Clinical Overview

Ventricular tachycardia (VT) is a wide-complex tachyarrhythmia originating in the ventricular myocardium or the His-Purkinje system, below the AV node, defined as three or more consecutive ventricular beats at a rate exceeding 100 bpm. Because the impulse does not travel through the normal atrial-to-AV-node-to-ventricle pathway, the resulting QRS complex is wide and the atria and ventricles can beat independently of one another.

This dataset’s PVT label documents paroxysmal ventricular tachycardia specifically — a self-terminating, episodic run of VT captured on a clinical or ambulatory ECG, generally with a palpable pulse throughout. That is a temporal-pattern description (how the episode starts and stops), not a hemodynamic-status one, and it is a fundamentally different concept from “pulseless VT.” Pulseless VT is the same family of wide-complex rhythm, but with no measurable pulse — a cardiac-arrest presentation managed as a shockable rhythm under the ACLS algorithm (immediate defibrillation and CPR), the same pathway used for ventricular fibrillation. The content and monitoring guidance on this page describe paroxysmal VT with a pulse; it does not apply once a patient loses their pulse.

Three electrophysiologic mechanisms produce VT: reentry around a fixed anatomic or functional obstacle — most often a zone of scar from a prior myocardial infarction — is the dominant mechanism behind sustained monomorphic VT; enhanced automaticity, from ventricular or Purkinje tissue spontaneously depolarizing faster than the SA node; and triggered activity, from early or delayed afterdepolarizations. A monomorphic VT (uniform QRS shape from beat to beat) implies a single, consistent reentrant circuit or ectopic focus; a polymorphic VT (QRS shape varying from beat to beat) implies a less stable electrical substrate.

Hemodynamic tolerance during VT varies widely and depends on the rate and how well the ventricle was pumping beforehand: a patient with preserved heart function may stay awake, alert, and hemodynamically stable — with a pulse — through an entire run, while the same rhythm in a patient with poor underlying heart function can cause hypotension, altered mental status, or signs of shock even without becoming pulseless. More than half of monomorphic VT occurs in patients with coronary artery disease and a fixed myocardial scar, usually from a prior heart attack, and VT overall is substantially more common with any underlying structural heart disease than in a structurally normal heart, where it can still occur less commonly. Any sustained, recurrent, or hemodynamically unstable episode warrants urgent evaluation regardless of pulse status, because VT can degenerate into ventricular fibrillation.

Presentation ranges from brief, asymptomatic runs found incidentally on a monitor to palpitations, lightheadedness, chest pain, shortness of breath, and syncope. A longer or faster run, especially in a structurally diseased heart, carries greater risk of hemodynamic compromise.

The most common cause is coronary artery disease with prior myocardial infarction and resulting ventricular scar. Other causes include nonischemic cardiomyopathy, myocarditis, valvular heart disease, heart failure, inherited channelopathies (long QT syndrome, Brugada syndrome, catecholaminergic polymorphic VT), electrolyte disturbances (particularly low potassium or magnesium), QT-prolonging and other antiarrhythmic medications, and stimulant use (cocaine, methamphetamine). Advanced age and reduced left ventricular function increase risk.

Interpretation Guide

Key Features:

• Rate: greater than 100 bpm by definition, most commonly 150-200 bpm, ranging roughly 100-250 bpm
• Rhythm: regular in monomorphic VT; can be irregular in rate and morphology in polymorphic VT — a wide-complex tachycardia either way
• P waves: usually not discernible, buried within the faster QRS-T complexes; when visible, they march through at their own slower, independent rate, dissociated from the QRS (AV dissociation) — a normal sinus beat occasionally “captures” the ventricles mid-run, producing a normal-duration QRS interrupting the wide-complex pattern
• PR interval: not measurable when P waves are dissociated from or absent relative to the QRS
• QRS complex: wide, generally ≥120 ms and often ≥160 ms, with a bizarre morphology; uniform beat-to-beat shape in monomorphic VT, varying shape in polymorphic VT; an extreme (“northwest”) frontal-plane axis and a QRS that is either entirely positive or entirely negative across the precordial leads V1-V6 (concordance) both favor VT over a supraventricular rhythm with aberrant conduction
• ST segment and T waves: not separately assessable during the tachycardia — obscured within the wide QRS complex at this rate in most leads
• QT interval: not measurable during the wide-complex run itself; QT prolongation on a baseline or post-conversion ECG is relevant to the underlying substrate (e.g., long QT syndrome) but is a distinct assessment from the arrhythmia itself
• Other findings: capture beats (a normal sinus beat producing a normal-duration QRS mid-run) and fusion beats (a hybrid QRS from a sinus and a ventricular impulse activating the ventricles simultaneously) are highly specific for VT when present, though seen only in a minority of tracings

[CLINICAL REVIEW NEEDED]: the dataset’s own annotation methodology does not publish the specific duration or beat-count threshold used to label a record “paroxysmal” versus another rhythm category; the clinical literature’s working definition of VT (three or more consecutive ventricular beats above 100 bpm, self-terminating) is used here as the closest documented match.

Key Leads

• Lead II — the standard rhythm-strip lead for tracking the wide-complex run itself and for spotting AV-dissociation clues (independent P waves, capture beats) over time.
• Lead V1 — carries the most diagnostic weight for distinguishing VT from a supraventricular rhythm conducting with aberrancy: a monophasic R wave, a qR complex, or an RSR’ complex with a taller left (“rabbit ear”) peak favors VT, while a typical right-bundle-branch-block pattern (taller right rabbit ear) — especially one matching the patient’s own baseline bundle-branch-block morphology — favors a supraventricular origin.

Differential Diagnosis

• Supraventricular Tachycardia (SVT) — a supraventricular rhythm conducting with aberrancy (a bundle-branch block or an accessory pathway) can also produce a regular wide-complex tachycardia. Findings favoring VT are AV dissociation, capture or fusion beats, an extreme axis, and precordial concordance; findings favoring SVT with aberrancy are a QRS pattern matching the patient’s known baseline bundle-branch block or a prior history of adenosine-responsive tachycardia. When genuinely uncertain from the strip alone, the safer default is to treat it as VT — it is both the more common and the more dangerous of the two.
• Ventricular Fibrillation (VF) — VF has no organized, discrete QRS complexes at all: a chaotic, disorganized, undulating baseline of varying amplitude with no repeating pattern. VT, including this paroxysmal, pulse-present form, still shows repetitive, identifiable QRS complexes, whether uniform or varying in shape. Sustained VT can degenerate into VF, but the two are ECG-distinct rhythms, and VF is always pulseless and always managed on the ACLS cardiac-arrest pathway — VT is not.
• Ventricular Flutter (VFL) — an extreme, very fast form of VT, typically 200-300 bpm, in which the QRS complex, ST segment, and T wave merge into a smooth, continuous sine-wave pattern with no individually distinguishable components, unlike VT’s still-identifiable discrete QRS complexes. Ventricular flutter is hemodynamically unstable and usually short-lived, rapidly degenerating into ventricular fibrillation.
• Premature Ventricular Contractions (PVC) — a single early ventricular beat, or a short patterned run such as a couplet, is a PVC or a PVC pattern rather than VT. The dividing line is duration and rate: three or more consecutive ventricular beats at a rate above 100 bpm meets the definition of ventricular tachycardia; anything shorter is described under the PVC pattern types instead.

Treatment Brief

Confirm this is a true wide-complex tachycardia and not artifact, and get a 12-lead ECG if the patient’s condition allows — precise VT-versus-SVT differentiation usually needs the full 12-lead rather than a single monitoring lead. Notify the responsible provider immediately for any new sustained wide-complex tachycardia.

Check for a pulse first, every time: if the patient has no palpable pulse, this page’s guidance does not apply. Pulseless VT is a cardiac-arrest, shockable rhythm managed per ACLS (immediate defibrillation and CPR), identical to the ventricular fibrillation pathway — not the stable-rhythm approach below.

For a patient who does have a pulse, assess hemodynamic stability: hypotension, altered mental status, ongoing chest pain, or signs of shock mean an unstable patient who still needs urgent synchronized cardioversion (not defibrillation — synchronization avoids delivering the shock on a vulnerable T wave). A stable patient with a tolerated, sustained episode is typically managed with continuous monitoring, IV access, and either an IV antiarrhythmic per provider order (procainamide, sotalol, or amiodarone are guideline-recognized options for acute conversion) or synchronized cardioversion, particularly if drug therapy is contraindicated (for example, a prolonged QT limits procainamide or sotalol) or the episode does not resolve.