ST-segment elevation myocardial infarction (STEMI) composes approximately 25% to 40% of myocardial infarction (MI) presentations. There has been remarkable progress in the treatment and clinical outcomes in STEMI patients over the past 2 decades. Where available within a reasonable time period, reperfusion with percutaneous coronary intervention (PCI) has been accepted as the preferred reperfusion strategy for STEMI (Fig. 37-1). As the number of patients receiving primary PCI has increased, mortality has declined (Fig. 37-2). In-hospital and 1-year mortality rates are currently 4% to 6% and 7% to 18%, respectively.^1-4 Few other interventions in clinical medicine require the complex organization of health care delivery systems and the high level of technical expertise to achieve optimum outcomes. In this chapter, we review the evidence for PCI in STEMI, including management of patients presenting to non–PCI-capable centers as well as selected technical aspects of PCI including adjunctive pharmacotherapy.

PCI Versus Fibrinolysis Therapy

PCI has been shown to be superior to fibrinolytic therapy in numerous large, randomized clinical trials in not only PCI-capable hospitals but also non–PCI-capable centers^5-14 (Fig. 37-3). In the 2 largest trials, DANAMI-2 (Danish Acute Myocardial Infarction 2) and PRAGUE-2 (Primary Angioplasty After Transport of Patients from General Community Hospitals to Catheterization Units With/Without Emergency Thrombolysis Infusion), most of the patients presented to hospitals without PCI facilities.^8-12 A large 2009 meta-analysis of randomized controlled trials (RCT) and observational studies, comparing primary PCI (with balloon angioplasty or stenting) to fibrinolysis, found that PCI was associated with significant reductions in short-term (≤6 weeks) mortality of 34% in RCTs and 23% in observational studies with significant reductions in long-term (>1 year) mortality (24%) and reinfarction (51%).¹⁴

PCI has also been demonstrated to be superior to fibrinolysis in specific high-risk patient subgroups. There is substantial evidence of benefit for patients with anterior MI in subgroup analyses from randomized trials. For example, in the PAMI (Primary Angioplasty in Myocardial Infarction) trial, the benefit of primary percutaneous transluminal coronary angioplasty (PTCA) compared to fibrinolysis was limited to patients with anterior wall STEMI.¹⁵ Efficacy in anterior MI was directly addressed in a study in which 220 such patients were randomly assigned to primary PCI or alteplase.¹⁶ Primary PCI was associated with significant reductions in in-hospital mortality (2.8% vs 10.8%), postinfarction angina or positive exercise test (11.9% vs 25.2%), repeat revascularization (22% vs 47.7%), and, at 6 months, mortality (4.6% vs 11.7%) and revascularization (31.2% vs 55.9%). For patients with cardiogenic shock, a population in which fibrinolysis is generally not effective, observational data from the GUSTO-I (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) trial and the randomized SHOCK (Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock?) trial demonstrated benefit with an early invasive strategy with revascularization by either PCI or coronary artery bypass grafting (CABG).^17-19

Management at Non–PCI-Capable Centers

Transfer for Primary PCI

The results from randomized trials indicate that outcomes are better when patients with STEMI who present to non-PCI hospitals are transferred to a PCI facility for primary PCI compared with being given fibrinolytic therapy at the local hospital^5,6,8-12 (Fig. 37-4). The additional treatment delay of primary PCI compared with fibrinolytic therapy (door-to-balloon [D2B] time minus door-to-needle [D2N] time) in these trials ranged from 55 to 103 minutes. There are currently many statewide and nationwide efforts to improve D2B times (Fig. 37-5), including transfer from noninterventional hospitals.^20-25 It has been shown that with well-defined goals, commitment from administrative and clinical leaders, standardized protocols, integrated systems of transfer, and data feedback to monitor progress, D2B times can be improved not only at PCI centers but also for patients presenting to noninterventional hospitals. Current guidelines recommend the D2B time be ≤90 minutes for patients presenting to a PCI facility and ≤120 minutes for patients transferred from a non-PCI facility.^5,6 In 2013, a study of 96,738 STEMI patients undergoing PCI at 515 hospitals enrolled in the ACCCathPCI Registry showed that median D2B times decreased from 83 minutes from July 2005 to June 2006, to 67 minutes from July 2008 to June 2009 (P < .001) The percentage of patients who met the guideline recommendation of ≤90 minutes increased from 59.7% to 83.1% (P < .001).²⁶ In contrast to PCI centers, recent evidence indicates that 40% to 75% of patients transferred from non-PCI facilities continue to have a total D2B >120 minutes^27-29 (Fig. 37-6).

Recommendations regarding triage of STEMI patients with an expected delay ≥120 minutes for fibrinolytic therapy versus transfer for primary PCI remains an area of some controversy.³⁰ Propensity-matched data from the National Registry of Myocardial Infarction found no mortality benefit from primary PCI when the PCI-related delay (D2B-D2N time) exceeded 120 minutes³¹ (Fig. 37-7). The meta-analysis by Boersma³² of randomized trials comparing fibrinolytic therapy versus primary PCI also suggested that primary PCI has a mortality advantage, with PCI-related delays of up to 2 hours.³² Data evaluating the impact of treatment delay with primary PCI on mortality suggest that patients presenting early after the onset of symptoms have much more impact than patients presenting late after the onset of symptoms.^33,34 Currently, guidelines recommend that patients with cardiogenic shock, patients who are ineligible for fibrinolytic therapy, and patients who can be treated within 120 minutes should be transferred for primary PCI.^5,6

Facilitated or Pharmacoinvasive PCI

Most patients with acute MI (AMI) present to hospitals without interventional facilities, and the time delay required to transfer patients for primary PCI has led to a great deal of interest in pharmacologic reperfusion combined with mechanical reperfusion (facilitated PCI). Facilitated PCI is the use of pharmacologic therapy to establish reperfusion as rapidly as possible followed by immediate PCI to maximize Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow rates and to stabilize the ruptured plaque^34,35 (Fig. 37-8). Primary PCI has the advantage of >97% successful reperfusion, but the challenges of availability and time delay. Fibrinolysis has the advantage of availability and rapid treatment, but the disadvantage of incomplete reperfusion (50%-70%) and the increased risk of bleeding. Patients undergoing primary PCI for AMI who arrive at the catheterization laboratory with an open versus closed infarct-related artery have higher procedural success rates, better recovery of left ventricular function, and lower early and late mortality.³⁶ These factors led to a series of trials to examine the benefit of facilitated PCI, which has now evolved to “pharmacoinvasive” PCI.³⁰

The ASSENT-4 PCI (Assessment of the Safety and Efficacy of a New Treatment Strategy With Percutaneous Coronary Intervention) trial, which randomized patients to tenecteplase-facilitated PCI versus PCI alone found a higher incidence of death, reinfarction, and stroke with facilitated PCI.³⁷ In a meta-analysis, facilitated PCI using a fibrinolytic or glycoprotein IIb/IIIa inhibitors in combination with PCI also was associated with higher rates of death, reinfarction, stroke, and bleeding compared with primary PCI alone.³⁸ The major limitations of the meta-analysis were the heterogeneity of the treatment regiments, the lack of P2Y₁₂ inhibitors, and the fact that most patients were treated at PCI centers. In addition, the meta-analysis included few patients with an expected delay >120 minutes, which is the specific patient population most likely to benefit from facilitated PCI.³⁹

The FINESSE (Facilitated Intervention With Enhanced Reperfusion Speed to Stop Events) trial randomized patients to facilitated PCI with half-dose reteplase plus abciximab or abciximab alone versus primary PCI alone. Although the trial was underpowered due to slow enrollment, the 1-year mortality rates were 6.3%, 7.4%, and 7.0%, respectively (P = not significant). However, there was a significant increase in TIMI major and minor bleeding in the group that received early administration of abciximab compared to the group that received abciximab at the time of primary PCI (10.1% vs 6.9%; P = .008).⁴⁰ A subsequent reanalysis of the 2452-patient FINESSE trial found a significant improvement in the 90-day composite end point (death, ventricular fibrillation after 48 hours, cardiogenic shock, and congestive heart failure) as well as mortality at 1 year with facilitated PCI in patients at high risk who presented early after the onset of symptoms.⁴¹

Since that time, a number of large randomized trials have demonstrated the clinical benefit of a pharmacoinvasive strategy with fibrinolysis followed by routine coronary angiography with PCI compared with fibrinolysis alone.^42-44 A meta-analysis of early routine PCI after fibrinolysis compared with fibrinolysis alone demonstrated a significant reduction in reinfarction and recurrent ischemia at 30 days with no significant increase in bleeding events. These benefits were maintained out to 12 months⁴⁵ (Fig. 37-9).

Most recently, the STREAM (Strategic Reperfusion Early After Myocardial Infarction) trial compared a pharmacoinvasive strategy to primary PCI and found a trend in the primary end point (a composite of death, shock, heart failure, and reinfarction at 30 days), which was 12.4% versus 14.3%, but the pharmacoinvasive strategy was superior when delays were prolonged (≤55 minutes: 10.6% vs 10.3%; 55-97 minutes: 13.9% vs 17.9%; >97 minutes: 13.5% vs 16.2%).^46,47 Therefore, the data currently support a pharmacoinvasive approach for the patient who cannot be treated with primary PCI within 120 minutes.^30,48

Rescue PCI

Rescue PCI is the mechanical reopening of an infarct artery after unsuccessful fibrinolytic therapy. Rescue PCI is differentiated from facilitated PCI in that rescue PCI is generally not planned. With current fibrinolytic therapy, successful reperfusion (TIMI grade 3 flow) is achieved in only 50% to 70% of patients. Consequently, almost half of patients who undergo fibrinolytic therapy may be candidates for rescue PCI.

In the initial experience with rescue PCI, procedural outcomes were often suboptimal, but with the introduction of stents and P2Y₁₂ inhibitors, procedural outcomes have improved, and several randomized trials documented improved outcomes with rescue PCI.^49-51 The RESCUE (Randomized Evaluation of Salvage Angioplasty With Combined Utilization of Endpoints) trial investigators randomized 151 patients with anterior wall MI treated with fibrinolytic therapy who had an occluded infarct artery within 8 hours of symptom onset to rescue PCI versus conservative care.⁴⁹ The rescue PCI group had a lower composite event rate of death or congestive heart failure and better exercise left ventricular ejection fraction (43% vs 38%; P = .04). These benefits occurred despite the fact that stents were not yet available and despite, what the authors felt, was a strong investigator bias not to randomize patients presenting very early after MI. The MERLIN (Middlesbrough Early Revascularization to Limit Infarction) trial investigators randomized patients with STEMI and failed thrombolysis (<50% ST-segment resolution at 60 minutes) to rescue PCI versus conservative care.⁵⁰ There was no difference in 30-day mortality (the primary end point), but event-free survival was better with rescue PCI (P = .02). The REACT (Rescue Angioplasty Versus Conservative Treatment or Repeat Thrombolysis) trial randomized patients with STEMI and failed fibrinolysis (<50% ST-segment resolution at 90 minutes) to rescue PCI, repeat fibrinolysis, or conservative care.⁵¹ Patients treated with rescue PCI had a lower incidence of the composite end point (death, reinfarction, stroke, or heart failure) than patients treated with either repeat fibrinolytic therapy or conservative care. The problem with a rescue strategy is that it is frequently challenging to determine which patient has successful reperfusion, and this leads to inherent delay. Unfortunately, in real life, only 11% to 35% of patients in need of rescue PCI actually receive it.⁵²

A major limitation of the rescue PCI approach is the lack of a reliable noninvasive method to detect reperfusion after thrombolytic therapy. The electrocardiogram is very specific in predicting patency of the infarct artery when there is complete (>70%) resolution of ST-segment elevation, but this occurs in only a minority of patients. In most patients, there is partial or no resolution of ST-segment elevation, and the patency status of the infarct artery is uncertain. Consequently, acute angiography is often required to determine infarct artery patency.

In summary, we have made remarkable progress in the treatment of STEMI by improving timely access to PCI. In 2016, patients who present to a PCI center should undergo PCI with a D2B time of ≤90 minutes, and patients from a non-PCI hospital should be transferred to a PCI hospital if they can be treated in ≤120 minutes.^5,6 For patients beyond 120 minutes, it now appears that a pharmacoinvasive approach (fibrinolysis followed by PCI within 24 hours) is the best strategy, but the ideal regimen and timing of revascularization remain areas of controversy.^30,39,48

Before Procedure

The electrocardiogram (ECG) is critical to establishing a diagnosis of STEMI and triggering a management cascade. Transmission of an ECG taken in the field by emergency medical services to a PCI-capable hospital can facilitate rapid mobilization of the catheterization laboratory, thereby reducing transit time through the emergency department and thereby overall D2B time. When primary PCI is planned for patients with known or suspected AMI, a limited history and physical examination should be performed to avoid delays in initiating the catheterization procedure. Patients are given 325 mg of soluble chewable aspirin, intravenous unfractionated heparin, and sublingual nitroglycerin and are transported promptly from the emergency department to the catheterization laboratory. A P2Y₁₂ inhibitor should be given as soon as possible based on evidence from multiple trials, discussed later, since the rate of emergent CABG following primary PCI for STEMI is low.

Procedural Considerations

Radial Versus Femoral Access

Bleeding portends a worse prognosis in STEMI. Access site–related bleeding can be reduced via a radial approach. Evidence supporting better outcomes with radial catheterization comes from a 2015 meta-analysis of 4 large, contemporary, multicenter trials and trials of patients (n = 17,133) with acute coronary syndromes^53-57 (Fig. 37-10). Comparing radial with femoral access, the risk was lower in terms of major bleeding (relative risk [RR], 0.57; 95% confidence interval [CI], 0.37-0.88), death (RR, 0.73; 95% CI, 0.59-0.90), and major adverse cardiac events (MACE; RR, 0.86; 95% CI, 0.75-0.98). However, in certain clinical situations, such as a patient with cardiogenic shock or cardiac arrest, a transfemoral approach may be preferable to facilitate use of larger guide catheters and peripheral hemodynamic support devices that are not able to be delivered radially.

Aspiration Thrombectomy

Intracoronary thrombus is found in a significant proportion of patients with STEMI. Thrombus may obstruct distal blood flow and increases subsequent myocardial ischemia. Although aspiration thrombectomy may reduce thrombus burden, there is a lack of evidence to demonstrate a significant clinical benefit from routine use. The TOTAL (Randomized Trial of Routine Aspiration Thrombectomy With PCI Versus PCI Alone in Patients With STEMI Undergoing Primary PCI), TASTE (Thrombus Aspiration in ST-Elevation Myocardial Infarction in Scandinavia), and TAPAS (Thrombus Aspiration During Percutaneous Coronary Intervention in Acute Myocardial Infarction Study) trials are the largest studies of manual thrombectomy in STEMI.^58-61 These studies randomly assigned patients to manual thrombectomy followed by PCI or PCI alone.