blocking drugs with different actions on B1- and B2-adrenoceptors on the responses of the Doppler measurements to isoprenaline would support the differences in distribution of the femoral and posterior tibial arteries and allow a conclusion that the muscle vascular beds contain essentially B2-adrenoceptors with respect to stimulation by isoprenaline. The results obtained in three separate studies using the Doppler technique do suggest that this non-invasive technique may be of value in investigating the physiology, and/or pharmacology of the peripheral circulation in man.

Continuous wave Doppler ultrasound was used together with B-mode real time ultrasound to study feto-placental blood flow in utero. The results of 887 examinations on 221 patients are presented. The fetal heart rate acceleration slope and pulsatility index (P.I.) of the audiofrequency ultrasound display were analysed. There was a significant reduction in fetal heart rate (P less than 0.001) and P.I. (P less than 0.001) with advancing gestational age in normal pregnancy. In contrast, in retarded intrauterine growth a significant increase in P.I. values was observed in 77% of patients.

Continuous wave (C/W) Doppler ultrasound is a non-invasive and inexpensive method of assessing both the fetal circulation in utero and the cerebral circulation of the newborn. We have used spectrum analysed C/W Doppler signals to study the feto-placental circulation in utero and the cerebral circulation of the new born particularly in relation to the development of intraventricular haemorrhage ( I V H ) . In normal pregnancy umbil ical arterial blood flow was found to be continuous with a significant diastolic flow component, indicating that placental vascular resistance was low. Analysis of the ratio of peak systolic flow (A) to end diastolic flow (B) at various gestational ages showed that there was a progressive fall in placental resistance with advancing gestational age ( I ) . The mean A/B ratio at 16 weeks (5.3,SD+I.I) was significantly different (P<0.001) from that obtained at term (2 . I .SD = 0.3). Fetal blood velocity waveform analysis in cases of retarded intrauterine growth ( R I U G ) demonstrated that in 77% of instances there was no diastolic flow in the umbil ical arteries indicating increased placental resistance and this phenomenon was noted to be present in all cases where fetal death occurred in utero.