Acute Coronary Syndrome

(Myocardial infarction including NSTE-ACS/NSTEMI and STEMI)

65 y/o M with h/o HTN, CAD, HLD, previous MI, CKD, DM, smoking presents with acute onset chest pain. Reports two episodes of chest and L arm pain similar to previous angina episodes within the past 24 hours. Pain severity acutely increased prior to presentation. Medications include ASA with last use within previous 7 days. Records show coronary artery stenosis ≥ 50%. Family h/o MI-related death 1st degree M relative <55 y/o and 1st degree female relative <65 y/o. Hypotension, diaphoresis, pulmonary crackles, and transient mitral regurgitation on exam. Pain not reproducible with palpation.

• TIMI risk score

  • ≥ 2 indicated need for urgent evaluation

  • ≥ 4 indicates high likelihood of CAD as the cause of chest pain (LR 11.2)

• Stat troponins values > 0.150; obtain repeat troponins at 3 and 6 hours s/p initial draw

• Stat EKG obtained within 10 minutes of presentation shows NSTE-ACS vs. STEMI (see below for specific treatment)

Treatment

• Initial therapy

  • Aspirin: Chew non-enteric coated 325 mg at symptom onset

  • Nitroglycerin 0.4 mg sublingually q5 minutes for up to 3 doses as BP allows

  • SPO2 <90%: Start oxygen 4L by NC

  • Heparin 60 u/kg IV bolus (max 4,000 u) followed by 12 u/kg/hr infusion (max 1,000 u/hr) to maintain aPTT 1.5-2.0 until revascularization (see STEMI) or 48 h s/p symptom onset

  • Consider morphine 4-8 mg IV q15 min for refractory chest pain

• Treatment based on EKG findings

  • NSTE-ACS

    • ST depression in contiguous leads ≥ 0.5 mm, T wave inversion, and new onset Q waves

    • Able to take aspirin; administer clopidogrel 600 mg loading dose

  • STEMI: ST elevation and new onset L bundle branch block (see notes for details)

    • Percutaneous coronary intervention (PCI) capable facility: Complete PCI within 12 hours of symptoms onset and administer clopidogrel 600 mg s/p procedure

    • PCI not available and pt < 75 y/o with CrCl > 30: Transfer to a capable facility (preferred) or administer clopidogrel 300 mg and fibrinolytic therapy (tPa)

• Additional therapy

  • Start carvedilol 6.25 mg BID and titrate as tolerated

  • Start lisinopril 2.5 mg qd within 24 hours of symptoms onset; titrate to 10 mg qd

  • Continue clopidogrel 75 mg qd maintenance therapy x12 months

  • Start atorvastatin 80 mg qd

• Establish outpatient appointment with cardiologist upon discharge

Notes

• Epidemiology

  • CAD risk factors include HTN, HLD, DM, current smoking, and family h/o CAD

  • Average age at first MI is 65 years

  • Most predictive s/sx include abnormal stress test, h/o peripheral arterial disease, diaphoresis, acute hypotension, and EKG changes

• Myocardial infarction terminology

  • MI definition: Ischemia-induced cardiac muscle damage resulting in elevated troponins (>3x ULN) and one of the following

    • Signs or symptoms of ischemia

    • New, significant EKG changes (see below)

    • New cardiac wall motion abnormality on echo

  • Ischemia subtypes

    • Type 1: Thrombotic occlusion of a vessel

    • Type 2: Myocardial oxygen demand exceeds oxygen supply

  • Non-ST elevation myocardial infarction (NSTEMI)

    • Term no longer used by the American College of Cardiology

    • Now grouped with unstable angina and known as non-ST elevation acute coronary syndrome (NSTE-ACS)

• Troponins >3x ULN are considered significant; this value varies locally and >0.150 is used an example above because it applies to this author’s local institution

• EKG changes

  • ST elevation: Anatomically contiguous lead changes that meet any of the following criteria:

    • ≥ 2 mm in men or ≥ 1.5 mm in women for leads V2-3

    • ≥ 1 mm for leads V1, V4-6, I-III, AVL, AVF

  • New onset L bundle branch block in the setting of acutely elevated troponins is considered an MI (STEMI) equivalent

• Absolute contraindications to fibrinolytic therapy (e.g. tPa)

  • Blood pressure

    • Systolic BP > 180 mmHg, diastolic BP > 100 mmHg

    • R vs. L arm pressure > 15 mmHg

  • CNS

    • Closed head trauma within previous 3 months

    • Any history of intracranial bleeding

    • Ischemic stroke > 3 hours or within previous 3 months

    • Structural CNS disease (vascular malformation, neoplasm, etc.)

  • Pregnancy

  • ESRD

  • Metastatic malignancy

  • Surgery within the past 4 weeks

Thrombolysis in MI Risk Score

1 point for each:

• Age>64

• 3+ CAD risk factors

• Known CAD with >50% stenosis

• Aspirin use within past 7 days

• 2+ anginal episodes within preceding 24 hours

• Elevated troponin I

• ST segment deviation >0.5mm on admission ECG

Interpretation

• Low risk (0-2): Stress test

• Intermediate (3-4) to high (5-7) risk: Coronary angiography within 24 hours

• Immediate coronary angiography for hemodynamic instability, heart failure/new MR, recurrent chest pain, ventricular arrhythmia