Sinus tachycardia (ST) is the basic rhythm that can be classified as tachycardia and is not associated with an arrhythmia.
Sinus tachycardia (ST) is typically a normal response to fever and other forms of stress that increase the metabolic demands of the infant or child. ST will not display a fixed rate but will rise and fall as the demands of the body change. ST in infants and children is common and results from exercise, illness, metabolic stress, etc.
When ST is present, identification of the cause is of primary importance. Other common causes for ST are anemia, anxiety, fever, injury, hypoxia, hypovolemia, and toxins/drugs. Once the cause is identified, it should be treated appropriately.
Remember that ST is a rapid heart rate compared with the normal heart rate that should be present. The “normal” rate is determined by the child’s/infant’s age. “Normal” for the may also vary depending on the child’s baseline, health status, and any underlying disease processes.
Sinus Tachycardia ECG Characteristics
The ECG produced by ST has specific characteristics that when recognized will help you make the determination that a rhythm truly is ST. These characteristics are listed below.
- Heart Rate: Rate variability depending on activity and stress level
- P-waves: P-waves should be present and normal
- PR interval: Constant and normal duration
- R-R interval: Variable
- QRS complex: Narrow (≤0.09 sec.)