There remain a small but sizable number of patients who develop restenosis after sirolimus-eluting stent (SES) implantation. However, the cause of SES restenosis has not been fully elucidated. The study population consisted of 52 patients with 69 lesions who underwent noninvasive coronary imaging by 64-slice multidetector computed tomography before SES deployment. Agatston calcium scores in target lesions were measured. All patients underwent follow-up coronary angiography at 8 months. Three coronary segments (in stent, proximal edge, and distal edge) were analyzed by quantitative coronary angiography. Agatston calcium score in target lesions averaged 214.7. Late lumen losses in the proximal edge, stent, and distal edge were 0.16 ± 0.45, 0.47 ± 0.58, and 0.07 ± 0.29 mm, respectively. Lesions with restenosis at follow-up showed a trend to produce higher preprocedural calcium scores (629) compared to those without restenosis (153, p = 0.08). There was a significant positive correlation between lesion calcium score and in-stent late lumen loss (r = 0.47, p <0.01). In conclusion, assessment of coronary calcium by multidetector computed tomography might be useful to predict outcomes after SES implantation.
The introduction of electron-beam computed tomography has allowed physicians to assess coronary calcium burden using the Agatston score. Some previous reports have shown that a high calcium score detected by electron-beam computed tomography induces high restenotic rates after plain balloon angioplasty or bare-metal stent implantation. Recently, multidetector computed tomography (MDCT) has been shown to permit visualization of coronary artery stenosis. In addition, coronary calcium score obtained by MDCT has been shown to be equivalent to that by electron-beam computed tomography. In the era of drug-eluting stents (DESs), calcium deposition may affect drug diffusion, penetration, and activity. Therefore, it is of paramount importance to investigate whether calcium influences the drug eluted from the stent to exert antirestenotic activity.
Methods
The study population consisted of consecutive 52 patients (69 lesions) with stable angina who underwent noninvasive coronary imaging by 64-slice MDCT (SOMATOM Sensation Cardiac 64, Siemens, Forchheim, Germany) as part of a routine diagnostic process before percutaneous coronary intervention (PCI) with sirolimus-eluting stents (SESs; Cypher, Johnson and Johnson, Miami Lakes, Florida) from February 2005 through December 2008. Follow-up coronary angiograms were obtained 8 months after SES implantation in all patients. All patients gave written informed consent. The study protocol was approved by the ethics committee at our institution.
Patients were scanned in the supine position from the level of the pulmonary arteries through the base of the heart. All patients received atenolol 50 mg orally 2 hours before scanning if the heart rate was >60 beats/min. Scanning parameters for 64-slice MDCT were 32- × 0.6-mm collimation, 330-ms rotation time, 3.8-mm/rotation table feed, 120-mV tube voltage, and effective 77 mA. The dataset was reconstructed with a small field of view tightly confined around the heart. Vessel wall calcifications were quantified on a separate workstation (Wizard, Siemens) based on the standard built-in algorithm using an Agatston score equivalent adapted for MDCT. All scans were analyzed by an experienced cardiologist who was blinded to information on follow-up coronary angiograms. The analyzer identified a target lesion that was covered by a SES on baseline coronary angiogram. Using reproducible landmarks such as a side branch, the same segment was determined on multidetector computed tomographic scans. The analyzer calculated Agatston calcium score in the target lesion, target vessel, and all coronary arteries.
All patients were advised to maintain life-long use of aspirin. Ticlopidine (200 mg/day) or clopidogrel (75 mg/day) was prescribed for ≥12 months. SESs were available in diameters of 2.5 to 3.5 mm and in lengths of 13 to 33 mm. Coronary angioplasty was performed using standard techniques. Dilatation before and after the procedure and rotational atherectomy were performed at the discretion of the operator. Operators were blinded to information from Agatston calcium scores. Use of a balloon shorter than the stent was recommended to avoid geographic miss, which is considered a technical predictive factor of SES restenosis. Coronary angiograms obtained at baseline, after the procedure, and at 8-month follow-up were analyzed using a computer-based system (CMS 6.0, Medis Medical Imaging Systems, Leiden, Netherlands). Three coronary segments (in-stent, proximal-edge, and distal-edge segments) were analyzed by quantitative coronary angiography. Proximal- and distal-edge segments included up to 5 mm on either side of the in-stent segment. Binary restenosis was defined as stenosis >50% of the reference diameter in the segment. Late lumen loss was defined as the difference between minimal lumen diameter at completion of the stenting procedure and that measured at follow-up.
Discrete variables are presented as numbers and percentages. Continuous variables are expressed as mean ± SD and were compared by Student’s t test. Linear regression was performed to assess the correlation between coronary calcium score and late lumen loss. All analyses were performed using SPSS 11.5 for Windows (SPSS, Inc., Chicago, Illinois). A p value <0.05 was considered statistically significant.
Results
This study population consisted of 52 patients with 69 lesions. Baseline clinical characteristics are listed in Table 1 . Mean age and body mass index were 67.2 ± 8.3 years and 24.3 ± 3.1 kg/m 2 , respectively. There were 2 patients (3.8%) with body mass index >30 kg/m 2 . Diabetic patients (57.7%) were more prevalent compared to previously reported registries of SES in daily clinical practice. Four patients (7.7%) were on hemodialysis. Baseline lesion and procedural characteristics are presented in Table 2 . Noninvasive coronary imaging by MDCT showed Agatston coronary calcium scores in the target lesion and target vessel of 214.7 ± 372.5 and 346.1 ± 607.3, respectively. Number of SESs implanted in the lesion averaged 1.6 ± 0.8. Direct stenting was performed in 8.7% of procedures. Usage of rotational atherectomy was 7.2%.
| Age (years) | 67.2 ± 8.3 |
| Men | 37 (71.2%) |
| Height (cm) | 161.7 ± 8.3 |
| Weight (kg) | 63.8 ± 11.5 |
| Body mass index | 24.3 ± 3.1 |
| Diabetes mellitus | 30 (57.7%) |
| Hypertension | 34 (65.4%) |
| Hyperlipidemia | 21 (40.4%) |
| Current smoker | 9 (17.3%) |
| Hemodialysis | 4 (7.7%) |
| Previous myocardial infarction | 1 (1.9%) |
| Previous percutaneous coronary intervention | 5 (9.6%) |
| Previous coronary artery bypass grafting | 0 |
| Use of aspirin | 35 (67.3%) |
| Use of statin | 25 (48.1%) |
| Target lesion artery | |
| Left anterior descending coronary artery | 35 (50.7%) |
| Right coronary artery | 22 (31.9%) |
| Left circumflex coronary artery | 12 (17.4%) |
| American College of Cardiology/American Herat Association classification | |
| A | 10 (14.5%) |
| B1 | 9 (13.0%) |
| B2 | 20 (29.0%) |
| C | 30 (43.5%) |
| Procedural characteristics | |
| Number of stents | 1.6 ± 0.8 |
| Maximum inflation pressure (atm) | 16.5 ± 2.1 |
| Direct stenting | 6 (8.7%) |
| Rotational atherectomy | 5 (7.2%) |
| Agatston coronary artery calcium score ⁎ | |
| In target lesion | 214.7 (8.7, 81.7, 261.0) |
| In target vessel | 346.1 (26.1, 119.9, 375.5) |
| In entire coronary tree | 915.2 (152.8, 505.9, 888.2) |
⁎ Data are expressed as mean (twenty-fifth percentile, median, seventy-fifth percentile).
There were no in-hospital adverse clinical events related to PCI. Clinical follow-up was obtained 8 months after the index procedure in all patients. Neither death nor myocardial infarction was documented in the study population. No stent thrombosis occurred; however, 6 patients (12%) underwent target lesion revascularization.
Angiographic follow-up was obtained at 8 months and available for all lesions. Table 3 presents serial quantitative coronary angiographic data. Mean lesion reference vessel diameter and lesion length were 2.68 ± 0.61 and 13.16 ± 8.01 mm, respectively. Postprocedure minimum lumen diameters in proximal-edge, in-stent, and distal-edge segments were 3.04 ± 0.66, 2.67 ± 0.50, and 2.30 ± 0.54 mm, respectively. Late lumen loss in proximal-edge, in-stent, and distal-edge segments averaged 0.16 ± 0.45, 0.47 ± 0.58, and 0.07 ± 0.29 mm, respectively. Angiographic in-segment binary restenotic rate was 13.0% (proximal-edge segment 1.4%, in-stent segment 13.0%, distal-edge segment 0%).
| Before procedure | |
| Reference diameter (mm) | 2.68 ± 0.61 |
| Minimal lumen diameter (mm) | 0.75 ± 0.51 |
| Diameter stenosis (%) | 74.8 ± 14.1 |
| Lesion length (mm) | 13.16 ± 8.01 |
| After procedure | |
| Minimal lumen diameter (mm) | |
| Proximal | 3.04 ± 0.66 |
| In stent | 2.67 ± 0.50 |
| Distal | 2.30 ± 0.54 |
| Diameter stenosis (%) | |
| Proximal | 12.3 ± 9.1 |
| In stent | 13.8 ± 7.1 |
| Distal | 15.3 ± 8.7 |
| 8-month follow-up | |
| Minimal lumen diameter (mm) | |
| Proximal | 2.87 ± 0.62 |
| In stent | 2.19 ± 0.75 |
| Distal | 2.23 ± 0.54 |
| Diameter stenosis (%) | |
| Proximal | 12.7 ± 12.4 |
| In stent | 25.3 ± 21.6 |
| Distal | 15.2 ± 11.6 |
| Late loss (mm) | |
| Proximal | 0.16 ± 0.45 |
| In stent | 0.47 ± 0.58 |
| Distal | 0.07 ± 0.29 |
| Binary restenosis | |
| Proximal | 1 (1.4%) |
| In stent | 9 (13.0%) |
| Distal | 0 |
| Total segment | 9 (13.0%) |
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