Narrow Complex Tachycardia

Supraventricular Tachycardia
1. Rapid heart rhythms originating in the atrium or Atrioventricular Node
2. Transmit via the Bundle of His and result in rapid ventricular response

Sinus Tachycardia
Supraventricular Tachycardia
1. Atrioventricular Nodal Reentry (AVNRT)
  2. Signal down the slow AV nodal pathway and retrograde up the fast AV nodal pathway
  3. In 10% of cases, the signal reentry route is reversed
2. Atrioventricular Reciprocating Tachycardia (AVRT)
  2. Includes Wolff-Parkinson-White Syndrome (characterized by delta wave)
  3. Accessory pathway outside the AV Node
    1. Orthodromic (narrow complex): Signal down the AV Node and up the accessory path
    2. Antidromic (wide complex): Signal down the accessory path and up the AV Node
3. Atrial Tachycardia (AT)
  1. Abnormal focus of atrial automaticity (outside the SA Node)
  2. Unlike AVNRT and AVRT, no accessory pathway is involved
4. Junctional Ectopic Tachycardia
Other Atrial Tachycardias with rapid ventricular response
1. Atrial Fibrillation
2. Atrial Flutter

Sinus Tachycardia (regular)
Irregular Supraventricular Tachycardia (may also present as wide complex if aberrancy)
1. Atrial Fibrillation
Regular Supraventricular Tachycardia
1. Atrial Flutter
2. Atrioventricular Nodal Reentry (AVNRT): 60% of SVT cases (esp. women)
3. Atrioventricular Reciprocating Tachycardia (AVRT): 30% of SVT cases
4. Atrial Tachycardia (AT): 10% of SVT cases
5. Junctional Ectopic Tachycardia
6. Secondary causes (very high Heart Rates >220-240, refractory or recurrent tachydysrythmia)

Common
1. Orthodromic Atrioventricular Reciprocating Tachycardia (Orthodromic AVRT, or ORT)
  1. Most common in children (typical, narrow complex SVT)
2. Atrioventricular Nodal Reentry (AVNRT)
  1. Second most common SVT in children (but rare in young children)
Uncommon
1. Ectopic Atrial Tachycardia
  1. Similar to sinus rhythm except for altered P Wave appearance and more rapid rate
2. Atrial Flutter (uncommon in children outside the newborn period)
3. Atrial Fibrillation (very rare in children)
Congenital Heart Disease (CHD) history
1. CHD predisposes patients to scarring with risk of reentrant pathways
2. Intra-atrial reentrant Tachycardia (IART)
  1. Appears similar to Atrial Flutter
  2. Typically treated with rate control on Diltiazem (if over age 2-5 years), followed by cardioversion

Timing
1. Rapid onset and resolution
  1. Supraventricular Tachycardia
2. Slow onset and resolution
  1. Sinus Tachycardia
Precipitating factors
1. Caffeine or stimulants, stress (see triggers above)
  1. Supraventricular Tachycardia or Sinus Tachycardia
2. Cardiovascular disease or onset with activity
  1. Ventricular Tachycardia

Thyromegaly (Hyperthyroidism, Thyroiditis)
Cardiovascular
1. Tachycardia (regular or irregular rhythm)
2. Cardiac Murmur (valvular heart disease)
3. Friction Rub (Pericarditis)
4. Third Heart Sound (CHF)

Precautions
1. Paroxysmal Supraventricular Tachycardia does not require routine labs in many cases (esp. known prior history of PSVT)
2. Patients who are asymptomatic after PSVT resolves, and without underlying other risks need not undergo laboratory testing
Initial tests to consider
1. Thyroid Stimulating Hormone (TSH)
2. Basic metabolic panel
3. Complete Blood Count
4. Chest XRay
Additional tests to consider (in adults)
1. Ambulatory EKG Monitoring (e.g. Zio Monitor, Holter Monitor or Event Monitor)
Additional tests to consider for concerns of underlying Cardiomyopathy
1. Brain Natriuretic Peptide (ntBNP)
2. Echocardiogram

Background
1. No lab testing is indicated in routine PSVT that resolves without symptoms
2. Repeat EKG and reevaluate patient history and exam 15 minutes after return to sinus rhythm
  1. Asymptomatic patients with normal ekg and exam after return to sinus rhythm need no further testing
  2. Consider lab testing driven by specific positive symptoms, signs or risk factors after return to sinus rhythm
Serum Troponin Is NOT typically indicated in Supraventricular Tachycardia (SVT)
1. SVT is rarely due to acute occlusive Myocardial Infarction
2. ST Depression is commonly seen as a stress response to Tachycardia, but is not indicative of a coronary event
3. Serum Troponin Is often elevated in SVT (esp. if prolonged) but is not associated with 90 day adverse outcomes
Despite low efficacy and resulting Cascades of Care, Troponin Is obtained in 80% of ED SVT evaluations (abnormal in 30% of cases)
1. Gabrielli (2022) Cardiol Rev +PMID: 35148534 [PubMed]
Troponin Indications
1. Persistent concerning EKG changes after conversion to sinus rhythm
2. Symptoms and signs specifically suggestive of underlying Acute Coronary Syndrome (not attributable to SVT alone)
References
1. Mattu and Swaminathan (2022) EM:Rap 22(12): 7-8

Uncertain diagnosis or management
Recurrent Supraventricular Tachycardia refractory to medications
High risk profession or activity (e.g. truck driver, airline pilot, rock climbing, Scuba Diving)
Ablation considered over medication (patient preference)
Wolff-Parkinson-White Syndrome (characterized by delta wave) or other preexcitation
Structural heart disease (e.g. Hypertrophic Cardiomyopathy)
Syncope associated with Supraventricular Tachycardia
Wide complex QRS on EKG

Claudius, Behar and Bar Cohen in Herbert (2014) EM:Rap 14(5):1-2
Hebbar (2002) Am Fam Physician 65(12):2479-86 [PubMed]
Helton (2015) Am Fam Physician 92(9): 793-800 [PubMed]
Nasir (2023) Am Fam Physician 107(6): 631-41 [PubMed]
Cardiopulmonary Resuscitation Guidelines

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