Proliferative and lipid metabolism response to balloon angioplasty in canine renal arteries

Animal models of restenosis

Percutaneous transluminal coronary angioplasty is a widely used technique for recanalizing arteries that are occluded by atherosclerotic plaque, but its usefulness is limited by the occurrence ofrestenosis in a high proportion of patients. The development of new therapies for this currently intractable problem will be facilitated by the use of animal models of restenosis that are predictive of drug efficacy in humans. Two approaches for improving predictivity can be identified. In the first of these, the goal is to maximize the anatomical and procedural resemblance of the model to humans. The second approach seeks to maximize the pathophysiological and molecular biological resemblance of the model to humans. Tangible progress is being made toward the first goal, but lack of understanding of the basic biology of human restenosis is hampering progress toward the second.

A new model of endovascularly induced renal artery stenosis in normocholesterolemic versus hypercholesterolemic rabbits

RATIONALE AND OBJECTIVES

The authors determine the feasibility of creating renal artery stenosis by overdilatation and deendothelialization and compare the model in normocholesterolemic versus hypercholesterolemic rabbits.

METHODS

Thirty male New Zealand White rabbits were randomized into two groups: group A (n = 15) was fed a normal diet and group B (n = 15) was fed a cholesterol-rich diet 4 weeks before stenosis induction. An aortogram was performed, then the right renal artery was overdilated with an angioplasty balloon-catheter, and deendothelialized. After 6 weeks, groups A and B were compared by angiographic and pathologic study.

RESULTS

Comparison of group A versus group B showed that 12 arteries (80%) versus 6 (40%) were angiographically stenotic (P < 0.05); 14 (93%) versus 12 (80%) contained neointima (NS), 12 (80%) versus 3 (20%) showed medial disorganization (P < 0.01), and 9 (60%) versus 2 (13%) presented adventitial fibrosis (P < 0.01).

CONCLUSIONS

A new model of endovascularly induced renal artery stenosis has been developed in rabbits. Medial proliferation and adventitial fibrosis are more frequent in normocholesterolemic rabbits.

Experimental models of coronary artery restenosis

The study of potentially effective drug therapies and mechanical devices for the prevention of restenosis after percutaneous coronary revascularization has relied heavily on the use of experimental animal models. To date, greater than 50 experimental studies have been reported and have suggested that at least nine different classes of pharmacologic agents inhibit the intimal proliferative response to arterial injury. However, no pharmacologic intervention has yet been shown to reproducibly reduce the incidence of restenosis after coronary balloon angioplasty in humans. To identify the reasons for the apparent nonspecificity of the animal models and to determine which model should most reliably predict the efficacy of individual therapies in humans, the distinguishing characteristics of the experimental models were compared. Particular attention was paid to the size and morphologic structure of the treated artery, the susceptibility of the species to spontaneous and diet-induced arterial disease, the nature of the stimulus to intimal proliferation and several practical and logistic considerations. Finally, the reported efficacies of specific drug therapies in the respective animal models and in humans were compared. This review suggests that significant interspecies and occasionally intraspecies differences do exist among the respective animal models, particularly in the extent and composition of the neointimal thickening.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of serum lipid levels on restenosis after coronary angioplasty

Although the association of serum lipid levels with the risk of atherosclerosis is well-recognized, the relation between these levels and restenosis after coronary angioplasty is uncertain. This study examines 186 patients enrolled in a trial of fish oil for prevention of restenosis. Fasting lipid levels (cholesterol, high density lipoprotein (HDL) cholesterol and triglycerides) were measured before angioplasty, and in 90 patients repeated at 6-month follow-up. Fifty-nine patients (32%) developed clinical restenosis confirmed by angiography. Patients who went on to develop restenosis underwent multivessel angioplasty (p less than 0.05) and were more likely to be on lipid-lowering therapy at baseline (27 vs 13%; p less than 0.05). In addition, they had higher baseline cholesterol/HDL ratios (6.5 +/- 2.2 vs 5.9 +/- 2.0; p less than 0.05) and triglyceride levels (233 +/- 210 vs 183 +/- 112 mg/dl; p less than 0.05). Multiple logistic regression analysis confirmed cholesterol/HDL ratios at baseline (p = 0.021) and follow-up (p = 0.0008) to be independent predictors of risk for restenosis. Using these data, regression lines have been developed that predict risk of restenosis based on type of procedure and on lipid values. These results suggest that serum lipid levels may be associated with the risk of clinical restenosis after coronary angioplasty.

Use of the perforated balloon catheter to infuse marker substances into diseased coronary artery walls after experimental postmortem angioplasty

A perforated balloon catheter was used in human coronary arteries after postmortem angioplasty had been performed. The catheter used has a standard angioplasty balloon with a pattern of laser-produced holes, 25 microns in size, which generate streams of fluid under pressure. Studies of the routes by which marker substances enter diseased arterial tissue when infused by the perforated balloon after experimental angioplasty are described. A colored marker dye entered the new crevices and dissection planes created by the angioplasty, but did not extend greater than 2 cm either proximal or distal to the perfused segment. Horseradish peroxidase entered tissue not only from the lumen and adventitia as occurs with its infusion into normal tissue with the perforated balloon, but also extended from new crevices and dissection planes created by the angioplasty. Platelet aggregation, coagulation and cell proliferation, the likely causes of restenosis after angioplasty, originate in the sites of greatest tissue disruption and blood stasis. These postmortem studies suggest that active drugs are delivered to the arterial wall in a manner likely to be effective in preventing these events.