In PALS (Pediatric Advanced Life Support), sinus tachycardia is identified by a heart rate usually below 220 beats per minute in infants and below 180 beats per minute in children. These thresholds, established by the American Heart Association and reaffirmed in the 2025 tachyarrhythmia algorithm, are the key numbers used to distinguish sinus tachycardia from more dangerous rhythms like supraventricular tachycardia (SVT).
Heart Rate Thresholds by Age
The two numbers to remember are straightforward:
- Infants (under 1 year): usually less than 220 bpm
- Children (1 year and older): usually less than 180 bpm
These are upper boundaries, not exact cutoffs. A heart rate just below 220 in an infant doesn’t automatically confirm sinus tachycardia, and a rate just above it doesn’t automatically confirm SVT. Context matters. But these thresholds give you a strong starting point for deciding which rhythm you’re likely dealing with.
To put those numbers in perspective, normal pediatric heart rates vary widely by age. A healthy awake newborn can have a heart rate anywhere from 85 to 205 bpm. Infants aged 3 months to 2 years typically run between 100 and 190 bpm while awake. Children aged 2 to 10 normally range from 60 to 140 bpm, and kids over 10 fall between 60 and 100 bpm. Sinus tachycardia means the rate is elevated beyond what’s expected for the child’s age, but it’s being driven by the body’s normal pacemaker responding to some physiological demand.
ECG Features That Confirm Sinus Tachycardia
Heart rate alone isn’t enough to make the call. The PALS tachycardia algorithm identifies sinus tachycardia using three features together:
- P waves present with normal shape: Each heartbeat is preceded by a visible P wave that looks like a typical sinus P wave. This confirms the rhythm is originating from the heart’s normal pacemaker.
- Variable R-R interval: The spacing between beats changes slightly, especially with breathing or activity. This beat-to-beat variability is a hallmark of a normal sinus rhythm that’s simply running fast.
- Heart rate within the expected range: Below 220 for infants, below 180 for children.
When all three features are present, the rhythm is probable sinus tachycardia. The word “probable” is intentional in the algorithm. There can be overlap between sinus tachycardia and SVT, particularly when rates fall in a gray zone, so clinical judgment still plays a role.
How Sinus Tachycardia Differs From SVT
The distinction between sinus tachycardia and SVT is one of the most important decisions in the PALS tachycardia algorithm because the treatments are completely different. SVT in infants commonly produces rates of 250 to 300 bpm, well above the 220 threshold. In SVT, P waves are either absent or appear after the QRS complex rather than before it. The R-R interval is fixed, meaning the spacing between beats is perfectly regular with no variation.
Sinus tachycardia, by contrast, has a gradual onset and a rate that fluctuates with the child’s condition. If you give a febrile child fluids and bring the fever down, the heart rate drifts lower. SVT snaps on and off abruptly, often flipping from a normal rate to 250+ in an instant. That clinical behavior, combined with the ECG findings, helps distinguish the two even when the rate falls in an ambiguous range.
Common Causes in Children
Sinus tachycardia is never the primary problem. It’s the heart’s normal response to something else going on. The PALS approach is to identify and treat the underlying cause rather than treat the fast heart rate itself. The most common triggers include fever, dehydration, pain, infection, anxiety, exercise, and certain medications.
This is a critical distinction. You would not give adenosine or attempt cardioversion for sinus tachycardia. Those interventions are reserved for SVT and other pathological tachyarrhythmias. For sinus tachycardia, the algorithm directs you to “search for and treat cause.” A child who is tachycardic from dehydration needs fluids. A child who is tachycardic from pain needs analgesia. Once the underlying trigger resolves, the heart rate comes down on its own.
Putting It Together in the Algorithm
When you encounter a pediatric patient with tachycardia and a pulse, the PALS algorithm asks you to evaluate the QRS width first (narrow vs. wide complex), then assess for the features described above. If the QRS is narrow, you look at P-wave morphology, R-R variability, and heart rate to decide between sinus tachycardia and SVT. If you identify probable sinus tachycardia, you move straight to investigating the cause rather than pursuing rhythm-specific interventions.
The key takeaway for exam and clinical purposes: sinus tachycardia in PALS means a rate under 220 in infants, under 180 in children, with visible normal P waves and beat-to-beat variability. Those three criteria together point you toward treating the patient’s underlying condition, not the rhythm.