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Figure 1. Posterolateral (posterior, inferobasal) transmural ischemia causes reciprocal ST-segment depressions in V1–V3 (ocasionally V4). Leads V7–V9 must be placed to reveal the ST-segment elevations.

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Introduction to ECG Interpretation

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Figure 3. Changes on resting ECG that may reveal cause of arrhythmias (arrhythmia substrates).

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Arrhythmias and arrhythmology

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Figure 1. (A) The relation between the action potential and the ECG curve. Ischemia primarily affects the repolarization, which is reflected on ST-T changes on the ECG curve. (B) Note that the reference level for measuring deviation (elevation or depression) of the ST segment is the PR segment (the terminal portion of the PR interval). (C) and (D) Shows how to measure the magnitude of ST segment elevation and depression.

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Myocardial Ischemia & Infarction

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Figure 1. These ECGs show the difference between normal conduction, left bundle branch block (LBBB) and right bundle branch block (RBBB). As evident from these ECGs, the cardinal difference between normal conduction and bundle branch blocks is the QRS duration: bundle branch blocks are caused by dysfunctional bundle branches, which results in slow (and abnormal) activation of ventricular myocardium and thus prolonged QRS duration. A QRS duration of 120 ms (0.12 s) is required to diagnose bundle branch block. Also note that both left bundle branch block (LBBB) and right bundle branch block (RBBB) cause marked ST-T changes, including ST elevations, ST depressions and inverted (negative) T-waves. These ST-T changes are due to abnormal repolarization and they are expected to occur in both LBBB and RBBB. Finally, note that there are marked difference in the ECG pattern between LBBB and RBBB. These ECGs are printed at paperspeed 50 mm/s.

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Conduction Defects

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Figure 1. ECG changes seen in left ventricular hypertrophy (LVH) and right ventricular hypertrophy (RVH). The electrical vector of the left ventricle is enhanced in LVH, which results in large R-waves in left sided leads (V5, V6, aVL and I) and deep S-waves in right sided chest leads (V1, V2). Right ventricular hypertrophy causes large R-waves in right sided chest leads and deeper S-waves in left sided leads.

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Cardiac Hypertrophy & Enlargement

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Figure 1. ECG changes seen in hyperkalaemia.

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Drugs & Electrolyte Imbalance

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Figure 2. Brugada syndrome. Note the gigantic J wave in V2 and V3. This may be confused with right bundle branch block. Paper speed 50 mm/s.

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Genetics, Syndromes & Miscellaneous

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Figure 6. Overview of test results. 58 year old male with left main disease.

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Exercise Stress Testing (Exercise ECG)

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Pacemaker ECG Interpretation CRT ICD

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Pacemaker & CRT: ECG, Function, Troubleshooting and Management

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Figure 2. The fetal circulation.

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Pediatric and neonatal ECG interpretation

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The normal electrocardiogram (ECG) waves. ECG interpretation.

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Basic Cardiac Anatomy & Physiology

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Figure 7. The heart's main electrical vectors seen from the horizontal plane. V1 and V5 are exploring electrodes and the reference is composed of the average of the electrodes placed on the limbs (this reference is called Wilson's central terminal). Inspired by MacFarlane et al (Springer, Comprehensive Electrocardiology, 2010).

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Characteristics of the Normal ECG

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