Background

Abbreviation: STEMI

RV infarction accompanies ~25% of inferior STEMIs Hemodynamically significant only 10% of the time Do NOT reduce preload (caution with NTG) Optimise preload (ensure volume replete)

Posterior (aka inferolateral) infarction is rarely isolated (~3-8% of all AMIs) Treat as STEMI Look for reciprocal changes, except in aVR and V1 Apply V7, V8, V9 leads and repeat ECG looking for ST elevation Usually will see changes in V6 OR II, III, aVF



Fourth Universal Definition of STEMI

Any of the following:[1]

1 mm of ST elevation in any two contiguous leads except V2 and V3. The acceptable degree of ST elevation in V2 and V3 changes based on age and gender.

In women: 1.5mm elevation in V2 and V3

In men under 40: 2.5mm elevation in V2 and V3

In men 40 and older: 2mm elevation in V2 and V3

ACS Anatomical Correlation Chart

Ischemic Changes Location Coronary Artery STE V1-V3, TWI

Q waves in V1-V3 over time Septal Septal branch STE V2-V4 Anterior LAD STE I, aVL, V5, V6

STD inf leads Lateral Circumflex STE I, aVL, V2-6 Anterolateral LAD + circumflex = Left main or 2 critical lesions STE II, III, aVF

STD in aVL (most common lead to see reciprocal change) Inferior RCA STE V1 (only lead looking at RV)

STE III > II (III more R facing)

STE V1 > V2, STE V1 + STD V2 Right ventricle RCA STD in V1, V2, V3;

R>S in V1

Tall R waves in V1-V3 (Q waves on back of heart) w/ upright TWs

Posterior aka Inferolateral RCA (90%), LCA (10%) STE avR>V1

Doesn't apply in SVT Anterolateral Left Main

ECG vectors

Prehospital

Hyperoxia may increase myocardial injury Avoid supplemental oxygen unless hypoxic [2]

Activate cath lab for patients with STEMI on prehospital ECG even if ST elevation has resolved by time of arrival at hospital [3]

STEMI Stages of Development

Stages of STEMI development

Stage Duration Timing Finding ECG 1 30min - hours Hyperacute T waves >6mm limb leads

>10mm precordial leads Normalizes in days, weeks, or months 2 Minutes - hours ST segment elevation 0.1mV in two or more contiguous leads ST segment resolution occurs over 72hrs; completely resolves within 2-3wks 3 Within 1hr; completed within 8-12hr Q waves Persist indefinitely in 70% of cases

Clinical Features

Risk of ACS

Clinical factors that increase likelihood of ACS/AMI:[4][5]

Clinical factors that decrease likelihood of ACS/AMI:[6]

Pleuritic chest pain

Positional chest pain

Sharp, stabbing chest pain

Chest pain reproducible with palpation

Gender differences in ACS

Women with ACS: Less likely to be treated with guideline-directed medical therapies [7] Less likely to undergo cardiac catheterization [7] Less likely to receive timely reperfusion therapy [7] More likely to report fatigue, dyspnea, indigestion, nausea or vomiting, palpitations, or weakness, [7] although some studies have found fewer differences in presentation [8]

More likely to delay presentation [7]

Men with ACS: More likely to report central chest pain



Factors associated with delayed presentation[7]

Female sex

Older age

Black or Hispanic race

Low educational achievement

Low socioeconomic status

Additional features

Signs/symptoms may include

Differential Diagnosis

Disease STEMI Pericarditis Pain Constant Varies with motion Fever No Yes ST changes focal Diffuse elevation Reciprocal changes Yes No Q waves Yes No Pulmonary edema Sometimes No Wall motion Abnormal Normal

Evaluation

Workup

ECG Use the J-point for measurement in 2 contiguous leads [9] J point is where there is a sudden change in direction When possible, compare to old ECGs Repeating ECGs will increase sensitivity

CBC

Chem 7

Troponin

PT/PTT

Consider CXR

Diagnosis

Inferior and right sided STEMI

Look for ST segment elevation, reciprocal ST depression, and hyperacute T waves

Classic STEMI

Men In males ≥ 40 years old 2mm in V2-V3 and 1mm in all other leads [10] In males < 40 years old 2.5mm in V2-V3 and 1mm in all other leads [10]

Women ≥1.5 mm in V2-V3 and 1 mm (0.1mV) in all other leads [10]



Posterior STEMI

Up to 10% of STEMIs; usually associated with inferior MI

≥0.5 mm STE is diagnostic

Look at V1-V3 [11] [12] Large R waves (posterior Q waves) STD Upright T waves



Post-arrest STEMI/NSTEMI

Get immediate ECG after arrest

STEMI: go to cath lab immediately (AHA/ACCF Class IB) [13]

NSTEMI: go to cath within 2 hrs if VT/VF, intractable ischemic pain, ADCHF (AHA/ACC Class IA)[14]

New LBBB alone is no longer STEMI criteria for cath lab as of 2013 per ACC/AHA guidelines [15]

Hemodynamically unstable or new HF pts with new LBBB should be discussed with a cardiologist for PCI or fibrinolytics

Sgarbossa's Original Criteria

≥3 points = 98% probability of STEMI [16] ST elevation ≥1 mm in a lead with upward (concordant) QRS complex - 5 points ST depression ≥1 mm in lead V1, V2, or V3 - 3 points ST elevation ≥5 mm in a lead with downward (discordant) QRS complex - 2 points Least specific of criteria, see Smith's modification



Smith's Modified Sgarbossa 3rd Rule

Changes the 3rd rule of original Sgarbossa's Criteria to be ST depression OR elevation discordant with the QRS complex and with a magnitude of at least 25% of the QRS increases Sn from 52% to 91% at the expense of reducing Sp from 98% to 90%[17]

Pacemakers in AMI Sgarbossa criteria can be applied to paced rhythms [18] [19] Low sensitivity but high specificity

DeWinter T-waves [20] High risk of ACUTE (vs subacute in Wellen's) anterior MI (proximal LAD occlusions) [21] Look for 1-3 mm STD at J-point in mid precordial leads with tall symmetric T waves [22]

ST elevation in aVR [23] Reflects subendocardial ischemia in LV (L main vs multi vessal disease) [24] Look for STE >1-1.5 mm in aVR Can also bee seen in hemorrhage, type A Dissection, massive PE



Management

Thrombolytics vs PCI

Primary treatment is centered on PCI within 90 min (if available) or thrombolysis if treatment delay is greater than 120min.

Percutaneous coronary intervention (preferred option) Goal: PCI should be attempted if the procedure can be started within 120 minutes (faster than 90 minutes is the goal, the faster the better)

If the PCI cannot be commenced within 120 minutes then fibrinolysis should be given to suitable candidates Fibrinolytics Goal: if it is determined that PCI cannot be performed within 120 minutes then fibrinolytics should be given, and they should be given within 30 minutes

Adjunctive Therapies

Aspirin 162-325mg chewable or 600mg PR Nitroglycerin Do not give if RV MI

Do not give with phosphodiesterase inhibitors O2 For SpO2 <90%

Avoid hypoxia but supplemental O2 without hypoxia can increase infarct size [2] AVOID trial [25] (2015) indicated larger infarct size, more recurrence and arrhythmia for STEMI patients without hypoxia who were treated with O2

Antiplatelet Options Clopidogrel See drug link for specific age, indication related dosages Generally, loading dose of 600 mg if PCI anticipated (otherwise give 300 mg)

Ticagrelor May significantly reduce mortality as compared to clopidogrel [26] 180mg loading dose, followed by 90mg BID Ticagrelor offers no added benefit in STEMI when given pre-hospital vs. in-hospital (ambulance vs. cath lab) [27]

GPIIB/IIIa Inhibitors Abciximab, Eptifibatide

Defer to cardiologist for administration

Given right before PCI depending on specific institutional protocols Beta blockers[28] Per AHA guidelines, IV beta blockers should not be given to patients with STEMI routinely, but may be considered for hypertension treatment barring contraindications as below: Low output state, signs of HF Increased risk of cardiogenic shock (age > 70, sinus tachycardia > 110 bpm or HR < 60 bpm, SBP < 120 mmHg) Increased time since onset of STEMI Relative contraindications -- asthma, COPD, PR interval > 0.24 sec, AV block

be given to patients with STEMI routinely, but may be considered for hypertension treatment barring contraindications as below: PO beta blockers should be initiated within 24 hours of STEMI ACE inhibitor or ARB[29][30] Give within 24 hours in stable patients, typically not given in ED

Careful initial dosing, starting at 2.5 mg/day of lisinopril, increasing slowly up to 10 mg/day Statin in STEMI patients going to cath lab may have less 30-days MACEs and reinfarction post-PCI in SECURE-PCI trial in 2018[31] 80 mg atorvastatin immediately before cath lab and 24 hours after PCI

Perform in conjunction with your cardiologist

No cases of rhabdomyolysis or liver failure reported in the atorvastatin group

Anticoagulation

Heparin is required after thrombolysis to prevent re-thrombosis since all thrombolytics are short acting. Any patient receiving PCI requires heparinzation to prevent thrombosis during the procedure. There is minimal to no benefit for heparin in NSTEMI patients who are not receiving immediate PCI.[32]

Heparin (UFH) Bolus 60U/kg (max: 4000U) followed by 12U/kg/h (max: 1000U/h)

Titrate to PTT 1.5-2.5 x control LMWH <75yo with serum creatinine < 2.5mg/dL (men) or < 2.0mg/dL (women): 30mg IV bolus followed by 1mg/kg SC q12h

≥ 75yo 0.75mg/kg SC q12h

CrCl < 30 mL/min 1mg/kg SC QD

Fondaparinux creatinine < 3.0mg/dL: 2.5mg IV bolus then 2.5mg SC QD started 24hr after bolus

Monitor anti-Xa levels Bivalirudin 0.75mg/kg IV bolus followed by 1.75mg/kg/h

CrCl < 30 mL/min 0.75mg/kg IV bolus followed by 1.0mg/kg/h



Special Scenarios

Consider therapeutic hypothermia cooling protocol for patients with documented cardiac arrest felt to be caused by lethal cardiac rhythm (e.g. ventricular fibrillation)

Patients with cardiac arrest and ST elevation at any point, even if resolved, should still under go emergent coronary angiography[33]

Rescue PCI

Failed reperfusion: consider if repeat ECG 90 minutes after infusion fails to show reduction of elevated ST segments by 50%

Recurrent significant ST elevation following successful lysis

Persistent hemodynamically unstable arrythmias, persistent ischemic symptoms, or worsened cardiogenic shock

Even in those with successful reperfusion, its reasonable to do angiography within the index hospitalization, even within hours of thrombolytic therapy

Post-STEMI complications

Cath site hematoma

Heart failure or cardiogenic shock Hemodynamic support, consider norepinephrine or dobutamine Mechanical support e.g. balloon pump or Impella, usually placed in cath lab

Ventricular tachycardia or ventricular fibrillation --> if sustained and > 48 hours after STEMI may need ICD

Pericarditis, < 1 week from STEMI --> treat with high dose aspirin, avoid NSAIDs

Bradycardia, if AV nodal involvement, rarely responds to atropine, likely will require pacing

Free wall or ventricular septal rupture

Dressler's syndrome, > 1 week post MI

Disposition

Admit direct to cath lab

If not at tertiary care center consider tPA depending transfer time and transfer to cardiac cath lab center

See Also

References