Clinical Electrocardiography (ECG) Interpretation

Clinical ECG Interpretation

From cell to reperfusion

The section on Clinical Electrocardiography offers an in-depth exploration of the fundamental principles and practical applications of ECG in cardiovascular medicine. This section provides a clear, step-by-step guide to understanding and interpreting ECGs, blending theoretical knowledge with real-world cases to equip clinicians with the skills necessary to enhance patient outcomes. Authored by Dr. Araz Rawshani, it is one of the world’s most-read resources on ECG interpretation. This comprehensive section guides users from basic concepts to advanced levels of understanding, incorporating the latest guideline recommendations. Additionally, self-assessment tests are available for each topic covered.

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Figure 1. Types of ST segment elevations on ECG.

ST segment elevation in acute myocardial ischemia and differential diagnoses

ST segment elevation in acute myocardial ischemia ST segment elevations

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.

ST elevation myocardial infarction (STEMI) without ST elevations on 12-lead ECG

ST elevation myocardial infarction (STEMI) without ST segment elevations on

Figure 1. Various T-wave abnormalities, including T-wave changes related to myocardial ischemia.

T-waves in ischemia: hyperacute, inverted (negative), Wellen’s sign & de Winter’s sign

T-wave changes in acute myocardial infarction & ischemia A thorough

Figure 1. Examples of STE-ACS (STEMI). Note that these patients presented with pathological Q-waves, which means that these ECGs were recorded several hours after symptom onset or those are signs of old infarction.

ECG signs of myocardial infarction: pathological Q-waves & pathological R-waves

Pathological Q-waves are evidence of myocardial infarction Myocardial infarction – particularly

Figure 1. Pathological R-wave progression is indicative of previous myocardial infarction.

Other ECG changes in ischemia and infarction

Pathological R-wave progression Normal R-wave progression implies that the R-wave

Figure 1. The component of the cardiac conduction system and the vascular supply. RCA = right coronary artery. LAD = Left anterior descending coronary artery. LCX = left circumflex coronary artery.

Supraventricular and intraventricular conduction defects in myocardial ischemia and infarction

Conduction defects caused by myocardial ischemia and infarction Bradycardia and

Figure 1. The coronary arteries and their relation to the ECG leads. Localization of myocardial infarction / ischemia is done by using ECG changes to determine the affected area and subsequently the occluded coronary artery (culprit).

ECG localization of myocardial infarction / ischemia and coronary artery occlusion (culprit)

Using the ECG to localize myocardial infarction / infarction and determine the

Figure 2. The electrocardiographic natural course in STEMI (ST elevation myocardial infarction).

The ECG in assessment of myocardial reperfusion

The ECG in assessment of myocardial reperfusion The ECG is

Figure 1. Chest pain is the hallmark of myocardial ischemia. It signals that there is ongoing (acute) myocardial ischemia. Careful assessment of the symptoms is crucial to promptly establish a working diagnosis. Chest pain due to myocardial ischemia is rather characteristic, which means that the vast majority of patients with acute coronary syndromes can be treated before troponin test results have arrived. Hence, assessment of symptoms and ECG is sufficient to manage patients with chest pain.

Approach to patients with chest pain: differential diagnoses, management & ECG

Approach to patients with chest pain: differential diagnoses, evaluation and management

NSTEMI (Non ST Elevation Myocardial Infarction) & Unstable Angina: Diagnosis, Criteria, ECG, Management

Non ST Elevation Acute Coronary Syndromes (NSTE-ACS): Non ST Elevation

ECGs showing acute STEMI in two patients with severe chest pain. STEMI = ST elevation Myocardial Infarction.

STEMI (ST Elevation Myocardial Infarction): diagnosis, criteria, ECG & management

STEMI (ST Elevation Acute Myocardial Infarction): Epidemiology, Diagnosis (ECG), Criteria

Long QT Syndrome (LQTS)

Please refer to the previous chapter: LQTS (Long QT Syndrome)

Interpretation of neonatal and pediatric electrocardiograms (ECG)

Definition of normal and pathological pediatric and neonatal ECG The

Reference values for pediatric and neonatal ECG

Neonatal period Table 1. Normal limits for ECG parameters during

Figure 1. The ECG grid. The x-axis represents time and y-axis represents amplitude of the electrical signals generated in the myocardium. The same ECG grid is used in children and adult patients.

Pediatric aspects of ECG leads & anatomy

ECG leads and recording ECGs in pediatric patients (children) Principles

Figure 1. Cross-sectional view of ventricular wall thickness in children (

Introduction to pediatric & neonatal ECG interpretation

Principles of pediatric & neonatal ECG interpretation Pediatric and neonatal

Introduction to Cardiac Pacing and Devices: Pacemaker, ICD, CRT

The artificial pacemaker is one of the great medical inventions

Components and construction of a pacemaker

Principles of myocardial excitability Myocardium is excitable not only by

Interpretation of Pacemaker ECG

Interpreting pacemaker ECGs Assessing pacemaker function requires knowledge of the

Basic cardiac pacing, pacemaker functions and settings

Stimulation threshold As previously discussed, myocardium may be excited by

Indications for pacemaker

Indications for pacemaker implantation Bradyarrhythmia is the main indication for

Assessment of Pacemaker Malfunction

Pacemaker malfunction, troubleshooting and ECG Conventional surface ECG can reveal

Figure 1. Components of the ventricular conduction system and the temporal association between the ECG waveforms and impulse transmission through the heart. Atrioventricular (AV) blocks occur due to dysfunction in the conduction system.

Overview of atrioventricular (AV) blocks

Atrioventricular block (AV block): definition, causes, diagnosis & management This

Figure 1. ECG in first-degree AV block. Both conventional paper speeds are shown.

First-degree AV block (AV block I, AV block 1)

First-degree AV block: ECG criteria, clinical characteristics & management In

Figure 1. Second-degree AV block Mobitz type 1, also known as Wenckebach block.

Second-degree AV block: Mobitz type 1 (Wenckebach) & Mobitz type 2 block

Second-degree AV block: ECG criteria, clinical characteristics & management In

Figure 1. Third-degree AV block (complete heart block, AV dissociation).

Third-degree AV block (3rd degree AV block, AV block 3, AV block III)

Third-degree (complete) AV block: ECG criteria, clinical characteristics and management

Management and treatment of AV block (atrioventricular blocks)

Management and treatment of AV blocks (AV-block 1, 2 &

Figure 1. Components of the ventricular conduction system and the temporal association between the ECG and impulse transmission through the heart. An intranventricular conduction delay may occur whenever any of the main components of the conduction system is dysfunctional.

Intraventricular conduction delay: bundle branch blocks & fascicular blocks

Intraventricular conduction delay (defect): constellations of bundle branch blocks and fascicular

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.

Left bundle branch block (LBBB): ECG criteria, causes, management

Left bundle branch block (LBBB): ECG criteria and clinical implications

Figure 2. Right bundle branch block (RBBB) and left bundle branch block (LBBB). Note that the paper speed is 50 mm/s (1 large box equals 100 ms). The hallmark of both RBBB and LBBB is the QRS duration which is by definitions 120 ms or longer. The distinction between RBBB and LBBB is simple, as illustrated in this figure.

Right bundle branch block (RBBB): ECG, criteria, definitions, causes & treatment

Right bundle branch block (RBBB) Right bundle branch block (RBBB)

Figure 1. ECG criteria (Sgarbossa criteria) for acute STEMI in the setting of LBBB. Each criteria gives 2 to 5 points. Studies show that a cut-off of ≥3 points yields a sensitivity of 20–36% and specificity of 90–98% for acute STEMI in the setting of LBBB.

Left bundle branch block (LBBB) in acute myocardial infarction: the Sgarbossa criteria

Left bundle branch block (LBBB) in acute myocardial infarction (AMI): clinical

Figure 1. Left anterior fascicular block (hemiblock) and left posterior fascicular block (hemiblock). Inspired by GS Wagner (Marriott's Practical Electrocardiography, Elsevier 2007) and AL Goldberg (Clinical Electrocardiography: A Simplified Approach, Elsevier Mosby 2006).

Fascicular block (hemiblock): Left anterior & left posterior fascicular block

Fascicular block (hemiblock): left anterior fascicular block & left posterior

ECG non-specific nonspecific intraventricular conduction delay

Nonspecific intraventricular conduction delay (defect)

Nonspecific intraventricular conduction delay A nonspecific intraventricular conduction delay exists if

Evaluation of chronic coronary syndromes (angina pectoris, coronary artery disease)

Stable Coronary Artery Disease (Angina Pectoris): Diagnosis, Evaluation, Management

Evaluation and management of stable coronary artery disease Chronic coronary

Atrial and ventricular enlargement: hypertrophy and dilatation on ECG

Principles of atrial and ventricular enlargement (hypertrophy and dilatation) Cardiac

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.

ECG in left ventricular hypertrophy (LVH): criteria and implications

ECG and clinical characteristics in left ventricular hypertrophy (LVH) The following

Figure 2. Two ECGs showing left and right ventricular hypertrophy.

Right ventricular hypertrophy (RVH): ECG criteria & clinical characteristics

ECG and clinical characteristics in right ventricular hypertrophy (RVH) Right ventricular hypertrophy

Biventricular hypertrophy ECG and clinical characteristics

Biventricular hypertrophy Simultaneous hypertrophy of the left and right ventricle is

Figure 1. The ECG contour of the normal P-wave, P mitrale (left atrial enlargement) and P pulmonale (right atrial enlargement)

Left atrial enlargement (P mitrale) & right atrial enlargement (P pulmonale) on ECG

Atrial enlargement: left atrial enlargement (P mitrale) and right atrial

The Coronary Arteries

Coronary arteries and arterial territories The two main coronary arteries

Figure 1. ST segment depression due to digoxin treatment.

Digoxin – ECG changes, arrhythmias, conduction defects & treatment

Digoxin ECG changes: arrhythmias, conduction defects and waveform changes Digoxin

ECG changes caused by antiarrhythmic drugs, beta blockers & calcium channel blockers

The effect of antiarrhythmic drugs, beta-blockers and calcium channel blockers

Figure 1. ECG changes seen in hyperkalaemia.

ECG changes due to electrolyte imbalance (disorder)

ECG changes due to electrolyte imbalance (electrolyte disorder) The normal cardiac action

Figure 1. Osborn wave (J wave). These waves occur due to hypothermia, hypercalcemia, early repolarization and Brugada syndrome.

ECG J wave syndromes: hypothermia, early repolarization, hypercalcemia & Brugada syndrome

J-wave syndromes: early repolarization pattern, Brugada syndrome, hypercalcemia and hypothermia

Figure 10. ECGs presenting Brugada syndrome type 1, type 2 and type 3, respectively.

Brugada syndrome: ECG, clinical features and management

Brugada syndrome: A life-threatening arrhythmia with unknown prevalence Pedro Brugada

Figure 1. Early repolarization pattern on ECG. Note the end-QRS notches and slurs, as well as the ST segment elevations.

Early repolarization pattern on ECG and early repolarization syndrome

The early repolarization pattern and syndrome: from ECG criteria to management

Figure 1. Echocardiogram showing takotsubo cardiomyopathy in acute phase (A) and resolution phase (B). Note the apical ballooning of the apical portion fo the left ventricle (A).

Takotsubo cardiomyopathy (broken heart syndrome, stress induced cardiomyopathy)

Takotsubo cardiomyopathy (broken heart syndrome, apical ballooning syndrome, stress induced

Figure 3. Chest leads of patient with acute pericarditis. Note the ST segment elevations, concave ST segments.

Pericarditis, myocarditis & perimyocarditis: ECG, criteria & treatment

Pericarditis, myocarditis and perimyocarditis: ECG changes and clinical features The

Figure 1. Electrical alternans in patient with cardiac tamponade. The ECG shows varying QRS and T-wave amplitudes.

Eletrical alternans: the ECG in pericardial effusion & cardiac tamponade

Eletrical alternans: an ECG sign of pericardial effusion and cardiac

Management of bradycardia (bradyarrhythmia)

Diagnosis and treatment of bradycardia (bradyarrhythmia) Acute bradycardia with hemodynamic

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Clinical ECG Interpretation

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