What is the most common cause of neonatal bradycardia (heart rate less than 100 beats/min)?

What is the most common cause of neonatal bradycardia (heart rate less than 100 beats/min)?

• A. Congenital heart disease
• B. Maternal drug intoxication (narcotics, alcohol, magnesium, barbiturates, digitoxin)
• C. Fever
• D. Hypoxemia

Answer: (D)

Neonatal bradycardia most often reflects inadequate oxygen delivery to tissues. When a newborn becomes hypoxic, the heart rate tends to fall as a reflex from increased vagal tone and impaired pacemaker activity. Because hypoxemia directly depresses cardiac conduction and function, it is the most common and urgent cause of a heart rate under 100 beats per minute in the neonate. While congenital heart disease, maternal drug effects, or other factors can influence heart rate, they are less commonly the primary trigger for bradycardia. Fever, in contrast, typically causes tachycardia, not bradycardia. The key takeaway is that improving oxygenation and ventilation to reverse hypoxemia is the priority when a neonate presents with bradycardia.

Neonatal bradycardia most often reflects inadequate oxygen delivery to tissues. When a newborn becomes hypoxic, the heart rate tends to fall as a reflex from increased vagal tone and impaired pacemaker activity. Because hypoxemia directly depresses cardiac conduction and function, it is the most common and urgent cause of a heart rate under 100 beats per minute in the neonate.

While congenital heart disease, maternal drug effects, or other factors can influence heart rate, they are less commonly the primary trigger for bradycardia. Fever, in contrast, typically causes tachycardia, not bradycardia. The key takeaway is that improving oxygenation and ventilation to reverse hypoxemia is the priority when a neonate presents with bradycardia.