Heart rate variability (HRV) refers to changes in the time between each. In general, variability is considered healthy and even positive as it enables people to adapt to the needs of their current setting, but can sometimes indicate other issues especially if the variations are more severe (>120ms) and are occurring without cause. HRV tends to decrease with age as older individuals bodies' tend to be less adaptive. Low HRV is associated with several negative physical and mental health outcomes.

Heart Rate Variability (HRV)

Increased QT dispersion and variability, along with decreased heart rate variability and an impaired exercise response with a decreased cardiac output are all proposed to have the potential to lead to sudden cardiac death in severe anorexia nervosa patients. 

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In some cases of anorexia nervosa, sudden cardiac death may result, in which there is no atherosclerotic heart disease to explain it. Certain factors may predispose patients to this fatal outcomes:

- Hypokalemia
- Hypoglycemia
- Bradycardia
- Cardiac autonomic dysfunction
- Cardiac structural changes

Anorexia Nervosa Predictive Factors of Sudden Cardiac Death

Mehler, P. S., Watters, A., Joiner, T., & Krantz, M. J. (2022). What accounts for the high mortality of anorexia nervosa? International Journal of Eating Disorders, 55(5), 633-636. https://doi.org/10.1002/eat.23664

What Accounts for the High Mortality of Anorexia Nervosa?

Hypokalemia, or low serum potassium, from malnutrition or purging may predispose anorexia nervosa patients to sudden cardiac death. Low potassium has the potential to contribute to QTc prolongation, which may trigger TdP.  Especially in conjunction with elevated serum aldosterone levels which further exacerbate it, hypokalemia has the potential to lead to deadly outcomes. Furthermore, low potassium may also indicate refeeding syndrome, which can lead to death by acute heart failure.

Hypokalemia and Sudden Cardiac Death in Anorexia Nervosa Patients

Hypoglycemia, or low blood glucose, may contribute to sudden cardiac death in anorexia nervosa patients. Serum glucose levels of 35mg/dl or below, and hemoglobin A1c levels of 5.0% or below are cause for concern. Anorexia nervosa patients are particularly susceptible to hypoglycemia as the disorder impairs gluconeogenesis, and refeeding in treatment may lead to paradoxical excessive insulin secretion. Furthermore, due to chronic malnutrition and hypoglycemia, anorexia nervosa patients may not notice symptoms indicating acute hypoglycemia and may not seek treatment or help in time. 

Hypoglycemia and Sudden Cardiac Death in Anorexia Nervosa Patients

Bradycardia, or an abnormally slow heart rate, can increase the risk of sudden cardiac death in anorexia nervosa patients. Bradyarrhythmias like sinus arrest, asystole, and junctional rhythm may lead to pulseless electrical activity (PEA) which can cause sudden cardiac death, especially when in conjunction with hypoglycemia.

Bradycardia and Sudden Cardiac Death in Anorexia Nervosa Patients

Cardiac structural changes and subclinical left ventricular heart failure may arise due to severe malnutrition, and can contribute to global longitudinal systolic (GLS) strain. Pericardial effusion and mitral valve prolapse may lead to sudden death via cardiac tamponade. Cardiac fibrosis, ipecac cardiomyopathy, and stress cardiomyopathy may similarly lead to sudden death by acute heart failure.

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