9.2 Sinus Tachycardia vs SVT

AHA PALS Provider Pediatric Advanced Life Support

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1 Chapter 1: Course Overview & Exam Logistics

1.1 Current Exam Facts 1.2 Audience, Prerequisites & Study Plan

2 Chapter 2: Systematic Pediatric Assessment

2.1 Pediatric Assessment Triangle (PAT) 2.2 Evaluate–Identify–Intervene Sequence 2.3 Primary Assessment: ABCDE 2.4 Secondary Assessment, SAMPLE & Vitals by Age

3 Chapter 3: Respiratory Distress & Failure

3.1 Respiratory Distress vs Failure 3.2 Recognition & Immediate Intervention Priorities 3.3 Oxygen Delivery & Basic Airway Support

4 Chapter 4: Airway Problems & Ventilation Strategies

4.1 Upper Airway Obstruction 4.2 Lower Airway, Lung Tissue Disease & Disordered Control 4.3 Bag-Mask Ventilation & Advanced Airways During CPR

5 Chapter 5: Shock Fundamentals & Hypovolemia

5.1 Compensated vs Hypotensive (Decompensated) Shock 5.2 Hypovolemic Shock 5.3 Isotonic Fluid Bolus 10–20 mL/kg & Reassessment

6 Chapter 6: Distributive, Cardiogenic & Obstructive Shock

6.1 Distributive & Septic Shock Pathway 6.2 Cardiogenic Shock 6.3 Obstructive Shock

7 Chapter 7: Pediatric BLS & High-Quality CPR

7.1 High-Quality CPR Metrics 7.2 Compression-Ventilation Ratios 7.3 CPR Quality Monitoring: ETCO2 & Diastolic BP

8 Chapter 8: Pediatric Cardiac Arrest Algorithm

8.1 Arrest Recognition & Systematic Approach 8.2 VF/pVT & Defibrillation Energy 8.3 Asystole & PEA 8.4 Epinephrine in Arrest: Dose & Timing

9 Chapter 9: Bradycardia & Narrow-Complex Tachycardia

9.1 Bradycardia with Poor Perfusion 9.2 Sinus Tachycardia vs SVT 9.3 Stable SVT: Vagal Maneuvers & Adenosine

10 Chapter 10: Unstable Tachycardia & Wide-Complex Rhythms

10.1 Unstable Tachycardia & Synchronized Cardioversion 10.2 Wide-Complex Tachycardia & VT with Pulse 10.3 Antiarrhythmics for Tachycardia with Pulse

11 Chapter 11: Reversible Causes & Special Circumstances

11.1 Reversible Causes: The H's and T's 11.2 Special Circumstances at Exam Level 11.3 Extracorporeal CPR (ECPR) Overview

12 Chapter 12: Post–Cardiac Arrest Care

12.1 Post-ROSC Oxygenation & Ventilation 12.2 Post-Arrest Hemodynamic Support 12.3 Temperature Control & Glucose 12.4 Neuroprognostication & Transport

13 Chapter 13: Vascular Access & Core Pharmacology

13.1 IV and Intraosseous Access 13.2 Epinephrine Dosing in Depth 13.3 Amiodarone, Lidocaine & Adenosine 13.4 Weight-Based Dosing Aids & Drugs to Avoid Routinely

14 Chapter 14: Team Dynamics & Megacode Readiness

14.1 High-Performance Team Roles 14.2 Closed-Loop Communication 14.3 Constructive Intervention, Debriefing & Exam Integration

9.2 Sinus Tachycardia vs SVT

Key Takeaways Explain This Topic AI

Sinus tachycardia is a physiologic response to fever, hypovolemia, pain, anxiety, or shock—treat the cause, not the rate with cardioversion or adenosine.

SVT is usually an abrupt reentrant rhythm; history often describes sudden onset (and sometimes sudden termination).

Teaching rate thresholds that favor SVT: infants often ≥220/min; children often ≥180/min—use with clinical context, not as the only clue.

ECG clues: sinus tach has normal P waves and variable R-R; SVT often has absent/abnormal P waves and a usually fixed (monomorphic) R-R.

Do not synchronized-cardiovert or "adenosine-treat" pure sinus tachycardia—fix fever, volume loss, hypoxia, and other drivers.

Last updated: August 2026

Why This Discrimination Dominates PALS Scenarios

Few rhythm decisions generate more exam and megacode errors than confusing sinus tachycardia with supraventricular tachycardia (SVT) . Both can produce very fast rates in infants and children. Only one is a primary electrical reentry problem that may need vagal maneuvers, adenosine, or cardioversion. The other is the heart’s appropriate response to an increased metabolic or circulatory demand. Cardioverting a febrile, dehydrated toddler in sinus tachycardia is the wrong therapy and can harm the child; delaying treatment of true SVT with poor perfusion is equally dangerous.

PALS expects you to use a bundle of clues —history, rate ranges, P waves, R-R pattern, and clinical context—not a single number in isolation.

Definitions (exam-level)

Sinus tachycardia: Each QRS is preceded by a normal sinus P wave; the rate is fast for age because the sinus node is accelerating under physiologic stress (fever, hypovolemia, hypoxia, pain, anxiety, anemia, shock, medications such as bronchodilators).

SVT (narrow-complex, most pediatric teaching cases): A reentrant supraventricular rhythm (commonly AV nodal reentrant tachycardia or AV reentrant tachycardia using an accessory pathway) that produces a usually regular, narrow QRS tachycardia, often without clearly visible normal sinus P waves. Onset is typically abrupt .

Wide-complex tachycardia and unstable management are covered in Chapter 10; this section focuses on narrow-complex discrimination and the "do not cardiovert sinus tach" rule.

Discrimination Table: History, Rate, ECG, Response

Feature Sinus tachycardia SVT (typical pediatric teaching)

History / onset Gradual; fits fever, volume loss, pain, respiratory distress, shock Often abrupt onset (± abrupt termination); may have prior SVT history

Clinical context Dehydration, sepsis, asthma, trauma, anxiety, anemia May look "too well" or "too fast for the story," or present with irritability/poor feeding in infants

Heart-rate ranges (teaching thresholds) Usually below SVT cutoffs for age, though high fever/shock can push rates up Infants often ≥220/min ; children often ≥180/min favors SVT

P waves Present, normal morphology, consistent PR relationship Absent, buried, or abnormal retrograde P waves; not normal sinus P before every QRS

R-R interval Variable —rate rises and falls with activity, fever curve, fluid status Usually fixed/regular (monomorphic clock-like regularity)

Response to treating cause Rate falls as fever/volume/pain/hypoxia correct Rate persists until reentry is interrupted (vagal, adenosine, cardioversion)

Response to adenosine Transient slowing may reveal sinus P waves; does not "cure" the need for cause treatment May terminate reentry and restore sinus rhythm

• Cardioversion? No — not indicated for sinus tachycardia Yes when unstable (Chapter 10); stable pathway in 9.3
• Heart-rate teaching thresholds — use carefully

PALS teaching commonly highlights:

• Infant SVT often ≥220/min
• Child SVT often ≥180/min

These are supportive thresholds , not absolute laws of nature. A severely shocked infant can approach very high sinus rates, and SVT can occasionally present at rates below the classic cutoff. Always integrate history + ECG morphology + variability . On exam items, when the vignette gives abrupt onset , rate ≥220 (infant) or ≥180 (child) , no visible P waves , and rock-regular R-R , the answer is SVT. When the vignette gives fever and diarrhea , rate 170 in a toddler , visible sinus P waves , and a rate that varies , the answer is sinus tachycardia—treat volume and fever.

P waves and R-R variability in practice

Obtain a monitor strip and, when the child is stable enough, a 12-lead ECG . Look in multiple leads for P waves. In sinus tachycardia you should find upright P waves in the inferior leads (in normal situs) with a stable PR relationship. In SVT, P waves may be invisible in the T wave, inverted, or dissociated from a normal sinus pattern.

R-R variability is a high-yield bedside clue: print a long strip. Sinus tachycardia "breathes" and drifts. Classic reentrant SVT often looks metronomic.

Loading diagram... Sinus Tachycardia vs SVT Decision Aids

• Management Implications: Treat the Right Problem
• Sinus tachycardia — treat the cause

Once you identify sinus tachycardia:

Do not perform synchronized cardioversion for rate control of sinus tachycardia.

Do not treat it as a primary arrhythmia with SVT drugs as the "cure."

Do search for and reverse the driver using the evaluate–identify–intervene loop:

• Fever → antipyretic care and infection workup as indicated
• Hypovolemia → isotonic fluid boluses with reassessment (Chapter 5)
• Hypoxia / respiratory failure → oxygen and ventilation (Chapters 3–4)
• Pain / anxiety → appropriate analgesia and calming measures
• Shock / anemia / toxins → cause-specific therapy

As the cause improves, the sinus rate falls. That response is both therapy and confirmation of your diagnosis.

SVT — rhythm-directed therapy (preview)

If the rhythm is SVT:

No cardiopulmonary compromise (stable enough): vagal maneuvers → adenosine pathway (Section 9.3).

Cardiopulmonary compromise (unstable): synchronized cardioversion per PALS energies (Chapter 10), with sedation if the patient is conscious enough and it will not delay shock delivery excessively.

While you discriminate, still support ABCs: oxygen as needed, monitors, IV/IO access, and continuous reassessment. A child can transition from "stable SVT" to shock quickly, especially infants who present with heart-failure signs after hours of unrecognized SVT (poor feeding, irritability, hepatomegaly, rales).

Common exam traps

• Trap Why it is wrong
• Cardioverting fever + dehydration tachycardia with visible P waves That is sinus tach—treat cause
• Calling every rate >160 "SVT" without ECG/history Misses sinus tach and overtreats
• Ignoring infant rates ≥220 with no P waves as "just sinus" Misses SVT
• Giving adenosine slowly "to be gentle" Wrong administration even when SVT is correct (see 9.3)
• Assuming SVT cannot cause cardiogenic shock features Prolonged SVT can produce pump failure signs
• Clinical scenarios

Scenario A — Sinus tachycardia: A 2-year-old with 48 hours of vomiting and diarrhea has heart rate 172/min, dry mucous membranes, capillary refill 3 seconds, temperature 38.9°C. Monitor shows P waves before each QRS and mild R-R variability. Diagnosis: sinus tachycardia from hypovolemia/fever. Therapy: oxygen if needed, isotonic fluid boluses with reassessment, antipyretic care—not cardioversion.

Scenario B — SVT: A 3-week-old suddenly becomes pale and irritable. Heart rate is 280/min, R-R is fixed, no clear P waves. The infant has been feeding poorly for hours and now has delayed refill. Diagnosis: SVT (infant rate far above 220 teaching threshold). Therapy: support ABCs; if signs of poor perfusion/cardiopulmonary compromise, move toward urgent synchronized cardioversion; if relatively stable, ice-to-face vagal maneuver and prepare adenosine (9.3).

Master the discrimination table and you avoid the two lethal errors of this chapter: shocking sinus tach, and missing SVT.