Ulf Kruger

A new method of intraoperative hydraulic impedance measurement provides valuable prognostic information about infrainguinal graft patency

PURPOSE Prognostic information about graft outcome, obtained by using a new method for intraoperative measurement of vascular impedance, was evaluated. METHODS Hydraulic impedance was measured in 136 infrainguinal bypass grafts that were entered into a multicenter trial. Seventy femoropopliteal and 66 femorocrural polytetrafluoroethylene (PTFE) grafts were used. The arterial impedance measurement involved a silicon bypass graft temporarily inserted between the proximal and distal anastomoses sites. A flowmeter probe and a pressure transducer were incorporated into the tube. The digitally stored waveforms were subjected to a fast Fourier transformation and both input (Z(x)) and characteristic (Z(0)) impedances, as well as phase relations, were computed and related to graft outcome after 3 years. RESULTS Significant prognostic information for both popliteal and crural grafts was provided by means of the phase angle of the first harmonic. Primary and secondary patency rates for popliteal bypasses were 45% +/- 1% and 65% +/- 2% for phase angles greater than -40 degrees (n = 57) and 37% +/- 1% and 40% +/- 1% for phase angles less than -40 degrees (n = 13, p(prim ) = not significant, p(sec) < 0.01). For crural grafts, the secondary patency rates were 49% +/- 1% and 61% +/- 2% for phase angles greater than -40 degrees (n = 53) and 15% +/- 1% and 0% for phase angles less than -40 degrees (n = 13, P <.01). All crural bypass grafts with phase angles less than -40 degrees occluded within 16 months. Steady flow resistance, as well as Z(x) and Z(0), failed to indicate a significant relation to graft prognosis. CONCLUSION This method provides reliable prognostic information regarding graft patency and opens hydraulic impedance measurement to clinical surgery. The phase lag between flow and pressure curves, as expressed by the phase angle of the first harmonic, provides significant prognostic information.

Treatment of Perigraft Seroma in Expanded Polytetrafluoroethylene Grafts by Sequential Fibrin Sealing of the Outer Graft Surface

BACKGROUND The recommended standard for treatment of perigraft seroma (PS) is the graft removal and the reconstruction using an alternative prosthesis. We assumed that a fibrin sealing of the outer surface of expanded polytetrafluoroethylene (ePTFE) grafts would prevent leakage and used this technique in the treatment and prevention of PS. METHODS Over a 10-year period, 24 patients were treated for PS after subcutaneous implantation of ePTFE grafts (14 arterial bypasses and 10 arteriovenous grafts). Affected graft segments were temporarily removed and underwent sequential fibrin sealing technique before reimplantation. In addition, an in vitro experiment was carried out to demonstrate the efficacy of fibrin sealing to prevent leakage through the ePTFE graft wall, after its hydrophobic barrier was destroyed by filling with saline solution under pressure. RESULTS A cure of PS was observed in 20 patients (84%) at a follow-up period of 37 ± 18 months. A later graft infection was not seen in any patient. The patency rate of reconstructed grafts appears to be unaffected. In the performed experiment we have demonstrated an elimination of leakage through the graft wall by the fibrin sealing technique. CONCLUSIONS Sequential fibrin sealing of the outer surface is an effective way to treat PS in ePTFE grafts. However, failure of this treatment cannot be precluded. Further studies are necessary that may provide further insights into the causes and best treatment of PS and the possibly important role of PS in the aneurysm enlargement after complete endovascular exclusion with ePTFE endografts.

Experimentelle Optimierung der Haemodynamik distaler termino-lateraler Bypass-Anastomosen, Entwicklung einer neuen Anastomosenform

Die subendotheliale Intimahyperplasie (IH) stellt eine der Hauptursachen fur die Ausbildung von Stenosen im Bereich von Anastomosen dar [1, 6]. Besondere Bedeutung hat die IH in termino-lateralen Anastomosen. Fur die Entstehung der IH sind neben anderen Faktoren, wie etwa dem sogenannten compliance mismatch, haemodynamische Ursachen wahrscheinlich, die wesentlich durch die Geometrie des Anastomosenbereiches bestimmt werden [2, 4, 5, 7]. Die klinische Bedeutung der IH wachst mit abnehmendem Gefasdurchmesser. So sind Spatverschlusse von femoro-infragenualen Bypassen, und besonders bei cruraler distaler Anastomose, am wahrscheinlichsten durch die Ausbildung der IH zu erklaren.

Lokale Hämodynamik und Energieverluste von cruralen Bypassanastomosen, in-vitro Untersuchung mittels Particle Image Velocimetry

Objective To study the local hemodynamics and energy losses of crural anastomoses using Particle Image Velocimetry.