Implantation and recovery of temporary metallic stents in canine coronary arteries
NL Eigler,
MJ Khorsandi,
JS Forrester,
MC Fishbein,
and
F Litvack
Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048.
OBJECTIVES. The purpose of this study was to test the feasibility of implanting and retrieving a heat-activated recoverable temporary stent and to determine its effect on the angiographic, gross and histologic appearance of a normal coronary artery wall. BACKGROUND. Permanent coronary stenting is associated with a significant incidence of thrombosis, bleeding and vascular complications. These may be avoided by temporarily stenting for a period of hours to several days. METHODS. Seventy-eight stents constructed from the shape-memory nickel-titanium alloy nitinol were deployed by balloon expansion in the coronary arteries of 28 dogs and left in place for up to 6 months. Thirty minutes to 1 week after implantation, 70 stents were recovered by flushing the coronary arteries with 3 to 5 ml of 75 degrees C lactated Ringer solution, with collapse of the stent over a recovery catheter and subsequent withdrawal. RESULTS. All stents were successfully recovered and removed percutaneously. Mean vessel diameter after stenting was 12 +/- 6% (p < 0.05) greater than baseline diameter. Mean vessel diameter after stent removal remained enlarged (6 +/- 3%, p < 0.05). No angiographic or gross evidence of thrombosis, dissection, embolization, migration or spasm was associated with implantation or recovery. Microscopic examination revealed minor intimal injury in 40 segments (51%). Microscopic focal medial necrosis was associated with mural platelet-fibrin thrombus in 23 stented segments (29%) and media was interrupted in 7 (9%). CONCLUSIONS. This study demonstrates the feasibility of a new method of temporary stenting that uses the thermoelastic properties of nitinol to permit reliable recovery of the stent in normal canine coronary arteries.
