Primary percutaneous coronary intervention in acute ST-elevation myocardial infarction: Periprocedural management

INTRODUCTION — Coronary reperfusion with primary percutaneous coronary intervention (PCI) improves outcomes in patients with acute ST-elevation myocardial infarction (STEMI), an MI with a new or presumably new left bundle branch block, or a true posterior MI if performed in a timely fashion. Most procedures are now performed with drug-eluting stents, which are associated with a lower rate of restenosis than bare-metal stents. (See "Percutaneous coronary intervention with intracoronary stents: Overview".)

This topic will address some of the technical aspects of PCI, as well as adjunctive medications when used in the periprocedural period. Issues related to the performance of primary PCI will be reviewed here. The determinants of outcome, the clinical trials demonstrating the benefit of primary PCI compared with fibrinolytic therapy, selection of a reperfusion strategy, the possible role of PCI after fibrinolysis, and the role of PCI in non-ST-elevation acute coronary syndromes are discussed separately. (See "Primary percutaneous coronary intervention in acute ST elevation myocardial infarction: Determinants of outcome" and "Acute ST-elevation myocardial infarction: Selecting a reperfusion strategy" and "Percutaneous coronary intervention after fibrinolysis for acute ST-elevation myocardial infarction" and "Non-ST-elevation acute coronary syndromes: Selecting an approach to revascularization".)

PERCUTANEOUS CORONARY INTERVENTION AFTER FIBRINOLYTIC THERAPY — Percutaneous coronary intervention after fibrinolytic therapy may be indicated in patients who remain unstable or in stable patients who have had incomplete reperfusion or as part of a pharmacoinvasive strategy. This issue is discussed elsewhere. (See "Percutaneous coronary intervention after fibrinolysis for acute ST-elevation myocardial infarction".)

TECHNICAL ISSUES

Radial versus femoral approach — Bleeding complications are common in patients with STEMI and they predict a worse prognosis [1]. Many of these major bleeds occur in relation to the access site for PCI, particularly when the femoral artery is used. The risk of bleeding is lower with radial artery access. In patients undergoing primary PCI, we prefer the radial to the femoral approach if performed by experienced operators. This issue is discussed in greater detail separately. (See "Periprocedural complications of percutaneous coronary intervention", section on 'Access site bleeding' and "Periprocedural complications of percutaneous coronary intervention", section on 'Radial artery access' and "Access-related complications of percutaneous access for diagnostic or interventional procedures", section on 'Access site bleeding' and "Percutaneous arterial access techniques for diagnostic or interventional procedures", section on 'Radial artery'.)

Intravascular imaging — The role of adjunctive intravascular imaging techniques, such as intravascular ultrasound (IVUS) and optical coherence tomography (OCT), has not been established in patients with primary PCI. Several registries have found discordant results. In the ADAPT–DES study in which 813 STEMI patients were enrolled, IVUS use was associated with improved outcomes in STEMI patients [2]. In the CREDO-Kyoto AMI Registry, 3028 patients with STEMI underwent PCI with or without IVUS. Following risk adjustment, there was no difference in target vessel failure between the groups (adjusted hazard ratio [HR] 1.14, CI 0.86-1.51) [3]. However, the risk of stent thrombosis was lower with IVUS guidance. Likewise, a randomized, multicenter trial of angiographic compared with OCT-guided drug-eluting stent placement found that OCT-guidance did not reduce the incidence of major adverse cardiac events. OCT guidance led to post-PCI stent optimization in 29 percent of patients [4].

With their superior temporal and spatial resolution compared with angiography, IVUS and OCT may result in additional balloon inflations, and/or stent deployment to treat angiographically silent findings such as minor edge dissections, strut metal apposition, and plaque prolapse. Whether this will translate into improved clinical outcomes await larger, prospective randomized trials.

Direct stenting — Low-profile stent delivery systems allow for a direct stenting technique (ie, placement of a stent without predilation). The advantages of direct stenting include less radiation exposure and contrast use, as well as shorter procedural times and a lower risk of distal embolization (ie, "no reflow phenomenon") caused by plaque fragmentation. (See "Suboptimal reperfusion after primary percutaneous coronary intervention in acute ST-elevation myocardial infarction", section on 'No reflow' and "Percutaneous coronary intervention with intracoronary stents: Overview".)

In patients with an acute STEMI undergoing primary PCI, we typically perform PCI with direct stenting unless there are anatomic factors that favor predilation, such as significant calcification, diffuse disease, TIMI 0 flow (table 1), or inadequate visualization of the lesion. Direct stenting may reduce the risk of no-reflow phenomenon caused by plaque fragment emboli and increases the likelihood of myocardial perfusion and salvage [5-7].

The data that describe the effect of direct stenting are limited to relatively small trials and observational studies. However, the aggregate data suggest that direct stenting may reduce the risk of short- and long-term mortality. A 2015 meta-analysis included three randomized trials and nine observational studies that compared direct stenting to predilation [8]. Analysis of the trials found that direct stenting was associated with a large but uncertain reduction in the risk of short-term mortality (odds ratio [OR] 0.29, 95% CI 0.07-1.2) and long-term mortality (OR 0.56, 95% CI 0.26-1.2). Analysis of the observational studies reported a similar reduction in short-term mortality (OR 0.45, 95% CI 0.29-0.68) and long-term mortality (OR 0.55, 95% CI 0.33-0.94). When analyzed together, the pooled data suggest a reduction in both short-term (OR 0.43, 95% CI 0.29-0.65) and long-term mortality (OR 0.56, 95% CI 0.37-0.86).

Selection of stent type — Drug-eluting stents (DES) are used in preference to bare-metal stents (BMS) in almost all PCI procedures because they reduce the incidence of restenosis and target vessel revascularization without causing a significant increase in the cumulative rate of adverse outcomes. (See "Intracoronary stents: Stent types", section on 'Bare metal stents'.)

The concern that rates of stent thrombosis with first-generation DES were higher than the rates with BMS are no longer relevant; second-generation DES have lower restenosis rates and lower stent thrombosis rates and, accordingly, have replaced both BMS and first-generation DES [9-14]. (See "Coronary artery stent thrombosis: Incidence and risk factors", section on 'Impact of ACS'.)

First-generation drug-eluting stents versus bare-metal stents — Many randomized trials, including TYPHOON, PASSION, SESAMI, DEDICATION, and HORIZONS AMI, have evaluated outcomes at one year or less. They demonstrated that the lower rate of restenosis of sirolimus- or paclitaxel-eluting stents relative to BMS, when used for primary PCI, is similar to that in other settings.

The long-term outcomes of first-generation DES and BMS have been compared in multiple trials and their meta-analyses. We believe that the best evidence comes from a 2012 meta-analysis that used individual patient data from nearly 6300 patients enrolled in 11 randomized trials of primary PCI that compared either paclitaxel- or sirolimus-eluting stents with BMS [15]. The following findings were noted after follow-up as long as six years (mean of 3.3 years):

●There was no significant difference in mortality, which was the primary end point of the study (8.5 versus 10.2 percent; HR 0.85, 95% CI 0.70-1.04).

●The rate of target vessel revascularization was lower with DES (12.7 versus 20.1 percent; HR 0.57, 95% CI 0.50-0.66).

●There was no significant difference in the cumulative rate of stent thrombosis (5.8 versus 4.3 percent; HR 1.13, 95% CI 0.86-1.47). However, the rate of very late stent thrombosis (events after two years) was higher for DES (HR 2.81, 95% CI 1.28-6.19).

●There was no significant difference in the cumulative rate of reinfarction (9.4 versus 5.9 percent; HR 1.12, 95% CI 0.88-1.41). However, after two years, the rate significantly increased for DES (HR 2.06, 95% CI 1.22-3.49).

This finding of a higher rate of very late stent thrombosis after DES was confirmed in a second meta-analysis [16].

Limitations of this meta-analysis include possible lack of applicability to sicker real world patients who were not included in the randomized trials.

Current-generation drug-eluting stents versus bare metal stents — In patients with STEMI, we prefer first- or second-generation DES to BMS. The use of a first- or second-generation DES is typically associated with a lower risk of death, repeat MI, and ischemia-associated target-vessel revascularization when compared with use of a BMS:

●The five-year results from the EXAMINATION trial showed that the rate of the combined outcome of all-cause death, an MI, or any revascularization was lower in patients who received an everolimus-eluting stent (EES; 21 versus 26 percent of those who received a BMS; HR 0.80, 95% CI 0.65-0.98) [17]. At ten years, the benefit of EES over BMS was maintained [18].

●A 2013 comprehensive network meta-analysis of STEMI patients found the following [19]:

•Comparing CoCr-EES or phosphorylcholine polymer-based zotarolimus-eluting stents (PC-ZES) with BMS, the one-year risk of cardiac death or MI was reduced with the former but not the latter (OR 0.63, 95% CI 0.42-0.92 and 0.86, 95% CI 0.50-1.49).

•Comparing CoCr-EES with BMS and PC-ZES with BMS, the one-year risk of target vessel revascularization was reduced with the former but not the latter (OR 0.45, 95% CI 0.29-0.66 and 0.60, 95% CI 0.34-1.05).

•Comparing CoCr-EES with BMS and PC-ZES with BMS, the one-year risk of definite stent thrombosis was reduced with the former but not the latter (OR 0.32, 95% CI 0.11-0.78 and 0.44, 95% CI 0.12-1.79).

•There were trends toward lower one-year rates of cardiac death or MI, definite stent thrombosis, and target vessel revascularization with CoCr-EES compared with PC-ZES (OR 0.73, 95% CI 0.40-1.30, 0.72, 95% CI 0.17-3.16, and 0.74, 95% CI 0.38-1.42, respectively).

●The COMFORTABLE AMI trial randomly assigned 1161 patients to either biolimus-eluting or BMS [20]. The biolimus on this stent was embedded in a biodegradable polymer. The primary endpoint was the composite rate of cardiac death, target vessel-related reinfarction, and ischemia-driven target-lesion revascularization at one year. The following findings were noted:

•The primary endpoint occurred less frequently in patients receiving the biolimus-eluting stent (4.3 versus 8.7 percent; HR 0.49, 95% CI 0.30-0.80).

•The difference in the primary endpoint was driven primarily by a lower risk of target vessel-related reinfarction (0.5 versus 2.7 percent) and ischemia-driven target-lesion revascularization (1.6 versus 5.7 percent).

•There was a lower rate of definite stent thrombosis with the biolimus-eluting stent (0.9 versus 2.1 percent) but the difference was not statistically significant.

Notably, the PC-ZES is no longer available and has been replaced by the Biolinx durable polymer ZES. The biolimus-eluting stent is not approved for use in the United States but is approved for use in Europe.

Bioresorbable versus durable polymer drug-eluting stents — Bioresorbable (biodegradable) polymer DES have been evaluated in patients in the setting of primary PCI. In those locations where the Orsiro stent is available, we believe it is a reasonable alternative to current-generation stents. (See "Intracoronary stents: Stent types", section on 'Bioresorbable polymer drug-eluting stents' and "Intracoronary stents: Stent types", section on 'Ultra-thin-strut bioresorbable drug-eluting stents'.)

A biolimus-eluting stent with a biodegradable polymer was evaluated in the COMFORTABLE AMI trial, which is discussed above. (See 'Current-generation drug-eluting stents versus bare metal stents' above.)

The BIOSTEMI trial randomly assigned 1300 STEMI patients undergoing primary PCI to biodegradable polymer sirolimus-eluting ultra-thin strut (Orsiro) stents or durable polymer everolimus-eluting stents [21]. The primary composite endpoint of target lesion failure (eg, cardiac death, target vessel MI, and clinically indicated target lesion revascularization) within 12 months occurred in 4 and 6 percent of the two groups, respectively (difference -1.9 percentage points; rate ratio 0.59, 95% Bayesian credibility interval 0.37-0.94). The difference was principally attributable to a lower rate of ischemia-driven target lesion revascularization. The event rate in both groups was lower than expected.

These data do not support a preference for the Orsiro stent; this was a moderate-sized trial with fewer endpoints than expected.

Drug-eluting balloons — Due to concerns of an increase in the rate of very late stent thrombosis with DES (see 'First-generation drug-eluting stents versus bare-metal stents' above), the efficacy and safety of a drug-eluting balloon (DEB) used in conjunction with a BMS was evaluated in the DEB-AMI trial [22]. In this study, 150 STEMI patients were randomly assigned to BMS, DEB (paclitaxel) plus BMS, or DES (paclitaxel). The primary end point of six-month angiographic in-stent late-luminal loss was not significantly different between the DEB-BMS and BMS groups and neither group performed as well as the DES group. In addition, DEB induced more uncovered and malapposed stent struts than BMS, but less than DES. The results of this study have limited applicability as a first-generation stent was the comparator. (See "Coronary artery stent thrombosis: Incidence and risk factors", section on 'Incomplete stent apposition'.)

In this patient population, one small study found that DEB angioplasty, compared with a current-generation DES, led to a similar fractional flow reserve at nine months [23].

Nonculprit percutaneous coronary intervention — The management of nonculprit lesions found at the time of primary PCI is discussed elsewhere. (See "Acute coronary syndromes: Approach to nonculprit lesions".)

Deferred stenting — Despite evidence of benefit in a few early studies, we do not recommend deferred stenting for STEMI patients undergoing primary PCI.

Coronary lesions causing acute STEMI often have substantial thrombus associated with them. This thrombus can embolize spontaneously or be pushed downstream with periprocedural intracoronary artery manipulation. Macro- or microembolization of this material to the distal circulation, which occurs in 5 to 10 percent of cases, is associated with worse clinical outcomes [24,25]. Interventions such as thrombectomy or the use of distal embolic protection devices have not been shown to improve patient important outcomes. (See "Suboptimal reperfusion after primary percutaneous coronary intervention in acute ST-elevation myocardial infarction", section on 'No reflow' and "Suboptimal reperfusion after primary percutaneous coronary intervention in acute ST-elevation myocardial infarction", section on 'Prevention'.)

A few observational studies and one small randomized trial raised the possibility that deferred (at a second procedure) placement of a stent might reduce the impact of thrombus-related impairment of distal flow [26-28]. The DANAMI 3-DEFER trial randomly assigned 1215 STEMI patients to either standard PCI with stenting or to deferred stent implantation 48 hours after the index procedure [29]. At a median follow-up of 42 months, there was no difference in the rate of the primary end point, a composite of all-cause mortality, hospital admission for heart failure, recurrent infarction, and any unplanned revascularization of the target vessel within two-year follow-up (18 versus 17 percent; HR 0.99, 95% CI 0.76-1.29).

Our recommendation to not perform deferred stenting in most cases is based an absence of clear benefit and the increased costs (eg, longer hospital stay and greater radiation and contrast exposure) associated with performing two procedures.

Intraaortic balloon counterpulsation — For patients who undergo primary PCI and receive aggressive antithrombotic therapy, we do not use an intraaortic balloon pump (IABP) for those without cardiac shock, acute mitral regurgitation, or acute ventricular septal rupture.

Studies performed before the routine use of stenting and aggressive antithrombotic therapy came to differing conclusions regarding the benefit from prophylactic IABP after primary PCI [30,31].

One observational study suggested benefit from the use of prophylactic IABP before primary PCI [32]. This issue was directly addressed in the CRISP AMI trial, which randomly assigned 337 patients who presented within six hours of acute anterior STEMI but without cardiogenic shock, to either IABP or no IABP prior to primary PCI [33]. There was no significant difference in the primary outcome of mean infarct size (expressed as a percentage of left ventricular mass and measured by cardiac magnetic resonance imaging at three to five days) between the IABP and no IABP groups (42.1 and 37.5 percent, respectively). At six months, there was no difference in the rate of all-cause death.

IABP use in cardiogenic shock is discussed elsewhere in detail. (See "Prognosis and treatment of cardiogenic shock complicating acute myocardial infarction", section on 'Intraaortic balloon pump'.)

Ischemic postconditioning — Ischemic postconditioning refers to the ability of a series of brief occlusions of either the coronary or a remote arterial circulation after a severe ischemic insult to protect against ischemic-reperfusion injury. An initial clinical trial of intermittent coronary artery occlusion in primary PCI suggested smaller infarct size and a higher myocardial blush grade. Before postconditioning can be recommended in patients who undergo primary PCI, additional studies are needed to confirm efficacy in a larger number of patients, to determine the optimal protocol, to assess treatment effect using a more accepted measure of infarct size after reperfusion (eg, SPECT imaging), and to determine long-term outcomes. (See "Myocardial ischemic conditioning: Clinical implications", section on 'Therapeutic applications'.)

Intracoronary hyperoxemic reperfusion therapy — Based upon success in the reduction of infarct size in animal models, an infusion of blood mixed with aqueous oxygen into the coronary arteries after primary PCI has been shown to be safe and feasible in humans [34].

However, benefit was not confirmed in the first outcome trial of this technology (AMIHOT) in which 269 patients with STEMI were randomly assigned after successful primary or rescue PCI to receive intracoronary hyperoxemic reperfusion or normoxemic blood autoreperfusion over 90 minutes [35]. There was no difference between the two groups in any of the primary efficacy end points (final infarct size at 14 days, ST-segment resolution, or change in regional wall motion score index at three months). At 30 days, the incidence of major adverse cardiac events was not different between the two groups.

Thrombectomy — We do not recommend routine use of thrombectomy in patients with STEMI. The role of thrombectomy in patients with STEMI is discussed separately. (See "Suboptimal reperfusion after primary percutaneous coronary intervention in acute ST-elevation myocardial infarction", section on 'Thrombectomy'.)

MEDICAL THERAPY — In patients with STEMI who undergo PCI, antiplatelet and anticoagulant therapies are given to reduce thrombotic complications and reduce mortality. In addition, beta blockers are commonly administered in the periprocedural period to treat ischemic symptoms and reduce the risk of mortality.

Antithrombotic therapy — All patients should receive aspirin and a P2Y₁₂ receptor inhibitor. The approaches to these and other antiplatelet therapies are discussed separately. (See "Acute ST-elevation myocardial infarction: Antiplatelet therapy", section on 'Patients receiving primary PCI' and "Acute ST-elevation myocardial infarction: Management of anticoagulation", section on 'Primary percutaneous coronary intervention'.)

Beta blockers — Beta blockers significantly reduce morbidity and mortality in patients with an acute MI. They are also beneficial in patients undergoing primary PCI and should be started intravenously or orally as soon as practical after diagnosis based on hemodynamic and electrical stability [36]. Administration should not delay the process of getting the patient to the catheterization laboratory as quickly as possible. (See "Acute myocardial infarction: Role of beta blocker therapy".)

A randomized trial demonstrated a higher left ventricular ejection fraction at six months and lower rate of major adverse cardiac events (defined as death, reinfarction, heart failure readmission, and malignant arrhythmia) at two years for patients pretreated with intravenous beta blockers [37].

A possible benefit from preprocedural intravenous administration of a beta blocker was shown in a retrospective analysis from the CADILLAC trial of 2082 patients [38]. At 30 days, patients who had received a preprocedural beta blocker had lower mortality than those who had not (1.5 versus 2.8 percent); the reduction in mortality was limited to patients who had not been receiving an oral beta blocker before admission. Although preprocedural use is preferred, lower mortality has also been seen in retrospective analyses when beta blocker therapy is initiated after primary PCI [39].

Treatment of no reflow — The role of intracoronary agents during PCI to prevent no reflow is discussed separately. (See "Suboptimal reperfusion after primary percutaneous coronary intervention in acute ST-elevation myocardial infarction", section on 'Prevention'.)

CORONARY ARTERY BYPASS GRAFT SURGERY — If coronary artery bypass surgery is necessary, mortality is increased in the first three to seven days after the infarction. This risk must be weighed against the estimated benefit from early surgery; surgery should be delayed in patients who are stable but should be performed during the initial hospitalization in those with critical anatomy [40]. (See "Coronary artery bypass graft surgery in patients with acute ST-elevation myocardial infarction".)

EARLY DISCHARGE IN LOW-RISK PATIENTS — Discharge at 72 hours is suggested for stable STEMI patients, based in part on the following two studies:

●In one study that used the Zwolle risk index, more than two-thirds of patients undergoing primary percutaneous coronary intervention (PCI) were classified as low risk (risk score ≤3) [41]. For these patients, the mortality rate was 0.1 percent at two days and 0.2 percent between 2 and 10 days post-myocardial infarction. It was suggested that such low-risk patients could safely be discharged early (48 hours after PCI). (See "Risk stratification after acute ST-elevation myocardial infarction", section on 'Zwolle primary PCI index'.)

●The potential safety of early discharge was evaluated in the PAMI-2 trial, which included 471 patients who were deemed to be at low risk after successful primary PCI (age ≤70, no malignant arrhythmias, native vessel being the infarct-related artery, one or two vessel disease, and left ventricular ejection fraction >45 percent) [42]. These patients were randomly assigned to traditional care or to accelerated care on a telemetry unit followed by hospital discharge on day three. Patients receiving accelerated care were discharged three days earlier (4.2 versus 7.1 days for traditional care) with a significant reduction in cost. At six months, there was no significant difference between the two groups in terms of mortality (0.8 versus 0.4 percent), unstable angina, reinfarction, stroke, heart failure, or their combined occurrence (15.2 versus 17.5 percent).

Despite scant randomized trials regarding early discharge, observational data have not identified a risk to early discharge. In a study linking the National Cardiovascular Data Registry CathPCI Registry to the United States Center for Medicare and Medicaid Services claims, 33,920 patients were examined [43]. There was no difference in 30-day mortality and major adverse cardiovascular events between short (≤3 days) and medium (4 to 5 days) length of stay (adjusted hazard ratio 1.00, 95% CI 0.74-1.34).

RECOMMENDATIONS OF OTHERS — Our recommendations are generally in agreement with those made in the 2014 guideline on myocardial revascularization from the European Society of Cardiology/European Association for Cardio-Thoracic Surgery [44].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: ST-elevation myocardial infarction (STEMI)".)

SUMMARY AND RECOMMENDATIONS

●Role of fibrinolysis – Pretreatment with fibrinolysis is limited to patients in whom primary percutaneous coronary intervention (PCI) is likely to be excessively delayed because of local logistic problems or interhospital transfer. Fibrinolytic therapy given just before planned PCI (previously called "facilitated PCI") is not recommended because outcomes may be worse. (See 'Percutaneous coronary intervention after fibrinolytic therapy' above and "Percutaneous coronary intervention after fibrinolysis for acute ST-elevation myocardial infarction".)

●Arterial access – For patients undergoing primary PCI, we prefer the radial, as opposed to the femoral, approach if performed by operators skilled in radial technique and if the anticipated impact on door-to-balloon time is negligible.

●Complete versus culprit-only PCI – The management of nonculprit lesions found at the time of primary PCI is discussed separately. (See "Acute coronary syndromes: Approach to nonculprit lesions".)

●Direct stenting or predilation – In patients with an acute ST-elevation myocardial infarction (STEMI) undergoing primary PCI, we typically perform PCI with direct stenting unless there are anatomic factors present that favor predilation, such as significant calcification, diffuse disease, TIMI 0 flow (table 1), or inadequate visualization of the lesion.

●Selection of stent type – We prefer durable polymer or bioresorbable polymer drug-eluting stents (DES) over bare-metal stents (BMS). (See 'Selection of stent type' above.)

●Antithrombotic therapy – All patients should receive aspirin and a P2Y₁₂ receptor inhibitor. The approaches to these and other antiplatelet therapies are discussed elsewhere. (See "Acute ST-elevation myocardial infarction: Antiplatelet therapy", section on 'Patients receiving primary PCI' and "Acute ST-elevation myocardial infarction: Management of anticoagulation", section on 'Primary percutaneous coronary intervention'.)

●Anticoagulation – Intravenous therapy with either heparin or bivalirudin should be given as soon as possible after presentation. (See "Acute ST-elevation myocardial infarction: Management of anticoagulation".)

●Beta blockers – Beta blockers reduce mortality in patients with STEMI undergoing primary PCI, and should be administered either intravenously or orally as soon as practical after diagnosis based on hemodynamic and electrical stability. (See 'Beta blockers' above.)

●Timing of discharge after PCI – Discharge within 72 hours is suggested for stable STEMI patients. (See 'Early discharge in low-risk patients' above.)