Stent thrombosis and restenosis remain drawbacks of drug-eluting stents in patients with acute myocardial infarction (AMI). Intravascular ultrasound (IVUS) guidance for stent deployment helps optimize its results in stable patients. The aim of this study was to examine the utility of routine IVUS guidance in patients with AMI undergoing percutaneous coronary intervention (PCI). Employing data from Korea Acute Myocardial Infarction Registry (KAMIR), we analyzed 14,329 patients with AMI from April 2006 through September 2010. Patients with cardiogenic shock and rescue PCI after thrombolysis were excluded. Clinical outcomes of 2,127 patients who underwent IVUS-guided PCI were compared to those of 8,235 patients who did not. Mean age was 63.6 ± 13.5 years and 72.3% were men. Patients undergoing IVUS-guided PCI were younger, more often men, more hyperlipemic, and had increased body mass index and left ventricular ejection fraction. Number of treated vessels and stents used, stent length, and stent diameter were increased in the IVUS-guided group. Multivessel involvement was less frequent and American College of Cardiology/American Heart Association type C lesion was more frequent in the IVUS-guided group. Drug-eluting stents were more frequently used compared to bare-metal stents in the IVUS group. There was no significant relation of stent thrombosis between the 2 groups. Twelve-month all-cause death was lower in the IVUS group. After multivariate analysis and propensity score adjustment, IVUS guidance was not an independent predictor for 12-month all-cause death (hazard ratio 0.212, 0.026 to 1.73, p = 0.148). In conclusion, this study does not support routine use of IVUS guidance for stent deployment in patients who present with AMI and undergo PCI.
Drug-eluting stents (DESs) have revolutionized the treatment strategy for coronary artery disease. However, stent thrombosis and in-stent restenosis after DES implantation associated with a high mortality rate occur at a disturbing frequency. Intravascular ultrasound (IVUS) images show the coronary artery wall, plaque structure, and plaque composition. Incomplete stent expansion, procedural and acquired stent malapposition, and smaller minimum stent area after stent implantation measured by IVUS have been reported to correlate with restenosis and stent thrombosis. Thus, information about the coronary artery and implanted stents can be of great use in assessing coronary intervention strategies. In addition, IVUS provides the operator with more correct information on the real vessel size, which facilitates device selection. The approach of IVUS guidance in the setting of elective percutaneous coronary intervention (PCI) has previously been investigated, generally with a much shorter period of follow-up. These studies showed a significant decrease in the rate of restenosis and target vessel revascularization and decreased rates of dissection and ischemic complications in the IVUS-guided group. There are sparse data available on the clinical impact of IVUS-guided PCI in the setting of acute myocardial infarction (AMI) and its use remains a matter of controversy as shown by previous studies. This study examined the impact of IVUS guidance on clinical outcomes in this patient population.
Methods
This retrospective study was carried out in the Heart Center of Chonnam National University Hospital, Gwangju, Korea. Written consent for the procedures was obtained from all patients and permission to carry out the study was obtained from the hospital authorities (institutional review board number 05–49).
The Korea Acute Myocardial Infarction Registry (KAMIR) is a prospective, multicenter, observational registry designed to examine current epidemiology in hospital management and outcome of patients with AMI in Korea. The registry included 52 community and university hospitals and 14,329 patients were enrolled in this registry with 1-year clinical follow-up.
In total 14,329 patients with AMI (ST-elevation MI and non–ST-elevation MI) from April 2006 through September 2010 were assessed and followed for 12 month after PCI (follow-up rate 74.4%). We excluded patients with cardiogenic shock (n = 661), rescue PCI after intravenous thrombolysis (n = 624), and other missing data (n = 2,682); therefore 10,362 patients were included in this study. Clinical outcomes of 2,127 patients who underwent IVUS-guided PCI were compared to those of 8,235 patients who did not.
Hypertension was defined as systolic blood pressure >140 mm Hg and/or diastolic blood pressure >90 mm Hg at rest at repeated measurements or treatment with antihypertensive medications. Hyperlipidemia was defined as a total cholesterol level >200 mg/dl or treatment with a lipid-lowering agent. Coronary artery disease was defined as history of MI, revascularization procedure, or obstructive coronary artery disease. A final diagnosis of AMI was made according to European Society of Cardiology/American College of Cardiology diagnostic criteria of AMI. Patients’ medical documents were used to note demographic data, clinical characteristics, and relevant laboratory results. Peripheral blood samples were obtained using direct venipuncture on admission. Absolute creatine kinase-MB levels were determined by radioimmunoassay (Dade Behring, Inc., Miami, Florida). Cardiac specific troponin I levels were measured by a paramagnetic-particle chemiluminescent immunoenzymatic assay (Beckham, Coulter, Inc., Fullerton, California). Twelve-hour fasting serum levels of total cholesterol, triglyceride, and low- and high-density lipoprotein cholesterol were measured by standard enzymatic methods. Blood samples for high-sensitivity C-reactive protein were obtained on admission and analyzed turbidimetrically with sheep antibodies against human C-reactive protein; this has been validated against the Dade Behring method.
Two-dimensional echocardiography was performed in all patients and left ventricular ejection fraction was assessed. PCI was performed using a standard technique by the femoral route. Structure on coronary angiogram was classified according to criteria of American College of Cardiology/American Heart Association. Degree of coronary flow was classified by Thrombolysis In Myocardial Infarction flow. Presence of left main coronary artery stenosis was defined as luminal stenosis ≥50%. A left main coronary artery complex lesion was defined as significant stenosis of the left main trunk artery with the presence of other epicardial coronary artery stenoses. Multivessel disease was defined as the presence of a lesion with >50% diameter stenosis in a noninfarct-related coronary artery. Mostly culprit lesions and in some cases secondary lesions were also treated. Successful PCI was defined as Thrombolysis In Myocardial Infarction grade 3 flow with residual stenosis ≤50% in the infarct-related artery. In-hospital complications included atrioventricular block, bradycardia, ventricular tachycardia/ventricular fibrillation, atrial fibrillation, cardiogenic shock, no reflow, dissection, acute renal failure, metabolic acidosis/lactic acidosis, cerebrovascular event, or infection/sepsis. All patients were administered loading doses of aspirin 325 mg and clopidogrel 300 to 600 mg before PCI. Anticoagulation during PCI was performed according to routine practices of each hospital. After the procedure, aspirin 100 to 200 mg (1 time/day) was prescribed indefinitely. Clopidogrel was prescribed continuously for 1 year.
IVUS was performed before and/or after PCI using a standard technique at the discretion of the operator. IVUS was performed after intracoronary administration of nitroglycerin 200 μg using a 20-MHz, 2.9Fr IVUS imaging catheter (Eagle Eye, Volcano Corp., Rancho Cordova, California; or Atlantis S, Boston Scientific Corp., SCIMED, Minneapolis, Minnesota). Motorized pullbacks were performed at a speed of 0.5 or 1.0 mm/s, starting from a point ≥10 mm distal to the study lesion up to the ostium of the study vessel. In the IVUS-guided group, choice of the initial balloon size was based on the mean of the distal and proximal reference lumen diameters, which were determined from the cross-sectional area using the mathematical formula area = π × 1/2 diameter squared. This was to avoid the error of measuring a diameter of an irregular lumen. Reference segments were chosen as the healthiest segments proximal and distal to the lesion (maximum distance 10 mm from target lesion site without major side branches). Response to IVUS findings was at the discretion of the operator.
The primary end point of this study was a major adverse cardiac event at 12-month clinical follow-up. A major adverse cardiac event was defined as the composite of all-cause death, nonfatal MI, and target vessel revascularization. All-cause death included cardiac and noncardiac deaths. Nonfatal MI was defined as the presence of clinical symptoms, electrocardiographic change, or abnormal imaging findings of MI combined with an increase in creatine kinase-MB fraction or troponin T/I higher than the ninety-ninth percentile of the upper normal limit that was not related to an interventional procedure. Target vessel revascularization was defined as clinically driven repeat revascularization of a lesion in the same epicardial vessel treated at the index procedure at 12-month follow-up.
SPSS 17.0 for Windows (SPSS, Inc., Chicago, Illinois) was used for all analysis. Continuous variables were presented as mean ± SD; comparisons were conducted by Student’s t test. Discrete variables were presented as percentages and frequencies; comparisons were conducted by chi-square statistics or Fisher’s exact test as appropriate. All statistical tests were 2-tailed. A p value <0.05 was considered statistically significant. Propensity score matching was performed to decrease treatment selection bias and potential confounding in an observational study and to adjust significant differences in characteristics of patients or lesions. It was performed with regard to use of IVUS-guided PCI (pretreatment variables entered into the model included age, gender, body mass index, left ventricular ejection fraction, hyperlipidemia history, glucose, triglyceride, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, high-sensitivity C-reactive protein, target coronary arteries [left anterior descending, right, left circumflex, and left main coronary arteries], multivessel involvement, American College of Cardiology/American Heart Association lesion types C and B, and diameter stenosis of target coronary artery before PCI). A proportional Cox multivariate model was performed including IVUS use, propensity score, and postprocedure risk covariates that showed a p value <0.05 in univariate analysis for end points. Covariates included number of treated vessels, total number of stents, type of stents used (bare-metal stent/DES), stent length, stent diameter, and use of glycoprotein IIb/IIIa inhibitor, thrombus aspiration device, statin, clopidogrel, cilostazol, and calcium channel blocker. Results are presented as adjusted hazard ratios with 95% confidence intervals and p values. In our study population, because the number of 12-month all-cause death was relatively low (1.0% in IVUS group and 2.0% in non-IVUS group), we had to limit the number of variables in the Cox model.
Results
Mean age was 63.6 ± 13.5 years and 72.3% of patients were men (n = 7,478). Patients undergoing IVUS-guided PCI were younger, more often men, more hyperlipemic, and had increased body mass index and left ventricular ejection fraction. The IVUS group showed lower levels of serum glucose and high-sensitivity C-reactive protein. Use of statin, clopidogrel, cilostazol, and calcium channel blocker at discharge was higher in the IVUS group. There was no other difference between the 2 groups in baseline clinical and laboratory characteristics ( Table 1 ). Angiographic findings and procedural results are presented in Table 2 . Target coronary arteries (left anterior descending and left main coronary arteries) showed greater involvement and the left circumflex coronary artery, right coronary artery, and multivessel involvement were less frequent in the IVUS-guided group. American College of Cardiology/American Heart Association type C lesion was more frequently observed in the IVUS-guided group, whereas types B and A were less frequent. Number of treated vessels and stents used, stent length, and stent diameter were increased in the IVUS-guided group. DESs were more frequently used compared to bare-metal stents in the IVUS group. Preprocedure percent diameter stenosis of the target coronary artery was larger in the IVUS group. Use of a thrombus aspiration device was more frequently observed, whereas glycoprotein IIb/IIIa inhibitor use was less frequent, in the IVUS group. Stent thrombosis, in-hospital complications, and procedure success rates were almost similar between the 2 groups. Major adverse cardiac events were almost similar in the 2 groups ( Table 3 ). Twelve-month all-cause death was lower and nonfatal MI ( Figure 1 ) was higher in the IVUS group.
| Variables | IVUS Group | Non-IVUS Group | p Value |
|---|---|---|---|
| (n = 2,127) | (n = 8,235) | ||
| Age (years) | 61.29 ± 12.66 | 63.78 ± 13.34 | <0.001 |
| Men | 1,606 (75.6%) | 5,872 (71.3%) | <0.001 |
| Body mass index (kg/m 2 ) | 22.76 ± 6.70 | 21.19 ± 8.35 | <0.001 |
| Systolic blood pressure (mm Hg) | 129.26 ± 26.50 | 130.12 ± 38.55 | 0.337 |
| Heart rate (beats/min) | 76.66 ± 18.54 | 77.43 ± 23.31 | 0.16 |
| Left ventricular ejection fraction (%) | 54.09 ± 27.18 | 53.01 ± 17.95 | 0.035 |
| Killip class >I | 568 (26.7%) | 2,125 (25.8%) | 0.399 |
| Smoker | 1,274 (59.9%) | 4,739 (57.5%) | 0.05 |
| Diabetes mellitus | 551 (25.9%) | 2,203 (26.8%) | 0.431 |
| Hypertension | 1,020 (48.0%) | 4,120 (50.0%) | 0.088 |
| Hyperlipidemia | 299 (14.1%) | 952 (11.6%) | 0.002 |
| Coronary artery disease | 271 (12.7%) | 1,110 (13.5%) | 0.372 |
| Clinical presentation | |||
| ST-segment elevation myocardial infarction | 1,244 (58.5%) | 4,854 (58.9%) | 0.676 |
| Laboratory characteristics | |||
| Glucose (mg/dl) | 164.24 ± 73.77 | 169.01 ± 77.56 | 0.012 |
| Creatinine (mg/dl) | 1.17 ± 1.87 | 1.17 ± 1.91 | 0.973 |
| Total cholesterol (mg/dl) | 184.2 ± 44.8 | 185.2 ± 45.1 | 0.348 |
| Triglyceride (mg/dl) | 127.2 ± 104.5 | 135.0 ± 103.9 | 0.003 |
| Low-density lipoprotein cholesterol (mg/dl) | 115.1 ± 38.9 | 117.6 ± 38.7 | 0.012 |
| High-density lipoprotein cholesterol (mg/dl) | 44.6 ± 17.7 | 43.7 ± 15.2 | 0.024 |
| Hemoglobin A1C (%) | 6.68 ± 2.94 | 6.63 ± 1.91 | 0.493 |
| High-sensitivity C-reactive protein (mg/dl) | 0.26 ± 0.44 | 0.33 ± 0.47 | <0.001 |
| Creatine kinase-MB (U/L) | 130.14 ± 230.50 | 130.67 ± 223.32 | 0.924 |
| Troponin I (ng/ml) | 40.29 ± 102.56 | 44.86 ± 129.71 | 0.158 |
| N-terminal probrain natriuretic peptide (pg/ml) | 2,470.2 ± 5,516.8 | 2,837.1 ± 6,345.8 | 0.06 |
| Medications at discharge | |||
| Aspirin | 1,923 (90.4%) | 7,419 (90.1%) | 0.661 |
| Statin | 1,519 (71.4%) | 5,692 (69.1%) | 0.040 |
| Fibrate | 12 (0.6%) | 44 (0.5%) | 0.867 |
| Clopidogrel | 1,907 (89.7%) | 7,288 (88.5%) | 0.133 |
| Cilostazol | 585 (27.5%) | 1,990 (24.2%) | 0.001 |
| Calcium channel blocker | 168 (7.9%) | 538 (6.5%) | 0.026 |
| β Blocker | 1,605 (75.5%) | 6,163 (74.8%) | 0.557 |
| Diuretics | 368 (17.3%) | 1,388 (16.9%) | 0.625 |
| Variables | IVUS Group | Non-IVUS Group | p Value |
|---|---|---|---|
| (n = 2,127) | (n = 8,235) | ||
| Target coronary artery | |||
| Left anterior descending | 1,132 (53.2%) | 3,806 (46.2%) | <0.001 |
| Right | 622 (29.2%) | 2,764 (33.6%) | <0.001 |
| Left circumflex | 277 (13.0%) | 1,456 (17.7%) | <0.001 |
| Left main | 87 (4.1%) | 125 (1.5%) | <0.001 |
| Multivessel involvement | 1,062 (49.9%) | 4,386 (53.3%) | 0.006 |
| American College of Cardiology/American Heart Association lesion type | |||
| C | 867 (40.7%) | 3,110 (37.7%) | <0.001 |
| B | 836 (39.3%) | 3,730 (45.2%) | <0.001 |
| A | 66 (3.1%) | 330 (4.0%) | 0.111 |
| Procedural details | |||
| Number of treated arteries | 1.24 ± 0.53 | 1.2 ± 0.48 | 0.001 |
| Percutaneous coronary intervention with stent | 2,006 (94.3%) | 7,136 (86.7%) | <0.001 |
| Total number of stents | 1.6 ± 0.87 | 1.42 ± 0.74 | <0.001 |
| Bare-metal stent | 52 (2.4%) | 612 (7.4%) | <0.001 |
| Drug-eluting stent | 1,893 (89.0%) | 6,280 (76.2%) | <0.001 |
| Stent length (mm) | 24.3 ± 7.36 | 23.6 ± 6.9 | <0.001 |
| Stent diameter (mm) | 3.24 ± 0.50 | 3.13 ± 0.44 | <0.001 |
| Percent diameter stenosis before percutaneous coronary intervention | 87.52 ± 13.8 | 85.38 ± 17.5 | <0.001 |
| Percent diameter stenosis after percutaneous coronary intervention | 13.28 ± 12.5 | 12.54 ± 11.09 | 0.074 |
| Percutaneous coronary intervention success | 1,997 (93.8%) | 7,347 (89.2%) | 0.117 |
| Thrombus aspiration | 628 (29.5%) | 2,205 (26.8%) | 0.011 |
| Glycoprotein IIb/IIIa inhibitor | 208 (9.8%) | 1,054 (12.8%) | <0.001 |
| Stent thrombosis | 19 (0.9%) | 59 (0.7%) | 0.40 |
| In-hospital complications ⁎ | 140 (6.7%) | 594 (7.3%) | 0.295 |
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