Abstract
Background
Distal embolization of thrombus/platelet aggregates decreases myocardial reperfusion during primary percutaneous coronary intervention (PCI), and is associated with worse immediate and long-term prognosis of patients with ST-elevation myocardial infarction (STEMI).
Objective
Assess the efficacy of a mesh covered stent (MGuard™ stent, MGS) in preventing distal embolization and microvascular reperfusion impairment during primary PCI, compared with a bare metal stent (BMS).
Methods
Forty patients with STEMI referred for primary PCI were randomized for stenting the culprit lesion with the MGS (n = 20) or a BMS (n = 20). Blinded experts performed off-line measurements of angiographic epicardial and microvascular reperfusion criteria: TIMI flow grade, myocardial blush, corrected TIMI frame count (cTFC).
Results
At baseline clinical, angiographic and procedural variables were not different between groups. Post PCI TIMI flow grade was similar in both groups. We observed better myocardial Blush grade in group MGS compared to BMS (median value 3.0 vs 2.5, 2p = 0.006) and cTFC (mean cTFC: MGS 19.65 ± 4.07 vs BMS 27.35 ± 7.15, 2p < 0.001, cTFC mean difference MGS-BMS: 7.7, CI 95%: 3.94 to 11.46). MGS stent group had a higher percentage of successful angioplasty (cTFC ≤ 23: MGS 85% vs BMS 30%, 2p < 0.001). We had two cases of acute stent thrombosis (one for each group) at 30 days follow up, but no clinical events at 6 months follow up.
Conclusions
In this exploratory study, MGS significantly improved microvascular reperfusion criteria compared with a BMS in primary PCI. However its safety and impact on clinical outcomes should be verified in larger randomized clinical trials.
1
Introduction
Distal embolization of thrombus/platelet aggregates may decrease coronary and myocardial reperfusion after percutaneous coronary intervention (PCI) in ST-elevation myocardial infarction (STEMI); this is associated with worse immediate and long-term prognosis after PCI .
Several techniques employed to reduce distal embolization during primary PCI have failed to improve clinical outcomes. For instance, distal embolization protective devices have not shown improvements regarding microcirculation in patients with STEMI treated with PCI , neither have PTFE (polytetrafluoroethylene) tubularly coated stents shown improvements in this field . Adjunctive mechanical thrombectomy aspiration devices have appeared to significantly increase mortality . Catheter thrombus aspiration reduced distal embolization and improved reperfusion and mid-term clinical outcomes ; however, it is not necessarily a risk-free procedure; systemic embolization may occur and there is still controversy about its utility, as recently reported .
There are some isolated reports about the usefulness of the MGuard™ stent (MGS, a novel bare-metal stent combining a polymer-mesh sleeve attached to the external surface) in preventing distal embolization during STEMI PCI . During stent deployment the net stretches over the expanding stent, trapping the thrombus/plaque debris between the mesh and the artery wall isolating the prothrombotic raw surface of the intima from the blood stream.
Our aim was to assess the efficacy of MGS compared with a traditional bare metal stent (BMS) in preventing distal embolization during primary percutaneous coronary intervention (PCI) in patients with STEMI.
2
Methods
The present study was a multicenter randomized clinical trial, in which patients with STEMI < 12 h were enrolled from March 2009 to August 2010, with six months of clinical follow up. Patients with STEMI referred for primary PCI at 3 Chilean centers were randomized 1:1 (MGS:BMS) after the following clinical and angiographic inclusion criteria: a) STEMI < 12 h after chest pain onset. b) Both genders, between 18 to 75 years old. c) Angioplasty indicated for a single vessel with a diameter between 2.75 mm and 4.0 mm and length not exceeding 30 mm. During the 17 months of the enrollment, the 3 participating centers performed together about 370 primary PCIs, so the recruitment was about 10%.
Exclusion criteria were
- 1.
Myocardial infarction due to stent thrombosis or coronary bypass grafts occlusion.
- 2.
Failed thrombolytic therapy or rescue angioplasty for STEMI.
- 3.
Multivessel disease requiring immediate multiple revascularization.
- 4.
Left main disease.
- 5.
Bifurcated lesions.
- 6.
Heavily calcified or tortuous vessel.
Diagnosis of STEMI was based on chest pain for 30 min and ST-segment elevation > 1 mm in 2 or more contiguous leads on the 12-lead ECG. Ischemic time was determined as the time interval from symptom onset to first balloon inflation.
Before intervention, patients received unfractionated heparin 100 UI/kg iv bolus, acetylsalicylic acid (ASA), clopidogrel 600 mg, iv Nitroglycerin and oral β blockers. Administration of glycoprotein (GP) IIb/IIIa inhibitors and manual thrombus aspiration were at the treating physician’s discretion. During intervention, unfractionated heparin was administered to maintain the activated clotting time > 300 s. After stent implantation, clopidogrel was given 75 mg/d for 3 to 6 months. All patients were treated with ASA 100 mg/d. Patients were followed for a period up to 6 months, and major adverse cardiac events (MACE), including death, reinfarction, and target lesion revascularization were registered.
Blinded experts performed off-line measurements of angiographic epicardial and microvascular reperfusion criteria: TIMI flow grade, myocardial blush, TIMI frame count and percentage of patients with optimal result (cTFC ≤ 23) as previously described . Disagreements were resolved by consensus.
This protocol was approved by the ethics committee in all three centers.
2.1
Statistical analysis
The primary end point of the total study population was the cTFC. To calculate the sample size we used a cTFC mean value extracted from cTFC results of the TIMI group (Thrombolytic therapy cTFC mean result in the Anterior Descending Artery: 25.7 ± 4.1) and from data of the X-Sizer thrombectomy trial (control group cTFC mean result: 24.7 ± 14.1) .
Assuming a post PCI cTFC = 25.5 ± 8 in BMS group, a sample size of 20 patients in each group allows demonstration of 30% reduction in cTFC by MGS implantation in a 2-sided test (α = 0.05) with a power of 80%.
Data are presented as mean ± SD, median (interquartile range), or number (%) of patients. Differences in normally distributed continuous variables were tested by an unpaired Student’s t test. The Mann–Whitney U test was used to compare abnormally distributed continuous variables. Categorical data were compared with a χ 2 test and Fisher’s exact test for expected count < 5. A 2-sided P value ≤ 0.05 was considered statistically significant.
SPSS V15.0 statistical software system (SPSS Inc) was used for calculations.
2
Methods
The present study was a multicenter randomized clinical trial, in which patients with STEMI < 12 h were enrolled from March 2009 to August 2010, with six months of clinical follow up. Patients with STEMI referred for primary PCI at 3 Chilean centers were randomized 1:1 (MGS:BMS) after the following clinical and angiographic inclusion criteria: a) STEMI < 12 h after chest pain onset. b) Both genders, between 18 to 75 years old. c) Angioplasty indicated for a single vessel with a diameter between 2.75 mm and 4.0 mm and length not exceeding 30 mm. During the 17 months of the enrollment, the 3 participating centers performed together about 370 primary PCIs, so the recruitment was about 10%.
Exclusion criteria were
- 1.
Myocardial infarction due to stent thrombosis or coronary bypass grafts occlusion.
- 2.
Failed thrombolytic therapy or rescue angioplasty for STEMI.
- 3.
Multivessel disease requiring immediate multiple revascularization.
- 4.
Left main disease.
- 5.
Bifurcated lesions.
- 6.
Heavily calcified or tortuous vessel.
Diagnosis of STEMI was based on chest pain for 30 min and ST-segment elevation > 1 mm in 2 or more contiguous leads on the 12-lead ECG. Ischemic time was determined as the time interval from symptom onset to first balloon inflation.
Before intervention, patients received unfractionated heparin 100 UI/kg iv bolus, acetylsalicylic acid (ASA), clopidogrel 600 mg, iv Nitroglycerin and oral β blockers. Administration of glycoprotein (GP) IIb/IIIa inhibitors and manual thrombus aspiration were at the treating physician’s discretion. During intervention, unfractionated heparin was administered to maintain the activated clotting time > 300 s. After stent implantation, clopidogrel was given 75 mg/d for 3 to 6 months. All patients were treated with ASA 100 mg/d. Patients were followed for a period up to 6 months, and major adverse cardiac events (MACE), including death, reinfarction, and target lesion revascularization were registered.
Blinded experts performed off-line measurements of angiographic epicardial and microvascular reperfusion criteria: TIMI flow grade, myocardial blush, TIMI frame count and percentage of patients with optimal result (cTFC ≤ 23) as previously described . Disagreements were resolved by consensus.
This protocol was approved by the ethics committee in all three centers.
2.1
Statistical analysis
The primary end point of the total study population was the cTFC. To calculate the sample size we used a cTFC mean value extracted from cTFC results of the TIMI group (Thrombolytic therapy cTFC mean result in the Anterior Descending Artery: 25.7 ± 4.1) and from data of the X-Sizer thrombectomy trial (control group cTFC mean result: 24.7 ± 14.1) .
Assuming a post PCI cTFC = 25.5 ± 8 in BMS group, a sample size of 20 patients in each group allows demonstration of 30% reduction in cTFC by MGS implantation in a 2-sided test (α = 0.05) with a power of 80%.
Data are presented as mean ± SD, median (interquartile range), or number (%) of patients. Differences in normally distributed continuous variables were tested by an unpaired Student’s t test. The Mann–Whitney U test was used to compare abnormally distributed continuous variables. Categorical data were compared with a χ 2 test and Fisher’s exact test for expected count < 5. A 2-sided P value ≤ 0.05 was considered statistically significant.
SPSS V15.0 statistical software system (SPSS Inc) was used for calculations.
3
Results
3.1
Patient population
Forty patients with STEMI referred for primary PCI were enrolled in the study. Baseline and clinical variables were not different between groups as presented in Table 1 .
| Clinical characteristics | # Mguard stent (%) | # Other stent (%) | Significance |
|---|---|---|---|
| Female | 2 (10%) | 0 | NS a |
| Male | 18 (90%) | 20 (100%) | |
| Age (years) | 54 ± 11 | 58 ± 13 | NS b |
| Diabetes Mellitus 2 | 4 (20%) | 1 (5%) | NS a |
| Dyslipidemia | 12 (60%) | 7 (35%) | NS c |
| Hypertension | 9 (45%) | 8 (40%) | NS c |
| Obesity | 6 (30%) | 2 (10%) | NS a |
| Smoker | 15 (75%) | 11 (55%) | NS c |
| Previous Myocardial Infarction | 1 (5%) | 1 (5%) | NS a |
| AMI evolution Time (h:min) | 4:16 ± 3:41 | 4:20 ± 3:17 | NS d |
| Culprit vessel: | NS c | ||
| Left anterior descending | 8 (40%) | 10 (50%) | |
| Circumflex | 3 (15%) | 5 (25%) | |
| Right coronary artery | 9 (45%) | 5 (25%) | |
| Killip: | NS d | ||
| 1 | 17 (85%) | 17 (85%) | |
| 2 | 2 (10%) | 2 (10%) | |
| 3 | 0 | 1 (5%) | |
| 4 | 1 (5%) | 0 |
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