Randomized Comparison of Primary Percutaneous Coronary Intervention With Combined Proximal Embolic Protection and Thrombus Aspiration Versus Primary Percutaneous Coronary Intervention Alone in ST-Segment Elevation Myocardial InfarctionThe PREPARE (PRoximal Embolic Protection in Acute myocardial infarction and Resolution of ST-Elevation) Study
Joost D.E. Haeck, MD*,
Karel T. Koch, MD, PhD*,*,
Luc Bilodeau, MD ,
René J. Van der Schaaf, MD*,
José P.S. Henriques, MD, PhD*,
Marije M. Vis, MD*,
Jan Baan, Jr, MD, PhD*,
Allard C. Van der Wal, MD, PhD ,
Jan J. Piek, MD, PhD*,
Jan G.P. Tijssen, PhD*,
Mitchell W. Krucoff, MD ,
Robbert J. De Winter, MD, PhD*
* Department of Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
Department of Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
Department of Cardiology, Institut de Cardiology de Montréal, Montréal, Quebec, Canada
Duke Clinical Research Institute, Duke University Medical Center, Durham, North Carolina
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Abstract
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Objectives: The purpose of this study was to evaluate the effectiveness of combined proximal embolic protection with thrombus aspiration (Proxis Embolic Protection System [St. Jude Medical, St. Paul, Minnesota]) in ST-segment elevation myocardial infarction patients.
Background: Embolization during primary percutaneous coronary intervention (PCI) may result in microvascular obstruction, reduced myocardial perfusion, and impaired prognosis.
Methods: Two hundred eight-four patients were randomized to primary PCI with the Proxis system versus primary PCI alone after angiography. The primary end point was the occurrence of complete ( 70%) ST-segment resolution (STR) at 60 min measured by continuous ST-segment Holter.
Results: There was no significant difference in the occurrence of the primary end point (80% vs. 72%, p = 0.14). However, immediate complete STR (at time of last contrast) occurred in 66% of Proxis-treated patients and 50% in control patients (absolute difference, 16.3%; 95% confidence interval: 4.3% to 28.2%; p = 0.009). A significant lower ST-segment curve area (0 to 3 h after primary PCI) was observed in the Proxis arm (5,192 µV/min vs. 6,250 µV/min, p = 0.037). Major adverse cardiac and cerebral events at 30 days occurred with similar frequency in both groups (6 vs. 10).
Conclusions: There was no significant difference in complete STR at 60 min in this proof-of-concept study. However, we observed a significant difference in immediate complete STR in Proxis-treated patients, better STR at later time points, and a reduction of electrocardiogram injury current over time, compared with control patients. The results suggest that primary PCI with the Proxis system may lead to better immediate microvascular flow in ST-segment elevation myocardial infarction patients. (The PREPARE Study; ISRCTN71104460)
Key Words: ST-segment elevation myocardial infarction • primary percutaneous coronary intervention • combined proximal embolic protection and thrombus aspiration
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Abbreviations and Acronyms
| | CI = confidence interval | | CK-MB = creatine phosphokinase myocardial band isoenzyme | | MACCE = major adverse cardiac and cerebral events | | MBG = myocardial blush grade | | PCI = percutaneous coronary intervention | | STEMI = ST-segment elevation myocardial infarction |
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Primary percutaneous coronary intervention (PCI) has been shown to be the superior treatment for ST-segment elevation myocardial infarction (STEMI) and effectively restores perfusion of the infarct-related artery (1). Despite its value, primary PCI using balloons and stents alone may dislodge atherothrombotic material adherent to the ruptured plaque, causing microvascular obstruction and limiting myocardial salvage. Embolization of atherothrombotic material during primary PCI is considered an important determinant of microvascular obstruction and is associated with impaired ST-segment resolution, increased infarct size, reduced recovery of ventricular function, and a 5-fold increase in 5-year mortality (2–6). Most randomized trials of thrombus aspiration catheters and distal embolic protection devices did not show a treatment benefit, thereby not supporting the use of any embolic protection device or thrombus aspiration catheter in the setting of STEMI (7–15). Recently, the TAPAS (Thrombus Aspiration during Percutaneous coronary intervention in Acute myocardial infarction Study) showed that thrombus aspiration before stenting of the infarct-related artery resulted in improved myocardial blush grade (MBG) and clinical outcome 1-year after primary PCI (16,17).
The Proxis device (St. Jude Medical, St. Paul, Minnesota) (Fig. 1) is a novel system of combined proximal embolic protection and thrombus aspiration. In a registry of 172 patients, we showed that the Proxis system was feasible and safe in the setting of primary PCI in patients with STEMI. The results demonstrated good angiographic outcomes, excellent ST-segment resolution, and low 1-year mortality (18). On the basis of these findings, the randomized, controlled PREPARE (Proximal Embolic Protection in Acute Myocardial Infarction and Resolution of ST-Elevation) trial was designed to evaluate the effectiveness of combined proximal embolic protection with thrombus aspiration during mechanical reperfusion therapy in STEMI.
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Methods
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Patient selection and treatment.
The PREPARE trial is an investigator-initiated, randomized, open trial with blinded evaluation of end points, in which 2 hospitals with 24/7 coronary intervention facilities in the Netherlands (Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands) and in Canada (Institut de Cardiologie de Montréal, Montréal, Canada) participated. The institutional review board of both hospitals approved the study. Written informed consent was obtained from all patients.
Patients were eligible for the trial if they had symptoms of myocardial infarction <6 h after onset, electrocardiographic evidence of persistent ST-segment elevation of at least 200 µV in 2 or more contiguous leads. Exclusion criteria were individuals younger than 18 years of age, contraindications to the use of glycoprotein IIb/IIIa receptor antagonists, coexistent condition associated with a limited life expectancy, prior coronary artery bypass grafting or lytics, recurrence of myocardial infarction in the same myocardial area, an electrocardiogram (ECG) unsuitable for ST-segment resolution evaluation (left bundle branch block, ventricular pacemaker, and atrial fibrillation). Patients were included after the first angiogram provided Thrombolysis In Myocardial Infarction (TIMI) flow grade 0 to 1 and a coronary anatomy suitable for treatment with the Proxis system. Patients were not included if any of the following applied: left main occlusion, left main stenosis of more than 30%, heavy proximal calcifications, a small infarct-related artery (<2.5 mm in diameter), and a proximal location of the lesion leading to an insufficient "landing zone" for the Proxis system (generally <10 to 12 mm). Informed consent was obtained after suitability of coronary anatomy of the patient for the treatment with the Proxis system had been established. Patients who consented were subsequently randomized 1:1 to a strategy of primary PCI with combined embolic protection and thrombus aspiration or to primary PCI alone.
The Proxis system was used in patients randomized to primary PCI with combined embolic protection and thrombus aspiration. The Proxis system is a single-operator full-length flexible catheter (6- or 7-F guiding catheter compatible) and based on a carbon dioxide gas (CO2) inflation system. It was deployed proximal to the target lesion before crossing. Inflation of the sealing balloon suspends antegrade flow during the period of lesion intervention. Stagnated blood and emboli liberated after each lesion intervention were retrieved by gentle aspiration. Crossing of the coronary occlusion with the wire, balloon dilation, and stent placement was performed through the Proxis system and carried out under full proximal blockade of the vessel. Aspiration and embolic protection by temporary proximal vessel occlusion were repeated during each step of the PCI procedure (18).
Primary PCI was performed in a standard manner with approved wires, balloons, and stents in patients randomized to primary PCI alone. All patients received 300 mg of aspirin, clopidogrel (600 mg followed by 75 mg/24 h), unfractionated heparin (70 U/kg) before PCI. Use of glycoprotein IIb/IIIa receptor antagonists was left to operator discretion. After the procedure, patients were transferred to the coronary care unit. Standard therapies after PCI included aspirin (at least 80 mg daily), clopidogrel (75 mg daily), beta-blockers, lipid-lowering agents, and angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, according to European Society of Cardiology guidelines (19). Stabilized patients from referring hospitals were transferred back after a minimum of 6 h.
Data collection.
Continuous digital 12-lead ECG/Holter monitoring (Northeast Monitoring 180+, Natick, Massachusetts) for ST-segment analysis was started on arrival at the catheterization laboratory before PCI. Continuous ECG monitoring was continued a minimum of 6 h after PCI. Continuously updated ST-segment resolution analysis was performed by a central core laboratory (eECG Core Laboratory, Duke Clinical Research Institute/Duke University Medical Center, Durham, North Carolina) using previously published methodology (20,21). In brief, ST-segment levels were measured 60 ms after the J-point in the most abnormal lead. ST-segment recovery was determined over serial time points by comparing ECGs recorded at each specified time interval with the most abnormal "peak" ECG in the data recorded between study enrollment and arrival in the catheterization laboratory. The 12-lead summated ST-segment deviation versus time trend curves were used to calculate ST-segment injury curve areas. Changes during the interventional procedure were excluded from analysis. All ST-segment recovery end points were read blinded to any treatment assignment or clinical information.
After the PCI procedure, a coronary angiogram was obtained, and TIMI-graded coronary flow, MBG, and angiographic signs of distal embolization were estimated as previously described (5,22,23). Two experienced investigators (K.T.K., R.J.dW.), blinded to all other data, assessed all angiograms. In case of any discrepancies, a third experienced investigator (J.P.S.H.) determined the angiographic parameters. Cardiac creatine phosphokinase-myocardial band isoenzyme (CK-MB) levels were measured at admission, and after 5, 7, 10, 12, 18, and 24 h. Retrieved debris before and after target lesion intervention was collected in separate filters. Aspirated material was assessed by inspection and histopathologic analysis of the filter content. A pathologist (A.C.VdW.), blinded to the angiographic findings and the result of PCI, performed the histopathologic analyses. Information about clinical events was obtained from hospital records and from telephone interviews with the study participants at 30 days.
End point definitions.
The primary end point of the study was the occurrence of complete (70%) resolution of ST-segment elevation 60 min after last contrast injection. Complete ST-segment resolution (dichotomous) was defined as a reduction of at least 70% of the ST-segment deviation of the most deviated lead relative to the peak ST-segment deviation before PCI. Secondary ECG end points were the occurrence of complete (70%) resolution of ST-segment elevation immediately after PCI (at the time of last contrast injection) and at 30, 90, and 120 min after last contrast injection; percentage of ST-segment elevation resolution (continuous) immediately after PCI and at 30, 60, 90, and 120 min after last contrast injection; and ST-segment curve area. Percentage of ST-segment elevation resolution was defined as the percentage change between the most abnormal lead in the most abnormal ECG in the recording session before the PCI (the "peak" ECG) and the ST-segment level in that same lead at each of the designated time points (immediate end PCI, 30, 60, 90, and 120 min after last contrast injection). ST-segment curve area was defined as the area under the summated 12-lead absolute ST-segment deviation versus time trend curve from the last contrast injection to 3 h after PCI, reported as µV/min. Angiographic end points were TIMI-graded coronary flow, MBG, and the presence of angiographic signs of distal embolization (5,22). The enzymatic end point was infarct size measured by a biochemical biomarker of myocardial necrosis (CK-MB). Clinical end points were overall major adverse cardiac and cerebral events (MACCE). Overall MACCE included death, spontaneous or procedural myocardial infarction, stroke, and percutaneous or surgical target vessel revascularization. All deaths were cardiovascular unless an unequivocal noncardiac cause could be identified. The myocardial infarctions and target vessel revascularizations were classified according to standardized definitions of the Academic Research Consortium (24). Stroke was defined as a new focal neurologic deficit of vascular origin lasting more than 24 h. Stroke was further classified as the result of intracranial hemorrhage, ischemia (if a computed tomography or MRI scan was available), or uncertain cause. All suspected clinical events were adjudicated by a blinded critical events adjudication committee.
Statistical analyses.
The main clinical analysis consists of a single comparison between the treatment groups of the percentage of patients with more than 70% resolution of the ST-segment elevation at the time of last contrast injection. We designed our study to have a power of beta = 80% to detect an improvement in percentage of patients with complete (>70%) ST-segment resolution by 15% with a level of significance of alpha <0.05. These assumptions yielded a sample size of 140 patients in each treatment arm.
All data were analyzed on an intention-to-treat basis. Discrete variables are reported as counts and continuous variables, mean ± SD, or median and interquartile range. Chi-square and Fisher exact probability test were used to test equality of the event rates. The 95% confidence interval (CI) for the rate difference is calculated via the exact method. Data are expressed as mean ± SD or as medians, whenever appropriate. Student t test or Mann-Whitney U test were used accordingly. For all statistical analyses, we used the SPSS software package, version 16.0 (SPSS Inc., Chicago, Illinois). A value of p < 0.05 in the 2-tailed test was regarded as significant. Because the study was not powered for clinical outcomes, the event rates are presented for descriptive purposes only, and no statistical comparisons were done.
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Results
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Patients and treatment.
Between March 1, 2006, and June 27, 2008, 284 STEMI patients, at 2 centers in the Netherlands and Canada, were randomized to receive either primary PCI with combined proximal embolic protection and thrombus aspiration (n = 141) or primary PCI alone (n = 143). Randomization flow is shown in Figure 2. Baseline demographic and angiographic characteristics were well matched between the 2 randomized cohorts, except for a higher incidence of current smoking in the control group and an older population in the Proxis-treated group (Table 1). Almost all patients had a complete occlusion of the infarct-related artery at the first angiogram: there was a TIMI flow grade of 0 to 1 in 274 of the 281 patients (98%).
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Figure 2 Randomization Flow
MACCE = major adverse cardiac or cerebral events; MBG = myocardial blush grade; PCI = percutaneous coronary intervention; TIMI = Thrombolysis In Myocardial Infarction.
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Procedural results.
The procedural results are summarized in Table 2. The Proxis system was adequately positioned in 132 of 141 patients (94%). As shown in Table 2, combined proximal embolic protection and thrombus aspiration resulted in a 3-min delay in arterial puncture to first balloon inflation compared with the control group. Direct stenting was performed in a minority of patients (15%). No emergency coronary artery bypass graft surgery was required, and there were no intraprocedural deaths or strokes. Furthermore, no dissection or vessel trauma at the site where the Proxis system had been inflated was observed.
ST-segment recovery.
Complete ST-segment resolution at 60 min after last contrast injection occurred in 101 of the 126 patients (80%) in the Proxis arm and in 72% (93 of 129) of patients in the control group (absolute difference, 8.1%, 95% CI: –2.4% to 18.6%; p = 0.14). Complete ST-segment resolution at the end of PCI occurred in 85 of 129 patients (66%) receiving combined proximal embolic protection and thrombus aspiration and in 67 of 135 patients (50%) in the control group (absolute difference, 16.3%; 95% CI: 4.3% to 28.2%; p = 0.009), with a median percent ST-segment resolution of 79% versus 69% respectively (p = 0.015) as shown in Table 3
and no evidence of heterogeneity. The difference between the 2 groups evanesced over time, as shown in Figure 3; however, the overall ST-segment curve area (0 to 3 h after primary PCI) was still significantly lower in the Proxis arm versus the control arm (5,192 µV/min vs. 6,250 µV/min, p = 0.037) (Table 3). Faster and more complete ST-segment resolution with the Proxis system was observed in a host of subgroups evaluated, including subgroups according to infarct-related artery and the use of glycoprotein IIb/IIIa receptor antagonists. The absolute differences varied between 9.8% and 28.6% (Table 4).
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Figure 3 Rates of Complete (>70%) ST-Segment Resolution at Different Time Periods After Primary PCI With Proxis System or Alone
PCI = percutaneous coronary intervention; STR = ST-segment resolution.
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Angiographic, enzymatic, histopathologic, and 30-day clinical outcomes.
Combined proximal embolic protection and thrombus aspiration tended to improve post-procedural TIMI flow grade (p = 0.06). No statistical difference in MBG was observed. The rates of angiographically documented signs of distal embolization were slightly less frequent and infarct size measured by peak of CK-MB was smaller in the Proxis-treated patients. But none of these differences reached statistically significance (Table 5).
Debris was confirmed on pathology in 84 of the 112 patients (75%). In 73 of the 84 patients (87%), debris was extracted before dilation or stent placement. In 29 of the 84 patients (35%), debris was aspired before and after target lesion intervention and in 11 of the 84 patients (13%) only after target lesion intervention. Histopathologic analysis of the filter content showed in 42 of the 84 patients (50%) only thrombus, in 41 of the 84 patients (49%) thrombus and plaque components, and in only 1 patient (1%) only plaque components. No difference in the composite of debris before and after target lesion intervention was observed.
As shown in Table 6, overall MACCE occurred with similar frequency with or without combined proximal embolic protection and thrombus aspiration (4% vs. 7%). Two patients died in each treatment group of progressive heart failure. None of the repeat angiograms showed evidence of a (re)stenotic lesion or complication at the site where the Proxis system had been inflated.
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Discussion
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The PREPARE trial is the first proof-of-concept trial to test the effectiveness of primary PCI with combined proximal embolic protection and thrombus aspiration compared with primary PCI.
The difference in the pre-specified primary end point, 80% versus 72% of patients with complete (70%) ST-segment resolution at 60 min, did not reach statistical significance. Yet, the intention-to-treat analysis showed a significantly higher immediate ST-segment resolution in favor of Proxis-treated patients and a significant reduction of overall injury current over time. While ST-segment recovery parameters are ultimately surrogate electrocardiographic biomarkers, they reflect intensity and duration of myocardial ischemia and have consistently been associated with infarct size, ejection fraction, and mortality in patients with myocardial infarction (2–4,25). Although the primary end point of 70% ST-segment resolution at 60 min and important secondary end points, such as MBG, were not statistically significant different between the 2 groups, there was a measurable effect very early with reperfusion that then equilibrated across groups over time. Mechanistically, this very early measurable difference in ST-segment recovery is conceptually consistent with prevention of distal embolization. Although the difference in ST-segment resolution with the Proxis system was transient, improved microcirculatory reperfusion within the first hour after restoration of epicardial flow may translate into a clinically relevant reduction in infarct size and clinical outcomes, although the current study was underpowered to answer this question definitively.
Multiple explanations may be proposed as to why combined proximal embolic protection and thrombus aspiration leads to enhance myocardial reperfusion as observed by early ST-segment recovery. In contrast to distal protection devices and manual thrombus aspiration devices, the Proxis system provides embolic protection before wire crossing of the thrombotic coronary occlusion. Inflation of the sealing balloon suspends antegrade flow in the infarct-related artery during every manipulation and engagement of the thrombotic occlusive lesion with wires, balloons, and also later with stents. Hence, the Proxis system prevents both embolization during lesion crossing and protects the distal side branches of the infarct-related artery. In the PREPARE trial, debris was extracted in 48% of patients at the time of target lesion stent placement, which likely provides additional protection against distal embolization. In addition to embolic protection and thrombus aspiration, the intracoronary evacuation of biologically active inflammatory mediators produced at the site of the plaque could contribute to improvement of microcirculatory flow (26). Pathophysiological mechanisms that involve thrombus composition (i.e., platelets, inflammatory cells, and plaque components), myocardial perfusion, and microvascular obstruction are still unknown and need further investigation (27). Another interesting although unproven explanation for our results may be ischemic post-conditioning (28). The sequential and repetitive inflations of the sealing balloon of the Proxis system may have prevented reperfusion injury by inducing repetitive transient episodes of ischemia at the time of myocardial reperfusion.
The success of this randomized multicenter study was enhanced by the fact that technical success rates with the Proxis system in primary PCI were high. In 94% of the cases, combined proximal embolic protection and thrombus aspiration were performed. Atheromatous and/or thrombotic debris was retrieved in 75% of patients, similar to the 77% rate of histologically confirmed material demonstrated in our registry. The use of the Proxis system resulted in only a 3-min delay in arterial puncture to first balloon inflation time.
Our findings support the beneficial effect of the Proxis system. In addition, the favorable outcome in immediate ST-segment resolution occurred despite a lower frequency of direct stenting with the Proxis system, which is associated with reduction of microvascular injury (29). Notably, the percentage of patients with complete ST-segment resolution in the control arm of our study was comparable at all time points to that in the treatment and control arms of the EMERALD (Enhanced Myocardial Efficacy and Recovery by Aspiration of Liberated Debris) trial (15). In that study, ST-segment resolution over time was superimposable for the control and distal protection arms.
The PROXIMAL (Proximal Protection During Saphenous Vein Graft Intervention) trial recently demonstrated equivalent effectiveness of the Proxis system compared with distal embolic protection in PCI of saphenous vein grafts (30). The PREPARE trial identifies another application of combined proximal embolic protection and thrombus aspiration. Our study was designed to include a selection of STEMI patients (i.e., TIMI flow grade 0 to 1, 200 µV ST-segment elevation). Since the Proxis system demonstrated the ability to aspirate atherothrombotic material after target lesion intervention, other subset of patients, in particular myocardial infarction patients with "spontaneously reperfused arteries," may also benefit from combined proximal embolic protection and thrombus aspiration, which were not included in our trial. Larger prospective randomized trials with relevant clinical end points are needed to demonstrate an effect of proximal protection with the Proxis system on patient outcome in primary PCI.
Study limitations.
First, the PREPARE trial was underpowered to detect differences in clinical events. The study measured surrogate end points, which may provide insight into a mechanistic impact that may translate into clinical benefit. Second, our study was conducted in 2 high-volume centers with experienced operators, proficient with the Proxis system. Therefore, the results may not be extrapolated to settings with less experienced operators and/or to low-volume centers. Third, the results of our study may not be applicable to other patient and lesion subtypes. Mainly due to the necessity of a "landing zone" for the Proxis system (>10 to 12 mm), patients with a myocardial infarction related to an ostial left anterior descending coronary artery were excluded. The slight preponderance of myocardial infarctions related to the right coronary artery in our trial may be due to this necessity for a "landing zone." Finally, because most patients were referred from other non-PCI hospitals and were transferred back after a relatively short observation time, CK-MB values were complete in only 62% of the patients.
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Conclusions
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There was no significant difference in complete (>70%) ST-segment resolution at 60 min in this proof-of-concept study. However, we observed a significant difference in immediate complete ST-segment resolution in Proxis-treated patients, better ST-resolution at later time points, and a reduction of ECG injury current over time, compared with control patients. The results of the PREPARE trial suggest that primary PCI with combined proximal embolic protection and thrombus aspiration may lead to better immediate microvascular flow in STEMI patients.
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Acknowledgments
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The authors gratefully acknowledge the technical and nursing staff of the Cardiac Catheterization Laboratories and Coronary Care Units of the 2 centers (Heads Martin G. H. Meesterman, Danielle Larocque, and Ronald Schmeddes); Wim J. Rohling, Dr. Krischan D. Sjauw, Nathalie Hardy, and Maguy Shabani for the data management; and Dr. Cindy Green, Senior Statistician to the Duke eECG Core Laboratory.
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Footnotes
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This study is supported by grants from St. Jude Medical and from the University of Amsterdam.
* Reprint requests and correspondence: Dr. Karel T. Koch, Department of Cardiology, Cardiac Catheterization Laboratory B2-125, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands (Email: k.t.koch{at}amc.uva.nl).
Manuscript received June 29, 2009;
accepted July 9, 2009.
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J. Am. Coll. Cardiol. Intv.,
June 1, 2011;
4(6):
634 - 642.
[Abstract]
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B. E. Claessen and G. D. Dangas
Thrombus Aspiration in Primary Percutaneous Coronary Intervention: How to Manage Failure
J. Am. Coll. Cardiol. Intv.,
June 1, 2011;
4(6):
643 - 644.
[Full Text]
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R. Jaffe, A. Dick, and B. H. Strauss
Prevention and Treatment of Microvascular Obstruction-Related Myocardial Injury and Coronary No-Reflow Following Percutaneous Coronary Intervention: A Systematic Approach
J. Am. Coll. Cardiol. Intv.,
July 1, 2010;
3(7):
695 - 704.
[Abstract]
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S. R. Dixon, C. L. Grines, and W. W. O'Neill
The Year in Interventional Cardiology
J. Am. Coll. Cardiol.,
May 18, 2010;
55(20):
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Abstract
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