What are the electrocardiogram (ECG) leads corresponding to myocardial infarctions (MIs)?

From the Guidelines

The diagnosis of myocardial infarction (MI) is primarily guided by ECG leads that correspond to specific locations of the heart, with anterior wall MIs showing changes in leads V1-V4, inferior wall MIs in leads II, III, and aVF, and lateral wall infarctions in leads I, aVL, V5, and V6, as indicated by the American Heart Association electrocardiography and arrhythmias committee 1. The ECG leads are essential for accurate diagnosis and localization of the infarct, identification of the culprit vessel, and determination of the extent of myocardial damage.

• For anterior wall MIs, leads V1-V4 show characteristic changes, reflecting damage to the left anterior descending artery territory.
• Inferior wall MIs appear in leads II, III, and aVF, indicating right coronary artery occlusion.
• Lateral wall infarctions manifest in leads I, aVL, V5, and V6, corresponding to circumflex or diagonal branch involvement.
• Posterior wall MIs show reciprocal changes in V1-V3 (tall R waves and ST depression rather than Q waves and ST elevation), often requiring additional posterior leads V7-V9 for direct visualization.
• Right ventricular infarctions, usually accompanying inferior MIs, are best seen in right-sided lead V4R. These lead patterns help clinicians guide appropriate reperfusion strategies, and ST elevation of at least 1mm in two contiguous leads (or 2mm in V1-V3 for men) along with reciprocal ST depression in opposite leads strengthens the diagnosis of acute MI, as recommended by the American College of Cardiology Foundation 1. The standard 12-lead body-surface ECG is now capable of providing a more accurate correlation of the waveform changes to the involved vessel and to the site of occlusion within that vessel, allowing for more accurate diagnosis and treatment of myocardial infarctions.

From the Research

Leads for Corresponding Myocardial Infarctions

• The 12-lead electrocardiogram (ECG) is the most immediately accessible and widely used initial diagnostic tool for guiding management in patients with suspected myocardial infarction (MI) 2.
• Careful interpretation of the ECG might yield subtle features suggestive of ischemia that might facilitate more rapid triage of patients with subtle acute coronary occlusion or, conversely, in identification of ST-elevation MI mimics (pseudo ST-elevation MI patterns) 2.
• The use of additional ECG leads, such as right precordial and posterior leads, does not increase detection of ischemia in low-risk patients presenting with chest pain 3.
• The application of rules, such as the modified Sgarbossa criteria, can help identify acute MI in left bundle branch block or ventricular pacing, and differentiate normal ST elevation from subtle ECG signs of left anterior descending coronary artery occlusion 2.

Diagnostic Tools and Techniques

• The development of high-sensitivity cardiac troponin assays has improved the rule-in and rule-out and risk stratification of acute MI without ST elevation 2.
• The use of lead aVL can help in the recognition of inferior MI 2.
• A 16-lead ECG, which includes additional right-sided precordial and posterior leads, did not provide additional information for risk stratification in low-risk patients presenting to the ED with chest pain 3.

Treatment and Management

• The addition of clopidogrel to aspirin in patients with acute myocardial infarction has been shown to reduce mortality and major vascular events in hospital 4.
• The use of dual antiplatelet therapy, including aspirin and clopidogrel, is important in the management of patients with ST-elevation myocardial infarction (STEMI), and poor response to this therapy can increase the risk of major adverse cardiovascular events (MACE) 5.