Intravascular Ultrasound-Guided PCI

Abstract & Commentary

Synopsis: IVUS guidance with PCI results in improved long-term clinical outcomes and cost-effectiveness.

Source: Gaster AL, et al. Heart. 2003;89:1043-1049.

It is well known that intravascular ultrasound (IVUS) evaluation of a coronary vessel adds considerable information to the "luminogram" produced by coronary angiography. During percutaneous coronary intervention (PCI), IVUS provides information about true reference vessel size and lesion composition that can improve device selection, as well as detailed information about adequacy of stent implantation, including stent underexpansion and malapposition. In addition, randomized trials such as CRUISE,1 have demonstrated lower clinically driven target vessel revascularization rates (TVR) in IVUS-guided PCI. Despite this, widespread use of IVUS guidance has not been readily embraced due to concerns about increased procedure duration and operator expertise. Much of the published literature on IVUS guidance has come from very high volume centers with exceptional expertise in image acquisition and interpretation and the use of IVUS guidance in the average cath lab may, in fact, be a different animal entirely. Another frequently cited concern is the added cost of IVUS guidance, approximately $650 per imaging catheter, which, interestingly, does not seem to have limited the use of drug-eluting stents (DES), currently priced around $2695, well over twice as costly as a comparable "bare" coronary stent. In fact, the biggest reason contributing to low rates of IVUS guidance in PCI practice today is simply that we’ve learned to get away with not using it, believing that, to quote Gaster and associates, "I do not need this extra information to perform a good coronary intervention."

Gaster et al from Odense University Hospital and the University of Southern Denmark report the results of a randomized, prospective study comparing 5-year major adverse clinical events (MACE) and cost outcomes after PCI with or without IVUS guidance. Patients with stable angina who were referred for scheduled PCI were randomized to receive PCI with IVUS guidance or with coronary angiographic guidance (CAG) only. The protocols for CAG and IVUS guidance are described in detail. Patients in both groups received documentary IVUS at baseline (preintervention) and after completion of the intervention. The interventional cardiologist was blinded to the IVUS information in the CAG patients. IVUS-guided stent deployment was optimized according to criteria adapted from the MUSIC study.2 Clinical outcomes included freedom from MACE (death, Q wave MI, need for repeat revascularization) and "coronary artery disease related" costs during the follow-up period.

Without giving specific numbers as to procedures performed, Gaster et al describe their study site as "a relatively low-volume center for PCI." One hundred and eight male patients undergoing PCI between May 1996 and October 1998 were included in the study. Equal numbers received CAG vs IVUS guidance. There were no significant differences between the groups with regard to clinical, demographic, or angiographic variables. Of note, 4 patients (3 in the IVUS group and 1 in the CAG group) did not undergo PCI based on reassessment of the target lesion. Median follow-up was 2.5 years (0.6-3.8, 25th and 75th percentiles). There was no difference in procedural success rate or duration and no difference in angiographic diameter stenosis or minimal lumen diameter (MLD) between the groups. Procedures in the IVUS-guided group demonstrated larger final balloon size and inflation pressure, larger acute gain, relative acute gain, MLD, and minimal lumen cross sectional area by IVUS criteria. Sixty-four percent of IVUS-guided procedures obtained optimal stent deployment by MUSIC criteria compared with 16% in the CAG-guided group (P < .01).

MACE rates were significantly lower in the IVUS-guided group (P = .04), with 78% remaining MACE-free compared with 59% in the CAG group. This difference was due primarily to lower rates of repeat PCI in the IVUS group (31% vs 61%; P = .004). Despite higher initial procedural costs, cumulative costs were found to be significantly lower in the IVUS group, less than half when compared to patients receiving CAG guidance.

Gaster et al concluded that IVUS guidance with PCI results in improved long-term clinical outcomes and cost-effectiveness. They stress that these results suggest that PCI, performed on a routine basis to optimize stent deployment, can substantially improve outcomes outside of the setting of a high-volume IVUS center. They acknowledge that the small sample size of this study precludes them from identifying any subgroup of patients more likely to benefit from IVUS guidance during PCI.

Comment by Sarah M. Vernon, MD

The era of the DES has arrived, and most interventional cardiologists in the United States have been quick to embrace the use of this new technology in their clinical practice. In response to the question, "In which coronary lesion do you elect to implant a DES?" many operators respond, "All of them." But in practice, this probably isn’t really the case. The most obvious reason for this is that the largest Cypher sirolimus-eluting Velocity stent currently available is 3.5 mm in diameter, but in addition, the release of the Cypher stent has not, perhaps, been as seamless as Cordis stockholders might have hoped. At our institution, like many others, the array of unexpired Cypher stents on the shelf at any given time has not always included the appropriate diameter and length for the patient on the table. So, even in October 2003, we still need to remember how to optimally implant both "bare" and drug-eluting coronary stents.

While it seems certain that DES will improve clinical outcomes overall, we can’t simply assume that restenosis and subacute thrombosis are now extinct. While published data regarding outcomes with widespread clinical use of DES in clinical practice are not yet available, it seems that subacute thrombosis rates after DES implantation have been higher than in pre-approval clinical trials. A recent letter to cath lab directors from Cordis stresses the importance of patient and lesion selection, adequate antiplatelet therapy, and proper technique for stent deployment. Just as for bare stent implantation, optimal DES implantation includes appropriate size selection, lesion predilitation, and complete stent apposition (which probably means high-pressure postdilitation).

This report from Gaster et al reminds us that even in the flurry of excitement surrounding the introduction of DES, we shouldn’t forget that we can also improve outcomes by not forgetting the basics, in this case, IVUS guidance for optimal sent implantation. The study is limited by its small size and low-risk patient population and is dated by the use of non-drug eluting stents. In addition, the 66% clinically driven repeat PCI rate in the CAG group is quite high, especially given this low-risk patient population. Still, the results are compelling and suggest that in the hands of an average interventional operator, IVUS guidance might substantially improve both clinical and economic outcomes for patients undergoing PCI.

Dr. Vernon, Assistant Professor of Medicine; Director, VAMC Cardiac Catheterization Laboratory, University of New Mexico Health Sciences Center, Albuquerque, NM, is on the Editorial Board of Clinical Cardiology Alert.

References

1. Fitzgerald PJ, et al. Circulation. 2000;102:523-530.

2. de Jaegre P, et al. Eur Heart J. 1998;19:1214-1223.