We describe a simple and robust alternative to ultrasonic methods for the measurement of pulse propagation velocity (PWV) which detects the passage of the diameter wave as it passes two sites a known distance apart. Two probes each containing an infra-red emitting diode and a phototransistor are placed on the skin near to the vessel of interest. The energy returning to each probe depends on the amount of blood the beam has passed through, and this varies as the vessel pulsates. The output from each probe is displayed in real time on a portable PC. PWV is estimated beat-by-beat from the delay between the start ofthe systolic upswing in the signals from the two sites.In order to verify that our device measures changes in arterial diameter its signals were compared to those obtained simultaneously from an echo tracking pulsed ultrasound system. Transit time measurements from the two devices on the radial and femoral arteries in 6 subjects agreed closely. Additional validation experiments on 2 1 subjects undergoing cardiac catheterization have shown that transcutaneous measurements of PWV using the infra-red device agree well with intra-arterial measurements obtained with a cannula and pressure transducer.We conclude that the optical technique for measuring PWV is a useful addition to the methods available for determining blood vessel elasticity. Its simplicity and ease of use make it suitable for large scale measurements in the 'field'. Three such studies are currently in progress.

The purpose of this study was to evaluate the efficacy and safety of a new hydrodynamic percutaneous thrombectomy catheter in the treatment of thrombosed hemodialysis fistulas and grafts. Twenty-two patients (median age: 47 years; range: 31-79 years) underwent mechanical thrombectomy for thrombosed hemodialysis fistulas or polytetrafluoroethylene (PTFE) grafts. In all cases, an Oasis hydrodynamic catheter was used. Five patients had native fistulas and 17 had PTFE grafts. Six patients required repeat procedures. All patients with native fistulas and 15 of the 17 with PTFE grafts also underwent angioplasty of the venous limb following the thrombectomy. Major outcome measures included technical success, clinical success, primary and secondary patency, and complication rates. Twenty-eight procedures were performed in total. The technical success rate was 100% and 90% and clinical success was 86% and 76% for native fistulas and grafts, respectively. The primary patency at 6 months was 50% and 59% for fistulas and grafts, respectively, and the secondary patency at 6 months was 75% and 70% for fistulas and grafts, respectively. Two patients died of unrelated causes during the follow-up period. The Oasis catheter is an effective mechanical device for the percutaneous treatment of thrombosed hemodialysis access. Our initial success rate showed that the technique is safe in the treatment of both native fistulas and grafts.

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Photodynamic therapy (PDT) has been proposed as a treatment for intimal hyperplasia (ll{). We studied the effect of PDT on the development of ill following endothelial injury, using the photosensitizer Metatetrahydroxyphenyl-chiorin (mTHPC) and 652 nm illumination. 9 minipigs were used in 3 groups of 3 . Pigs in the first group (balloon alone; BA) were anaesthetised and the lower 4 cm of abdominal aorta was denuded using a balloon catheter through the right femoral artery. In the second group (light alone, LA) the procedure was repeated, followed by illumination of the denuded area at an energy density of 20 Jcm2 using a transparent PDT catheter. In the third group pigs were sensitized with an intravenous injection of 0.3 mg/kg of m-THPC 4 hours prior to balloon injury and illumination (PDT Group). Animals were allowed to recover for 8 weeks before being killed and perfusion fixed with 1 0% formal saline. 5sections were cut from the treated segments and stained for elastin. Specimens were measured by a computerised morphometry system and the areas of the lumen (L), intima (I) and media (M) were measured. The degree of intimal hyperplasia was expressed as a) IIM; b) I/(I+M) and c) JJ(I+L) to take account of changes that could have occurred to the media and the overall diameter of the vessel. We found that when compared to BA controls, the lumenal area was decreased by 46% in LA group and increased by 44% in PDT group. The intimal area was increased 10 fold in the LA group and 14 fold in the PDT group. The changes in the medial areas were minimal. These results show that both light alone and PDT produced more intimal hyperplasia than balloon injury alone (P < 0.002 for both groups, Student's t test). When allowance is made for the large increase in lumenal area associated with PDT the degree of intimal hyperplasia I/(I+L) was significantly reduced in PDT treated vessels when compared to those treated with light and balloon alone in spite of the greater absolute area of the intima in the PDT group. We conclude that PDT under the above conditions not only failed to prevent IH, but was associated with a significant increase of intimal area. The increase in the dimensions of the PDT treated vessels reduced the detrimental effect of JR and improved the overall diameter of the lumen. 390 1SPIE Vol. 2395 0-8194-1742-4/95/$6.00 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/21/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx