ST Elevation Criteria for Myocardial Infarction

Standard ST Elevation Criteria

• The European Society of Cardiology recommends that ST elevation should be measured at the J-point (where the QRS complex meets the ST segment) 1
• Standard calibration of ECG is 10mm/mV, so 0.1 mV equals 1 mm on the vertical axis 1
• ST elevation must be present in at least two contiguous leads, as recommended by the American Heart Association 2
• Lead-specific ST elevation thresholds are:
  • ≥2.5 mm (0.25 mV) in men under 40 years in precordial leads V2-V3,
  • ≥2 mm (0.2 mV) in men 40 years and older in precordial leads V2-V3,
  • ≥1.5 mm (0.15 mV) in women in precordial leads V2-V3,
  • ≥1 mm (0.1 mV) in all other leads, as recommended by the European Society of Cardiology 1, 3, 2

Special Considerations

• For inferior MI, the European Society of Cardiology recommends recording right precordial leads (V3R and V4R) to identify concomitant right ventricular infarction 1, 3
• For suspected posterior MI, the European Society of Cardiology recommends that ST depression in leads V1-V3 may indicate posterior MI, especially when the terminal T-wave is positive (ST elevation equivalent) 1, 3
• The European Society of Cardiology also recommends confirmation by ST elevation ≥0.5 mm in posterior leads V7-V9 for suspected posterior MI 1, 3

Important Caveats and Pitfalls

• Left bundle branch block (LBBB) may interfere with ST-segment analysis and should not be considered diagnostic of acute MI in isolation, as stated by the American College of Cardiology 2
• The 2013 ACCF/AHA guidelines removed new LBBB as a STEMI equivalent due to its infrequent occurrence, as reported by the American College of Cardiology 4
• Non-diagnostic ECGs may occur in some patients with acute coronary occlusion, and early presentation may show hyperacute T-waves before ST elevation develops, as noted by the European Society of Cardiology 3

Clinical Application

• When STEMI is suspected, a 12-lead ECG must be acquired and interpreted as soon as possible to facilitate early diagnosis and triage, as recommended by the European Society of Cardiology 1
• If the initial ECG is equivocal but clinical suspicion remains high, serial ECGs should be performed to detect dynamic changes, as recommended by the European Society of Cardiology 3
• In patients with suspected posterior MI, extending the standard 12-lead ECG with leads V7-V9 may identify patients who would otherwise be missed, as recommended by the European Society of Cardiology 3
• Clinical judgment remains essential, particularly in cases with atypical presentations or non-diagnostic ECGs with high clinical suspicion for acute coronary occlusion, as stated by the European Society of Cardiology and the American Heart Association 3, 2

Differentiating Recent vs. Old STEMI on 12-Lead ECG

Clinical Context and ECG Features

• The American College of Cardiology and American Heart Association emphasize that a working diagnosis of STEMI requires both symptoms consistent with myocardial ischemia and electrocardiographic signs, with clinical correlation with symptoms and timing being mandatory 5, 6.
• Serial ECGs are critical, as 11% of patients ultimately diagnosed with STEMI had an initial nondiagnostic ECG, with 72.4% showing diagnostic changes within 90 minutes 7, 8.

ECG Features of Acute/Recent STEMI

• The European Heart Journal notes that acute STEMI shows ST-segment elevation with hyperacute T-waves and preserved R-waves, while old MI demonstrates pathologic Q-waves, normalized or inverted T-waves, and persistent but diminished ST elevation 6.
• ST-segment elevation measured at the J-point in ≥2 contiguous leads is a key feature, with specific criteria for men and women in different leads 6.
• Reciprocal ST-depression in opposite leads is also a feature of acute STEMI 5.

ECG Features of Old/Healed MI

• Pathologic Q-waves persist indefinitely, with loss of R-wave amplitude or absent R-waves in affected leads 6.
• Normalized or persistently inverted T-waves, and ST segments returning to baseline or showing minimal persistent elevation, are also characteristic of old MI 6.

Key Distinguishing Algorithm

• The American College of Cardiology recommends assessing ST-segment morphology, with acute STEMI showing convex upward ST elevation, and old STEMI showing minimal or absent ST elevation 6.
• Evaluating T-wave configuration, with acute STEMI showing hyperacute or upright T-waves, and old STEMI showing inverted or flattened T-waves, is also crucial 6.
• Examining Q-waves, with acute STEMI showing absent or small Q-waves, and old STEMI showing deep, wide pathologic Q-waves, is an important step 6.

Special Considerations

• The American College of Cardiology notes that posterior MI may be represented by ST depression in V1-V3 with positive terminal T-waves, and can be confirmed with ST elevation in posterior leads V7-V9 7, 8.
• Right ventricular involvement in inferior STEMI can be identified with right-sided leads (V3R, V4R) showing ST elevation >0.5 mm 6.
• The European Heart Journal recommends that if ST elevation is present with compatible symptoms, acute STEMI should be assumed, and reperfusion protocols activated immediately, without delay for biomarkers 5, 6, 7, 8.

Diagnosis dan Pengelolaan Occlusion Myocardial Infarction (OMI)

Kriteria Diagnostik

• American Heart Association merekomendasikan bahwa STEMI anterior didefinisikan sebagai elevasi ST-segmen ≥2 mm (0,2 mV) pada pria ≥40 tahun atau ≥2,5 mm pada pria <40 tahun di lead V2-V3, atau ≥1,5 mm pada wanita di lead V2-V3, dengan ≥1 mm di lead lainnya, yang harus ada di minimal 2 lead yang berdekatan 9
• Elevasi ST yang tidak memenuhi kriteria voltage STEMI namun disertai dengan gelombang T hiperakut (tall, peaked T-waves) yang proporsional lebih besar dari gelombang R dapat mengindikasikan OMI 10
• Depresi ST resiprokal di lead inferior (II, III, aVF) atau lateral (I, aVL) yang menyertai elevasi ST anterior minimal dapat mengindikasikan OMI 11
• Elevasi ST di lead aVR dengan depresi ST multilead (≥8 lead) menunjukkan oklusi left main atau proksimal LAD 11

Fitur EKG Lainnya

• Rasio amplitudo gelombang T terhadap gelombang R (T/R ratio) yang tinggi di lead V2-V4, terutama jika disertai dengan penurunan amplitudo gelombang R, dapat mengindikasikan OMI 10
• QTc yang memanjang (>450 ms pada pria, >460 ms pada wanita) dapat membedakan OMI dari early repolarization normal 11

Implikasi Klinis

• Pasien dengan OMI yang tidak memenuhi kriteria STEMI mengalami keterlambatan signifikan ke kateterisasi, dengan median 437 menit vs 41 menit untuk STEMI(+) OMI, menurut European Heart Journal 11
• Hanya 28% pasien STEMI(-) OMI menjalani kateterisasi dalam 90 menit, dibandingkan 76% pada STEMI(+) OMI, menurut Circulation 10
• Keterlambatan ini terjadi meskipun mortalitas dan troponin puncak pada STEMI(-) OMI lebih mirip dengan STEMI(+) OMI daripada pasien tanpa oklusi, menurut American Heart Association 9

STEMI Electrocardiographic Diagnostic Criteria

Voltage Thresholds for ST‑Segment Elevation

• Precordial leads V2‑V3:

  • Men ≥ 40 years: ST‑elevation ≥ 2.0 mm (0.2 mV).
  • Men < 40 years: ST‑elevation ≥ 2.5 mm (0.25 mV).
  • Women (all ages): ST‑elevation ≥ 1.5 mm (0.15 mV).
    These age‑ and sex‑specific thresholds reflect normal physiologic variation.* 12, 13

• All other leads (I, II, III, aVL, aVF, V4‑V6): ST‑elevation ≥ 1.0 mm (0.1 mV).** 12, 13

• Special lead locations:

  • Leads V4‑V5: ≥ 0.5 mm (0.05 mV); for males < 30 years, ≥ 1.0 mm is preferred.** 12
  • Posterior leads V7‑V9: ≥ 0.5 mm (0.05 mV).** 12, 13
  • Right‑sided leads V3R‑V4R: ≥ 0.5 mm (≥ 1.0 mm in men < 30 years).** 13

Requirement for Contiguous Leads

• ST‑elevation must be present in at least two anatomically contiguous leads to satisfy diagnostic criteria.** 12, 13

• Defined contiguous lead groups:

  • Anterior: V1‑V6.** 12
  • Inferior: II, III, aVF.** 12
  • Lateral: I, aVL, V5‑V6.** 12

STEMI Equivalents Requiring Immediate Reperfusion

• Posterior STEMI equivalent: Isolated ST‑depression ≥ 0.5 mm in leads V1‑V3 with upright (positive) terminal T‑waves indicates a posterior occlusion.** 13

  • Confirmation by recording posterior leads V7‑V9; ST‑elevation ≥ 0.5 mm confirms transmural posterior infarction.** 13

• New left bundle‑branch block (LBBB): In a patient with ischemic symptoms, a new LBBB is treated as a STEMI equivalent. Concordant ST‑elevation (elevation in leads with positive QRS deflection) is the most reliable marker of acute coronary occlusion in this setting.** 13

  • Prior ECGs are valuable to determine whether the LBBB is new.** 13

• Right‑ventricular infarction: In inferior STEMI, recording right‑sided leads V3R‑V4R; ST‑elevation ≥ 1.0 mm indicates right‑ventricular involvement and mandates specific hemodynamic management.** 13

Measurement Technique

• ST‑segment deviation should be measured at the J‑point (junction of QRS end and ST‑segment start). Standard ECG calibration is 10 mm/mV, so 0.1 mV equals 1 mm on the vertical axis.** 12, 13

Reciprocal ST‑Depression

• Presence of reciprocal ST‑depression in anatomically opposite leads increases diagnostic specificity for acute coronary occlusion. 12
  
  • Example: Inferior STEMI (II, III, aVF elevation) typically shows reciprocal depression in I and aVL.
   12
  
  • Example: Anterior STEMI (V1‑V6 elevation) typically shows reciprocal depression in II, III, and aVF.** 12

Conditions That Can Mimic STEMI

• Left ventricular hypertrophy may produce ST‑elevation in precordial leads.** 13
• Early repolarization (especially in young males) can present with J‑point elevation.** 13
• Acute pericarditis shows diffuse ST‑elevation without reciprocal depression.** 13
• Brugada syndrome produces characteristic right‑precordial ST‑elevation.** 13

Clinical Implementation Algorithm (Key Steps with Evidence)

All facts are derived from the American Heart Association (Circulation) and the American College of Cardiology (Journal of the American College of Cardiology) guidelines.