Doctor123.org

Acute Coronary Syndromes: Unstable Angina and NSTEMI

Chest x-rayConsider transthoracic echocardiography if not recently performed (1)[B]. Follow-Up Tests & Special Considerations

para>ST-segment depression and/or T-wave inversion:

  • ≥1-mm ST depression in ≥2 contiguous leads
  • T-wave inversions, other changes
  • ST depression and/or tall R wave in V1/V2 with upright T waves may indicate transmural STEMI of posterior wall.
  • If initial ECG is nondiagnostic but symptoms persist with suspicion for ACS, perform serial ECGs at 15-30-minute intervals.
  • NSTEMI is strictly defined as a rise and fall in serum biomarkers (usually troponin I or T, as they are more sensitive for detecting NSTEMI) exceeding the 99th percentile of a normal reference population. Troponin concentration rises 3-6 hours after onset of ischemic symptoms but can be delayed to 8-12 hours (troponin T is not specific in patients with renal dysfunction).
  • CK-MB increases 3-4 hours after onset of myocardial injury.
  • Myoglobin: early marker for myocardial necrosis; increases 2 hours after onset of myocardial necrosis
  • Patients with negative biomarkers within 6 hours of the onset of symptoms should have biomarkers remeasured 8-12 hours from onset of symptoms

Follow-Up Tests & Special Considerations

  • Patients with ischemia are recommended to undergo an assessment of left ventricle (LV) function to identify impaired function and/or need for appropriate medications such as ACE inhibitors, beta-blockers, and aldosterone antagonists.
  • Fasting lipid profile
  • Complete blood count(CBC), basic metabolic panel, activated partial thromboplastin time (aPTT)
  • Other laboratory tests:Lactate dehydrogenase: increases within 24 hours, peaks 3-6 days, baseline 8-12 days (not routinely ordered)Leukocytes: increase within several hours after MI, peak in 2-4 daysBrain natriuretic peptide (BNP): increases with MI, may not indicate heart failure

Pregnancy Considerations

Findings mimicking NSTEMI in pregnancy: ST depression after anesthesia, increase in CK-MB after delivery, and mild increase in troponin in preeclampsia and gestational hypertension. Spontaneous coronary dissection is a rare cause of ST elevation in pregnancy.

Diagnostic Procedures/Other

  • Coronary angiography (discussed under "Treatment"ť)
  • If serial cardiac enzymes are negative and symptoms have resolved, consider stress testing, including either standard exercise treadmill test (ETT), stress echocardiography, or stress nuclear study (1)[B].
  • Transesophageal echocardiography, contrast chest CT scan, or MRI generally are reserved for differentiating acute coronary syndrome and other causes of chest pain from aortic dissection.

Test Interpretation

  • Subendocardial myocardial necrosis may be present.
  • Atherosclerosis

Treatment

General Measures

  • Bed/chair rest with continuous ECG monitoring
  • Antiarrhythmics as needed
  • Anxiolytics as needed
  • Deep vein thrombosis prophylaxis
  • Continuation of aspirin, clopidogrel or prasugrel or ticagrelor, beta-blockers, ACE inhibitors (or ARBs if ACE intolerant), lipid-lowering therapy
  • Tight BP control
  • Treatment for depression PRN (common post-MI)
  • Cardiac rehabilitation and increased physical activity
  • Smoking cessation
  • Annual influenza vaccine

Medication

First Line

  • Aspirin, nonenteric-coated, initial dose of 162-325 mg PO or chewed to all patients (1)[A]In patients planned for PCI who are not at high risk for complex disease requiring coronary artery bypass graft (CABG) surgery, administer clopidogrel, loading dose 300-600 mg followed by 75 mg/day (1)[A]; or prasugrel, loading dose 60 mg followed by 10 mg/day (1)[B]; or ticagrelor, loading dose 180 mg followed by 90 mg BID (1)[B]. (Ticagrelor increases the risk of fatal intracranial hemorrhage [ICH] compared with clopidogrel and should be avoided in those with a prior history of ICH [1]).Patients unable to take aspirin should receive a loading and maintenance dose of either clopidogrel, ticagrelor, or prasugrel.
  • Nitroglycerin (NTG) sublingual 0.4 mg every 5 minutes for total of 3 doses, then assess need for intravenous IV NTG (1)[C]
  • Supplemental oxygen 2-4 L/min, maintaining arterial oxygen saturation >90% (1)[B]
  • Morphine sulfate 2-4 mg IV (with increments of 2-8 mg IV repeated at 5-15-minute intervals (1)[A]
  • Oral beta-blocker (cardioselective agent such as metoprolol or atenolol preferred) in patients without signs of heart failure, cardiogenic shock, or other contraindications (1)[B]
  • Risk stratify using the TIMI or GRACE score to select use of early invasive approach (within 12-24 hours of admission) versus medical therapy.
  • Risks and benefits of the early invasive approach:33% relative risk reduction for both the end points of refractory angina and rehospitalization at 6-12 months (2)[A]27% and 22% relative risk reduction in rates of MI at 6-12 months and 3-5 years, respectively (2)[A]Doubled risk of procedure-related MI and increased risk of minor periprocedural bleeding (1)[A]
  • Invasive management
  • Subsequent recommendations (1)[A]: For patients with elevated risk for clinical events or refractory angina or hemodynamic or electrical instability, initiate anticoagulant: enoxaparin or unfractionated heparin (UFH) or bivalirudin. Prior to angiography, add GP IIb/IIIa inhibitor (eptifibatide or tirofiban) or thienopyridine (clopidogrel or ticagrelor).
  • Medical managementFor low-risk or selected intermediate-risk patients; based on patient or physician preference; or in chronic renal insufficiency stage IV: Initiate anticoagulant therapy: enoxaparin or UFH or fondaparinux; enoxaparin or fondaparinux preferable. Initiate clopidogrel, prasugrel, or ticagrelor (1)[B].
  • Contraindications: Prasugrel and ticagrelor are contraindicated in patients >75 years or those with history of CVA/TIA or increased bleeding risk.

Second Line

  • ACE inhibitor in patients with pulmonary congestion or left ventricular ejection fraction (EF) ≤40%. Substitute ARB for ACE-intolerant patients (1)[A].
  • Nondihydropyridine calcium channel blocker (CCB) (verapamil or diltiazem) to reduce myocardial oxygen demand when beta-blockers are contraindicated if normal EF (1)[B]. Use oral long-acting CCB only after beta-blockers and nitrates have been fully used (1)[C].
  • Long-term nitrate therapy for recurrent angina/ischemia or heart failure (1)[C].
  • Sublingual NTG at discharge (1)[C]
  • Lipid-lowering therapy: high-dose statin (preferred due to nonlipid benefit on vascular function) (1)[A], niacin, or fibrate (1)[C]

Issues for Referral

Cardiology consultation is appropriate for likely UA/NSTEMI, particularly regarding the complexities of anticoagulation/antiplatelet therapy.

Surgery/Other Procedures

  • Coronary reperfusionPCI with stent placementCABG surgery
  • Intra-aortic balloon pump for severe ischemia, hypotension, refractory pain

Inpatient Considerations

Admission Criteria/Initial Stabilization

  • All patients with definite or suspected acute MI, ongoing pain, positive cardiac markers, ST deviations, hemodynamic abnormalities, probable or definite ACS
  • Bed rest with continuous ECG monitoring, assess for reperfusion therapy, relieve ischemic pain, treat life-threatening complications, admit to coronary care unit.

Ongoing Care

Follow-up Recommendations

  • Follow-up within 2-6 weeks (low risk) and 14 days (high risk).
  • Refer to cardiac rehabilitation.

Diet

  • Diet low in saturated fat, cholesterol, and sodium
  • Request dietary consult

Patient Education

  • Education on new medications, diet, exercise, smoking cessation, lifestyle modification
  • Resume exercise, sexual activity after outpatient reevaluation

Prognosis

UA/NSTEMI patients have lower in-hospital mortality than those with STEMI but a similar or worse long-term outcome.

Complications

  • Cardiogenic shock
  • Heart failure
  • Myocardial rupture
  • Ventricular aneurysm
  • Dysrhythmia
  • Acute pulmonary embolism
  • Acute thromboembolic stroke
  • Pericarditis/Dressler syndrome
  • Depression (increases mortality risk)
  • Hyperglycemia

References

1.Anderson JL, Adams CD, Antman EM, et al. 2012 ACCF/AHA focused update incorporated into the ACC/AHA 2007 guidelines for the management of patients with unstable angina/non-ST-elevation myocardial infarction: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2013;61(23):e179-e347. [View Abstract]2.Roger VL, Go AS, Lloyd-Jones DM, et al. Heart disease and stroke statistics-2012 update: a report from the American Heart Association. Circulation. 2012;125(1):e2-e220. [View Abstract]

Additional Reading

  • Hoenig MR, Aroney CN, Scott IA. Early invasive versus conservative strategies for unstable angina and non-ST elevation myocardial infarction in the stent era. Cochrane Database Syst Rev. 2010;(3): CD004815. [View Abstract]
  • 2012 Writing Committee Members, Jneid H, Anderson JL, et al. 2012 ACCF/AHA focused update of the guideline for the management of patients with unstable angina/non-ST-elevation myocardial infarction (updating the 2007 guideline and replacing the 2011 focused update): a report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines. Circulation. 2012;126(7):875-910. [View Abstract]

Codes

ICD10

  • I24.9 Acute ischemic heart disease, unspecified
  • I20.0 Unstable angina
  • I21.4 Non-ST elevation (NSTEMI) myocardial infarction
  • I20.1 Angina pectoris with documented spasm

ICD09

  • 411.1 Intermediate coronary syndrome
  • 410.70 Subendocardial infarction, episode of care unspecified
  • 413.1 Prinzmetal angina

SNOMED

  • 394659003 Acute coronary syndrome (disorder)
  • 4557003 Preinfarction syndrome (disorder)
  • 401314000 Acute non-ST segment elevation myocardial infarction (disorder)
  • 71772004 Vasospasm (finding)

Clinical Pearls

  • Discontinue NSAIDs, nonselective or selective cyclooxygenase (COX)-2 agents, except for ASA, due to increased risks of mortality, reinfarction, hypertension, heart failure, and myocardial rupture.
  • Discontinue clopidogrel or prasugrel or ticagrelor 5-7 days before elective CABG.
  • Do not use nitrate products in patients who recently used a phosphodiesterase-5 inhibitor (24 hours of sildenafil or 48 hours of tadalafil).
  • Duration of antithrombotic therapy after NSTEMI depends on type of stent received and medications administered.
  • Avoid beta-blockers in cocaine user.