[Ultrastructural characteristics of cellular reaction to experimental catheter-induced lesions of arterial blood vessels].

Unlabelled: After angioplasty, restenosis remains the major drawback of the procedure with an incidence of between 20-40%. It is a matter of concern whether the cellular alterations start immediately after directional atherectomy (DA) and if they are dependent on the depth of the lesion.

Method: Cellular alterations immediately after DA were investigated using peripheral atherectomy in normal vessels of 30 pigs (A. femoralis, A. carotis communis). DA was used to remove material. The arteries were assigned to two groups according to the depth of vessel injury. (Group 1: lesions to the intima; Group 2: lesions to the media.) 68 arteries with 41 intimal and 27 media lacerations were excised 4 to 24 hours later and processed for transmission electron microscopy, histology and immunohistochemistry.

Results: Immediately after DA, thrombus formation at the site of the altered segment was found. A transient infiltration of polymorphonuclear leukocytes (PMN) occurred, especially if the media was lacerated, followed by the transformation of contractile smooth muscle cells (SMC) into the synthetic subtype. A marked myoproliferative response was found in Group 2 whereas only moderate tissue hyperplasia was seen in Group 1.

Conclusion: The present data provides evidence that cellular alteration of the atherectomized vessel begins immediately after atherectomy. Subsequent to the initial temporary PMN infiltration, an activation of local SMC occurs at a very early stage. These effects and, in particular, a myoproliferative response were found lesions injured the internal elastic membrane, while only minor effects were seen when the lesion affected the intimal layer.