J. Heckenkamp

Pulsatility index determination by flowmeter measurement: a new indicator for vascular resistance?

Background: Peripheral resistance (R) is measured by flow (Q) and a pressure difference (P1-P2), where R equals (P1-P2)/Q. The pulsatility index (PI) has been used to assess peripheral vascular resistance by measuring flow velocities. Alternatively, PI can be expressed by the ratio of the flow volume amplitude and mean flow volume which both are quantified by a flowmeter. While reflected flow due to a distally located stenosis will considerably influence PI, this parameter theoretically could provide a good estimation of resistance. The appropriateness of this presumption has not been evaluated in this setting though, why the correlation of PI in flow recordings was examined by comparing PI with the true R using the stenosis of the internal carotid artery (ICA) as a clinical model. Methods: The volume flow in the ICA was measured by a transit-time flowmeter in 400 patients undergoing carotid endarteriectomy. The pressure in the common carotid artery (CCA) proximal to and in the ICA distal to the stenosis was determined by direct puncture allowing the calculation of a pressure gradient (PG) and R in analogy to Ohm’s law. R and PI were then correlated using Spearman’s correlation. Results: The blood flow in the ICA ranged from 2 to 478 ml/min with a median value of 165. The median PG was 14 mm Hg (0 to 88). Median R was 0.08 mm Hg × min / ml (0–26.5). PI varied between 0.8 and 114.1 with a mean of 1.9. Since a concentration of R and PI values in the lower ranges was observed, a logarithmic transformation was performed. Log PI showed only weak correlation to log R (r = 0.426, p < 0.0001). Conclusions: Log PI was intermediately correlated to log R in carotid artery stenosis, with a low discriminating power in the lower ranges due to the close distribution of measurements. Further studies are required to clarify the role of PI in hemodynamic questions and its general usefulness in other fields of vascular surgery like in peripheral bypass surgery.

Occupation-related vascular disorders of the upper extremity : Two case reports

Hypothenar hammer (HH) syndrome and vibration-induced white finger (VWF) syndrome are the main occupation-related vascular diseases of the upper extremity. The clinical presentation is similar to that of Raynaud’s phenomenon. The characteristic history will lead to the appropriate diagnosis being confirmed by angiographic features in HH and by functional tests in VWF. While in HH the underlying cause, which is mostly thought to be an aneurysm of the ulnar artery, might be cured surgically, in VWF only medical treatment offers relief from the symptoms. The knowledge of these entities is necessary to suspect such disorders so that further exposure to risk factors like repetitive hypothenar trauma or work with vibrating hand-held tools can be avoided, which is of great importance for the overall prognosis of these patients.

Materialwahl bei Prothesenshunt: evidence based?

ZusammenfassungDie Zahl der terminal niereninsuffizienten dialysepflichtigen Patienten steigt. Diese Patienten sind auf einen dauerhaften Zugang zum Gefäßsystem angewiesen. Trotz Überlegenheit der nativen arteriovenösen (AV-) Fisteln ist dieser autologe Zugang nicht immer verfügbar. Als Ersatz wird weltweit PTFE zur Prothesenshuntanlage bevorzugt. Mittels einer umfassenden Literaturrecherche soll evaluiert werden, inwieweit diese bevorzugte Verwendung von PTFE den Kriterien der “evidence based medicine” entspricht. Es waren lediglich 6 Publikationen über prospektiv randomisierte Studien zu finden. Diese umfassen zudem nur kleine Patientenkollektive (minimal 17 vs. 18, maximal 64 vs. 65). Unter Berücksichtigung der Kriterien der “evidence based medicine” ist den genannten Publikationen die Wertigkeit der Kategorie II zuzuordnen bzw. aus den Ergebnisse lässt sich eine Therapieempfehlung Grad B für die Verwendung von PTFE als Shuntmaterial ableiten.AbstractThe population of patients with end-stage renal disease (ESRD) is increasing. These patients require a durable vascular access. The creation of autologous AV fistulas remains the preferred procedure. However, autologous veins may be unavailable or unsuitable. In these patients, the use of PTFE prostheses as a substitute is favoured worldwide.By means of an extensive literature search this study was designed to evaluate if the use of PTFE meets the criteria of evidence based medicine.Six prospective randomized trials were retrieved. The number of patients in these publications ranged from 17 vs. 18 patients to 64 vs. 65 patients. Considering the criteria of evidence based medicine the published data reached a level of evidence II and therefore only allow therapeutically recommendations grade B to the use of PTFE prostheses.

Vaskuläre photodynamische Therapie reduziert die Entwicklung von Intimahyperplasie an ePTFE Bypässen im Großtiermodell

Background: Vascular bypass surgery has a failing frequency of 30% during the first year, mainly due to intimal hyperplasia (IH). This negative effect is most pronounced in artificial grafts. Photodynamic therapy (PDT) is a technique in which laser light activates photosensitizer dyes to produce local free-radicals resulting in an eradication of cells in the vascular wall. The aim of this study was to determine the effectiveness of PDT to reduce IH in a preclinical porcine PTFE bypass model. Material and Methods: Seven pigs were used. PTFE grafts were bilaterally placed into the circulation as bypasses from the common to the external iliac arteries. The right sides served as controls (C). Before implantation of the left grafts, the arterial connecting sites of the left distal anastomoses were PDT-treated. The left external iliac arteries were pressurized at 180 mmHg for 5 minutes with the photosensitizer Methylene Blue (330µg/ml), and thereafter endoluminally irradiated with laser light (γ = 660 nm, 100 mW/cm2, 150 J/cm2). After 4 weeks the specimens were formalin fixed and embedded in paraffin. Cross sections through the midportions of the distal end-to-side anastomoses and through the distal grafts were used for histology and morphometric evaluation (n = 7). Results: No systemic side effects and no graft occlusions were noted. PDT-treated anastomoses showed reduced IH in the mid-portions of the anastomoses (Area of IH: µm2/µm graft: C: 6970 ± 1536, PDT: 2734 ± 2560; P < 0.005) as well as in the grafts (C: 5391 +- 4031, PDT: 777 ± 1331; P < 0.02). Conclusions: Adjuvant PDT, performed in an endovascular fashion, was a safe method to reduce prosthetic graftstenosis in a preclinical setting. This study underscores the clinical potential of PDT to inhibit the development of clinical bypass graftstenosis.

Hemmung invasiver vaskulärer Zellmigration durch ionisierende Strahlung

Background: Ionizing irradiation is a successful approach to inhibit vascular restenosis. The specific mechanisms by which it modulates the post-interventional vascular injury response have not been fully elucidated. This study investigates how γ-irradiation (γ-RT) affects vascular cell invasive migration, a key factor in the development of restenosis. Methods: Smooth muscle cell (SMC) migration (calibrated microscopy) into a three-dimensional collagen matrix and the release of metalloproteinases (ELISA, zymography) were quantitated after γ-RT (20 Gy). The γ-RT effects on fibronectin bound TGF-β were elucidated by quantitating the proliferative activity of untreated SMCs, seeded on the irradiated TGF-β ([3H]-thymidine incorporation). Molecular weight changes in the collagen matrix after γ-RT were also assessed (SDS-PAGE). Results: γ-RT of SMCs decreased invasive migration by 63% at 7 days (p<0.0001) without significantly affecting the release of metalloproteinases. γ-RT of TGF-β (21%; p<0.05) did significantly decrease SMC proliferation but there was no molecular weight structure change in the collagen matrix after γ-RT. Conclusions: These data indicate that clinically relevant doses of γ-RT reduce invasive cellular migration and alter the functional activity of matrix components. Its inhibition of clinical restenosis may not only result from cellular growth arrest, but also from the reduction of invasive migration and interference with bioregulatory matrix molecules.