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CLINICAL STUDY: INTERVENTIONAL CARDIOLOGY

Vascular morphometric changes after radioactivestent implantation: a dose-response analysis

Paul Wexberg, MD, BM^*,*, Christian Kirisits, MScDSc, Mariann Gyöngyösi, MD, PhD^*, Michael Gottsauner-Wolf, MD^*, Meinhard Ploner, MSc, Boris Pokrajac, MD, Richard Pötter, MD and Dietmar Glogar, MD^*

^* Division of Cardiology, Department of Internal Medicine II, University of Vienna, Vienna, Austria
Department of Radiotherapy and Radiobiology and University of Vienna, Vienna, Austria
Division of Biometrics, Department of Medical Computer Sciences, University of Vienna, Vienna, Austria

Manuscript received July 10, 2001; revised manuscript received October 15, 2001, accepted November 1, 2001.

^* Reprint requests and correspondence: Dr. Paul Wexberg, Division of Cardiology, Department of Internal Medicine II, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
paul.wexberg{at}akh-wien.ac.at

OBJECTIVES: The goal of this study was to evaluate the dose-dependency of morphometric changes in the coronary arterial wall after radioactive stenting.

BACKGROUND: Radioactive stents have been found to reduce intrastent intimal hyperplasia (IIH) but lead to a characteristic type of restenosis occurring predominantly at the stent edges.

METHODS: Fifteen patients underwent intravascular ultrasound (IVUS) examination after implantation of a P-32 radioactive stent and at the six-month follow-up. The post-stent IVUS measurements on seven predefined locations of each lesion were subjected to a computer algorithm for the development of dose-volume histograms (DVH). Thus, we derived the radiation doses delivered to at least 10% and 90% of the adventitia (DV10, DV90). The IIH and vascular remodeling at follow-up were correlated with the doses in each segment.

RESULTS: The IIH was most pronounced at the stent edges and lowest in the stent-body, whereas we detected a significant expansive remodeling within the stent body. The delivered doses correlated with a decreased IIH (r = 0.52, p < 0.001 for DV10 and r = 0.62, p < 0.001 for DV90) and with expansive remodeling (r = 0.48, p = 0.009 for DV10 and r = 0.50, p = 0.006 for DV90). A DV10 >90 Gy or a DV90 >15 Gy reduced IIH and induced expansive remodeling. Plaque growth was not reduced by radioactive stents.

CONCLUSIONS: The DVH analysis reveals a dose-dependent increase of external elastic lamina area behind radioactive stents, whereas plaque growth is not reduced but inverted into an outward direction from the stent. A DV10 >90 Gy or a DV90 >15 Gy results in a beneficial long-term outcome after radioactive stenting.

Abbreviations and Acronyms   DV90   DVH   dose-volume histogram   DV10   the dose of radiation delivered to at least 10% of the adventitial volume   DV90   the dose of radiation delivered to at least 90% of the adventitial volume   EEL   external elastic lamina   IIH   intrastent intimal hyperplasia   IVUS   intravascular ultrasound   LA   lumen area   LDR   low-dose rate   PA   plaque area