Ultrasound Doppler Flowmetry Research Articles

Renal denervation by endocardial ablation system

Background: Transcatheter renal denervation (TRD) obviously may be done with endocardial ablation systems which allow exactly the same mode/parameters of energy delivery while small 5-7F endocardial catheters may be easily manipulated in renal artery. However, in contrast with novel renal ablation devices still at the development stage, endocardial ablation systems are mature equipment with proven success, predictable behavior and lower price. Greater length/diameter of endocardial ablation electrode provide greater contact area meaning proportionally lower current density and thereby risk of overheating, i.e. more safe ablation. Objective: To assess the safety and efficacy of TRD done by endocardial ablation system. Methods: We performed bilateral TRD using endocardial ablation catheter 5F, 4 mm in 52 patients (aged 53.7±9.6 years, 27 male) with true drug-resistant hypertension. Sequentially 4-8 point RF ablations separated radially and axially in renal artery and segmental branches were done in temperature-control mode with target T=60 C. All patients were instructed to continue existed pharmacotherapy. Efficacy was evaluated by the changes in office and ambulatory BP at 6 and 12 months after TRD. Safety endpoints included adverse events, changes in renal blood flow (ultrasound doppler flowmetry) and renal function (proteinuria, serum creatinine) at 1 week, 6 and 12 months after TRD (NCT01499810 at ClinicalTrials.gov). Results: No acute damage of renal arteries from RF ablation was detected by intraoperational angiography. There were 7 minor periprocedural events typical for endovascular procedures and non-related to RF ablation. At the time of this analysis 39 and 25 patients completed respectively 6 and 12 months follow-up. No significant changes in renal blood flow or renal function were detected at 6 or 12 months after TRD. Office BP dropped significantly by -27,5 (p<0,001)/-13,9 p<0,001 (mmHg, systolic/diastolic) at 6 months and then further decreased by -32,6 (p<0,001)/-15,5 p<0,001 at 12 months after TRD. The lowering of mean 24-h BP was quite modest at 6 months -11,5 (p<0,001)/-6,8 (p<0,001) however also continued to decrease and reached powerful level of -15,4 (p<0,001)/-10,4 (p<0,001) at 12 months follow-up. Conclusions: TRD done by endocardial ablation system is safe in patients with resistant hypertension and causes significant long-term lowering of BP which tends to increase over time.

AB0486 High frequency ultrasound and laser doppler flowmetry for the evaluation of digital dermal thickness and fingertip blood perfusion in systemic sclerosis patients

BackgroundModified Rodnan skin score (mRss) and high frequency ultrasound (US) are employed to evaluate dermal thickness (DT) in systemic sclerosis (SSc) patients (1-3). Laser Doppler flowmetry (LDF) is used to...

Sturge-Weber syndrome

Encephalotrigeminal angiomatosis (Sturge–Weber syndrome) is a rather uncommon congenital condition characterized by the combination of venous angioma of the leptomeninges over the cerebral cortex with ipsilateral angiomatous lesions of the face, and sometimes the skull, jaws, and oral soft tissues. A case of portwine stain with intraoral gingival hemangioma is presented. There were no other systemic manifestations. Patient reported with a complaint of localized tumor-like swelling in gums. Based on the presence of sharply demarcated vascular lesion unilaterally on the face and with ipsilateral intraoral vascular hyperplasia in the lip and gingiva, a variant of encephalotrigeminal angiomatosis was diagnosed. Ultrasound Doppler flowmetry was used to determine the blood flow. Dental management included plaque control instructions, scaling, root planning, and excision of the lesion done under general anesthesia. Close follow-up and meticulous plaque control have kept the oral condition under fairly good control.

Scleraxisexpression is coordinately regulated in a murine model of patellar tendon injury

This study investigated the expression of Scleraxis in a murine model of patellar tendon injury in which the central third of the patellar tendon was unilaterally injured. The presence of tendon pathology was assessed using dual photon microscopy, conventional histology and microCT. Tendon pathology was also quantified noninvasively over a 12-week period using high-frequency ultrasound and laser Doppler flowmetry. Gene expression (Scx, Tnmd, and Col1a1) was determined at defined end-points (1, 4, 8, and 12 weeks) using qPCR on RNA from individual patellar tendons on injured and uninjured sides. There was significant development of tendon pathology as gauged by ultrasound and laser Doppler over 12 weeks. Injured tendons demonstrated significant histological and microCT evidence of pathological change, and disorganized collagen with reduced density. The expression of Scx and Col1a1 was unchanged at 1 week, significantly upregulated at 4 and 8 weeks, and had returned to baseline by 12 weeks. Tnmd expression was unchanged at 1 week, and significantly increased at 4, 8, and 12 weeks. Patellar tendon injury was associated with marked increases in the expression of Scx, Tnmd, and Col1a1. Our data suggest new roles for Scleraxis in coordinating the response to injury in the pathogenesis of tendon disorders.

Dynamic infrared imaging for analysis of fingertip temperature after cold water stimulation and neurothermal modeling study

The human hand is considered to be the terminus of the nervous system. It contains numerous capillary vessels, and it plays an important role in the regulation of the autonomic nervous system. We have used infrared thermography and ultrasound Doppler flowmetry to investigate characteristics of the temperature variation of the hand and the blood flow after cold stimuli. We have also developed an image processing algorithm to measure temperature of various parts of the hand via sequential thermal images. Measured results show that local cold stimuli will induce oscillation of temperature, which may be due to neuroregulation during rewarming. Finally, in order to explain the mechanism of autonomic nervous system (ANS) regulation we have developed an ANS regulation model on the basis of the knowledge of the physiology and bioheat transfer. The results computed using our model are in good agreement with the experimental results.

A Comparison of Ultrasound and Laser Doppler for Measuring Capillary Recruitment Using Models in vitro

PURPOSE: Contrast enhanced ultrasound (CEU) and laser Doppler flowmetry (LDF) have been used to measure capillary recruitment in vivo in muscle and skin. However, it is imperative that only change in capillary surface area is measured and that measurements are not influenced by change in flow. Accordingly, we compare two methods: CEU and LDF, using artificial capillary tubing systems. METHODS: Phospholipid microbubbles, as contrast medium (approx. 2×108/ml, CEU), or red blood cells (3-9% hematocrit, LDF) were used in isotonic saline. Delivery was by syringe pump and CEU measurements were made using a HDI 5000 with L7-4MHz transducer at a mechanical index of 1.0 that was capable of destroying all bubbles in the ultrasound beam to construct a pulsing interval (time) versus video-intensity curve and calculation of capillary tubing volume (CTV) in the field of interest as well as tubing flow velocity (CTFV). LDF was conducted using a Perimed PeriFlux PF2 operating at 632 nm with a Pf 108 probe. For CEU we used microdialysis tubing (280 μm) and for LDF, polymer tubes of 250, 100 and 50 μm. Measurements were made when tubing diameter was varied with volume delivery rate (VDR) constant. VDR was varied with tubing diameter constant. Tubing capillary surface area was increased by connecting lengths of tubing in zig-zag series, or by flow-sharing with lengths of tubing connected to a manifold (VDR was constant for each, and each pattern was in the field of interest). RESULTS: CEU estimates of CTV were not affected by flow rate and increased whether tubing surface area was increased by connecting tubes in series or parallel. CEU measured changes in CTFV followed prediction. The LDF signal decreased as the diameter of the capillary tubes increased at constant VDR. However, the LDF signal increased as the VDR increased and as the surface area was increased by zig-zag lengths of capillary in series, but it decreased overall when surface area was increased with capillary tubes in parallel. CONCLUSIONS: These modeling studies indicate that CEU measures changes in capillary recruitment and is not affected by VDR. LDF signal derives mostly from non-vectorial speed and should be used with caution to measure capillary recruitment and may fail to detect capillary recruitment if manifold sharing occurs and mean cell speed falls. CEU can measure increases in capillary surface area that occur in exercise or following insulin action and may provide information as to whether capillary recruitment results from either flow redistribution from short to tortuous capillaries and/or by flow sharing into capillaries of similar properties.

Regional vascular responses to ATP and ATP analogues in the rabbit kidney in vivo: roles for adenosine receptors and prostanoids

Our knowledge of the effects of P2-receptor activation on renal vascular tone comes mostly from in vitro models. We aimed to characterise the pharmacology of ATP in the renal circulation in vivo. In pentobarbitone anaesthetized rabbits, we examined total renal and medullary vascular responses to ATP (0.2 and 0.8 mg kg(-1)), beta, gamma-methylene ATP (beta, gamma-mATP, 7 and 170 microg kg(-1)), alpha, beta-mATP (0.2 and 2 microg kg(-1)) and adenosine (2 and 6 microg kg(-1)) using transit-time ultrasound and laser Doppler flowmetry, respectively. We also determined whether adenosine receptors, NO or prostanoids contribute to the actions of the purinoceptor agonists. Renal arterial boluses of ATP, beta,gamma-mATP, and adenosine produced biphasic changes; ischaemia followed by hyperaemia, in total renal and medullary blood flow. alpha,beta-mATP induced only ischaemia. The adenosine receptor antagonist 8-(p-sulphophenyl)theophylline reduced the responses to adenosine and the hyperaemic responses to ATP and beta,gamma-mATP only. NO synthase inhibition (Nomega-nitro-L-arginine) did not significantly alter responses to the P2 receptor agonists. Subsequent cyclooxygenase inhibition (ibuprofen) reduced the ATP- and beta, gamma-mATP-induced increases in renal blood flow. All other responses remained unchanged. In the rabbit kidney in vivo, alpha, beta-mATP sensitive receptors mediate vasoconstriction. beta,gamma-mATP and ATP induce vasodilation at least partly through adenosine receptors. ATP induced renal vasodilatation is independent of NO and partly dependent on prostanoids in the bulk of the kidney, but not in the vasculature controlling medullary blood flow.

Computerized evaluation of the peripheral blood flow during maximal vasodilatation in humans using venous occlusion plethysmography

Forearm blood flow was studied with venous occlusion plethysmography after ischaemic exercise in 10 healthy volunteers and 10 hypertensive patients. The peak blood flow was calculated by three methods: the manual conventional graphic technique and by fitting of a tangent to the inflow curve with the help of a computer. In addition a computer-aided derivation of an exponential curve adapted to the initial part of the inflow curve was used for the calculation of the maximal blood flow. With the two tangential techniques the peak mean blood flow values did not differ significantly and were 58 ml min-1 100 ml-1 tissue while the exponential derivation procedure gave in both groups about 40% higher maximal flow values. The effect of venous occlusion on the linear velocity of the brachial arterial blood flow blood was studied with Ultrasound Doppler Flowmetry. The maximal flow velocity after ischaemic exercise decreased by about 18% during 50 mmHg venous occlusion; the influence of the venous stasis was least during the first heart beats after the onset of the venous occlusion. The effect of the venous stasis was similar but less pronounced in the hypertensive patients. In conclusion, forearm blood flow during maximal vasodilatation is reduced by venous occlusion and the best estimate of the flow is obtained from the earliest part of the venous occlusion inflow curve, as indicated by the use of the computer-aided exponential derivation technique.

Techniques for assessing the activity of topically applied retinoids

The retinoid drugs have profound effects on many aspects of skin biology. The exact activity profile depends on the particular analog and its route of administration. The topical retinoids used at present have marked therapeutic effects on epidermal cell production and desquamation. All- trans-retinoic acid (tretinoin) also acts on dermal connective tissue and microvasculature in a way that is less well established but may also be of therapeutic benefit. We investigated both tretinoin and motretinide in normal subjects and in patients with ichthyosis. The quantitative dansyl chloride test has been particularly useful in monitoring the desquamatory action of these topically applied retinoids. Both compounds resulted in enhanced rates of epidermopoiesis and desquamation. Marked changes in the cytochemical profile of the epidermis were also detected, changes that differed somewhat from the alterations induced by the systemic administration of etretinate. Changes in dermal structure and vascularization were monitored by A-scan ultrasound and laser Doppler flowmetry. However, only minor changes were recorded, probably because of the comparatively short application time. These newer techniques for investigating skin structure and function offer considerable opportunities for delineating the action of retinoids.

An implanted ultrasound doppler probe for microvascular monitoring: an experimental study

An experimental investigation is presented into the use of pulsed ultrasound Doppler flowmetry with a percutaneously implanted probe as a monitor of microvascular anastomotic patency. The method accurately indicated and distinguished between experimental arterial and venous occlusion in epigastric island flaps. In free flaps it had advantages over manipulative, intra-operative tests of anastomotic patency and was a reliable post-operative monitor of flap circulation in the experimental model. The technique appears to have great potential as a post-operative monitor for free flaps, including those without a visible surface.