Clinical Hemorheology and Microcirculation - Volume 48, issue 1-3

Authors: Lamby, P. | Prantl, L. | Fellner, C. | Geis, S. | Jung, E.M.

Article Type: Research Article

Abstract: Background: The immediate evaluation of microvascular tissue flaps with respect to microcirculation after transplantation is crucial for optimal monitoring and outcome. The purpose of our investigation was to evaluate the clinical value of contrast-enhanced ultrasound (CEUS) and contrast-enhanced MRI (ceMRI) for monitoring the integrity of tissue flaps in plastic surgery. Methods: To this end, we investigated 10 patients (47 ± 16 a) between postoperative day 7 and 14 who underwent flap surgery in order to cover tissue defects in various body regions. For CEUS we utilized the GE LOGIQ E9® equipped with a linear transducer (6–9 MHz). After application of …2.4 ml SonoVue®, the tissue perfusion was detected in Low MI-Technique (MI < 0.2). The perfusion curves were quantitatively analyzed using digital video sequences (QONTRAST®, Bracco, Italy) regarding peak % and relative blood flow (RBF). Furthermore, we investigated all tissue flaps using contrast-enhanced MRI (Magnetom Symphony TIM®, Siemens) with a 3D-VIBE sequence and a time resolution of 7s. Thus, the transplants were completely captured in all cases. As perfusion parameters, the positive enhancement integral (PEI) as well as the maximum intensity projection time (MIP-time) were collected. For comparison of both applications, all parameters were displayed in color-coded resolution and analyzed by three independent readers. Depending on the flap thickness, 1–3 regions of interest (ROI) were investigated. Each ROI measured 1 × 3 cm. Results: The subcutaneous ROI-1 showed a significantly lower rating regarding RBF in the ceMRI compared to CEUS (Mann-Whitney Rank-Sum test, p < 0.05). ROI-2 and -3 did not show any significant differences between the two applications. The frequency distribution showed good accordance in both modalities. Both imaging techniques detected 1 partial flap necrosis within the random area of cutaneous and subcutaneous layers, 1 hematoma as well as 1 insufficient perfusion over all tissue layers. After subsequent reoperation, graft loss could be prevented. Conclusion: At present, both technologies provide an optimal assessment of perfusion in cutaneous, subcutaneous and muscle tissue layers, whereby the detection of fatty tissue perfusion is currently more easily detected using CEUS compared to ceMRI. Show more

Keywords: Plastic surgery, tissue flaps, MRI, ceMRI, GD-DTPA, contrast enhanced ultrasound, CEUS, Sonovue, microcirculation

DOI: 10.3233/CH-2011-1405

Citation: Clinical Hemorheology and Microcirculation, vol. 48, no. 1-3, pp. 105-117, 2011

Authors: Ruef, P. | Gehm, J. | Gehm, L. | Pöschl, J.

Article Type: Research Article

Abstract: Red blood cells (RBC) of neonates have a shorter survival time and they are more susceptible to mechanical alterations than RBC of adults. Irreversible alteration of the membrane of RBC of preterm neonates, term neonates and adults due to tether formation was studied by means of a micropipette technique. Shear stress and forces were applied with this technique in an axisymmetric configuration and were calculated with an approximation method. The applied shear stress and forces that induced tether formation were lowest for RBC of preterm neonates (1.5 Pa, 1.8 pN), in between for RBC of neonates (1.7 Pa, 2.1 pN) …and highest for RBC in adults (1.9 Pa, 2.6 pN). Decreased mechanical stability of the membrane of neonatal RBC may in part cause the shorter life span, the greater tendency to endocytosis and the higher amount of irregularly shaped cells of neonatal RBC compared to RBC in adults. Show more

Keywords: Erythrocyte, preterm, RBC, neonate, plastic deformation, tether

DOI: 10.3233/CH-2011-1390

Citation: Clinical Hemorheology and Microcirculation, vol. 48, no. 1-3, pp. 119-128, 2011

Authors: Jung, F. | Mrowietz, C. | Hiebl, B. | Franke, R.P. | Pindur, G. | Sternitzky, R.

Article Type: Research Article

Abstract: One thousand two hundred and fifty-six subjects (apparently healthy subjects and patients with cardiovascular diseases) were registered in a prospective study including demographical and clinical data, rheological parameters (hematocrit, plasma viscosity, erythrocyte aggregation, erythrocyte deformability) as well as the erythrocyte velocity in human nailfold capillaries under resting and postischemic conditions. A multivariate regression analysis showed that under resting conditions there was no correlation between rheological parameters and erythrocyte velocity in capillaries. The blood flow regulation seemed to be so effective, that pathological changes of the blood fluidity showed no effect on the velocity of an erythrocyte passing the capillaries. During …vessel paralysis in the early phase of the postischemic hyperemia following a stasis of three minutes in the vasculature distal to a pressure cuff at the upper arm a very clear correlation between the plasma viscosity and the maximum postischemic erythrocyte velocity in ipsilateral cutaneous capillaries could be observed (p < 0.0001) while none of the other rheological parameters seemed to play a role. In a subgroup of diabetic patients the erythrocyte aggregation (measured during stasis) also correlated with the erythrocyte velocity (p = 0.0175) besides the plasma viscosity. This shows that a correlation of rheological parameters with the capillary perfusion could only be found during vessel paralysis. In of diabetic patients besides the plasma viscosity also the erythrocyte aggregation correlated with the mean capillary erythrocyte velocity. Theses results are in agreement with the hypothesis from Barras that plasma viscosity determines the perfusion of microvessels. Under certain conditions e.g. diabetic disorder, also the erythrocyte aggregation plays a role. Show more

Keywords: Rheological parameters, microcirculation, capillary microscopy

DOI: 10.3233/CH-2011-1392

Citation: Clinical Hemorheology and Microcirculation, vol. 48, no. 1-3, pp. 129-139, 2011

Authors: Clevert, D.A. | Sommer, W.H. | Helck, A. | Saam, T. | Reiser, M.

Article Type: Research Article

Abstract: Purpose: To evaluate neovascularisation within carotid atherosclerotic plaques with contrast enhanced ultrasound. Methods: We used contrast-enhanced ultrasound to examine 33 patients with carotid atherosclerotic plaques. Plaque size and echogenicity were analyzed and we correlated neovascularization within the plaques. Results: There were 41 atherosclerotic plaques, 27 plaques enhanced after the injection of a contrast agent. Among the group of enhancing plaques we found 8 soft- and 19 mixed plaques. The overall thickness ranging in enhanced plaques was from 1.8 to 4.6 mm. In all cases the contrast uptake in the plaques was later than in the carotid artery. Among the 14 …unenhanced atherosclerotic plaques, 4 plaques presented as hard plaques, three calcified plaques, two soft plaques and five presented as mixed plaques. The overall thickness ranging in unenhanced plaques was from 1.7 to 6 mm. Conclusion: Contrast-enhanced ultrasound allows the non invasive, dynamic evaluation of neovascularisation within carotid plaques. Show more

Keywords: Carotid artery, contrast enhanced ultrasound, plaque neovascularisation

DOI: 10.3233/CH-2011-1403

Citation: Clinical Hemorheology and Microcirculation, vol. 48, no. 1-3, pp. 141-148, 2011

Authors: Helck, A. | Sommer, W.H. | Wessely, M. | Notohamiprodjo, M. | Reiser, M. | Clevert, D.A.

Article Type: Research Article

Abstract: Purpose: To evaluate the benefit of CEUS (contrast enhanced ultrasound) regarding depiction of ischaemic lesions and AVFs (arterio venous fistula) in renal transplants compared to standard ultrasound (US) (grey-scale and color Doppler). Materials and methods: In this study 22 patients suspected of having acute vascular complication after renal transplantation were investigated using standard ultrasound (grey-scale US and color Doppler US) and CEUS, respectively. Validity of the respective US-techniques regarding depiction of ischaemic lesions and AVF was compared. Dynamic CTA (computed tomography angiography) served as the standard of reference. Results: In 10 renal transplants arterial embolism associated with kidney infarctions were …observed. Very good correlation to dynamic CTA was yielded using CEUS, whereas grey scale US and color Doppler US was limited in the accurate depiction of renal infarctions. Additionally CEUS was superior in displaying arteriovenous fistulas compared to standard US. Conclusion: CEUS as a fast and bedside available imaging modality not associated with dose exposure or renal toxicity facilitates improved detection of ischaemic lesions and AVFs compared to standard US and thus should be considered for short term follow up of renal transplants. Show more

DOI: 10.3233/CH-2011-1398

Citation: Clinical Hemorheology and Microcirculation, vol. 48, no. 1-3, pp. 149-160, 2011

Authors: Battig, Alexander | Hiebl, Bernhard | Feng, Yakai | Lendlein, Andreas | Behl, Marc

Article Type: Research Article

Abstract: Polydepsipeptides, alternating copolymers consisting of α-amino acids and α-hydroxy acids, are degradable polymers. Depsipeptide-based polymers of varied architectures can be synthesized via ring-opening polymerization of various morpholine-2,5-dione derivatives. Thermoplastic phase-segregated multiblock copolymers with poly(ε-caprolactone) (PCL) and poly(iso-butyl-morpholinedione) segments have been synthesized from the macrodiols and an aliphatic diisocyanate as a coupling agent. The respective multiblock copolymers showed shape-memory capabilities and good elastic properties, making them attractive candidates for potential application as biomaterials for controlled drug release systems, scaffolds to be applied in tissue engineering or biofunctional implants. Thus, these abilities cumulate to form multifunctional materials, combining degradability with shape-memory capability. …The advantages of depsipeptide-based multiblock copolymers compared to previously reported poly(ether)ester-derived biomaterials having shape-memory property may result from their different degradation products, as the resulting α-amino acids may act as a buffer for the hydroxy acids, thereby stabilizing pH values. In this context, we report on the biological evaluation of material samples in accordance with international standards (EN DIN ISO 10993-5 and 10993-12). Here, extracts of the substrates were exposed to a continuous fibroblast like cell line (L929) to study cytocompatibility of extractable substrates. Cell viability, morphology, LDH-release (as a parameter for the functional integrity of the cell membrane), activity of the mitochondrial dehydrogenases (as a parameter of the cell activity) and assembly of the actin- and vinculin cytoskeleton indicated no incompatibilities between the extracts and L929 cells. These results suggest that depsipeptide-based multiblock copolymers are promising candidates for soft, multifunctional implant materials. Show more

DOI: 10.3233/CH-2011-1391

Citation: Clinical Hemorheology and Microcirculation, vol. 48, no. 1-3, pp. 161-172, 2011

Authors: Haacke, N. | Unger, J.K. | Haidenhein, C. | Russ, M. | Hiebl, B. | Niehues, S.M.

Article Type: Research Article

Abstract: Objective: In a porcine, aortic graft model we found 5 animals to develop and survive unnoticed, complete infrarenal aortic occlusion and 2 pigs with an acute occlusion but rather unspecific clinical symptoms. We investigated the pigs' vascular system to classify the anatomic capabilities to compensate for an acute abdominal aortic occlusion. Design of study: Retrospective analysis of CT scans and clinical data to specify unexpected results in a case series of infrarenal occlusion in a porcine model. Setting: Collaborative study of experimental and clinical departments. Subjects: Fifteen healthy female minipigs. Interventions: All pigs underwent an infrarenal aortic graft intervention. Anesthesia …and perioperative management of the animals were preformed along the standard operating procedures of the local Department of Experimental Medicine. All animals received perioperative antibiotics, ASS, and carprofen for postoperative analgesia. Arterial pressure, heart rate, body temperature, and diuresis were monitored during surgery and therapeutic interventions. Main outcome measures: Contrast media based computed tomography (CT) with total body scans were performed at 1, 4, 10, 12 weeks after surgery. Comparable scans of cardiovascular healthy subjects (humans and pigs) and patients with a Leriche's syndrome were analyzed. Results: Neither acute (within the first 12 h after surgery) nor stepwise total aortic occlusion show unmistakable clinical signs. In pigs, the epigastric artery (EGA) – which is in connection with suprarenal lumbal arteries, subclavian and external iliac artery – is highly developed associated to the high number of mammary glands of about 7 on one side. In humans, the ratio of aortic to EGA-diameter is 1 : 0.15. In minipigs we found a ratio of 1 : 0.43 which changed during aortic occlusion resulting in a ratio of 1 : 0.58. Pigs with a slowly developing occlusion demonstrated an enlargement of the ureteric artery of about 210% completing a sufficient collateral system. Conclusion: While in the human Leriche's syndrome months are needed to enlarge the EGAs for a partial collateral support of an infrarenal aortic occlusion the pig's EGA is a naturally sufficient collateral system capable to cover immediately for an acute infrarenal aortic occlusion. Further collateral enlargement even provides a permanent, sufficient hind limb perfusion in pigs. As the sufficient collateral system probably reduce pressure and shear rates in the infrarenal aortic segment after cross clamping, pigs might have a higher predisposition to produce early thrombosis related graft occlusions tan humans. Show more

Keywords: Porcine model, abdominal aortic occlusion, paresis, rectal prolapse, Leriche syndrome, aortic surgery

DOI: 10.3233/CH-2011-1401

Citation: Clinical Hemorheology and Microcirculation, vol. 48, no. 1-3, pp. 173-185, 2011

Authors: Fellner, C. | Prantl, L. | Rennert, J. | Stroszczynski, C. | Jung, E.M.

Article Type: Research Article

Abstract: Postoperative monitoring of transplanted free flaps is an essential tool to reveal possible complications. The aim of this study was to compare the value of time-intensity-curve- (TIC-) analysis based on grey scale data of contrast-enhanced ultrasound (CEUS) and dynamic contrast-enhanced (DCE-) magnetic resonance imaging (MRI). Postoperative imaging was performed in 11 patients following free flap transplantation and TIC analysis was obtained in identical regions of interest (ROI) of CEUS and DCE MRI data. Microcirculation was assessed in superficial (0–1 cm), middle (1–2 cm), and deep (2–3 cm) ROIs in one or two different positions within the flap resulting in a …total of 46 ROIs evaluated (in very thin flaps only superficial and middle ROIs were assessed). For both imaging methods, mean signal increase was found to be significantly higher in ROIs of normally perfused flaps (n = 40) compared to ROIs with compromised microcirculation (n = 6). Although TIC analysis allows quantification of microcirculation in different regions of the flap, in this preliminary study no distinct threshold could be defined to differentiate flaps with normal and compromised microcirculation. Show more

Keywords: CEUS, MRI, TIC analysis, microcirculation, DCE, free flaps, plastic surgery

DOI: 10.3233/CH-2011-1399

Citation: Clinical Hemorheology and Microcirculation, vol. 48, no. 1-3, pp. 187-198, 2011

Authors: Clevert, D.-A. | Sommer, W.H. | Helck, A. | Reiser, M.

Article Type: Research Article

Abstract: Purpose: The aim of the study was to evaluate whether contrast enhanced ultrasound (CEUS) can improve the visualization of in-stent restenosis after carotid stenting of the internal carotid artery (ICA) in comparison to color-coded duplex sonography (CCDS) and power Doppler. Material and Methods: The study included the follow up of thirty patients after carotid artery stenting (CAS). Intrastenotic flow detection and lengths of in-stent restenosis were the main criteria. A high-end ultrasound machine (Siemens, ACUSON, Sequoia or S2000™) with a multi-frequency linear 9 MHz or 15 MHz transducer was used to carry out contrast-enhanced ultrasound with SonoVue®. In cases of …treatment of a high degree in-stent stenosis intra-arterial digital subtraction angiography (DSA) was used. Results: All patients were examined using all diagnostic ultrasound tools of the study. In five patients (17%) an in-stent restenosis of the internal carotid artery (ICA) was found. Two patients need a reintervention. The results show that the contrast enhanced ultrasound could improve the diagnostic assessment capabilities in comparison to CCDS and power Doppler for patients with in-stent restenosis after carotid stenting of the ICA. Conclusion: Contrast enhanced ultrasound is a reliable method for the evaluation of in-stent restenosis after carotid stenting of the ICA. CEUS provides a reduction in intrastenotic flow artefacts, resulting in better visualisation and detection of the complete length of the stenosis in comparison with CCDS and power Doppler. In order to elucidate hemodynamic changes, additional Doppler examinations are still necessary. Show more

Keywords: Carotid artery, contrast enhanced ultrasound, in-stent restenosis

DOI: 10.3233/CH-2011-1400

Citation: Clinical Hemorheology and Microcirculation, vol. 48, no. 1-3, pp. 199-208, 2011