Stenting or balloon angioplasty of stenosed autologous saphenous vein grafts in pigs

Coronary artery brachytherapy

Coronary artery disease is the leading cause of mortality in the West with over 1.2 million angioplasties performed annually. Despite the introduction of stents, restenosis occurs in 30-40% of vessels, which until recently has only been treated effectively by coronary artery bypass surgery. Coronary artery brachytherapy appears to provide an alternative, less invasive remedy. The mechanisms of restenosis and how these are inhibited by radiation are described here. The practicalities of radiation delivery and the history of the development of intravascular radiation as an effective clinical tool are outlined. Finally, the pitfalls of the current technology and the areas in which future research must be targeted for the field to develop are discussed.

PTA and stenting of benign venous stenoses in the pelvis: long-term results

PURPOSE

To provide follow-up data on endovascular intervention for venous stenoses in the pelvis.

METHODS

Between 1985 and 1995, 35 patients presented with 42 stenoses of the pelvic veins after operative thrombectomy and creation of an arteriovenous fistula, combined with intraoperative venous angioscopy. All patients underwent angioplasty and, if unsuccessful, percutaneous insertion of an endovascular stent (n = 7).

RESULTS

Angioplasty with and without endovascular stenting was technically successful in 34 of 35 patients (97%). Average length of the stenoses was 20.6 mm (range 10-90 mm), average diameter before dilation 4.1 mm (range 2-6 mm), and average diameter after dilation 10.1 mm (range 5-18 mm). Intraoperative angioscopy showed pathologic findings (intimal laceration or residual thrombotic material) in 14 patients. After an average follow-up period of 4.13 years, 24 (69%) patients had patent veins. The difference in the primary patency rate between patients with angioscopically abnormal veins (6 of 14 patients, corresponding to a patency rate of 43%) and patients with angioscopically normal veins after thrombectomy (18 of 21 patients, corresponding to a patency rate of 86%) was statistically significant (p<0.01, log rank test).

CONCLUSIONS

Percutaneous transluminal angioplasty and/or stenting are good treatment modalities for pelvic vein stenosis following surgical thrombectomy. Angioscopically abnormal veins have a poorer long-term patency, regardless of the type of intervention.

The molecular and cellular biologic basis for the radiation treatment of benign proliferative diseases

Since its discovery, radiation has been used to treat numerous ailments, including many benign conditions. The most susceptible disorders have included keloids, heterotopic bone formation, and, most recently, vascular restenosis. These disorders are proliferative in nature and fall under the category of excessive wound healing or scar formation after trauma. In addition, radiation has been used for its immunosuppressive quality, eg, in organ transplantation to suppress graft rejection and in the treatment of autoimmune diseases. In this article, we have chosen keloids as an archetype for radiation use with benign conditions; the radiation inhibition of vascular restenosis will be used as a prototype to explore a paradigm for the molecular and cellular basis of radiation treatment for selected benign disorders. Vascular restenosis is currently one of the new frontiers of radiation therapy and offers opportunities to explore the role of inflammatory or immune cell responses in benign conditions that lead to excessive fibrogenesis and require treatment. The pathophysiology of surgical wound healing has not been avidly studied in the radiobiologic laboratory setting. However, the paradigm we propose for the effectiveness of radiation treatment for benign conditions is based on the model offered by Clark. He describes three phases of molecular and cellular events in which an inflammatory phase precedes the fibrogenic phase, occurs within hours of injury, and continues for weeks. We postulate that the radiosensitive targets within the vascular milieu are the monocyte/macrophages that would otherwise act as the trigger for the induced cytokine cascade, leading to the myofibroblast being recruited from a quiescent to a proliferative phase, resulting in fibrogenesis.

Foreign body contamination during stent implantation

The treatment of coronary artery disease using stents has become a widely accepted technique. However, the inadvertent co-implantation of contaminating factors with the stent has received little attention. We studied histological cross-sections of stented porcine coronary arteries and observed contamination of some vessels with surgical glove powder and textile fibres. The contaminating particles were associated with a foreign body reaction. Such a reaction could delay the wound-healing response of a stented vessel and thereby prolong the period in which subacute thrombosis could occur. It is also proposed that air contamination could affect the thrombogenicity of the stent. Appropriate measures should be followed to reduce the chance of contamination occurring.

Intravascular elasticity imaging using ultrasound: feasibility studies in phantoms

A technique is described for measuring the local hardness of the vessel wall and atheroma using intravascular ultrasound. Strain images were constructed using the relative local displacements, which are estimated from the time shifts between gated echo signals acquired at two levels of intravascular pressure. Time shifts were estimated using one-dimensional correlation with bandlimited interpolation around the peak. Tissue-mimicking phantoms with typical morphology and hardness topology of some atherosclerotic vessels were constructed. Hard and soft regions could be distinguished on the strain image, independently of their contrast in echogenicity. Thus, the potential of ultrasonic hardness imaging to provide information that may be unavailable from the echogram alone was demonstrated. The strain images of the homogeneous and layered phantoms showed some artifacts that need to be corrected for, to obtain images of the modulus of elasticity. For in vitro and in vivo experiments, the spatial resolution of the technique needs to be improved. Furthermore, two-dimensional correlation techniques may be necessary in case of nonradial expansion and an off-centre catheter position.