How is bradycardia (slow heart rate) managed in patients with anorexia?

Management of Bradycardia in Anorexia Nervosa

Carefully controlled refeeding is the primary treatment for bradycardia in anorexia nervosa patients, as it effectively reverses the cardiac manifestations including sinus bradycardia. 1

Pathophysiology and Clinical Significance

Bradycardia in anorexia nervosa is extremely common, occurring in up to 95% of patients 2. This bradycardia results from:

• Increased parasympathetic (vagal) tone
• Cardiac muscle atrophy due to prolonged starvation
• Metabolic adaptations to conserve energy
• Possible hypothyroidism (often functional/reversible)

Heart rates can be profoundly low, with studies showing rates as low as 26 beats per minute 2. Despite these alarming rates, most cases are physiologic adaptations rather than primary cardiac pathology.

Assessment Algorithm

1. Evaluate severity and symptoms:

   • Document heart rate (often <50 bpm, sometimes <30 bpm)
   • Check for hypotension (common)
   • Assess for symptoms: syncope, pre-syncope, chest pain, dyspnea
   • Evaluate QTc interval (prolongation indicates higher risk)

2. Risk stratification:

   • High risk: HR <40 bpm, QTc prolongation, syncope, electrolyte abnormalities
   • Moderate risk: HR 40-50 bpm, asymptomatic
   • Low risk: HR >50 bpm, asymptomatic, no electrolyte abnormalities

Management Approach

Asymptomatic Bradycardia

• No specific cardiac intervention is needed for asymptomatic bradycardia in anorexia nervosa 3
• Nutritional rehabilitation is the definitive treatment
• Monitor cardiac parameters during refeeding
• Avoid unnecessary pacemaker implantation in otherwise healthy young patients

Symptomatic Bradycardia

1. Acute management of severe symptomatic bradycardia:

   • IV atropine (0.5-1 mg) may be used for temporary management of severe symptomatic bradycardia 4
   • Monitor for response and repeat if necessary (maximum 3 mg total)

2. Definitive management:

   • Carefully controlled refeeding program is the primary treatment 1
   • Avoid rapid refeeding which can cause "refeeding syndrome" with dangerous electrolyte shifts
   • Monitor electrolytes (especially phosphate, potassium, magnesium) during refeeding
   • Correct electrolyte abnormalities that may worsen arrhythmias

Important Considerations

• Pacemaker implantation is rarely indicated and should be avoided in most cases 3
• Long-term follow-up studies show that bradycardia can persist for years without complications in weight-stable anorexia patients 3
• Cardiac dimensions and function typically normalize with weight restoration 5
• Monitor for QT prolongation which increases risk of ventricular arrhythmias

Refeeding Protocol

1. Start with modest caloric increases (typically 30-40 kcal/kg/day initially)
2. Increase calories gradually by 100-200 kcal every 2-3 days
3. Monitor vital signs, electrolytes, and cardiac parameters during refeeding
4. Supplement phosphate, thiamine, and other micronutrients as needed
5. Target weight gain of 0.5-1 kg per week for inpatients

Pitfalls to Avoid

1. Overly aggressive refeeding can cause dangerous fluid shifts and electrolyte abnormalities 1
2. Unnecessary cardiac interventions for asymptomatic bradycardia
3. Failure to recognize bradycardia as a potential sign of anorexia nervosa 2
4. Treating bradycardia in isolation without addressing the underlying eating disorder
5. Ignoring other cardiac complications such as QT prolongation, hypotension, and reduced cardiac mass

Bradycardia in anorexia typically resolves with weight restoration, with studies showing increases in heart rate, blood pressure, and cardiac dimensions following successful nutritional rehabilitation 5.