Clinical Guides
Ventricular Tachycardia
A clinically focused guide to adult ventricular tachycardia in India, integrating broad-complex rhythm diagnosis, haemodynamic stability, immediate shock and drug pathways, reversible causes, structural and inherited disease, ablation, implantable devices and evidence limitations.
MedNext Academy | 13 min read
Ventricular Tachycardia
A clinically focused guide to adult ventricular tachycardia in India, integrating broad-complex rhythm diagnosis, haemodynamic stability, immediate shock and drug pathways, reversible causes, structural and inherited disease, ablation, implantable devices and evidence limitations.
Summary
Ventricular tachycardia is a rapid rhythm originating below the His bundle. It may be monomorphic, with a relatively constant QRS appearance, or polymorphic, with beat-to-beat variation; it may be sustained, self-terminating or pulseless. The same ECG label spans very different substrates, from scar-related re-entry after myocardial infarction to idiopathic outflow-tract VT, myocarditis, cardiomyopathy, electrolyte disturbance, drug-induced torsades de pointes and inherited electrical disease. The immediate priorities are pulse, perfusion and rhythm, not a premature aetiological label.
A pulseless patient with VT follows the cardiac-arrest pathway with high-quality CPR and prompt unsynchronized defibrillation. A patient with a pulse but hypotension, altered mental state, shock, ongoing ischaemic chest discomfort or acute heart failure requires synchronized cardioversion, with sedation when feasible but no dangerous delay. Stable wide-complex tachycardia still requires monitored expert treatment because stability can deteriorate and misdiagnosis can cause harm. When the mechanism is uncertain, treat a broad-complex tachycardia as VT until proved otherwise.
After termination, determine why it occurred. Preserve the ECG, compare sinus-rhythm tracing, correct reversible triggers and investigate structural, ischaemic, inflammatory, toxic and inherited causes. Long-term decisions may include disease-specific treatment, catheter ablation and an implantable cardioverter-defibrillator, but an ICD terminates malignant rhythms rather than removing every substrate. This draft is educational, does not provide an individual shock, infusion, ablation or device order, and remains quarantined following MedNext Clinical Team review.
How Common Is It?
The frequency of VT depends heavily on the population studied. Sustained monomorphic VT is encountered most often in people with structural heart disease, especially myocardial scar, but it also occurs with dilated, arrhythmogenic and hypertrophic cardiomyopathies, cardiac sarcoidosis, myocarditis, congenital heart disease and prior cardiac surgery. Idiopathic VT occurs in apparently normal hearts and usually has a different prognosis, yet apparently normal echocardiography does not exclude a concealed cardiomyopathy or inflammatory substrate.
Hospital, device-clinic and electrophysiology cohorts cannot be converted into a population prevalence. Implantable devices record asymptomatic episodes that would otherwise be missed, while sudden deaths may occur before a diagnostic ECG is captured. Definitions also differ: nonsustained VT may mean three or more ventricular beats ending within 30 seconds, whereas sustained VT continues beyond 30 seconds or requires earlier termination because of compromise. Monitor algorithms can misclassify artefact or supraventricular rhythms, so electronic counts need adjudication.
No source used here gives a current nationally representative Indian incidence of every VT phenotype. India's burden is shaped by coronary disease, cardiomyopathy, repaired congenital disease, acute myocarditis, medication access and distance to emergency defibrillation or specialist electrophysiology. The relevant service measures are witnessed arrest response, ECG-confirmed episodes, time to shock, reversible-cause treatment, access to coronary and structural evaluation, and completion of device or ablation follow-up. A single imported percentage would hide these clinically important differences.
Risk Factors
Prior myocardial infarction and ventricular scar are major substrates for sustained monomorphic VT because surviving conduction channels permit re-entry. Other structural risks include reduced left-ventricular function, dilated or arrhythmogenic cardiomyopathy, hypertrophic cardiomyopathy, cardiac sarcoidosis, myocarditis, Chagas disease in relevant travel contexts, congenital heart disease, ventricular aneurysm and previous cardiac surgery. Heart failure severity informs risk but ejection fraction alone does not explain every arrhythmia or determine every device decision.
Acute triggers include myocardial ischaemia, hypoxaemia, acidosis, fever, sympathetic surge and disturbances of potassium, magnesium or calcium. QT-prolonging medicines, drug interactions, bradycardia and electrolyte loss can precipitate torsades de pointes. Sodium-channel-blocking drugs or toxins can widen QRS and provoke ventricular arrhythmia. Ask about antiarrhythmics, antimicrobials, antipsychotics, antidepressants, antiemetics, diuretics, digoxin, recreational stimulants, herbal products and organophosphate or other poisoning where clinically plausible. Do not stop chronic medicines indiscriminately; perform an urgent interaction and toxicity review.
Inherited risk includes long-QT syndrome, Brugada syndrome, catecholaminergic polymorphic VT and familial cardiomyopathy. Red flags are exertional syncope, nocturnal agonal breathing, unexplained seizure, a family history of sudden death, multiple affected relatives or a characteristic resting ECG. Age does not eliminate genetic disease, and a young athlete with VT is not assumed to have a benign sports response. Conversely, premature ventricular beats alone do not prove a lethal substrate. Risk is established through phenotype, imaging, rhythm morphology, clinical course and selective genetic evaluation with counselling.
Diagnosis
History
Establish whether the patient has a pulse and whether symptoms began during the tachycardia. Ask about collapse, chest pain, dyspnoea, palpitations, seizure-like activity, exercise, fever, recent infarction, heart failure, myocarditis, congenital disease, ablation and implanted devices. Record every medicine, dose change, overdose possibility and family sudden-death history. For recurrent episodes, document onset, duration, device therapy, shocks and preceding bradycardia or long-short sequence.
Examination
Assess airway, breathing, circulation, blood pressure, oxygenation, perfusion and consciousness continuously. Look for pulmonary oedema, shock and ongoing ischaemia. Determine pulse regularity and whether monitor complexes correspond to a palpable pulse, because artefact can coexist with a normal pulse. Signs such as variable first heart sound, cannon venous waves or changing systolic pressure may suggest AV dissociation but are neither sensitive nor required. Examine for heart failure, valve disease, infection, toxidrome and neuromuscular or endocrine clues after stabilization.
Investigations
Acquire a 12-lead ECG during tachycardia and continuous rhythm strip without delaying a shock. Broad QRS, AV dissociation, capture or fusion beats, extreme axis and concordance support VT, but absence does not exclude it. Preserve the post-conversion ECG for Q waves, QT, Brugada pattern, pre-excitation and conduction disease. Check glucose, electrolytes, magnesium, calcium, renal function, acid-base status and targeted troponin or toxicology. Echocardiography assesses structure and function; coronary evaluation follows ischaemic probability. Cardiac MRI can reveal scar or inflammation when available. Ambulatory monitoring, device interrogation, electrophysiology study and phenotype-directed genetic testing are selected by cardiology, not ordered as a universal panel.
Differential Diagnosis
The principal electrocardiographic differential for regular wide-complex tachycardia is VT versus SVT with aberrant conduction or pre-excitation. Pre-existing bundle-branch block does not prove a supraventricular origin, and haemodynamic stability does not exclude VT. Clinical probability rises with structural heart disease or prior infarction, but idiopathic VT can occur in a structurally normal heart. When confident distinction is not possible in real time, use a VT-safe treatment pathway and obtain expert help.
Irregular wide-complex rhythms include atrial fibrillation with aberrancy, pre-excited atrial fibrillation, polymorphic VT and torsades de pointes. Torsades is polymorphic VT in the setting of prolonged repolarization and appears to twist around the baseline; treating it as routine monomorphic VT can worsen risk. Bidirectional VT suggests specific substrates such as catecholaminergic polymorphic VT or digoxin toxicity but is not diagnosed from a single descriptive word. Ventricular fibrillation is chaotic without organized output and is managed as cardiac arrest.
Other mimics include paced rhythms, severe hyperkalaemia, sodium-channel-blocker toxicity and ECG artefact. Tremor or movement can generate apparent broad complexes while native QRS complexes continue underneath; check the patient, pulse, another lead and electrode contact without delaying treatment when perfusion is genuinely absent. Accelerated idioventricular rhythm is usually slower and often transient after reperfusion. Frequent premature ventricular complexes and nonsustained VT require contextual risk assessment but are not automatically managed like sustained unstable VT. The differential is a safety hierarchy, not an invitation to postpone cardioversion in a deteriorating patient.
Management
If VT is pulseless, activate the arrest response, begin high-quality CPR and defibrillate promptly according to the current shockable-rhythm algorithm. If a pulse is present but the persistent tachyarrhythmia causes hypotension, acute altered mental state, signs of shock, ischaemic chest discomfort or acute heart failure, perform synchronized cardioversion with device-appropriate energy. Prepare airway support and sedation when feasible, but do not delay the shock. Polymorphic VT cannot be reliably synchronized and requires an unsynchronized shock when sustained or unstable under the local resuscitation protocol.
For stable monomorphic wide-complex tachycardia, maintain monitoring, IV access and immediate cardioversion capability while seeking expert consultation. The 2025 AHA algorithm lists procainamide or amiodarone infusions as options and restricts adenosine consideration to a regular monomorphic rhythm. Choice depends on QT interval, heart failure, blood pressure, structural disease, interactions and local availability. Do not give verapamil to undifferentiated wide-complex tachycardia. Correct hypoxia, ischaemia, acidosis and potassium or magnesium disturbance. Torsades requires withdrawal of QT-prolonging factors, magnesium and specialist consideration of rate acceleration or pacing; recurrent electrical storm needs intensive multidisciplinary care.
Long-term management targets substrate and sudden-death risk. Revascularization treats ischaemia but does not automatically abolish scar VT. Guideline-directed heart-failure and cardiomyopathy care is essential. An ICD is considered for secondary prevention after cardiac arrest or haemodynamically significant VT when a transient reversible cause does not fully explain risk, and in selected primary-prevention phenotypes. Catheter ablation reduces recurrent monomorphic VT and device therapies in appropriate patients but may not replace an ICD. Decisions require electrophysiology review, imaging, prognosis, comorbidity and informed preference.
Prescribing Information
Antiarrhythmic infusions are high-risk monitored treatments. The 2025 AHA tachyarrhythmia algorithm lists procainamide at 20 to 50 mg per minute until suppression, hypotension, QRS widening beyond 50 percent or a maximum cumulative 17 mg/kg, followed by 1 to 4 mg per minute; it advises avoiding procainamide with prolonged QT or congestive heart failure. It lists amiodarone 150 mg over 10 minutes, repeatable for recurrent VT, followed by 1 mg per minute for the first six hours. These are algorithm details, not an instruction to prescribe without local authorization, infusion safeguards and senior review.
Amiodarone can cause hypotension acutely and, with cumulative exposure, thyroid, pulmonary, hepatic, ocular, neurological and skin toxicity; it has many interactions and a very long half-life. Procainamide can worsen hypotension and prolong QRS or QT. Lidocaine has a role in selected ventricular arrhythmias but requires weight-based dosing, hepatic and neurological caution. Magnesium is indicated for torsades or documented deficiency rather than every monomorphic VT. Correct potassium carefully with renal function and serial measurements.
Avoid stacking drugs when the rhythm or previous dose is uncertain. Record total dose, infusion concentration, pump rate, QT and QRS changes, blood pressure and response. Review interacting medicines and remove a causative agent only with an explicit replacement or monitoring plan. Chronic amiodarone or other antiarrhythmic therapy should have a named prescriber and surveillance schedule; an ICD shock does not itself justify an unsupervised dose increase. The patient-specific balance between drugs, ablation and device programming belongs to an electrophysiology service.
When to Refer
Every sustained VT episode requires urgent senior assessment. Transfer immediately when there is cardiac arrest, haemodynamic compromise, recurrent VT, electrical storm, ongoing chest pain, acute heart failure, significant electrolyte or drug toxicity, suspected myocarditis, pregnancy, congenital heart disease or inability to provide continuous monitoring and cardioversion. Contact the receiving centre early, send the tachycardia and sinus-rhythm ECGs, and report shocks, synchronization, energies, drug doses, electrolyte results and response. A transient return to sinus rhythm does not remove the need to establish substrate and recurrence risk.
Electrophysiology referral is indicated for sustained monomorphic VT, recurrent ICD therapies, possible idiopathic VT suitable for ablation, uncertain broad-complex mechanism, arrhythmogenic cardiomyopathy and inherited arrhythmia syndromes. Heart-failure, imaging, interventional cardiology, genetics or inflammatory-disease expertise may also be required. Survivors of cardiac arrest need systematic evaluation rather than a device implanted without asking whether acute ischaemia, toxin, electrolyte disturbance or another reversible factor was responsible.
In India, verify which hospital can provide coronary angiography, cardiac MRI, electrophysiology, catheter ablation and ICD implantation or follow-up. Transfer to the nearest safe stabilization facility may precede tertiary transfer. If a device is implanted, follow-up must include wound review, interrogation, programming, battery surveillance and a plan for shocks. A patient living far from the implanting centre needs a shared-care route. Referral documentation should address affordability and transport without assuming that lack of immediate access makes long-term prevention optional.
Red Flags
Absence of a pulse, unresponsiveness or abnormal breathing means cardiac arrest: begin CPR and attach a defibrillator immediately. With a pulse, hypotension, altered consciousness, shock, persistent ischaemic discomfort and acute heart failure are cardinal signs for urgent synchronized cardioversion. Deterioration can occur despite an initially normal blood pressure, so do not leave a patient with sustained wide-complex tachycardia unmonitored or send them unaccompanied for imaging.
Polymorphic VT, prolonged QT, recurrent syncope, multiple device shocks or three or more sustained ventricular arrhythmia episodes in a short period suggest a particularly high-risk state. Stop and review QT-prolonging or sodium-channel-blocking exposures, correct electrolytes and obtain critical-care and electrophysiology support. Fever with a Brugada pattern, exercise-triggered bidirectional VT, a family cluster of sudden deaths, or new ventricular arrhythmia with myocarditis features demands phenotype-specific evaluation. Seizure-like movements can be cerebral hypoperfusion from arrhythmia and should not be dismissed as epilepsy without rhythm assessment.
After cardioversion, red flags include recurrent ectopy progressing to VT, persistent chest pain or ST changes, bradycardia, high-grade block, worsening shock, pulmonary oedema and neurological deficit. Following ICD implantation, fever, pocket redness, drainage, swelling, syncope or shocks require prompt device-centre contact; repeated shocks are an emergency. Patients must know not to drive themselves after syncope or a shock. A wearable's normal display cannot overrule witnessed collapse, a diagnostic ECG or device electrogram.
Indian Clinical Context
The Government of India's 2021 HWC emergency-care manual emphasizes rapid assessment, transfer and early defibrillation for pulseless VT within the capabilities of primary emergency services. It is a training document that explicitly expects updating as knowledge advances. Current institutional resuscitation protocols should therefore control shock technique, antiarrhythmic dosing and post-arrest care. The 2025 AHA algorithm is used here for current tachyarrhythmia infusion details, while Indian referral decisions must reflect actual local capacity and national or state protocols.
Access varies markedly between facilities. A medical officer may recognize a wide rhythm and stabilize transfer but lack invasive coronary evaluation, cardiac MRI, an electrophysiology laboratory, ablation or device services. District cardiac units and medical colleges have heterogeneous capability; advanced services are concentrated in tertiary public and private centres. The safest destination is the centre able to deliver the next required intervention, not simply the closest building labelled cardiac. Confirm availability, send ECG evidence and arrange monitored transport with defibrillation capability when risk warrants it.
ICDs and ablation generate continuing obligations. Up-front cost, device procurement, travel for interrogation, lead management, generator replacement and time away from work can influence decisions. These constraints must be discussed transparently without presenting a cheaper but unsafe alternative as equivalent. Remote follow-up can support but not replace device interrogation or emergency care. Patients should carry device identification, diagnosis, drug list and prior ECGs. This guide makes no claim that every Indian district offers equal access, and it does not quote a national procedure price or success rate without verified programme data.
NMC Competency Mapping
NMC undergraduate competencies relevant to VT begin with cardiovascular physiology and safe ECG skills. PY5.6 includes abnormal ECG patterns, arrhythmias, heart block and myocardial infarction, while PY5.13 addresses recording and interpreting a normal ECG in supervised or simulated learning. General Medicine IM1.17 includes ordering and interpreting a 12-lead ECG within clinical investigation, and IM1.18 addresses performance and interpretation of a 12-lead ECG. These competencies support recognition and escalation; they do not by themselves credential a learner to deliver shocks or antiarrhythmic infusions independently.
A learner should assess pulse and stability, identify a wide-complex tachycardia, state why VT is the safe presumption when the mechanism is uncertain, and distinguish synchronized cardioversion from unsynchronized defibrillation. They should recognize monomorphic versus polymorphic morphology, look for AV dissociation, capture and fusion, review QT, and identify reversible factors such as ischaemia, potassium or magnesium disturbance, hypoxia and drugs. They should explain why normal blood pressure does not make sustained VT benign.
Advanced objectives include building a post-event evaluation for scar, cardiomyopathy, myocarditis and inherited disease; explaining the different purposes of antiarrhythmic drugs, catheter ablation and an ICD; and communicating limitations of ejection-fraction-only risk prediction. Simulation should include pad placement, synchronized mode confirmation, failure to synchronize, pulseless deterioration and safe handover. Device implantation, programming, electrophysiology study and ablation require specialist training. The mapping is transparent educational alignment, not a substitute for credentialing or local resuscitation governance.
Key Exam Pearls for NEET PG
A regular broad-complex tachycardia is VT until proved otherwise, particularly with prior infarction or structural heart disease. AV dissociation, capture beats, fusion beats, extreme axis and precordial concordance favour VT, but no single absent sign excludes it. Stability does not establish a supraventricular origin. Monomorphic VT suggests a stable activation circuit, often scar-related; polymorphic VT implies changing activation and requires attention to QT, ischaemia and acute instability. Torsades de pointes is polymorphic VT associated with prolonged repolarization.
Pulseless VT is a shockable cardiac-arrest rhythm treated with CPR and unsynchronized defibrillation. VT with a pulse that causes hypotension, shock, altered consciousness, acute heart failure or ischaemic discomfort requires synchronized cardioversion. Stable monomorphic wide tachycardia is managed with monitoring, cardioversion readiness, expert consultation and an appropriate antiarrhythmic pathway. Adenosine is considered only for regular monomorphic broad tachycardia in the current adult algorithm, never as a reflex treatment for irregular or polymorphic rhythms. Verapamil is unsafe in undifferentiated VT.
Magnesium is a classic treatment for torsades, together with removing QT-prolonging causes and correcting electrolytes; amiodarone may worsen a QT-driven problem. An ICD detects and terminates ventricular arrhythmia but does not cure the scar, prevent every episode or replace heart-failure treatment. Catheter ablation can reduce recurrent monomorphic VT and ICD shocks, yet recurrence remains possible. Secondary-prevention device decisions require exclusion of a completely reversible cause and consideration of prognosis. Preserve the presenting ECG and device electrograms because post-conversion sinus rhythm may conceal the diagnosis.
Frequently Asked Questions
Should every stable broad-complex tachycardia be assumed to be ventricular tachycardia?
Yes for acute safety when the mechanism is uncertain. A patient can remain alert and normotensive during VT, and inappropriate treatment of presumed SVT can be harmful. Use continuous monitoring, obtain a 12-lead ECG, prepare for cardioversion and seek expert interpretation while following a VT-safe algorithm.
What is the difference between cardioversion and defibrillation in ventricular tachycardia?
Synchronized cardioversion times the shock to the QRS and is used for unstable VT with a pulse when synchronization is possible. Pulseless VT requires immediate unsynchronized defibrillation with CPR. Sustained polymorphic VT cannot be synchronized reliably and is shocked using the applicable resuscitation pathway.
Does an implantable cardioverter-defibrillator cure ventricular tachycardia?
No. An ICD detects and treats dangerous ventricular rhythms, reducing sudden-death risk in appropriately selected patients, but it does not remove scar or every trigger. Heart-failure and substrate treatment, medicine review, programming, follow-up and sometimes catheter ablation remain necessary. Device shocks themselves require clinical review.
When is catheter ablation considered for ventricular tachycardia?
Electrophysiology teams consider ablation for recurrent sustained monomorphic VT, repeated ICD therapies or selected idiopathic VT, among other scenarios. Benefit and risk depend on substrate, ventricular function, access route, prior procedures and centre expertise. Ablation can reduce recurrence and shocks but may not remove the need for an ICD.
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