Noninvasive blood flow measurements by Doppler ultrasound with application to renal artery flow determination.

A description of a new Doppler ultrasound flow measuring instrument is given along with representative measurements of blood flow in the canine renal artery and the human aortic arch, renal artery, and transplanted kidney renal artery. The instrument is briefly described, and a discussion of the limitations of the technique is presented.

New videodensitometric method for measuring renal artery blood flow at routine arteriography: validation in the canine model.

A contrast medium was injected in the aortic arch and selectively in a renal artery to estimate the renal blood flow as a percentage of the cardiac output by the videodensitometric (VD) method. Twenty-six paired VD measurements in four mongrel dogs were obtained and the results compared to electromagnetic (EM) flow readings from the aortic arch and a renal artery. The relative renal blood flow estimated by the VD method averaged 9.1% and correlated with the EM flow average of 9.6% with r = 0.96. Previous in vitro investigations of relative flow in a model have now been validated in vivo. These results suggest that videodensitometry could be a clinical tool for measuring renal blood flow in conjunction with routine arteriography.

Partial splenic embolization guided by blood flow measurements.

The author used blood flow measurements to guide partial splenic embolization procedures in five patients. The measurements were obtained by time density analysis of contrast medium injections in the splenic artery using digital subtraction angiographic techniques and modified software. The blood flow measurements demonstrated blood flow changes occurring as a result of the embolization. The embolization procedures continued until the blood flow in the splenic artery had been reduced to 50% of its original value. The blood flow measurements appear to predict the amount of parenchymal reduction achieved by embolization and show promise as a method of monitoring these procedures.

Assessment of cerebral blood flow in man by video dilution technique: a preliminary report.

Video dilution technique (VDT) is currently performed in conjunction with routine cerebral angiography to determine carotid blood flow in humans. Preliminary results indicate that the blood flows (as a percentage of cardial output) of the common, internal, and external carotid arteries are 8.5%, 5.5%, and 3.0%, respectively (SD less than 1%). In contradistinction to previous techniques, VDT provides a safe and highly accurate method of determining carotid blood flow in human subjects. The usefulness of this technique in normal and pathologic states is discussed.

Assessment of peripheral blood flow in man by video dilution technique: a preliminary report.

Video dilution technique is now available for clinical use in evaluating patients with peripheral vascular disease. The measurements can easily be performed in any modern angiographic suite. The only additional equipment required is a videodensitometer, video tape recorder, and a strip chart recorded. The new technique has been developed and tested in a hydrodynamic model and compared to volumetric flows. Further, the video dilution technique has been compared to electromagnetic flow readings using a canine model to measure the cerebral, renal, splanchnic, and extremity circulation and has proven to be extremely accurate (n = 389; r = 0.99). By applying the technique to patients with peripheral vascular disease, it is possible to evaluate the hemodynamic significance of stenotic lesions and arteriovenous shunts. Other uses of video dilution technique include evaluating the effects of vasoactive drugs and the adequacy of transluminal angioplasty.

Bronchial blood flow measured by video dilution technique in sheep.

Bronchial blood flow was studied with the video dilution technique (VDT) in seven sheep. All animals were anesthetized (thiamylal and halothane) and ventilated. A videodensitometer and a videotape replay of the fluoroscopic image of dye moving through the common bronchial artery were used to construct dye mass vs. time curves. The areas under the curves were inversely proportional to flow in the bronchoesophageal artery, the site of dye injection. At thoracotomy, an electromagnetic flow probe (EMFP) was placed on the common bronchial artery (the major branch of the bronchoesophageal artery) to measure blood flow changes simultaneously by EMFP and by VDT. These two methods of measurement of blood flow to the airways were compared to validate the use of VDT in this circulation. Common bronchial artery blood flow was increased by injection of radiocontrast dye into the fluoroscopically positioned bronchoesophageal artery catheter causing hyperosmotically induced hyperemia. In 160 simultaneous measurements in five sheep, the percent change in flow as measured by EMFP and VDT correlated closely (r = 0.96). When flow changed because of spontaneous aortic pressure changes or pharmacologic intervention (28 simultaneous measurements in five sheep), the percent change in flow by EMFP and VDT also correlated well (r = 0.98). Bronchial blood flow changes in sheep can be measured accurately using the video dilution technique.

Surgically induced carotid subclavian steal syndrome. Diagnosis by video dilution technique.

A rare occurrence of carotid subclavian steal syndrome following carotid subclavian bypass for arm ischemia was described. Blood flows in the carotid artery and carotid subclavian bypass, at rest and following arm exercise, were determined by video dilution technique during the angiographic procedure. There was no obstruction of the inflow or outflow of the proximal or distal anastomoses to account for the steal (55%). Rather, increased arterial flow to the subclavian artery due to the patient's status as a bilateral amputee was thought to be the cause. The diagnosis and subsequent correction by takedown of this bypass and conversion to an axillary-to-axillary bypass were performed. Video dilution technique offers a unique and accurate way to study steal phenomena in conjunction with routine angiography and does not add to the patient's cost or risk.

Video dilution technique. An accurate measure of blood flow during routine arteriography.

The video dilution technique for measuring blood flow consists of electronically and mathematically processing video-taped selective arteriograms to measure the flow in selectively catheterized arteries and to express this flow as a fraction of the flow in any reference artery. Flows were measured by video dilution and an electromagnetic flowmeter in ten dogs; the correlations were excellent. Video dilution flows were also measured in 105 patients. The technique is accurate, simple, and adds no risk to routine selective arteriography.

Carotid blood flow in man determined by video dilution technique: II. Vascular abnormalities.

Carotid blood flows were evaluated in 31 individuals with vascular abnormalities using the video dilution technique. In patients with stenoses, angiographically estimated at 70%, blood flow was usually, but not always, measured less than normal. The technique proved to be useful in the evaluation of the efficiency of collateral arterial pathways and in the evaluation of superficial temporal-middle cerebral arterial bypass grafts. It was also helpful in estimating contralateral increase in arterial flows with cross compression techniques for the preoperative evaluation of patients subjected to carotid sacrifice. In a limited number of patients video dilution flows correlated with the degree or proximal arterial spasm and were useful in the preoperative study of these patients. The demonstration of flow abnormalities in patient with seizure disorders may be useful in the medical and surgical management of these individuals.

Carotid blood flow in man determined by video dilution technique: 1. Theory, procedure, and normal values.

The blood flows in the common, internal, and external carotid arteries were determined as a percentage of the cardiac output by video dilution technique in 20 normal subjects during routine angiography. Nine women and 11 men, ages 19-63 years, displayed a mean flow in the common carotid of 8.5% (SD +/- 0.9%; n = 40); internal carotid, 5.3% (SD +/- 1.0%; n = 24); and external carotid, 3.2% (SD +/- 0.4%; n = 24). Relative flow is calculated by a modification of the Stewart-Hamilton principle. The technique is fast, simple, highly accurate, and avoids the errors connected with previous videodensitometric mean transit time techniques. The method can be used in routine angiography without prolonging the catheterization procedure or adding to the patient's risk or cost.

Carotid blood flow response to Conray-60: diagnostic implications.

The vasoactive effect of the angiographic contrast medium Conray-60 (iothalamate meglumine 60%) on carotid blood flow was studied by the video dilution technique in 26 subjects during routine neuroangiography. After a test series of 1 ml injections of contrast material into the carotid arteries at designated time intervals, an increase in carotid blood flow was found in normal controls at 30 sec, while a significant decrease in flow was observed in patients with atheromatous disease and avascular intracranial masses (p less than 0.01). Test responses in patients with intracranial aneurysm, neoplasm, and granulomatous vasculitis are also reported. The differential effect of contrast material on the cerebral circulation correlates well with several pathologic states of the central nervous system and may be used as a simple test to diagnose and evaluate a variety of vascular disorders.

Aortic compliance in hypercholesterolemic Watanabe rabbits compared to normal New Zealand controls.

This study was designed to test the hypothesis that severe atherosclerosis changes aortic compliance. Compliance of a vessel is defined as change in volume per unit change in pressure and is a measure of the stiffness or distensibility of the vascular wall. Part of the energy delivered by the left ventricle in systole is used to propel the blood forward into the aorta and part of it to distend the aorta and major vessels. During diastole, the arterial walls recoil and provide energy for propulsion of blood, thereby making blood flow continuous. It is known that Watanabe hereditary hyperlipidemic rabbits develop severe atherosclerosis beginning at 6 months of age. Compliance of the ascending thoracic aorta was studied angiographically in eight Watanabe hereditary hyperlipidemic rabbits of ages greater than 6 months and six normal lipidemic New Zealand white rabbits of ages greater than 6 months, used as controls. The normal New Zealand white rabbits had an average blood cholesterol of 27.4 mg/dL, SD = 13.8, and a regional compliance in the ascending aorta of 0.004 mL/mm Hg, SD = 0.002, compared to the Watanabe hereditary hyperlipidemic rabbits with a cholesterol of 583.1 mg/dL, SD = 162.7, and a compliance of 0.0022 mL/mm Hg, SD = 0.0015. These are significant differences (p less than .05). In addition, the histopathology of the aorta of the Watanabe hyperlipidemic rabbit compared to that of the controls showed a significant decrease in the number of medial lamellar elastin units, an indicator of the decreased elasticity of the blood vessel wall.

Superior mesenteric artery vasoactivity in hyperlipidemic Watanabe rabbits versus normal lipidemic New Zealand controls.

Recent in vitro studies on isolated coronary and mesenteric arteries have shown that hyperlipidemia appears to hypersensitize the vascular arterial smooth muscle to drugs such as ergonovine and that this increased contractility seems to be mediated by a serotinergic mechanism. This results in vasospasm with exposure to certain vasoactive drugs such as serotonin or norepinephrine. However, in vivo quantification of this observed phenomenon has not been done. In the present study we used Watanabe hereditary hyperlipidemic (WHHL) rabbits (cholesterol level 459 +/- 216 mg/dL) and the normal lipidemic New Zealand white (NZW) rabbit (cholesterol level 35 +/- 19) as a control in the study of hyperlipidemia and blood flow changes in response to various vasoactive drugs. Blood flow measurements were made by the video dilution technique (VDT) following catheterization of the superior mesenteric artery. The serotinergic vasoactive drug ergonovine maleate was injected into the superior mesenteric artery at low dose (0.002) mg/kg) and high dose (0.004 mg/kg). A significant decrease (p less than .05) in blood flow was observed in response to high-dose ergonovine maleate in WHHL rabbits compared to the NZW rabbits. This in vivo experiment confirms the in vitro studies showing that hyperlipidemia sensitizes mesenteric arteries in the presence of serotinergic stimuli. The vasodilators verapamil hydrochloride and calcitonin gene-related peptide (CGRP) injected into the superior mesenteric artery caused a marked increase in flow in both the WHHL and the normal lipidemic NZW rabbits. This model can be used in the assessment of superior mesenteric artery ischemia and its reversal.

Drainage routes of bronchial blood flow in anaesthetized sheep.

The systemic circulation to the lung supplies the trachea and airway walls and may be important in the pathophysiology of asthma and pulmonary oedema. An understanding of the venous drainage pathways of this bronchial blood flow may be therapeutically important. The purpose of this study was to understand the normal drainage pathways in sheep. In seven anaesthetized, ventilated sheep we injected echo contrast agents into a systemic vein or into the bronchial artery while performing echocardiography to determine whether the drainage could be observed to the right heart and/or to the left heart. During transoesophageal echo (n=5) or heart surface echo (n=2), cephalic vein injection of <8 microm diameter gelatin microballoons promptly opacified the right but never the left-sided circulation. Air in agitated saline in the seven animals showed the same result. By contrast, injection into the bronchial artery promptly opacified the left atrium, left ventricle, and aorta but not the right-sided circulation in all seven microballoon injections and all but one of the air in agitated saline injections. The failure of the echo agents to pass through the pulmonary circulation may be related to sheep pulmonary intravascular macrophages or the surface forces on air bubbles of small size promoting collapse. The main conclusion is that there are bronchopulmonary anastomoses that connect the bronchial circulation to the pulmonary venous circulation connecting distal to the pulmonary capillaries. Any bronchial venous drainage to the right-sided circulation must have been below the detection level of the instruments and would in any case appear to be much less that the post-pulmonary capillary anastomoses noted. Pulmonary venous hypertension would be expected to have a direct effect on the bronchial circulation.

Vasodilator response in the lower extremity induced by contrast medium. I Canine model.

The vasodilator response induced by injections of contrast medium was observed in 11 dogs by electromagnetic flow technique. The experiments were performed to further understand video dilution technique (VDT) measurements in patients with arterial obstructive disease. Responses were observed with regard to the contrast dose relationship, time to peak flow, and abnormal flow produced up to 4 ml caused increasing magnitude of peak flow. The time to peak flow was relatively constant for all doses. Mechanical constrictions depressed th peak flow magnitude but did not affect the time to peak. Emboli produced both depression of the flow magnitude and a delay in time to peak flow. The data suggest that the VDT vasodilatory response curves obtained in patients should correlate with the degree of obstructive disease and delay in the peak flow implies outflow disease.

Vasoactivity of verapamil in the canine hindlimb and sympathetic nervous system interaction.

Since enhanced sensitivity to verapamil in essential hypertension has been noted, a relationship between verapamil and the sympathetic nervous system has been suggested. It has also been noted that both verapamil and lumbar sympathectomy appear to decrease the vasospasm seen in Raynaud's phenomenon. To further investigate the possible interrelationship between verapamil and the sympathetic nervous system, a unilateral lumbar sympathectomy was performed on eight dogs. Two weeks later the femoral artery blood flow response to intra-arterial verapamil was compared on the sympathectomy limb side and the non-sympathectomy limb side. Blood flow measurements were done without surgical trauma by video dilution technique. Although baseline femoral artery blood flow was unchanged and equal on both sides following sympathectomy (4.6% of cardiac output), there was a significant rise, p less than 0.05, in the blood flow response to verapamil on the side of sympathectomy. Therefore, sympathectomy appears to enhance the calcium channel blocking properties of verapamil.

Absolute flow measurements using pulsed Doppler US. Work in progress.

Quantitative flow measurements were assessed in both laboratory and canine models using pulsed Doppler ultrasonography (US). A hydrodynamic model consisting of a Harvard pulsatile pump, a water bath, tubing, and a variable resistance reservoir was used to obtain absolute volumetric flow measurements. Parameters including angle of incidence, size of tubing, stroke volume, stroke rate, sample volume, and transducer frequency were changed independently. The effect of varying these parameters on the determination of absolute flow was analyzed. Absolute flow measurements using duplex US were performed in the canine aorta and femoral artery with reference to the electromagnetic flow probe. These data are presented, along with methods to reduce error in flow measurements that can be directly applied to quantitative estimates of blood flow in humans.

Effect of intra-arterial CO2 insuffflation on occlusive arterial disease in the lower leg.

Twenty patients with a mean age of 79 years were followed over a period of 6 months after intra-arterial insufflation of CO2 in the lower extremity. All patients had severe peripheral occlusive arterial disease caused by atherosclerosis and were scheduled for amputation. A significant increase of the distal perfusion pressure was obtained in the majority of the cases resulting in pain relief and healing of ulcers and gangrenes.

The effect of lumbar sympathectomy on postsynaptic vascular smooth muscle response in the lower limb in dogs.

The intent of this experiment was to study the postsynaptic vasoactive response to tolazoline hydrochloride and sodium-meglumine diatrizoate (Renografin-76) after a unilateral lumbar sympathectomy in a dog model. Both lower extremities were examined using the video dilution technique before and 1-2 weeks after unilateral lumbar sympathectomy (SE). Results showed (1) resting blood flow in the femoral artery as a percentage of cardiac output did not change after sympathectomy (mean and SD before and after SE: 7.0% +/- 2.3 and 6.0% +/- 2.9 respectively n = 13); (2) the reactive hyperemia in the femoral artery caused by sodium-meglumine diatrizoate (Renografin-76) was unchanged after sympathectomy; (3) the vasodilator effect of tolazoline hydrochloride decreased significantly after sympathectomy (p less than 0.05).

Computerized tomography using a modified orthogonal tangent correction algorithm.

A modified orthogonal tangent correction algorithm is presented for computerized tomography. The algorithm uses four X-rays scans spaced 45 degrees apart, to reconstruct a transverse axial image. The reconstruction procedure is interative in which image matrix elements are corrected by alternately matching the two sets of orthogonal scan data. The algorithm has been applied to phantom data as well as to video recorded fluoroscopic data.