Myocardial Infarction, ST Elevation

BETA BLOCKERS

Oral β-blockers are recommended within 24 hours of presentation for patients with STEMI (Class I, LOE B) and NSTE-ACS (Class I, LOE A) and should be continued at discharge. β-Blockers decrease heart rate, contractility, blood pressure, and myocardial oxygen consumption. While early β-blockers do not reduce short-term mortality in patients with ACS, they decrease ischemia, reinfarction, and ventricular arrhythmia. Furthermore, β-blockers improve long-term survival in patients with MI complicated by heart failure and ventricular arrhythmia. The long-term duration of routine β-blocker therapy after myocardial infarction without heart failure or hypertension has not been prospectively addressed, but guidelines recommend a 3-year treatment course then reassess the clinical need for the medication. Meta-analysis from the reperfusion era suggests β-blockers can reduce MI (RR 0.72 [95% CI, 0.62-0.83], NNT = 209) and angina (RR 0.80 [95% CI, 0.65-0.98], NNT = 26) at the expense of increased heart failure (RR 1.1 [95% CI, 1.05-1.16], NNH = 79) and increased cardiogenic shock (RR 1.29 [95% CI, 1.18-1.41], NNH = 90)with no significant impact on mortality. While oral β-blockers are an important part of ACS management, IV β-blockers should usually be avoided as they increase the risk for shock (Class III, LOE B). In addition, oral β-blockers are contraindicated in patients with signs of acute heart failure, evidence of low-output state, increased risk for cardiogenic shock, second- or third-degree heart block, and active asthma. When β-blockers are contraindicated due to asthma exacerbation, then nondihyophyidine calcium channel blockers could be considered as long there are no contraindications (Class I, LOE B).

RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM INHIBITORS

Angiotensin Converting Enzyme (ACE) inhibitors have been shown to lower mortality in patients with recent myocardial infarction and reduced left ventricular ejection fractions (LVEF) less than 40% (Class I, LOE A). Furthermore, ACE inhibitors should be strongly considered in patients with diabetes mellitus and stable chronic kidney disease (Class I, LOE A). In patients who are intolerant to ACE inhibitors, angiotensin receptor blockers (ARBs) should be considered. While meta-analyses suggest a small (0.48% absolute, NNT = 208) reduction in 30-day mortality with ACE inhibitors in ACS, the clinical significance of this finding is unclear and ACE inhibitor should be used with caution without the above indications given the risk for renal dysfunction and hypotension.

Aldosterone antagonists (eg, eplerenone, spironolactone) are recommended for patients with AMI and LVEF less than or equal to 40% (Class I, LOE B). In the EPHESUS (Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival) study, demonstrated significantly reduced rates of death from cardiovascular causes or hospitalization for cardiovascular events (relative risk, 0.87; 95% CI, 0.79-0.95; P = 0.002, NNT = 30) in patients with eplerenone initiated within days of admission.

HIGH-INTENSITY STATIN THERAPY

High-intensity statin therapy should be given to all patients with ACS without contraindications (Class I, LOE A). Statins should be started at moderate to high doses as soon as possible on admission and continued indefinitely. The benefits of statin therapy are well known in the primary prevention for high-risk patients and in secondary prevention for patients with CAD. There may also be an early acute benefit in patients with NSTE-ACS. Several studies have demonstrated reduced rates of periprocedural MI with high-dose statin loading before PCI; therefore, a statin is recommended before PCI when possible (Class IIa, LOE A for statin naive).

ANTICOAGULATION USE WITH ANTIPLATELET THERAPY IN ACS

The choice of stent, P2Y12 antagonist, duration of dual antiplatelet therapy, and anticoagulant is important for patients that require anticoagulation after ACS. This includes patients with atrial fibrillation, venous thromboembolism, mechanical heart valves, and left ventricular thrombus. When anticoagulation is warranted, warfarin is the most common anticoagulant agent and clopidogrel and aspirin the most common antiplatelet agents used. Very little data support the safety of the novel anticoagulants and P2Y12 inhibitors in this setting. In addition, patients with a history of gastrointestinal bleeding who require anticoagulation and antiplatelet therapy should also receive proton pump inhibitors (PPIs) (Class I, LOE C). A PPI can also be considered in patients without history of gastrointestinal bleeding when anticoagulation and antiplatelet therapy are warranted (Class IIa, LOE C). While there were early concerns over potential interactions with certain PPIs and clopidogrel metabolism, more recent registry and randomized trials suggest reductions in bleeding complications without increased cardiac events with the combination of PPIs and clopidogrel.

Triple therapy (aspirin, clopidogrel, and warfarin) after PCI is associated with two- to fivefold greater risk of major bleeding compared to dual antiplatelet therapy. Recent studies suggest that aspirin can often be omitted when anticoagulation is warranted after PCI. In the 573 patient randomized WOEST trial, omission of aspirin decreased major bleeding complications (44.4% vs 19.4%, NNH [by adding aspirin] 4, p < 0.0001) without any increase in ischemic events. Similar findings were noted in a meta-analysis of 1263 patients from six randomized trials as well as a larger real world registry of 12,165 patients undergoing PCI requiring anticoagulation.

Left ventricular (LV) mural thrombus is found in 3% to 15% of anterior MIs treated with percutaneous coronary revascularization. Pooled studies have noted a fivefold increased risk for systemic embolism with LV thrombus after anterior MI, and anticoagulation therapy decreases this embolic risk. Thus, anticoagulation is recommended for patients with acute MI and asymptomatic LV mural thrombus (Class IIa, LOE C). Anticoagulation after anterior MI without mural thrombus formation is controversial. Currently, the guidelines suggest that anticoagulation therapy may be considered for patients with STEMI and anterior apical akinesis or dyskinesis (IIb, LOE C). However, in a recent retrospective analysis of 460 undergoing PCI for anterior MI without LV thrombus, anticoagulation was actually associated with an increased incidence of stroke (3.1% vs 0.3%, p = 0.02), major bleeding (8.5% vs 1.8%, p < 0.0001), mortality (5.4% vs 1.5%, p = 0.04), length of stay, and readmissions. Furthermore, after propensity matching, anticoagulation was still associated with a fourfold greater incidence of net adverse cardiac events. These findings certainly question the routine use of triple therapy in this population without LV thrombus. Until larger randomized trials are conducted, if anticoagulation is used in this setting, clinicians should probably omit aspirin, add proton pump inhibitors, target lower INR ranges, shorten the anticoagulation course (3 months), and use radial access when possible.

SECONDARY PREVENTION

All patients with ACS should be referred to a comprehensive cardiovascular rehabilitation program (Class I, LOE B). These programs provide patient education, regular exercise, monitor risk factors, and address lifestyle modification. The pneuomococcal vaccine is recommended for patients 65 years and older and high-risk patients with cardiovascular disease (Class I, LOE B). In addition, annual influenza vaccination is recommended for all patients with ACS (Class I, LOE C), and based on randomized controlled trial data has been shown to reduce MACE (NNT = 17) and hospitalization for ACS (NNT = 31). NSAIDs have been associated with increased cardiovascular risk and should largely be avoided in patients with ACS (Class III, LOE B). For patients with chronic musculoskeletal pain, acetaminophen, nonacetylated salicylates, tramadol, or low dose narcotics should be used as required (Class I, LOE C). If NSAIDs are required when these therapies are insufficient, then the nonselective naproxen is preferred over other NSAIDS (Class IIa, LOE C).

PRACTICE POINT

Late Hospital ACS Care and Hospital Discharge

All patients with ACS should be discharged with dual antiplatelet therapy.
- Options for P2Y12 antagonists include clopidogrel, prasugrel, and ticagrelor after PCI.
- Options for P2Y12 antagonists include clopidogrel and ticagrelor with medical management without PCI.
All patients with ACS should receive high-intensity statin therapy.
All patients with MI should receive oral β-blocker therapy for at least 3 years after myocardial infarction and indefinitely for patients with congestive heart failure and/or hypertension.
All patients with reduced LVEF ≤ 40% should receive an ACEI or ARB and aldosterone antagonist unless contraindications.
When anticoagulation is warranted in patients with PCI for ACS, warfarin is preferred and aspirin can usually be omitted.
All patients should be counseled about smoking cessation, diet, and exercise.
All patients should be referred to cardiac rehabilitation programs at discharge.

Discharge checklist