Author + information
- Runlin Gao, MD∗ ( and )
- Gregg W. Stone, MD
- ↵∗Fu Wai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences, 167 Beilishi Road, Beijing 100037, China
We thank Dr. Messori for his interest and comment on the low device thrombosis rates reported in the ABSORB China trial (1). The ABSORB China trial was rigorously conducted with 100% data monitoring and high (99%) clinical follow-up rates at 1 year. An independent clinical events committee adjudicated all events. We are thus confident the results are true. Stent thrombosis (ST) rates are often low in Asian populations. For example, 1-year ST with zotarolimus-eluting stents occurred in 2.3% of 1,119 patients in the global RESOLUTE AC (RESOLUTE All-Comers) trial, versus 0.5% of 1,750 patients in the RESOLUTE AC China Registry (2,3). The ABSORB China trial showed similarly low device thrombosis rates with both ABSORB and XIENCE stents. The 95% confidence intervals (CI) around the device thrombosis rates in ABSORB China trial were also wide, given that only 480 patients were studied.
The meta-analyses performed by Dr. Messori showed a risk difference of 0.67%, p = 0.03, but a pooled odds ratio (OR) of 2.21, p = 0.06. For completeness, we have added the EVERBIO II (Comparison of Everolimus- and Biolimus-Eluting Stents With Everolimus-Eluting Bioresorbable Vascular Scaffold Stents II) trial in a revised meta-analysis pooling 6 randomized controlled trials. The Mantel-Haenszel method, which gives the least biased results when including studies with groups with no events, resulted in a pooled OR of 2.22 (95% CI: 0.97 to 5.07; p = 0.06) (Figure 1). The exact method for absolute risk, appropriate for analyzing rare events, also showed statistical nonsignificance between ABSORB and XIENCE (0.72%; 95% CI: −0.04% to 1.24%; p = 0.06). Using only the ABSORB II, III, Japan, and China (N = 3,389) trials, which shared similar trial designs, patient eligibility criteria, and treatments, the relative risk was 2.09, p = 0.08 (4). Despite the large sample sizes involved, these meta-analyses still lack power to detect very small differences in low-frequency events such as device thrombosis.
Nonetheless, we concur that the collective data show a strong trend towards higher device thrombosis rates with ABSORB compared with XIENCE. Nonetheless, cardiac and all-cause mortality were not increased with bioresorbable vascular scaffolds (BVS), and measures of overall clinical effectiveness at 1-year were similar with BVS and XIENCE (4), the metallic stent with the lowest ST profile. Most ABSORB thrombosis events occurred early (0 to 30 days), suggesting underlying technical causes that may be mitigated by improved device sizing, better lesion preparation, intravascular imaging guidance, and the routine use of high-pressure post-dilation to achieve optimal device expansion and lesion coverage (4,5). Device thrombosis with ABSORB clustered in very small vessels (reference vessel diameter <2.25 mm by quantitative coronary angiography), which were not intended for the device. Moreover, unlike metallic stents, ABSORB promotes return of long-term physiological function and restoration of normal vascular adaptive responses. Other secondary benefits include “unjailing” side branches, avoiding the full metal jacket, treating in-stent restenosis without an addition metallic layer, and permitting noninvasive imaging follow-up. Finally, avoidance of a permanent implant is an attractive option for many patients and physicians for cultural, religious, or personal reasons. In summary, the safety and effectiveness profile of the ABSORB stent has been demonstrated at 1 year when used in appropriate patients and lesions, and the outcomes will improve over time with optimized operator technique, experience, and device iteration.
Please note: The ABSORB China trial was sponsored by Abbott Vascular. Dr. Gao has received research funding from Abbott Vascular. Dr. Stone is a consultant to Reva Corp.
- American College of Cardiology Foundation
- Gao R.,
- Yang Y.,
- Han Y.,
- et al.,
- for the ABSORB China Investigators
- ↵Stone GW. One-Year Patient-Level Pooled Meta-analysis From 4 ABSORB Trials in 3389 Randomized Patients. TCTMD website. Available at: http://www.tctmd.com/show.aspx?id=132166. Accessed November 17, 2015.