This diagnostic comparison image shows two 12-lead electrocardiograms (ECGs) used to illustrate the differentiation between Wide Complex Tachycardia (WCT) and baseline rhythms. Panel A displays a Wide Complex Tachycardia characterized by a rapid ventricular rate and significantly widened QRS complexes (approximately 170 ms). The morphology is relatively uniform with prominent S-waves in the precordial leads and notable baseline artifact. Panel B shows the patient's baseline ECG, presenting a narrow QRS complex rhythm with visible P-waves preceding each QRS, consistent with sinus rhythm or a supraventricular origin. The comparison highlights clinical diagnostic challenges where Supraventricular Tachycardia (SWCT) with aberrancy may mimic Ventricular Tachycardia (VT). This material is intended for advanced medical education in cardiology and electrophysiology, specifically focusing on ECG interpretation and the application of predictive models for arrhythmia classification.

Two diagnostic 12-lead electrocardiogram (ECG) tracings (labeled A and B) from a 7-year-old male patient showing wide-complex tachyarrhythmias. Figure 1A demonstrates a regular, wide QRS tachycardia at a rate of approximately 215 BPM. The morphology exhibits features consistent with a right bundle branch block (RBBB) pattern and a superior axis, suggestive of left anterior fascicular block. Figure 1B shows a subsequent episode of wide-complex tachycardia at a slower rate of 132 BPM, maintaining the RBBB-like morphology and superior QRS axis deviation. Key diagnostic parameters provided in the ECG headers include a QRS duration of 110 ms in Figure 1B and a markedly shifted P-R-T axis between the two recordings. Both tracings represent ventricular fascicular tachycardia (VFT), a specific type of idiopathic ventricular tachycardia often characterized by a RBBB pattern and axis deviation. The images serve as educational materials for distinguishing fascicular ventricular tachycardia from other forms of supraventricular or ventricular arrhythmias based on QRS morphology, axis, and rate.

This diagnostic image displays two comparative 12-lead electrocardiograms (ECGs) representing wide-complex tachycardia localized to the ventricular outflow tract. Panel A illustrates a regular wide-complex rhythm characterized by an inferior axis and a QS pattern in leads aVR and aVL. The precordial transition is early, occurring before lead V3, which is a visual marker often associated with a left ventricular outflow tract (LVOT) origin. Panel B demonstrates a similar wide-complex tachycardia but with distinct morphological variations: it features a QR pattern specifically in lead V1, an inferior axis where the R-wave voltage ratio in lead II/III is greater than 1, and a precordial transition occurring at lead V3. These ECG findings are clinically significant for mapping the anatomical origin of idiopathic or post-surgical ventricular arrhythmias. The tracings are presented on standard grid paper (25 mm/sec) and serve as a comparative educational resource for identifying exit sites of ventricular tachycardia based on QRS morphology and axis transition.