01Approach to the Critical Patient/attcp52

Immediate stabilization

›Hemodynamic assessment on arrival

›If hypotension, altered mental status, acute heart failure, or ischemic chest pain

›Immediate synchronized cardioversion (Class I recommendation)

›Starting energy 50 to 100 J biphasic

›Sedation if patient is conscious

›If hemodynamically stable

›Rhythm identification before pharmacologic intervention

›12-lead ECG as first step

›Airway and oxygen

›SpO2 target >= 94% on supplemental oxygen

›High-flow oxygen for hemodynamic instability

›IV access established immediately

›Resuscitation bay for unstable presentation

›Continuous cardiac monitoring

›Defibrillator at bedside

Rhythm identification

›ECG interpretation priorities

›QRS width

›Narrow complex QRS <= 120 ms favors SVT

›Wide complex QRS > 120 ms requires VT exclusion

›Regularity

›Regular rhythm favors AVNRT, AVRT, or atrial flutter with fixed block

›Irregularly irregular favors atrial fibrillation or multifocal atrial tachycardia

›P wave relationship to QRS

›P buried in or just after QRS favors AVNRT

›Short RP interval favors AVRT

›Long RP interval favors atypical AVNRT or focal atrial tachycardia

02History/hx61

Symptom characteristics

›Core symptoms

›Palpitations

›Prevalence 86% in paroxysmal SVT

›Abrupt flip-switch onset and termination hallmark of PSVT

›Chest discomfort

›Prevalence 47% in paroxysmal SVT

›Distinguish from ischemic chest pain requiring urgent ECG

›Dyspnea

›Prevalence 38%

›Often exertional in context of elevated heart rate

›Lightheadedness or presyncope

›Prevalence 19%

›True syncope rare and more often vagally mediated than from SVT directly

›Episode characterization

›Duration and frequency of episodes

›Self-terminating versus requiring ED presentation

›Escalating frequency as indicator for prophylaxis or ablation

›Polyuria during or after episodes

›Classic for SVT due to atrial natriuretic peptide release

›Distinguishes SVT from panic disorder

›Prior episodes, prior ED visits, prior adenosine use

›Prior ablation and recurrence timeline

Triggers and risk factors

›Common triggers

›Caffeine, alcohol, energy drinks

›Dietary history including supplement use

›Stimulants

03Physical Exam/exam42

Vitals and general

›Hemodynamic snapshot

›Heart rate

›Typical SVT range 150 to 250 bpm

›Rate < 150 bpm consider sinus tachycardia or atrial flutter with variable block

›Blood pressure

›SBP < 90 mmHg indicates hemodynamic instability requiring cardioversion

›MAP < 65 mmHg is threshold for urgent intervention

›Respiratory rate and SpO2

›Respiratory distress may reflect underlying heart failure or anxiety

›Temperature

›Fever as potential trigger (infection, thyroid storm)

Cardiovascular exam

›Cardiac findings

›Regular rapid rhythm on auscultation

›Irregular rhythm suggests atrial fibrillation or multifocal atrial tachycardia

›Jugular venous pulsations

›Cannon A waves classic for AVNRT (simultaneous atrial and ventricular contraction)

›Frog sign visible neck pulsations during AVNRT

›Murmurs

›Valvular disease as substrate for arrhythmia

›Peripheral perfusion

›Cool extremities, prolonged capillary refill as markers of low output state

Systemic exam

›Thyroid

›Thyroid enlargement or tenderness

›Hyperthyroidism as treatable trigger

›Carotid bruits before carotid sinus massage

04Differential Diagnosis/ddx52

Life-threatening arrhythmias

›Ventricular tachycardia

›ICD-10 I47.2

›Wide complex tachycardia QRS > 120 ms

›AV dissociation, fusion beats, capture beats favor VT

›Brugada algorithm or Vereckei algorithm for differentiation

›Pre-excited atrial fibrillation in WPW

›ICD-10 I45.6 (WPW syndrome)

›Irregular wide complex tachycardia

›Rates can exceed 300 bpm via accessory pathway

›Avoid adenosine, diltiazem, verapamil, digoxin

›Atrial flutter with 1:1 conduction

›Very rapid ventricular rate 250 to 300 bpm

›Associated with accessory pathway or class Ic antiarrhythmic use

›Hemodynamic collapse risk

Supraventricular tachycardia subtypes

›AVNRT (atrioventricular nodal reentrant tachycardia)

›ICD-10 I47.1

›Most common PSVT subtype 60%

›P wave buried in or just after QRS

›Responds to adenosine or vagal maneuvers

›AVRT (atrioventricular reentrant tachycardia)

›ICD-10 I47.1

›30% of PSVT; requires accessory pathway

›Short RP interval in orthodromic AVRT

›Wide complex in antidromic AVRT

›Focal atrial tachycardia

›ICD-10 I47.1

05Laboratory Tests/lt35

Essential labs

›Electrolytes

›Potassium

›Hypokalemia lowers arrhythmia threshold

›Target correction to > 4.0 mmol/l for recurrent SVT

›Magnesium

›Hypomagnesemia associated with arrhythmia susceptibility

›Replicate if level low

›Calcium

›Hypercalcemia or hypocalcemia can promote arrhythmias

›Thyroid function

›TSH

›Hyperthyroidism as reversible trigger

›High clinical yield in new-onset SVT without clear cause

›Complete blood count

›Anemia as high-output trigger

›Infection with fever as contributing factor

Cardiac biomarkers

›Troponin

›Indication when chest pain or concern for ischemia

›Mild troponin elevation during SVT in young patients without structural heart disease does not indicate coronary disease

›Significant elevation or dynamic rise requires ischemia workup

›Sensitive troponin assay preferred in undifferentiated chest pain

›BNP or NT-proBNP

›Indication when heart failure suspected

›Tachycardia-mediated cardiomyopathy concern in prolonged SVT

›Guides admission decision in borderline cases

06Diagnostic Tests/dt51

Scoring Systems

›Risk stratification and classification tools

›2015 ACC/AHA/HRS SVT guideline algorithm for narrow QRS tachycardia

›Systematic step-by-step approach to differential diagnosis

›Distinguishes AVNRT, AVRT, focal atrial tachycardia, sinus tachycardia, atrial flutter

›Class I recommendation level

›Brugada algorithm for wide-complex tachycardia

›Step 1: Absence of RS complex in all precordial leads favors VT

›Step 2: RS interval > 100 ms in any precordial lead favors VT

›Step 3: AV dissociation favors VT

›Step 4: Morphologic criteria in V1 and V6

›Vereckei algorithm as alternative to Brugada

›aVR lead criteria for VT versus SVT with aberrancy

›Initial R wave, notched downstroke, or Vi/Vt ratio favor VT

›Limitations of scoring tools

›Clinical context and adenosine response may supersede algorithm

›Electrophysiology consultation for diagnostic uncertainty

MRI

›Cardiac MRI role in SVT workup

›Not indicated in acute SVT management

›No role in acute rhythm termination or diagnosis

›Structural assessment for recurrent or refractory SVT

›Myocardial fibrosis or cardiomyopathy as arrhythmia substrate

›Congenital heart disease anatomy

›Pre-ablation planning in select cases

›Anatomic mapping of accessory pathways (limited utility)

›Assessment of myocardial function before ablation

07Disposition/dispo41

Discharge criteria

›Suitable for discharge from ED

›Conversion to normal sinus rhythm achieved

›Post-conversion ECG reviewed and no delta wave or long QT

›Hemodynamically stable throughout and after conversion

›SBP >= 90 mmHg

›No chest pain or heart failure features

›Structural heart disease excluded or known and stable

›Known SVT with typical presentation and reliable follow-up

›No electrolyte abnormality requiring IV correction

›Oral electrolyte replacement at home feasible

›Discharge prerequisites

›Outpatient cardiology or EP follow-up arranged

›Within 1 to 2 weeks for first episode

›Ablation discussion arranged for recurrent cases

›Avoidance counseling provided

›Trigger modification: caffeine, alcohol, stimulants

Admission indications

›Admit to telemetry or monitored bed

›Failure to convert in ED after appropriate pharmacologic attempts

›Repeat episodes during observation period

›Hemodynamic instability requiring cardioversion

›Even if rhythm restored, monitor for recurrence

›Significant troponin elevation or new ECG changes

›Ischemia workup required as inpatient

›New-onset SVT in patient with known structural heart disease

›Cardiology or EP management inpatient

›Newly diagnosed pre-excitation syndrome

08Treatment/t107

Vagal maneuvers

›First-line non-pharmacologic termination

›Modified Valsalva maneuver (REVERT technique)

›Semi-recumbent position, blow into 10 ml syringe for 15 seconds

›Immediately supine with legs raised 45 degrees for 15 seconds

›43% conversion rate in REVERT trial (versus 17% standard Valsalva)

›Class I recommendation, ACEP Level A evidence

›Carotid sinus massage

›5 to 10 second firm pressure at carotid bifurcation

›Conversion rate 10 to 19%

›Contraindicated if carotid bruit present or recent CVA or TIA

›Diver's reflex

›Ice water facial immersion

›Useful in pediatric population

Adenosine

›Adenosine IV protocol

›First dose 6 mg rapid IV push followed immediately by 20 ml NS flush

›Administered in antecubital or proximal IV site

›Half-life approximately 10 seconds requires rapid delivery

›If no conversion after 1 to 2 minutes, second dose 12 mg IV rapid push

›Third dose 12 mg if still no response

›Overall conversion rate approximately 90% for AVNRT and AVRT

›Diagnostic use in undifferentiated tachycardia

›Terminates AVNRT and AVRT

›Unmasks flutter waves in atrial flutter without terminating

›No effect on VT

›Contraindications

›Pre-excited AF or suspected WPW with atrial fibrillation

›Severe reactive airway disease or asthma

›High-degree AV block or sick sinus syndrome without pacemaker

›Heart transplant recipients (increased sensitivity, use 1 to 3 mg)

›Common transient side effects

›Flushing, dyspnea, chest tightness lasting 20 to 30 seconds

›Warn patient before administration

Non-dihydropyridine calcium channel blockers

›Diltiazem IV

›First dose 0.25 mg/kg IV over 2 minutes (typical 15 to 20 mg)

›Conversion rate 64 to 98%

›Second dose if no response after 15 minutes

›0.35 mg/kg IV over 2 minutes (typical 20 to 25 mg)

›Maintenance infusion if indicated

›5 to 15 mg/hour IV titrated to heart rate

›Contraindications

›HFrEF (EF < 40%) due to negative inotropic effect

›Wide complex tachycardia of uncertain origin

›Pre-excited AF or WPW

›Severe hypotension

›Verapamil IV

›Initial dose 5 mg IV over 2 minutes

›May repeat 5 to 10 mg IV after 15 to 30 minutes if needed

›Total maximum 20 mg

›Conversion rate similar to diltiazem 64 to 98%

›Contraindications same as diltiazem

›HFrEF, wide complex tachycardia of uncertain origin, pre-excited AF

Beta-blockers

›IV beta-blockers for SVT

›Metoprolol IV

›2.5 to 5 mg IV over 2 minutes

›May repeat every 5 minutes up to 3 doses (maximum 15 mg)

›Useful alternative when diltiazem or verapamil contraindicated

›Esmolol IV (ultra-short acting)

›Loading dose 500 mcg/kg IV bolus over 1 minute

›Maintenance infusion 50 mcg/kg/minute

›Titrate by 25 to 50 mcg/kg/minute every 5 to 15 minutes

›Maximum 300 mcg/kg/minute

›Half-life 9 minutes allows rapid offset if hypotension occurs

›Contraindications

›Decompensated heart failure

›Significant reactive airway disease

›Bradycardia or high-degree AV block

Synchronized cardioversion

›Electrical cardioversion protocol

›Indications

›Hemodynamic instability at any time

›Failure of pharmacologic cardioversion after two adequate drug attempts

›Procedural steps

›Procedural sedation with midazolam or propofol when patient conscious

›Synchronized mode confirmed on defibrillator before shock delivery

›Starting energy 50 to 100 J biphasic

›Escalate energy if no conversion: 150 to 200 J

›Post-cardioversion

›Post-conversion ECG immediately

›Monitor for recurrence 30 to 60 minutes

›Identify and correct precipitating cause

Etripamil (novel agent)

›Etripamil intranasal

›FDA-approved for acute termination of PSVT

›Intranasal calcium channel blocker

›70 mcg per nostril (total 140 mcg) self-administered

›Efficacy data

›Conversion rate 64% versus 31% placebo at 30 minutes in NODE-301 trial

›Median time to conversion 17 minutes

›Role in clinical practice

›Pill-in-the-pocket equivalent for PSVT

›Requires pre-dispensing and patient education

›Not a first-line ED option but relevant for outpatient plan

Long-term pharmacologic prophylaxis

›Antiarrhythmic agents for prevention

›Beta-blockers (first-line for chronic prevention)

›Metoprolol succinate 25 to 100 mg orally once daily

›Atenolol 25 to 100 mg orally once daily

›Non-dihydropyridine CCBs (first-line alternative)

›Diltiazem extended-release 120 to 360 mg orally once daily

›Verapamil extended-release 120 to 480 mg orally once daily

›Flecainide (pill-in-the-pocket or daily dosing)

›Patients without structural heart disease only

›50 to 100 mg orally twice daily

›Contraindicated in HFrEF, coronary artery disease

›Propafenone (pill-in-the-pocket or daily dosing)

›Patients without structural heart disease only

›150 to 300 mg orally twice or three times daily

›Class Ic agent; contraindicated in structural heart disease

›Ablation preferred over long-term antiarrhythmic therapy for recurrent SVT

›Class I recommendation ACC/AHA/HRS 2015

09Special Populations/sp71

Pregnancy

›SVT in pregnancy

›Physiologic changes increasing susceptibility

›Increased blood volume and cardiac output

›Hormonal changes and increased adrenergic tone

›SVT prevalence increases with advancing gestation

›Vagal maneuvers

›First-line and preferred; safe in all trimesters

›Modified Valsalva modified for gravid abdomen positioning

›Adenosine in pregnancy

›Generally considered safe for acute termination

›Short half-life minimizes fetal exposure

›Class B evidence; preferred pharmacologic agent in pregnancy

›Drug safety profile

›Metoprolol (FDA category C) acceptable for chronic prevention with monitoring

›Verapamil second-line; avoid in first trimester if possible

›Flecainide and propafenone limited data; avoid unless refractory

›Sotalol acceptable with QTc monitoring

›Cardioversion in pregnancy

›Safe at all gestational ages when hemodynamic instability present

›Fetal monitoring during and after cardioversion

›Fetal effects of rapid maternal heart rate

›Uteroplacental insufficiency risk with prolonged maternal SVT

›Maternal hemodynamic stabilization protects fetal circulation

›Obstetric consultation for any arrhythmia in pregnancy

›Fetal monitoring when viable gestation

Geriatric

›SVT in older adults

›Higher prevalence

›Age > 65 associated with over 5x increased SVT risk

›Comorbid structural heart disease more common

›Drug considerations in older adults

›Adenosine at standard dose but monitor for prolonged AV block

›Diltiazem and verapamil increased hypotension risk

›Beta-blockers increased bradycardia and hypotension risk

›Renal dosing adjustments for all renally cleared agents

›Polypharmacy interactions

›Digoxin and verapamil combination increases digoxin toxicity risk

›QT-prolonging drug interactions require review before antiarrhythmic selection

›Fall risk during SVT episodes

›Lightheadedness and presyncope heightened risk in older adults

›Urgent evaluation and close follow-up

›Ablation in older adults

›Ablation safe and effective in older adults

›Preferred over long-term antiarrhythmic drugs given toxicity profile

›Tachycardia-mediated cardiomyopathy

›Greater risk with chronically elevated heart rate

›EF may improve significantly after rhythm control

Pediatrics

›SVT in children

›Prevalence

›Most common tachyarrhythmia requiring treatment in pediatric patients

›AVRT more common than AVNRT in infants; AVNRT predominates in older children

›Presentation differences

›Neonates and infants may present with irritability, poor feeding, or heart failure

›Older children report palpitations similar to adults

›Vagal maneuvers in pediatrics

›Diver's reflex (ice to face) effective in infants

›Valsalva feasible in children able to cooperate

›Adenosine dosing in pediatrics

›Initial dose 0.1 mg/kg IV rapid push (maximum 6 mg)

›Second dose 0.2 mg/kg IV (maximum 12 mg) if no response

›Neonates may be more sensitive; lower initial dose 0.05 mg/kg

›Cardioversion in pediatrics

›0.5 to 1 J/kg synchronized; escalate to 2 J/kg if no conversion

›Sedation required for conscious pediatric patients

›WPW in children

›More common cause of SVT in pediatric age group

›High-risk accessory pathway evaluation with EP study

›Ablation recommended for symptomatic WPW in children

›Long-term management

›Spontaneous resolution of SVT common in neonates by 12 months

›Prophylaxis with propranolol or digoxin (infants without WPW) when recurrent

›Pediatric cardiology consultation for all new pediatric SVT

10Background/b70

Epidemiology

›Prevalence and incidence

›Prevalence approximately 2.29 per 1,000 persons in the United States

›Approximately 89,000 new cases per year in the US

›SVT subtype distribution

›AVNRT accounts for approximately 60% of PSVT

›AVRT accounts for approximately 30% of PSVT

›Focal atrial tachycardia accounts for approximately 10% of PSVT

›Demographic patterns

›Approximately 50% of patients are aged 45 to 64 years

›Female sex associated with 2x increased risk

›Age > 65 associated with over 5x increased risk

›Lone PSVT without cardiovascular disease

›Accounts for 39% of cases

›Younger mean age 37 years

›Higher mean rate 186 bpm

›Morbidity and mortality

›Generally a benign condition

›Significant symptom burden affecting quality of life

›Tachycardia-mediated cardiomyopathy in approximately 1% of untreated PSVT

›WPW prevalence in general population

›0.1 to 0.3% of general population

›Sudden cardiac death risk in high-risk accessory pathways

Pathophysiology

›Reentry mechanisms

›AVNRT mechanism

›Dual AV node physiology with fast and slow pathways

›Typical AVNRT: slow anterograde conduction, fast retrograde

›Atrial activation nearly simultaneous with ventricular activation

›P wave buried in or distorting end of QRS

›AVRT mechanism

›Reentrant circuit incorporating accessory pathway and AV node

›Orthodromic AVRT: anterograde through AV node, retrograde through accessory pathway

›Antidromic AVRT: anterograde through accessory pathway, retrograde through AV node

›Antidromic produces wide complex tachycardia

›Focal atrial tachycardia mechanism

›Abnormal automaticity or triggered activity from ectopic atrial focus

›P wave morphology reflects site of origin

›Less responsive to adenosine than reentrant SVT

›Triggers and electrophysiologic basis

›Premature atrial or ventricular beats initiate reentry circuit

›Critical conduction velocity differences between fast and slow pathways enable reentry

›Electrolyte disturbances increase susceptibility

›Hypokalemia and hypomagnesemia alter conduction velocity

›Sympathetic stimulation increases automaticity and conduction speed

›Caffeine, stress, stimulants increase catecholamine levels

Therapeutic Considerations

›Evidence base for adenosine

›Conversion rate approximately 90% for AVNRT and AVRT

›Superior to verapamil for speed of action

›Class I recommendation ACC/AHA/HRS 2015 guideline

›Diagnostic information from adenosine response guides further management

›Catheter ablation evidence

›Success rates exceed 95% for AVNRT and AVRT

›Class I recommendation for patients with recurrent symptomatic PSVT who prefer ablation

›Major complication rate less than 1% in experienced centers

›AV block risk with AVNRT ablation at fast pathway site

›RF or cryotherapy used depending on anatomy and institution

›Ablation preferred over lifelong antiarrhythmic therapy in most patients

›Cost-effective strategy for recurrent SVT

›Antiarrhythmic drug selection principles

›Avoid class Ic drugs (flecainide, propafenone) in structural heart disease

›CAST trial demonstrated increased mortality in post-MI patients

›Non-dihydropyridine CCBs and beta-blockers safest for long-term use in structurally normal heart

›ACC/AHA/HRS Class I recommendation for chronic prevention

›Sotalol and amiodarone reserved for refractory cases or structural heart disease

›QTc monitoring required for sotalol

›Amiodarone significant toxicity profile limits use for benign SVT

›Tachycardia-mediated cardiomyopathy

›Reversible cause of reduced EF

›EF normalizes in majority after arrhythmia control

›Diagnosis of exclusion after structural causes ruled out

›Expected improvement over weeks to months after rhythm control

11Patient Discharge Instructions/pdi38

copy discharge instructions

›What you were treated for

›Supraventricular tachycardia (SVT)

›A fast heart rhythm starting in the upper chambers of the heart

›Usually not dangerous but can cause significant symptoms

›What happened in the ED

›Your heart rhythm was treated

›With vagal maneuvers or medication to restore a normal rhythm

›Your heart returned to a normal rate

›Medications prescribed

›Take all prescribed medications exactly as directed

›Do not stop beta-blockers or calcium channel blockers abruptly

›Avoid caffeine, alcohol, and energy drinks

›These are common triggers for SVT recurrence

›Avoid recreational stimulants such as cocaine, amphetamines, or MDMA

›What to do if SVT returns before your follow-up

›Try the modified Valsalva maneuver

›Blow into a syringe or through closed lips for 15 seconds

›Then lie flat and raise legs above heart level for 15 seconds

›This may stop the episode

›If maneuver does not work, come to the ED

›Warning signs to return to the emergency room immediately

›Chest pain or pressure that does not stop

›Especially with new shortness of breath or sweating

›Fainting or loss of consciousness

›Syncope during SVT episode

›Heart racing that does not stop after vagal maneuvers

›Rate > 150 bpm or lasting more than 15 to 20 minutes

12References/r27

Guidelines and key sources

›Major society guidelines

›2015 ACC/AHA/HRS Guideline for the Management of Adult Patients with Supraventricular Tachycardia

›Published in Journal of the American College of Cardiology 2016

›Comprehensive algorithm-based management recommendations

›ACEP Clinical Policy for Tachyarrhythmias

›Adenosine and cardioversion Level A recommendations

›Key trials and studies

›REVERT trial (Appelboam et al., Lancet 2015)

›Modified Valsalva 43% conversion versus 17% standard Valsalva

›Established modified Valsalva as preferred vagal maneuver

›NODE-301 trial for etripamil

›64% conversion rate versus 31% placebo

›FDA-approved intranasal PSVT termination

›CAST trial (Cardiac Arrhythmia Suppression Trial)

›Class Ic antiarrhythmics increased mortality post-MI

›Basis for contraindication in structural heart disease

›Evidence sources for this document

›JAMA 2021 SVT review

›Prevalence 2.29 per 1,000 persons, 89,000 new US cases per year

›Symptom prevalence data: palpitations 86%, chest discomfort 47%, dyspnea 38%

›Journal of the American College of Cardiology SVT epidemiology data

›Sex and age risk factors

›WPW prevalence 0.1 to 0.3%

›Coding standards

›ICD-10 I47.1 supraventricular tachycardia

›ICD-10 I45.6 Wolff-Parkinson-White syndrome

›SNOMED CT paroxysmal supraventricular tachycardia disorder

Evidence & Review

Evidence & Review