This diagnostic image is a 12-lead electrocardiogram (ECG) printed on standard grid paper, demonstrating new-onset atrial fibrillation. The ECG displays the standard limb leads (I, II, III), augmented limb leads (aVR, aVL, aVF), and precordial leads (V1-V6), with a rhythm strip for lead II at the bottom. The tracing is characterized by an irregularly irregular rhythm and the absence of discernible P waves. In their place, the baseline exhibits fine, irregular fibrillatory (f) waves, most prominently seen in lead V1 and the rhythm strip (indicated by a black arrow). The QRS complexes appear narrow and vary in their R-R intervals, a hallmark of irregular ventricular response in atrial fibrillation. Precordial leads V1 through V6 show a progression of R-wave amplitude. There is no evidence of significant ST-segment elevation or depression, suggesting an absence of acute myocardial infarction. This visual serves as a classic educational example of atrial fibrillation pathophysiology and diagnostic ECG features.

This diagnostic image is a 12-lead electrocardiogram (ECG) printed on standard grid paper, demonstrating classic features of atrial fibrillation. The tracing shows a rhythm characterized by 'irregularly irregular' R-R intervals, which are explicitly marked with green bidirectional arrows in the rhythm strip to highlight the variability in heart rate. A defining feature of this ECG is the complete absence of organized P waves preceding the QRS complexes. Instead, the baseline exhibits fibrillatory waves—small, rapid, and irregular oscillations—most clearly visible in the rhythm strip of Lead II (indicated by a solid red arrow) and Lead V1. The purple dashed arrow highlights the flat or undulating baseline where a P wave would normally be expected in sinus rhythm. The QRS complexes appear narrow, suggesting normal ventricular conduction despite the supraventricular arrhythmia. This visual material is a primary educational resource for cardiology and internal medicine, illustrating the fundamental diagnostic criteria for atrial fibrillation.

This diagnostic image is a 12-lead electrocardiogram (ECG) demonstrating a narrow-complex tachycardia, specifically identified as atypical atrial flutter. The tracing exhibits a 2:1 conduction ratio, where two P waves are visible for every QRS complex. A key diagnostic feature is the presence of upright flutter waves in the inferior leads (II, III, aVF), annotated with blue arrows, suggesting high-to-low atrial activation. In the precordial leads (V1-V6), the flutter waves remain positive across the entire sequence (noted by black arrows), demonstrating an 'absent precordial transition' that is characteristic of a left atrial origin rather than typical cavotricuspid isthmus (CTI)-dependent right atrial flutter. The ECG lacks the classic 'sawtooth' undulating morphology, instead showing discrete flutter waves. These findings are clinically significant in the context of post-ablation arrhythmias and tachycardia-mediated cardiomyopathy, helping to differentiate between focal atrial tachycardia and macroreentrant circuits originating in the left atrium.

A standard 12-lead electrocardiogram (ECG) displayed on a traditional grid background (25 mm/sec, 10 mm/mV). The tracing demonstrates typical Atrial Flutter (AFL). The most prominent feature is the continuous 'sawtooth' baseline pattern, consisting of rapid, regular flutter waves (F waves). These F waves are most clearly visualized in the inferior leads (II, III, and aVF), where they exhibit a predominantly negative deflection. Blue arrows in leads II, III, and aVF highlight these recurring macro-reentrant atrial oscillations. The ventricular rhythm is regular, suggesting a fixed atrioventricular (AV) conduction ratio, likely 2:1 or 4:1 given the flutter rate. Normal QRS complexes and T waves are present across all leads but are superimposed upon the undulating flutter baseline. Precordial leads (V1-V6) show small, upright flutter waves in V1, typical for counterclockwise cavotricuspid isthmus-dependent atrial flutter. This diagnostic image serves as a classic educational example for identifying supraventricular tachyarrhythmias and understanding the morphology of counterclockwise atrial flutter.

This diagnostic image displays a vertical comparison of three ECG rhythm strips demonstrating the progression and characteristics of different cardiac conduction abnormalities. The top strip, labeled 'NSR (FC) First Degree AV Block,' shows a sinus rhythm with a prolonged PR interval, indicating a delay in conduction between the atria and ventricles. The middle strip, labeled 'ECG possible CHB (KBM) Complete Heart Block,' illustrates third-degree atrioventricular (AV) block characterized by complete AV dissociation; P waves are present but occur independently of the slow, irregular QRS complexes (escape rhythm). The bottom strip, labeled 'ECG P waves, no QRS (Ventricular Asystole),' depicts a high-grade block where atrial activity (P waves) continues, but there is a total failure of ventricular conduction resulting in ventricular asystole. This sequence serves as an educational tool for identifying varying severity levels of heart blocks and the transition from conduction delay to lethal ventricular standstill.

This diagnostic image consists of a series of four electrocardiogram (ECG) rhythm strips demonstrating the rapid clinical progression of atrioventricular (AV) conduction abnormalities over a period of 4.5 hours. The top panel, labeled 'Time point 0', shows an ectopic atrial rhythm with organized P-wave activity and narrow QRS complexes. The second strip, recorded 2.5 hours later, displays a second-degree Mobitz type II AV block, characterized by intermittently dropped QRS complexes without preceding PR interval lengthening. The third strip, 30 minutes later, indicates a first-degree AV delay (prolonged PR interval) and intraventricular conduction delay (widened QRS). The final rhythm strip at 4.5 hours shows third-degree (complete) AV block, characterized by complete AV dissociation and a slow, wide QRS complex ventricular escape rhythm. This progression illustrates acute cardiac conduction system failure, typically associated with myocardial infiltration or severe injury, as seen in patients with leukemic infiltration of the heart.

A 12-lead electrocardiogram (ECG) demonstrating a regular wide complex tachycardia (WCT). The rhythm is characterized by a rapid ventricular rate and broad QRS complexes, indicating delayed ventricular depolarization. Key morphological findings include a Right Bundle Branch Block (RBBB) pattern, notably visible as an RSR' or notched morphology in the right precordial leads (V1, V2). There is significant left axis deviation (LAD), with predominantly negative QRS complexes in the inferior leads (II, III, and aVF) and positive complexes in leads I and aVL. This combination of RBBB morphology and left axis deviation in the context of wide complex tachycardia is a classic presentation of idiopathic left ventricular tachycardia, also known as Belhassen tachycardia or verapamil-sensitive fascicular ventricular tachycardia. The rhythm appears monomorphic, and the baseline shows no clearly identifiable P waves, suggesting atrioventricular dissociation or retrograde conduction common in ventricular arrhythmias.

This diagnostic image is a 12-lead electrocardiogram (ECG) demonstrating a regular, monomorphic wide-complex tachycardia (WCT). The ventricular rate is approximately 250 beats per minute, characterized by widened QRS complexes that maintain a consistent morphology across each lead. P waves are not clearly discernible, and there is no obvious evidence of atrioventricular (AV) dissociation on this tracing, making it visually challenging to differentiate between ventricular tachycardia (VT) and supraventricular tachycardia (SVT) with aberrant conduction. Notably, the limb leads aVR and aVL exhibit signs of potential lead reversal, complicating axis determination. The rhythm is monomorphic, suggesting a uniform ventricular depolarization pathway. This ECG is a critical educational example used to illustrate the emergency department presentation of tachyarrhythmias, often requiring clinical correlation and potentially electrical cardioversion. It serves as a teaching tool for advanced cardiac life support (ACLS) and cardiology-level interpretation of life-threatening arrhythmias.

This diagnostic image displays a vertical sequence of five electrocardiogram (ECG) tracings illustrating the progression of ischemia/reperfusion-induced ventricular arrhythmias. 1. Sinus Rhythm: Shows a baseline regular rhythm with identifiable QRS complexes and T waves. 2. VPBs (Ventricular Premature Beats): Demonstrates intermittent, wide, and premature QRS complexes disrupting the regular sinus cadence. 3. VT (Ventricular Tachycardia): A rapid, monomorphic sequence of wide QRS complexes with no visible P waves, indicating a sustained tachyarrhythmia. 4. SVF (Spontaneous Ventricular Fibrillation): A chaotic, high-frequency oscillatory pattern that spontaneously terminates, transitioning back into a more organized, regular ventricular rhythm. 5. NVF (Non-terminated Ventricular Fibrillation): A continuous, irregular, and low-amplitude chaotic baseline with no discernible organized electrical activity or termination within the observation period. This comparison is used to study the severity and duration of malignant arrhythmias in clinical and experimental cardiology settings.

This diagnostic image is a 12-lead electrocardiogram (ECG) mounted on a standard grid, displaying leads I, II, III, aVR, aVL, aVF, and V1-V6. The tracing demonstrates an irregularly irregular rhythm characteristic of atrial fibrillation. Key diagnostic features include the absence of distinct P waves, which are replaced by low-amplitude, chaotic fibrillary (f) waves, highlighted by blue arrows in the rhythm strip (lead II at the bottom). The QRS complexes are narrow and occur at varying intervals, indicating an inconsistent ventricular response. The ventricular rate is approximately 108 beats per minute, consistent with a rapid ventricular rate (RVR). There are no significant ST-segment or T-wave abnormalities visible; however, a right axis deviation is present. This ECG serves as an educational example for identifying supraventricular tachyarrhythmias and chaotic atrial electrical activity in a clinical setting.

Summary : This figure presents a 12-lead electrocardiogram (ECG) demonstrating severe QT interval prolongation, the R on T phenomenon, and the onset of torsades de pointes arrhythmia.

Two-part 12-lead electrocardiogram (ECG) comparison demonstrating drug-induced arrhythmia. (a) Initial ECG showing sinus bradycardia at approximately 40 bpm. Findings include narrow QRS complexes, prolonged QT interval, and T-wave abnormalities (inversions in inferior leads II, III, and aVF). This baseline demonstrates common findings in patients on QT-prolonging agents like sotalol. (b) ECG recorded during a syncopal event, displaying a transition from sinus rhythm into a polymorphic ventricular tachycardia (Torsades de Pointes). The tachycardia is characterized by wide QRS complexes (duration >120ms) with a shifting axis, rotating around the isoelectric line at a rapid rate of 150-200 bpm. The visual sequence illustrates the clinical progression from drug-induced QT prolongation to life-threatening ventricular arrhythmia. Educational focus is on identifying bradycardia, QT prolongation, and the morphology of polymorphic ventricular tachycardia in the context of syncope.

A 12-lead electrocardiogram (ECG) demonstrating a ventricular paced rhythm with a Right Bundle Branch Block (RBBB) morphology, indicative of inadvertent endocardial left ventricular (LV) lead placement. Visible pacing spikes precede each wide QRS complex. The QRS morphology in the precordial leads shows a transition from predominantly negative complexes in V1-V2 to tall, positive R-waves in leads V4-V6. Specifically, V1 displays a broad, slurred complex with terminal positivity, while V4-V6 exhibit prominent R-waves followed by minor secondary deflections. Secondary ST-T wave changes are present, including T-wave inversion in V1-V2 and upright T-waves in V4-V6 and the inferior leads (II, III, aVF). Minor ST-segment depression is noted in the lateral leads (V5-V6). This educational visual highlights the clinical significance of paced RBBB patterns in diagnosing lead malposition via an atrial septal defect into the left ventricle, which contrasts with the expected Left Bundle Branch Block (LBBB) pattern typically seen with right ventricular pacing.

This diagnostic image is a 12-lead electrocardiogram (ECG) demonstrating the phenomenon of phase 4 (bradycardia-dependent) left bundle branch block (LBBB) triggered by a cough. Panel A shows a standard 12-lead tracing (I, II, III, aVR, aVL, aVF, V1-V6). A 'cough artifact' is annotated in the rhythm strip, immediately followed by a transition from narrow QRS complexes to wide QRS complexes with a LBBB morphology. Panel B provides a zoomed-in view of the precordial leads V1-V6, highlighting the specific conduction changes. It documents an increase in the PR interval from 180 milliseconds (associated with narrow QRS complexes) to 200 milliseconds (associated with wide QRS complexes) following the cough. The morphology transition is most evident in leads V1 and V2 (deep S-waves) and lead V6 (monophasic R-wave). This tracing illustrates an uncommon mechanism where a physiological maneuver (coughing) alters cardiac conduction timing, leading to a rate- or pause-dependent bundle branch block during a myocardial perfusion stress test protocol.

This diagnostic image is a 12-lead electrocardiogram (ECG) with a rhythm strip (Lead II) illustrating complex cardiac conduction disturbances. The primary finding is a Second-Degree Atrioventricular (AV) Block with a 2:1 conduction ratio, characterized by regular P waves occurring at approximately double the frequency of the QRS complexes, where every second P wave fails to conduct to the ventricles. The conducted QRS complexes demonstrate a Right Bundle Branch Block (RBBB) morphology, most prominent in lead V1, which shows an rsR' pattern and wide, slurred S waves in leads I and V6. The ST-segment and T-waves show secondary repolarization changes consistent with the intraventricular conduction delay, including T-wave inversions in the right precordial leads (V1-V3). This ECG is an educational example of exercise-related or recovery-phase conduction system disease, demonstrating the coexistence of AV nodal or infra-nodal block and bundle branch block, which carries clinical significance for potential progression to complete heart block.

This diagnostic image is a 12-lead electrocardiogram (ECG) demonstrating a sinus rhythm with features characteristic of a Right Bundle Branch Block (RBBB). The ECG shows regular P waves preceding each QRS complex, indicating a sinus origin. The key diagnostic finding is the marked widening of the QRS complex (>120 ms). In the precordial leads V1 through V3, there are prominent, broad, and notched monophasic R waves (Rsr' pattern), which are classic indicators of delayed right ventricular depolarization. Leads V5 and V6 demonstrate slurred S waves. Secondary repolarization abnormalities, including T-wave inversion and ST-segment depression, are visible in the right precordial leads (V1-V3), which are common discordant changes in the setting of a bundle branch block. This tracing is an educational example of intraventricular conduction delay used to teach cardiac electrophysiology and the interpretation of morphological changes in ventricular depolarization.

This diagnostic image is a 12-lead electrocardiogram (ECG) demonstrating ventricular preexcitation characteristic of Wolff-Parkinson-White (WPW) syndrome. The tracing shows a short PR interval and prominent delta waves at the onset of the QRS complexes. Specifically, positive delta waves are visible in the precordial leads (V1 through V6), resulting in a dominant R-wave pattern in V1, which suggests an accessory pathway (AP) located on the left side of the heart. In the inferior leads (II, III, and aVF), the delta waves are negative (downward deflections), resembling pathological Q waves; this 'pseudoinfarction' pattern indicates the vector of initial ventricular activation is moving away from the inferior wall, highly suggestive of a left posteroseptal accessory pathway. The highest negative delta wave amplitudes are seen in leads II and III. This ECG is a classic educational example for identifying and localizing bypass tracts based on delta wave polarity and QRS morphology in patients with symptomatic or asymptomatic preexcitation.

This composite diagnostic image displays surface electrocardiograms (ECGs) from a patient with ventricular pre-excitation. Panel (a) shows a standard 12-lead ECG characterized by a shortened PR interval, the presence of a delta wave (slurring of the initial QRS upstroke), and widened QRS complexes, which are classic signs of Wolff-Parkinson-White (WPW) syndrome pattern. Panel (b) presents another 12-lead strip showing beat-to-beat variability: the first and third beats exhibit pre-excitation (short PR, delta wave, wide QRS), while the second beat displays a normal PR interval and narrow QRS morphology. Panel (c) provides a continuous Lead I rhythm strip illustrating this electrical alternation (alternance), where pre-excited beats alternate with normally conducted beats. The ECG findings are essential for identifying accessory pathway conduction and evaluating the results of catheter ablation procedures. Clinically, the alternation in Panel (b) and (c) can represent intermittent pre-excitation or fusion beats between normal atrioventricular conduction and an ectopic ventricular rhythm arising near a previous ablation site.

This diagnostic image is a standard 12-lead electrocardiogram (ECG) tracing on a red grid background, illustrating an acute inferior wall ST-elevation myocardial infarction (STEMI). The tracing displays the six limb leads (I, II, III, aVR, aVL, aVF) and the six precordial leads (V1-V6), with a continuous rhythm strip of lead II at the bottom. Purple circles highlight significant ST-segment elevation at the J-point in the inferior leads: II, III, and aVF. The ST elevation is approximately 1 mm or greater with a convex or upward-sloping morphology. Reciprocal ST-segment depression is visible in the high lateral leads (I and aVL), which is a classic finding in inferior STEMI. The precordial leads (V1-V6) show a normal R-wave progression without acute ST-segment changes. This ECG is a key educational tool for cardiovascular medicine, specifically for diagnosing acute coronary syndromes and identifying regional wall ischemia or infarction patterns.

This diagnostic image is a 12-lead electrocardiogram (ECG) printed on standard red-grid paper, demonstrating findings consistent with an acute inferior wall ST-segment elevation myocardial infarction (STEMI). Significant ST-segment elevation is clearly visible in the inferior leads (II, III, and aVF), with the elevation in lead III being particularly prominent and exhibiting a convex-upward morphology. Reciprocal ST-segment depression is noted in the high lateral leads (I and aVL). Blue arrows in leads II, III, and aVF highlight the pathognomonic ST-segment displacement. The ECG also includes precordial leads V1-V6 and a rhythm strip at the bottom showing leads V1, II, and V5. Key educational features include the visualization of injury patterns in an anatomical vascular distribution (right coronary artery or left circumflex), making it an essential resource for students learning to identify acute coronary syndromes and distinguish between inferior and lateral wall changes.