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Unsatisfactory late result of angiographically guided direct stenting is due to stent undersizing and underexpansion - observations derived from follow-up intravascular ultrasound examinations.

R. Gil, T. Pawłowski, R. Żurawski, S. Ciuka, A. Gziut, A. Krzywkowski
Catheterization Laboratory, Pomeranian Academy of Medicine, Szczecin, Poland


Background: Randomized trials exept costs and time savings did not prove superiority of direct stenting (DS) over stenting with predilatation. Intracoronary ultrasound (ICUS) is the best method to asses an influence of coronary intervention protocol on its late outcome.

The aim of our study was to elucidate possible causes of restenosis based on ICUS.

Methods: In this study 25 patients (20M, 5F; mean age 53 ± 8 y) with angiographically confirmed restenosis were examined with ICUS (mean follow-up 7,2 ± 3 months). In total we analysed 26 stents implanted with direct technique. ICUS examination was performed with 30 MHz (n=18) and 40 MHz (n=7) probes before proper dilatation. ICUS images were recorded during automatic pullback manouever at speed 0,5 mm/sec along the stented segment. Minimal vessel lumen, stent lumen, media to media diameter and total vessel area every 1 mm of the the stented segment was calculated. Aditionally, lumen and total vessel area, and also media to media diameter in proximal and distal reference segments were calculated. Stent undersizing was defined as ratio between nominal stent diameter and media to media diameter in target lesion less than 0,7. Stent underexpansion was defined as difference between total vessel area and minimal intrastent lumen bigger than 30%.

Results: Mean nominal size of implanted stent was 3,23 ± 0,67 mm, when media to media diameter at the target lesion was 4,05 ± 0,64mm. Average inflation pressure during DS procedure was 12,5 ± 3,44 atm. Redilatation was performed in 6 (24%) patients. Signs of stent undersizing and underexpansion were found in 62,5 % and in 50% patients, respectively. Measurements done during follow-up ICUS revealed that MUSIC trial criteria were reached only in 23%. Ultrasonic measurements from the stented and reference segments are shown in table below.





 
Proximal reference
Stented region
Distal reference


Lumen area (mm2)
9,55 ± 3,4
3,69 ± 1,67
9,11 ± 3,62


Stent diameter (mm)
 
3,27 ± 0,37
 


Stent area (mm2)/td>
 
6,31 ± 3,24
 


Total vessel diameter
4,43 ± 0,75
4,05 ± 0,64
4,39 ± 0,71


Total vessel area
15,57 ± 5,11
15,35 ± 6,41
14,4 ± 5,44





Conclusion: Our results have shown that poor late result of angiographically guided direct stenting is associated with high percentage of stent undersizing and underexpansion.








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© Copyright by Polskie Towarzystwo Kardiologiczne 2001