ECG patterns of ischaemia and infarction

Abbreviations

Overview and definitions

A patient with chest pain arrives, and one question has to be answered within minutes: is a coronary artery occluded now? This page teaches the ECG side of that question: the thresholds, the reciprocal changes, the contiguous and supplemental leads, the occlusion patterns that do not meet the classic criteria, and the mimics. Reperfusion choice and timing are taught in STEMI: reperfusion strategy, and the wider chest pain pathway in Chest pain evaluation.

The ESC calls the resting 12-lead ECG the first-line diagnostic tool in the assessment of patients with suspected ACS.^[1] ESC 2023 says that, based on the initial ECG, patients with suspected ACS can be differentiated into two working diagnoses.^[1]

^[1]

The 2025 NHFA/CSANZ guideline adopted a new term, acute coronary occlusion myocardial infarction (ACOMI), and states that ACOMI may present as STEMI or STEMI equivalents.^[4] The term covers both, and both should prompt consideration for emergency reperfusion.^[4] It was adopted to acknowledge ECG patterns beyond traditional ST elevation criteria that have been found to reflect occlusion without ST elevation, such as posterior MI and De Winter T waves.^[4]

Measuring the ST segment

ESC 2023, ACC/AHA 2025 and the current Fifth UDMI (2026) all state their ST elevation thresholds at the J-point, so get the measurement right first.^[1][2][12]

Fourth UDMI (2018), not restated in the Fifth (history): it described the J-point as the junction between QRS termination and ST-segment onset, with QRS onset as the reference point.^[5] The same Fourth UDMI (2018) text, also not restated in the Fifth, noted that tachycardia and baseline shift are common in the acute setting and can make this harder, so it recommended QRS onset as the reference point for the J-point.^[5] Fourth UDMI (2018), not restated in the Fifth (history): it said that, in patients with a stable baseline, the TP segment was a more accurate way to assess the shift and to distinguish pericarditis (PTa depression) from acute ischaemia.^[5]

ESC 2023, ACC/AHA 2025 and the Fifth UDMI (2026) all set a higher V2–V3 cut-point for men than for women, and for men under 40 than for men 40 or over.^[1][2][12] Fourth UDMI (2018), not restated in the Fifth (history): it noted that, in healthy men under 40, J-point elevation can be as much as 2.5 mm in V2 or V3, but it decreases with increasing age.^[5] The same Fourth UDMI (2018) text, also not restated in the Fifth, said that healthy women have less J-point elevation in V2 and V3 than men, so women need different cut-off points.^[5]

ST elevation thresholds: three sources side by side

ESC 2023 frames the criteria this way: in the appropriate clinical context, ST elevation measured at the J-point is considered suggestive of ongoing acute coronary occlusion in the cases below.^[1] The NHFA/CSANZ 2025 guideline calls ST elevation the key ECG criterion required to institute a reperfusion strategy for people with signs or symptoms of myocardial ischaemia, but says it is not specific to ACOMI, which may occur in other disease states, both cardiac and non-cardiac.^[4]

For ESC 2023, ACC/AHA 2025 and the Fifth UDMI (2026), these cut-points apply to new (ACC/AHA: new or presumed new) ST elevation at the J-point in at least two contiguous leads.^[1][2][12] The Fifth UDMI frames them as what the working diagnosis of STEMI requires.^[12] ESC 2023 and the Fifth UDMI each add, after their other-leads cut-point, that it applies in the absence of LV hypertrophy or LBBB.^[1][12] Fifth UDMI Table 5 words its ST elevation condition as in the absence of bundle branch block and/or LV hypertrophy.^[12] The ACC/AHA Table 3 footnote says ST changes may be observed in other conditions, including LVH and LBBB, that may obscure the diagnosis of STEMI.^[2]

^{[1] [2] [12]}

ST elevation cut-points by source

^{[1] [2] [12]}

The ACC/AHA table was adapted from the Fourth UDMI (2018; Thygesen et al.) and from Kontos et al. (2022).^[2]

^{[1] [2] [12]}

Reading the criteria at the margins

• Beyond the cut-points: the Fifth UDMI (2026) says the diagnosis of STEMI can be made in patients with alternative ECG changes that are suggestive of acute coronary occlusion, or in those who present late where the ST changes have evolved.^[12]
• Timing: the ECG changes of primary MI due to acute coronary occlusion depend on the time of presentation from the onset of persistent symptoms (Fifth UDMI).^[12]

ST depression and T wave changes

ACC/AHA 2025 notes that many patients with NSTE-ACS have either nonspecific ST or T wave changes or a normal ECG, and that the absence of ECG evidence of ischaemia does not exclude ACS.^[2] ESC 2023 notes that the ECG in NSTE-ACS may be normal in more than one-third of patients, although characteristic abnormalities are frequently present and increase the diagnostic probability of ACS.^[1] In its prehospital assessment text, ACC/AHA 2025 adds that ECG changes are not required to confirm a diagnosis of NSTE-ACS.^[2]

ST depression and T wave criteria by source

^{[2] [12]}

• Table and text differ on T wave inversion: Fifth UDMI Table 5 gives new or dynamic T wave inversion ≥1 mm in two contiguous leads, while its text gives T wave inversion >1 mm in two contiguous leads.^[12]
• Other findings: the Fifth UDMI (2026) says that, in addition to ST elevation, ECG findings associated with acute myocardial ischaemia include ST depression, T wave inversion, hyperacute or biphasic T waves, pathological Q waves and ventricular arrhythmias.^[12]
• Not specific: the Fifth UDMI says the ST depression, T wave inversion and global ischaemic changes it describes are not specific to MI, and can be observed in other cardiac and non-cardiac conditions.^[12]

Reciprocal change

The Fifth UDMI (2026) says that with an acute coronary pathology, ST elevation is typically regional and often accompanied by reciprocal ST depression.^[12] Regional ST elevation generally reflects an acute coronary occlusion requiring immediate restoration of blood flow to reduce infarct size.^[12] In contrast, in other conditions such as pericarditis or early repolarisation, ST elevation is often diffuse or global, not confined to a single coronary territory, and occurs without reciprocal changes.^[12]

Contiguous leads and supplemental leads

All three sets of cut-points require at least two contiguous leads (ESC 2023, ACC/AHA 2025, Fifth UDMI 2026).^[1][2][12] The Fourth UDMI (2018) used three contiguous lead groupings in its Q wave criteria for prior MI: I and aVL; V1–V6; and II, III and aVF.^[5]

The 2021 AHA/ACC chest pain guideline says a normal ECG may be associated with left circumflex or right coronary artery occlusions and posterior wall ischaemia, which is often electrically silent, and that right-sided ECG leads should therefore be considered when such lesions are suspected.^[3]

Posterior wall

• ESC 2023: ST depression in V1–V3 (especially when the terminal T wave is positive) and/or ST elevation in V7–V9 is highly suggestive of posterior coronary occlusion, often the left circumflex artery.^[1]
• Fifth UDMI (2026): posterior MI is suggested by ST depression ≥1 mm in V1, V2 and/or V3, particularly when the R wave amplitude is greater than the S wave (dominant) in V1 or V2, and is confirmed by ST elevation in the posterior leads V7–V9.^[12]
• Fourth UDMI (2018), not restated in the Fifth (history): it recommended a 0.5 mm ST elevation cut-off in V7–V9; it said specificity was higher at ≥1 mm, and that this cut-off should be used in men under 40.^[5]
• ACC/AHA 2025, Table 3: posterior leads (V7-V9) should be obtained in suspected left circumflex occlusion, particularly with isolated ST depression ≥0.5 mm in V1-V3 (no class or level given).^[2]

Right ventricle

• ESC 2023 text: in suspected inferior STEMI, it is recommended to record V3R and V4R to assess for ST elevation (no class or level given in the text; the formal row is in the recommendations table below).^[1]
• ESC 2023: ST elevation in V3R and V4R is highly suggestive of ongoing RV ischaemia.^[1]
• ACC/AHA 2025 text: right-sided leads should be obtained when there is concern for inferior STEMI, to evaluate for RV involvement (no class or level given).^[2]
• Fifth UDMI (2026): RV MI is indicated by ST elevation in the right precordial leads (V3R–V6R), especially when accompanied by ST elevation in aVR.^[12]
• Fourth UDMI (2018), not restated in the Fifth (history): it gave ST elevation ≥0.5 mm in V3R and V4R (≥1 mm in men under 30) as supportive criteria in inferior and suspected RV infarction.^[5]
• Fourth UDMI (2018), not restated in the Fifth (history): it also said that right precordial changes may be transient, and that their absence in V3R and V4R did not exclude RV infarction.^[5]

^{[12] [1] [2]}

High lateral MI

• NHFA/CSANZ 2025 counts high lateral infarction among ST elevation patterns often under-recognised in acute settings, and high lateral MI among its ACOMI patterns beyond the traditional criteria.^[4]

Occlusion without classic ST elevation

The Fifth UDMI (2026) says not all patients with acute coronary occlusion demonstrate ST elevation on the 12-lead ECG.^[12] ESC 2023 says the diagnosis of ongoing acute occlusion on ECG can sometimes be challenging, and some cases may warrant immediate reperfusion triage despite the absence of ST elevation.^[1] ST elevation is the most sensitive sign, but other ECG findings can suggest ongoing occlusion or severe ischaemia; if present, prompt triage for immediate reperfusion therapy is indicated, and the ESC sets them out in its online supplementary Figure S2.^[1]

In its prehospital assessment text, ACC/AHA 2025 says that when ST elevation or an equivalent finding is present on the initial ECG, initial management and triage should follow the STEMI treatment algorithm.^[2] Its Table 3 footnote also states that a new LBBB in an asymptomatic patient does not constitute a STEMI equivalent.^[2]

The Fifth UDMI (2026) says previous studies have shown that up to 1 in 4 patients managed as NSTEMI without classical ST elevation on the conventional 12-lead ECG have an acute occlusion of the culprit artery.^[12] It says that, in the right clinical setting, other ECG patterns may be considered equivalent to STEMI.^[12] It lists further ECG patterns that suggest acute coronary occlusion.^[12]

• Marked ST depression or hyperacute T waves in V1–V2 with reciprocal changes elsewhere.^[12]
• De Winter pattern: upsloping ST depression with tall, symmetric T waves in V2–V5 (citing de Winter and colleagues, 2008).^[12]
• Wellens syndrome: biphasic or deeply inverted T waves in V2–V3 during pain-free intervals (citing de Zwaan, Bär and Wellens, 1982).^[12]
• Aslanger pattern: ST elevation isolated to lead III with ST depression in any of V4–V6 with a positive T wave.^[12]
• "South African flag" sign: ST elevation in leads I, aVL and V2 with ST depression in lead III.^[12]

NHFA/CSANZ 2025 lists its own ACOMI patterns by name.^[4] Comparison of ECGs with coronary angiogram results has revealed multiple ACOMI patterns beyond the traditional ST elevation criteria, including high lateral MI, posterior MI, right ventricular MI, De Winter T waves, modified Sgarbossa criteria and transient STE.^[4]

ACOMI patterns beyond the classic ST elevation criteria

^{[4] [1] [12] [10] [11] [7] [2]}

Recognising these patterns should prompt urgent consultation with cardiology services for consideration of reperfusion strategy (NHFA/CSANZ 2025).^[4] The NHFA/CSANZ STEMI/ACOMI management rows apply to people with STEMI and to those with high lateral MI, posterior MI, RV MI, De Winter T waves, or LBBB with modified Sgarbossa criteria.^[4]

^[4]

Upsloping precordial J-point depression into tall, symmetrical T waves: a single-centre observational study

A single-centre observational study looked at patients with acute anterior wall MI referred for primary PCI between 1998 and 2008.^[9] Of 1890 patients who underwent primary PCI of the LAD, 35 (2%) had a static, distinct ECG pattern without ST elevation and an occlusion of the proximal LAD at urgent coronary angiography before PCI.^[9] The ECG showed ST depression at the J-point of at least 1 mm in precordial leads, with upsloping ST segments continuing into tall, symmetrical T waves.^[9] The authors concluded that in patients presenting with chest pain this pattern signifies proximal LAD occlusion.^[9]

Nitroglycerine and the repeat ECG

• ESC 2023 text: with an ECG compatible with ongoing STEMI and symptom relief after nitroglycerine, it is recommended to obtain another 12-lead ECG (no class or level given).^[1]
• ESC 2023: a reduction in chest pain after nitroglycerine can be misleading and is not recommended as a diagnostic manoeuvre.^[1]

LBBB, RBBB and paced rhythm

The Fifth UDMI (2026) says not all patients with acute coronary occlusion show ST elevation on the 12-lead ECG, and other confounders, such as bundle branch block, can obscure interpretation of the ST segment.^[12]

^{[1] [2] [4]}

The 2021 AHA/ACC chest pain guideline treated new LBBB alongside new ST elevation and ST depression: patients with chest pain and these findings should be treated according to STEMI and NSTE-ACS guidelines.^[3] The 2025 ACC/AHA ACS guideline is the newer US source, and it says new or presumably new LBBB should not be considered diagnostic of AMI in isolation.^[2]

From Sgarbossa to the modified criteria

The original criteria came from the baseline ECGs of GUSTO-1 trial patients with LBBB and enzyme-confirmed acute MI, compared blindly with controls who had chronic coronary disease and LBBB (NEJM, 1996).^[6][12] The criteria were then tested in an independent sample presenting with acute chest pain and LBBB.^[6] Of 26,003 North American patients, 131 (0.5%) with acute MI had LBBB.^[6]

Sgarbossa and modified Sgarbossa criteria

^{[6] [12] [7]}

The study used admission ECGs of all patients with an acutely occluded coronary artery and LBBB at 3 institutions, with ED patients with chest pain or dyspnoea and LBBB but no occlusion as controls: 33 and 129 ECGs.^[7] The authors set the cut point as the most negative ST/S ratio with at least 90% specificity, then computed and compared the diagnostic utility of the original and revised rules.^[7] Its sensitivity was 91%, against 52% for the weighted and 67% for the unweighted original rule.^[7] Its specificity was 90%, against 98% for the weighted and 90% for the unweighted original rule.^[7]

What the Fifth UDMI adds

• STEMI equivalent: the Fifth UDMI (2026) says that, in the right clinical setting, new or presumed new left and/or right bundle branch block accompanied by other signs of myocardial ischaemia may be considered equivalent to STEMI.^[12]
• Sgarbossa criteria, citing the 1996 report: among patients with pre-existing LBBB or ventricular pacing, ST elevation ≥1 mm concordant with the QRS, ST depression ≥1 mm in V1, V2 or V3, and ST elevation ≥5 mm not concordant with the QRS suggest acute coronary occlusion.^[12]
• Its Table 5 lists the same three Sgarbossa criteria, in the presence of LBBB or ventricular pacing.^[12]
• Modified Sgarbossa, citing Smith and colleagues (2012): the modified criteria may improve the detection of acute coronary occlusion with LBBB or ventricular pacing by replacing the absolute discordant ST elevation threshold with a proportional rule.^[12]

High-risk patterns that may precede occlusion

NHFA/CSANZ 2025 says certain high-risk ECG patterns, such as Wellens T waves, diffuse ST depression in multiple leads with ST elevation in aVR, and hyperacute T waves, are associated with potential progression to ACOMI.^[4] Recognising them should prompt urgent, continuous cardiac monitoring and consideration for coronary angiography.^[4]

High-risk ECG patterns and what the other held sources say

^{[4] [1] [12]}

The 1982 report by de Zwaan, Bär and Wellens

For Wellens syndrome (biphasic or deeply inverted T waves in V2–V3 during pain-free intervals), the Fifth UDMI (2026) cites de Zwaan, Bär and Wellens (1982).^[12] The 1982 report studied patients admitted with unstable angina.^[12][8] Of 145 patients consecutively admitted with unstable angina, 26 (18%) showed its characteristic precordial ST-T pattern, which the authors linked to a critical stenosis high in the LAD.^[8] Despite symptom control with nitroglycerin and beta blockade, 12 of 16 patients (75%) who were not operated on developed a usually extensive anterior wall infarction within a few weeks of admission.^[8] The authors concluded that urgent coronary angiography and, when possible, revascularisation should be done in unstable angina with this pattern.^[8]

Diffuse ST depression with ST elevation in aVR

• Fifth UDMI (2026): global ischaemic changes (diffuse ST depression along with ST elevation in aVR) may reflect left main stem or balanced three vessel CAD.^[12]
• Fifth UDMI: in the setting of secondary MI, global ischaemic changes are more common.^[12]

^{[4] [1] [12]}

ST changes are not specific to MI

ST elevation is not specific to ACOMI, which may occur in other disease states, both cardiac and non-cardiac (NHFA/CSANZ 2025).^[4] The Fifth UDMI (2026) makes the same point: ST elevation is not specific to MI and can also be found in early repolarisation or in other cardiac and non-cardiac conditions.^[12]

• ACC/AHA 2025: ST changes may be observed in other conditions, including acute pericarditis, LVH, LBBB, Brugada syndrome, right ventricular pacing, Takotsubo syndrome and early repolarisation, that may obscure the diagnosis of STEMI.^[2]
• Fifth UDMI (2026): its cardiac examples are myocarditis, pericarditis, Brugada syndrome, and Takotsubo syndrome or cardiomyopathies; its non-cardiac examples are pulmonary embolism, hyperkalaemia, hypothermia and elevated intracranial pressure.^[12]
• Fifth UDMI: the ST depression, T wave inversion and global ischaemic changes it describes are not specific to MI either, and can be observed in other cardiac and non-cardiac conditions.^[12]
• Fifth UDMI: more marked ECG changes, particularly ST elevation and depression, that do not resolve rapidly with treatment of the underlying cause should lead to reconsideration as to whether the diagnosis is primary MI. Its example is resolution of widespread ST depression after cardioversion for tachyarrhythmia.^[12]
• 2021 AHA/ACC chest pain: the ECG may identify non-ischaemic causes of chest pain, for example pericarditis, myocarditis, arrhythmia, electrolyte abnormalities, paced rhythm, hypertrophic cardiomyopathy, pulmonary hypertension, congenital long QT, or a normal variant.^[3]

Tools for telling them apart

• Reciprocal change and distribution: with an acute coronary pathology, ST elevation is typically regional and often accompanied by reciprocal ST depression; in other conditions such as pericarditis or early repolarisation it is often diffuse or global, not confined to a single coronary territory, and occurs without reciprocal changes (Fifth UDMI 2026).^[12]
• A prior ECG: ACC/AHA 2025 says a nondiagnostic ECG should be compared with prior ECGs, and a repeat ECG obtained during the ED course to assess for evolving changes.^[2]

^{[2] [12]}

Q waves, prior infarction and recurrent infarction

The Fifth UDMI (2026) says late presenters after MI due to an acute coronary occlusion are more likely to have pathological Q waves in two or more contiguous leads, and biphasic T waves or T wave inversions, than ST elevation or depression.^[12] Some patients presenting late may not necessarily have developed Q waves despite an acute coronary occlusion.^[12] Q waves are usually permanent but may regress and disappear over months to years.^[12]

The Fifth UDMI gives the classical definition of a pathological Q wave: a Q wave duration ≥40 ms and/or a depth of ≥25% of the R wave in the same lead.^[12] Its Table 5 lists pathologic Q waves with the same thresholds in two contiguous leads.^[12] It notes that prior versions of the UDMI suggested an alternative definition, but that the classical definition has a higher correlation with transmural MI in CMR imaging studies.^[12]

• Unrecognised MI: the Fifth UDMI (2026) says individuals with no known history of MI may have pathological Q waves identified on a routine ECG.^[12]
• The specificity of pathological Q waves is limited, so, when available, unrecognised (clinically "silent" or "old") MI should be confirmed by imaging, preferably CMR with late gadolinium enhancement (Fifth UDMI).^[12]
• Unrecognised MI is present in approximately 1 in 5 persons over 70 in the general population if CMR imaging is performed systematically, although most are small infarcts; it is relevant because it is associated with adverse prognosis (Fifth UDMI).^[12]
• Recurrent MI: the Fifth UDMI says diagnosing a new MI within the first month of the index event may be challenging, as ECG changes, cardiac biomarkers and imaging findings may reflect residual abnormalities.^[12]
• Recurrent symptoms are common but may stem from complications of the index MI, such as pericarditis, chest trauma after cardiopulmonary resuscitation, or heart failure, rather than recurrent MI (Fifth UDMI).^[12]
• Persistent ST elevation or T wave inversion may be caused by ventricular aneurysm or pericarditis (Fifth UDMI).^[12]
• Coronary angiography is often required to confirm recurrent MI, and to differentiate primary from procedure-related MI within 30 days (Fifth UDMI).^[12]

What the Fourth UDMI (2018) used for prior MI

For history, the Fourth UDMI (2018) used these ECG criteria for prior MI, in the absence of LVH and LBBB.^[5]

• Leads V2–V3: the Fourth UDMI (2018) counted any Q wave >0.02 s, or a QS complex.^[5]
• Leads I, II, aVL, aVF or V4–V6: the Fourth UDMI (2018) required a Q wave ≥0.03 s and ≥1 mm deep, or a QS complex, in any 2 leads of a contiguous lead grouping (I, aVL; V1–V6; II, III, aVF).^[5]
• Leads V1–V2: the Fourth UDMI (2018) counted an R wave >0.04 s with R/S >1 and a concordant positive T wave, in the absence of a conduction defect.^[5]
• Supplemental leads V7–V9: the Fourth UDMI (2018) applied its Q wave criterion for leads I, II, aVL, aVF or V4–V6 to V7–V9 as well.^[5]

What to do with the ECG: the recommendations

Taken together, the timing rows ask for an early ECG: as soon as possible at the point of FMC, with a target of under 10 min (ESC 2023), or within 10 minutes (ACC/AHA 2025; NHFA/CSANZ 2025).^[1][4][2] ESC 2023 and the ACC/AHA 2025 prehospital row specify a 12-lead ECG.^[1][2] ESC 2023 also recommends a repeat ECG with recurrent symptoms or diagnostic uncertainty, and extra leads in inferior STEMI or suspected total vessel occlusion with inconclusive standard leads.^[1]

^{[1] [2] [3]}

The table lists the 2025 rows first and the 2021 rows below them.^[2][3] The 2025 in-hospital rows are adapted from the 2021 chest pain guideline, and the 2025 prehospital serial-ECG row is modified from it.^[2] So the serial-ECG recommendation carries COR 1 in all three places, with LOE C-EO in 2021, B-NR for the 2025 in-hospital row and C-LD for the 2025 prehospital row.^[3][2] For posterior leads, the 2021 chest pain row is COR 2a, LOE B-NR, while the 2025 ACS Table 3 says posterior leads should be obtained in suspected left circumflex occlusion, particularly with isolated ST depression ≥0.5 mm in V1-V3, without a class or level.^[3][2]

^[4]

In this guideline, consensus recommendations are informed by expert opinion when there is indirect supporting evidence and GRADE is not applicable.^[4]

^[4]

• Timing: ACC/AHA 2025 says the timing of repeat ECGs should be guided by symptoms, especially recurrent chest pain, and any change in clinical condition.^[2]

ACC/AHA 2025 cites an observational study of 728 patients with suspected ACS who had serial prehospital ECGs: STEMI was diagnosed in 8% after an initial nondiagnostic ECG, at a median of 12 minutes after the first.^[2]

^{[1] [2] [4] [3]}

Pitfalls

• A normal first ECG does not exclude ACS: ACC/AHA 2025 says an initial nondiagnostic ECG does not rule out ACS, abnormalities may be dynamic, and the ECG should be compared with prior ECGs and repeated in the ED.^[2]
• The 2021 AHA/ACC chest pain guideline says a normal or unchanged ECG is reasonably useful but not sufficient to rule out ACS, so decisions should not rest on a single normal or nondiagnostic ECG.^[3]
• LVH, bundle branch blocks and ventricular pacing may mask signs of ischaemia or injury (2021 AHA/ACC chest pain).^[3]
• Anteroseptal ST depression may be posterior STEMI: ACC/AHA 2025 says ST depression in V1-V3 could indicate an evolving posterior STEMI and should be managed with a high index of suspicion, with a posterior lead ECG if warranted.^[2]
• The ECG is often normal or not diagnostic: the Fifth UDMI (2026) says many people do not have classical symptoms, and the ECG is often normal or not diagnostic of myocardial ischaemia.^[12]
• Symptom relief with nitroglycerine can mislead (ESC 2023).^[1]

Special populations

• Women: ≥1.5 mm in V2–V3 regardless of age (ESC 2023, ACC/AHA 2025, Fifth UDMI 2026); as history, the Fourth UDMI (2018), in text not restated in the Fifth, reported that healthy women had less J-point elevation in V2 and V3 than men.^{[1][2][12][5]}
• Young men: ≥2.5 mm in V2–V3 under 40 (ESC 2023, ACC/AHA 2025, Fifth UDMI 2026); as history, the Fourth UDMI (2018), in text not restated in the Fifth, also gave ≥1 mm cut-offs in V7–V9 for men under 40, and in V3R and V4R for men under 30.^{[1][2][12][5]}
• Older men: ≥2 mm in V2–V3 for men 40 or over (ESC 2023, ACC/AHA 2025, Fifth UDMI 2026); as history, the Fourth UDMI (2018), in text not restated in the Fifth, reported that J-point elevation in healthy men decreased with increasing age.^{[1][2][12][5]}
• Paced patients: ESC 2023 says a paced rhythm, like LBBB or RBBB, precludes accurate assessment of ST elevation when ongoing ischaemia is highly suspected; the Fifth UDMI (2026) says the Sgarbossa criteria suggest acute coronary occlusion among patients with pre-existing LBBB or ventricular pacing, and that the modified criteria may improve its detection.^[1][12]
• Tachyarrhythmia and secondary MI: the Fifth UDMI says global ischaemic changes are more common in secondary MI, and that more marked ECG changes, particularly ST elevation and depression, that do not resolve rapidly with treatment of the underlying cause should lead to reconsideration as to whether the diagnosis is primary MI (for example, resolution of widespread ST depression after cardioversion for tachyarrhythmia).^[12]
• Previous coronary bypass grafts and/or complex CAD (for example, chronic total occlusions with collateral supply): the Fifth UDMI says these patients may present with acute coronary or graft occlusion without typical ST elevation, and a high index of suspicion for MI is required.^[12]

Guidelines and regional differences

Primary region is ANZ, so start with the 2025 NHFA/CSANZ guideline, which replaced its 2016 predecessor.^[4] ESC 2023 and ACC/AHA 2025 are the newest ACS guidelines from those bodies in the cardiology guideline register (census 2026-10-05). ACC/AHA 2025 adapted its ECG interpretation table (Table 3) from the Fourth UDMI (2018) and from Kontos et al. (2022).^[2] The UDMI was itself updated in 2026: the Fifth UDMI provides an updated, evidence-based definition and classification of MI, and outlines its key updates from the Fourth UDMI (2018).^[12] This page therefore cites the Fourth UDMI (2018) only as history.

^{[1] [2] [4] [12]}

The evidence behind several rows is thin.^[4] The NHFA/CSANZ urgent-reperfusion row for ACOMI is strong with very low certainty, and its monitoring row is strong with low certainty.^[4] Its ECG-timing and additional-lead rows are consensus recommendations.^[4] The ESC and ACC/AHA threshold criteria themselves sit in the text and tables, without a class or level.^[1][2]

Exam pearls

• Know the four cut-points by heart (ESC 2023, ACC/AHA 2025, Fifth UDMI 2026): ≥2.5 mm (men under 40), ≥2 mm (men 40 or over), ≥1.5 mm (women, regardless of age) in V2–V3, and ≥1 mm elsewhere, for new ST elevation (ACC/AHA: new or presumed new) at the J-point in ≥2 contiguous leads. ESC 2023 and the Fifth UDMI each add, after their other-leads cut-point, that it applies in the absence of LV hypertrophy or LBBB, and the ACC/AHA footnote lists LVH and LBBB among conditions that may obscure the diagnosis.^[1][2][12]
• Posterior: ESC 2023 says ST depression in V1–V3 (especially with a positive terminal T wave) and/or ST elevation in V7–V9 is highly suggestive of posterior coronary occlusion; the Fifth UDMI (2026) says posterior MI is suggested by ST depression ≥1 mm in V1, V2 and/or V3, particularly with a dominant R wave in V1 or V2, confirmed by ST elevation in V7–V9.^[1][12]
• Right ventricle: the Fifth UDMI (2026) says RV MI is indicated by ST elevation in the right precordial leads (V3R–V6R), especially when accompanied by ST elevation in aVR; ESC 2023 calls ST elevation in V3R and V4R highly suggestive of ongoing RV ischaemia.^[12][1]
• De Winter T waves are an ACOMI pattern in NHFA/CSANZ 2025. The 2008 report by de Winter and colleagues describes, without ST elevation, 1–3 mm upsloping ST depression at the J point in V1 to V6 continuing into tall, positive, symmetrical T waves and, in most patients, 1–2 mm ST elevation in aVR. Fifth UDMI (2026) Table 5 describes de Winter T waves as tall, prominent, symmetrical T waves with upsloping ST depression in the precordial leads; its text, citing the 2008 report, lists the de Winter pattern (upsloping ST depression with tall, symmetric T waves in V2–V5) among patterns that suggest acute coronary occlusion.^{[4][10][11][12]}
• Wellens T waves sit with the NHFA/CSANZ 2025 high-risk patterns, not its ACOMI patterns: recognition should prompt urgent, continuous cardiac monitoring and consideration for coronary angiography. ESC 2023 relates Wellens sign (biphasic or prominent negative T waves) to severe proximal LAD stenosis. The Fifth UDMI (2026) lists Wellens syndrome (biphasic or deeply inverted T waves in V2–V3 during pain-free intervals) among patterns that suggest acute coronary occlusion.^[4][1][12]
• Modified Sgarbossa: the modified rule replaced the original ≥5 mm discordant criterion with a proportional one, an ST/S ratio of -0.25 or less, and is unweighted, requiring just 1 of 3 criteria.^[7]

References12ShowHide

1. [1]Byrne RA, et al. 2023 ESC Guidelines for the management of acute coronary syndromes. Eur Heart J, 2023.PMID 37622654
2. [2]Rao SV, et al. 2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for the Management of Patients With Acute Coronary Syndromes: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. J Am Coll Cardiol, 2025.PMID 40013746
3. [3]Gulati M, et al. 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. J Am Coll Cardiol, 2021.PMID 34756653
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