Clinical Guides
Supraventricular Tachycardia
A clinically focused guide to recognising and managing adult supraventricular tachycardia in India, separating rhythm diagnosis from haemodynamic stability, acute cardioversion from drug treatment, and recurrent-symptom control from electrophysiology and ablation decisions.
MedNext Academy | 12 min read
Supraventricular Tachycardia
A clinically focused guide to recognising and managing adult supraventricular tachycardia in India, separating rhythm diagnosis from haemodynamic stability, acute cardioversion from drug treatment, and recurrent-symptom control from electrophysiology and ablation decisions.
Summary
Supraventricular tachycardia is an umbrella term for rapid rhythms arising above the ventricles or using tissue above the His bundle as an essential part of the circuit. In acute care, the label often refers to a regular narrow-complex tachycardia caused by atrioventricular nodal re-entry or an atrioventricular re-entry circuit, but focal atrial tachycardia and atrial flutter can look similar. A rhythm name should not replace the first safety decision: determine whether the tachycardia is causing hypotension, altered consciousness, shock, ischaemic chest discomfort or acute heart failure.
Obtain a rhythm strip and 12-lead ECG without delaying treatment. A regular narrow tachycardia in a stable adult can be approached with a properly performed vagal manoeuvre and, when appropriate, monitored rapid intravenous adenosine. Instability attributable to the rhythm calls for synchronized cardioversion, with sedation when feasible but without dangerous delay. An undifferentiated broad-complex tachycardia should be managed as ventricular tachycardia until expert interpretation establishes otherwise.
After termination, save the ECG, look for pre-excitation and reversible contributors, and decide whether ambulatory monitoring or electrophysiology referral is needed. Recurrent symptomatic AVNRT or AVRT is frequently amenable to catheter ablation, but procedural success and complication estimates depend on mechanism, operator and centre. This educational draft does not authorize independent cardioversion, adenosine administration or ablation and remains reviewed following MedNext Clinical Team review.
How Common Is It?
The incidence of each supraventricular mechanism varies with age, sex, congenital substrate, structural heart disease and how cases are captured. AVNRT is a common regular paroxysmal SVT in adults; accessory-pathway-mediated AVRT often presents earlier, while focal atrial tachycardia has a different substrate and may become incessant. Atrial fibrillation and typical atrial flutter are supraventricular rhythms in anatomical terms but have distinct stroke-risk and long-term management pathways and should not be collapsed into a generic PSVT statistic.
Community prevalence is difficult to infer from emergency-department or electrophysiology cohorts. Brief self-terminating attacks may never be recorded, whereas patients with recurrent, prolonged or poorly tolerated episodes are overrepresented in specialist series. Palpitations attributed to anxiety may conceal a rhythm disturbance, and wearable recordings increase detection without always proving the mechanism. No authoritative source used here provides a contemporary, nationally representative Indian incidence for every SVT subtype, so the guide deliberately avoids a single headline number.
Clinical burden is better described by consequences: unpredictable palpitations, emergency visits, syncope risk in selected patients, treatment adverse effects, pregnancy-related uncertainty and loss of work or travel. Sustained rapid rhythms can occasionally cause tachycardia-induced cardiomyopathy. In India, delayed ECG capture and variable access to electrophysiology can prolong uncertainty. Service planning should count documented mechanisms, instability, recurrence and referral completion rather than assuming every regular palpitation represents the same disease.
Risk Factors
Most AVNRT reflects dual AV-nodal physiology and does not require overt structural heart disease. AVRT requires an accessory atrioventricular pathway; manifest pre-excitation may show a short PR interval and delta wave in sinus rhythm, but a concealed pathway can conduct only retrogradely and leave the resting ECG normal. Focal atrial tachycardia may arise without structural disease or accompany atrial scarring, cardiomyopathy, congenital heart disease, surgery, inflammation or drug toxicity. Increasing age and atrial disease shift the differential toward atrial tachycardia or flutter.
Episodes may be facilitated by adrenergic stimulation, sleep loss, fever, dehydration, anaemia, hyperthyroidism, pregnancy, alcohol, stimulants or sympathomimetic medicines, although an apparent trigger does not establish the circuit. Ask about caffeine and energy products, decongestants, bronchodilators, thyroid replacement, recreational substances and withdrawal states. Correcting a trigger may reduce attacks but cannot be assumed to eliminate an accessory pathway or AV-nodal re-entry substrate.
Features that raise the stakes include known pre-excitation, congenital or structural heart disease, previous myocardial surgery, ventricular dysfunction, exertional syncope, a family history of sudden unexplained death and use of drugs that affect conduction or repolarization. Pregnancy changes drug and procedural choices. Older people may tolerate the same rate less well because of coronary or diastolic disease. Risk assessment must separate probability of SVT from probability that a rapid rhythm will be poorly tolerated; neither can be decided from heart rate alone.
Diagnosis
History
Ask the patient to describe onset and offset, regularity, duration, neck pounding, polyuria, chest discomfort, breathlessness, presyncope and syncope. Abrupt onset and termination support a re-entry rhythm; a warm-up and cool-down pattern suggests automatic atrial tachycardia but is not definitive. Document exertional relation, pregnancy possibility, prior ECGs, structural disease, pre-excitation, medicines and family history. Establish whether concerning symptoms occurred during the recorded rhythm rather than before or after it.
Examination
Begin with airway, breathing, pulse, blood pressure, oxygen saturation, perfusion and mental state. Look for shock, pulmonary oedema and ongoing ischaemia. Note pulse regularity and compare the palpable or monitored rate with the ECG. Cannon venous waves or prominent neck pulsation can occur but are not a bedside mechanism test. Examine for valve disease, heart failure, thyrotoxicosis, anaemia, infection and stimulant toxicity while preparing treatment.
Investigations
Capture a 12-lead ECG during tachycardia and a long rhythm strip if this does not postpone emergency care. Assess QRS width, regularity, atrial activity, RP relationship, AV association, axis and response to vagal manoeuvre or adenosine. Repeat the ECG in sinus rhythm for pre-excitation, conduction disease and repolarization changes. Target glucose, electrolytes, magnesium, blood count, thyroid testing, pregnancy testing, troponin or toxicology to the presentation. Echocardiography is appropriate when structural disease or tachycardia-mediated dysfunction is suspected. Ambulatory monitoring must match symptom frequency; electrophysiology study defines mechanism when diagnosis or curative ablation requires it.
Differential Diagnosis
Sinus tachycardia is usually a physiological response with visible sinus P waves and a rate that varies with demand; search for sepsis, hypovolaemia, pain, hypoxia, anaemia, pulmonary embolism, thyrotoxicosis or stimulant exposure rather than suppressing the rate. Atrial flutter with fixed or variable AV conduction can mimic a regular SVT, particularly near 150 beats per minute. Focal atrial tachycardia may show abnormal P waves and may continue despite AV block. Atrial fibrillation is irregular, although very rapid recordings can appear deceptively regular over a short strip.
A regular narrow tachycardia may be AVNRT, orthodromic AVRT, atrial tachycardia or flutter. Surface ECG clues modify probability but do not always prove the mechanism. Adenosine may terminate an AV-node-dependent circuit; transient AV block can instead expose atrial activity without terminating flutter or atrial tachycardia. That response is diagnostic information, not proof that every slowing rhythm was AVNRT.
Any wide-complex tachycardia creates a separate safety problem. Ventricular tachycardia, SVT with bundle-branch aberrancy and pre-excited tachycardia are possibilities, but uncertainty should favour a VT-safe pathway. Irregular broad-complex tachycardia may represent pre-excited atrial fibrillation and can deteriorate; AV-nodal blockers may be hazardous. Artefact, pacemaker tracking and metabolic QRS widening also mimic arrhythmia. Compare previous ECGs, but never use a familiar bundle-branch block to dismiss instability or delay senior help.
Management
Place the patient on continuous ECG and blood-pressure monitoring, obtain intravenous access, support airway and breathing, and give oxygen only when hypoxaemic. If persistent tachycardia is causing hypotension, acute altered mental state, shock, ischaemic chest discomfort or acute heart failure, perform synchronized cardioversion using a trained team and the device-specific energy strategy. Sedate when feasible, but do not postpone a life-saving shock. If synchronization repeatedly fails in a critically unstable rhythm, follow the local resuscitation protocol and seek expert help immediately.
For a stable, regular narrow-complex tachycardia, use a correctly coached vagal manoeuvre; a modified Valsalva with strain followed by supine repositioning and passive leg elevation is often more effective than an unstructured attempt. Do not perform bilateral carotid massage, and avoid carotid massage when cerebrovascular or carotid disease makes it unsafe. If the rhythm persists and adenosine is appropriate, give it as a rapid IV push with immediate saline flush under resuscitation-ready monitoring. Record the continuous rhythm response.
If adenosine is unsuitable or ineffective, confirm the rhythm rather than cycling blindly through drugs. A beta blocker or non-dihydropyridine calcium-channel blocker may be considered for selected stable narrow-complex rhythms, but hypotension, heart failure, ventricular dysfunction, conduction disease, pre-excitation and drug interactions change safety. After recovery, address triggers and provide a recurrence plan. Electrophysiology consultation and catheter ablation should be discussed for recurrent symptomatic AVNRT or AVRT, patient preference, drug intolerance, high-risk accessory pathways or tachycardia-mediated dysfunction.
Prescribing Information
Adenosine briefly blocks AV-nodal conduction. The current American Heart Association adult tachyarrhythmia algorithm specifies 6 mg by rapid intravenous push followed immediately by normal saline, then 12 mg if required. It must be delivered with continuous rhythm monitoring, defibrillation or cardioversion capability and staff prepared for transient asystole, flushing, chest pressure, dyspnoea and bronchospasm. A slow infusion is ineffective because its circulating half-life is only seconds. Central administration, cardiac transplantation and dipyridamole can increase effect; methylxanthines can reduce it. Verify the local protocol and product before use.
Do not give adenosine merely because a rate is fast. It is appropriate only in a regular narrow-complex tachycardia, or in selected regular monomorphic broad-complex tachycardia within an advanced-life-support pathway. Avoid it in irregular or polymorphic wide-complex rhythms and do not use AV-nodal blockers for suspected pre-excited atrial fibrillation. Severe reactive airway disease is an important caution. Pregnancy, paediatric age and transplanted hearts require specific guidance and senior input.
Verapamil, diltiazem and beta blockers can worsen hypotension, bradycardia, AV block or decompensated heart failure; combining AV-nodal-blocking agents magnifies risk. Flecainide, propafenone, sotalol and amiodarone are not generic take-home substitutes for mechanism diagnosis and require specialist selection based on structural disease, QRS or QT, kidney or liver function and interactions. Written prescriptions must state indication, dose, route, monitoring and stop or review plan. This guide provides education, not a patient-specific prescription.
When to Refer
Use emergency transfer for ongoing haemodynamic compromise, syncope with an abnormal rhythm, ischaemic chest discomfort, acute heart failure, persistent broad-complex tachycardia, suspected pre-excited atrial fibrillation, recurrent episodes despite initial treatment or inability to monitor safely. Send ECGs and rhythm strips with the patient and communicate treatments, exact doses, response and adverse effects. A patient who has converted should not be discharged solely because the monitor now shows sinus rhythm if the episode included high-risk features or the diagnosis remains uncertain.
Refer to cardiology or electrophysiology for recurrent symptomatic documented SVT, uncertain mechanism, pre-excitation, congenital or structural heart disease, ventricular dysfunction, pregnancy-related recurrence, exertional symptoms, syncope, occupational safety implications or drug intolerance. Discussion should include observation, episodic treatment where suitable, regular drug therapy and catheter ablation. Ablation can be definitive for many re-entry circuits, but the target and risks differ between AVNRT, accessory pathways and atrial tachycardia.
Make referral practical in the Indian setting. Confirm whether the destination provides emergency cardioversion, echocardiography, electrophysiology study and ablation rather than assuming every cardiac unit does. If specialist access is distant, give a written ECG-backed diagnosis, red-flag plan and interim medicine responsibility. Patients with implanted devices or prior ablation need access to their procedure report and device details. Follow-up is incomplete until someone reviews recurrence, resting ECG, structural evaluation and the patient's preference for definitive treatment.
Red Flags
Treat hypotension, cold or mottled peripheries, confusion, collapse, ongoing ischaemic chest discomfort and acute pulmonary oedema as signs that the tachycardia may be causing dangerous compromise. Do not wait for a particular numerical rate, and do not let a young age create false reassurance. If the patient becomes pulseless, leave the tachycardia-with-a-pulse pathway and begin cardiac-arrest management with immediate defibrillation for a shockable rhythm according to the current resuscitation protocol.
A broad QRS, irregular broad complexes, alternating morphology, extreme axis, AV dissociation or capture or fusion beats should raise concern for ventricular tachycardia or pre-excited atrial fibrillation. Never give repeated AV-nodal blockers to an uncertain irregular wide rhythm. Syncope during exertion, known structural heart disease, a family history of sudden death, a short PR with delta wave or documented very rapid pre-excited rhythm demands specialist assessment even if the patient feels well after conversion.
Post-treatment red flags include persistent chest pain, new ST change, neurological deficit, recurrent hypotension, severe bronchospasm, prolonged bradycardia, high-grade AV block and immediate recurrence. A troponin rise must be interpreted in context rather than assumed to prove plaque rupture, but ongoing ischaemia still requires urgent care. In pregnancy, maternal instability takes priority while obstetric and cardiology teams coordinate treatment. Discharge advice should name symptoms that trigger ambulance activation and should not rely on a consumer wearable to exclude recurrence.
Indian Clinical Context
The Ministry of Health and Family Welfare's 2021 emergency-care manual for medical officers at Ayushman Bharat Health and Wellness Centres describes ECG recognition, monitored stabilization, vagal manoeuvres and prompt referral for tachyarrhythmia. It also states that its material requires periodic updating. Where its older dose or timing details differ from a current resuscitation algorithm, clinicians must use an institutionally approved contemporary protocol rather than treating the manual as a universal prescription. This guide therefore uses the 2025 AHA algorithm for the specific adenosine sequence.
Capacity is heterogeneous. A primary facility may have basic monitoring and transport but no synchronized cardioversion or electrophysiology; a district hospital may stabilize but not ablate; tertiary government, teaching and private centres may provide electrophysiology study and radiofrequency or cryoablation. The safe pathway is determined by actual equipment, trained staff, drug availability and transfer time. Phone advice cannot replace transfer when the patient is unstable.
Cost, travel, time away from work, language and fear of an invasive procedure influence whether recurrent SVT receives definitive treatment. Provide copies or photographs of diagnostic ECGs, because an asymptomatic clinic ECG may be normal. Explain that ablation is mechanism-specific and not the same as open-heart surgery, while avoiding guarantees. If long-term medication is chosen because ablation is inaccessible or deferred, document monitoring and contraindications. Public, charitable and private routes differ; verify referral acceptance and do not advertise a national waiting time, price or success rate without auditable local data.
NMC Competency Mapping
The NMC curriculum links this topic to cardiovascular physiology, ECG performance and clinical investigation rather than granting unsupervised arrhythmia treatment competence from reading alone. PY5.6 requires description of abnormal ECG patterns including arrhythmias and heart block, and PY5.13 addresses recording and interpretation of a normal ECG in a supervised or simulated setting. In General Medicine, IM1.17 covers ordering and interpreting investigations including a 12-lead ECG, while IM1.18 requires performance and interpretation of a 12-lead ECG at the specified competency level.
A learner should be able to assess physiological stability before naming the mechanism, obtain a technically adequate ECG, distinguish regular from irregular and narrow from broad tachycardia, and identify sinus rhythm, AVNRT or AVRT probability, flutter, atrial fibrillation and VT-safe differentials. They should describe the rationale for a vagal manoeuvre, the AV-nodal effect of adenosine, synchronized cardioversion for instability and why an uncertain broad-complex rhythm is not treated casually as SVT.
Higher-order learning includes constructing a referral handover, reconciling precipitating medicines, interpreting the post-conversion ECG for pre-excitation, and explaining when ambulatory monitoring, echocardiography or electrophysiology study adds value. Cardioversion, intravenous antiarrhythmic treatment and ablation require simulation, credentialing and supervised clinical experience. The NMC mapping is an educational alignment, not proof that a student or nonspecialist can independently administer these interventions in a setting without monitoring and resuscitation support.
Key Exam Pearls for NEET PG
Classify a tachycardia before reaching for a drug: regular or irregular, QRS below or at least 120 ms, and stable or unstable. AVNRT is commonly a regular narrow tachycardia with atrial activity hidden in or just after the QRS; orthodromic AVRT is also narrow because antegrade conduction uses the AV node and His-Purkinje system. Antidromic AVRT is broad. A short PR and delta wave in sinus rhythm indicate manifest pre-excitation, but their absence does not exclude a concealed accessory pathway.
For stable regular narrow SVT, the high-yield sequence is a properly performed vagal manoeuvre followed by rapid IV adenosine with flush and rhythm recording. Adenosine terminates AV-node-dependent AVNRT or AVRT; transient AV block may reveal flutter waves or atrial tachycardia without curing the atrial rhythm. It is not the answer for an irregular wide-complex tachycardia. If the rhythm causes hypotension, shock, acute heart failure, altered consciousness or ischaemic chest discomfort, synchronized cardioversion overrides the stable algorithm.
Adenosine has a seconds-long half-life and can cause transient flushing, chest discomfort or breathlessness. AV-nodal blockers can be dangerous in pre-excited atrial fibrillation. Recurrent symptomatic AVNRT and AVRT are classic electrophysiology and catheter-ablation conditions. Always preserve the tachycardia ECG, because the resting tracing may normalize. Examination answers should avoid fixed-energy claims when the algorithm instructs use of the device recommendation or relevant guideline, and should state that any undifferentiated broad regular tachycardia is treated as VT until proved otherwise.
Frequently Asked Questions
What is the first decision when a patient presents with suspected supraventricular tachycardia?
Decide whether the rhythm is causing haemodynamic compromise. Hypotension, altered consciousness, shock, ischaemic chest discomfort or acute heart failure calls for synchronized cardioversion rather than a prolonged diagnostic-drug sequence. At the same time obtain monitoring, intravenous access and an ECG if that does not delay treatment.
Does adenosine prove that a regular narrow tachycardia was AVNRT?
No. Termination supports an AV-node-dependent circuit such as AVNRT or orthodromic AVRT, but transient AV block can merely expose flutter waves or ongoing atrial tachycardia. The continuous rhythm strip, tachycardia ECG, post-conversion ECG and clinical context must be interpreted together.
When should a broad-complex tachycardia be treated as supraventricular tachycardia with aberrancy?
Only when a competent clinician can establish that diagnosis within a monitored advanced-care pathway. In routine acute uncertainty, a broad-complex tachycardia should be managed as ventricular tachycardia because misclassifying VT and giving inappropriate AV-nodal drugs can be dangerous. Adenosine is restricted to selected regular monomorphic cases in the current algorithm.
Can catheter ablation cure recurrent paroxysmal supraventricular tachycardia?
Catheter ablation can eliminate the critical pathway in many AVNRT and AVRT cases and is an important option for recurrent symptoms, drug intolerance or patient preference. It is not a generic procedure: mechanism, pathway location, structural disease, pregnancy, centre expertise, recurrence risk and complications must be discussed by an electrophysiology team.
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