Bradycardia: How Severe is Too Severe? Understanding Bradycardia in Eating Disorders

By Philip S. Mehler, MD, FACP, FAED, CEDS

Eating disorders are mental health disorders characterized by self-starvation, excessive exercising, bingeing, purging and malnutrition. While most mental health disorders tend to leave one’s physical health normal and intact, eating disorders can severely compromise an individual’s physical well-being.

When it comes to the eating disorder anorexia nervosa, medical complications (including cardiac issues) are common and account for more than half of all patient deaths (Löwe et al, 2001; Herzog et al, 1997). Over time, the medical complications associated with anorexia nervosa become more pronounced, leaving anorexia nervosa with the highest mortality of any psychiatric disorder (aside from opioid use disorder). One serious complication that commonly occurs alongside severe anorexia nervosa is a cardiac issue called bradycardia.


What is Bradycardia?

Bradycardia is an abnormally low heart rate — under 60 beats per minute (bpm). A normal heart rate, on the other hand, ranges from 60 to 100 beats per minute. Bradycardia can occur in individuals with eating disorders following substantial weight loss. As one’s weight drops, their muscles, including the heart muscle, start to lose muscle mass. As a result, the heart becomes smaller and less efficient. This causes a slowdown of the heart muscle as the parasympathetic nervous system must conserve energy to keep the rest of the body functioning normally. As the heart rate slows down, the heart is unable to pump oxygen-rich blood back to the body, and medical problems ensue.

Bradycardia is observed in up to 95 percent of patients with anorexia nervosa (Mehler & Brown, 2015) as nearly all the body’s vital organs and systems are adversely affected by continued starvation, purging and overexercising.

Symptoms of bradycardia that may show up in cases of severe anorexia nervosa include:

  • Fatigue
  • Dizziness or lightheadedness
  • Shortness of breath
  • Chest pains
  • Near-fainting or fainting
  • Mental fatigue (brain fog)

However, many patients will not feel any symptoms from their bradycardia, highlighting the need for healthcare professionals to evaluate patients at risk for this serious complication.


How is Bradycardia Linked to Eating Disorders?

Individuals with severe anorexia nervosa may be aware of their low heart rate and will often attribute bradycardia to having an “athletic heart.” They claim that exercising has made them a truly conditioned athlete with a low resting heart rate. While many of these patients may be exercising frequently, their starved, malnourished heart is actually not a result of their “athletic condition.” Should you ask these patients to mildly exert themselves, they will show an abnormally rapid heart rate (tachycardia, 100-150 bpm) just from walking across the room or standing up from a lying position; this does not occur in an athlete. Moreover, ultrasound of the heart in these patients reveals small, thin heart chambers versus a normal chamber size seen in athletes. Unfortunately, few medical providers are well-trained in understanding this issue. The idea of the “athletic heart” is often accepted by healthcare professionals, whereas a trained eating disorder expert would recheck the pulse following minor exertion and recognize that bradycardia — appearing alongside a very low body weight — is a likely indication of anorexia nervosa.


What Causes Bradycardia?

Bradycardia is more commonly observed in individuals with anorexia nervosa who are severely underweight. However, bradycardia is also found in individuals who have recently lost a significant amount of weight, even if they are not currently underweight. This may be part of atypical anorexia nervosa. Losing a large amount of weight very rapidly, surprisingly may place a great deal of stress on the heart. If left untreated, or treated at an insufficient level, cardiac issues like bradycardia can be life-threatening for individuals with eating disorders, if no continuous cardiac monitoring is available.


How Low is Too Low?

How do you know if a patient’s low heart rate is something to simply monitor or something that requires immediate attention? One number to watch for is a resting heart rate of less than 40 bpm. In this situation, patients may need to be admitted to a hospital immediately for monitoring and stabilization. In adolescents this number is closer to 45.

  • Under 60 bpm – A heart rate of under 60 bpm is considered slower than normal for most adults, although athletic adults and young adults may experience a resting heartbeat of under 60 bpm that drops even lower during sleep. If an individual with an eating disorder has a heart rate under 60 bpm, an evaluation may be warranted, even without obvious cardiac symptoms.
  • Under 50 bpm – A heart rate below 50 bpm is more likely to grab a physician’s attention as a cause for concern. However, some healthy, active adults have heart rates under 50 bpm, particularly endurance athletes. When an individual of low body weight or with a documented eating disorder has a heart rate lower than 50 bpm, further testing is needed.
  • Under 40 bpm – A heart rate under 40 bpm is not common, even among trained athletes, and is most likely a cause for concern. The American Psychiatric Association recommends that individuals with eating disorders, who have a heart rate lower than 40 bpm, be admitted to hospital for assessment and treatment.

Once a patient with severe anorexia nervosa and bradycardia arrives to the hospital, a refeeding protocol may be initiated to begin nutritional rehabilitation and weight restoration. In the hospital, the medical team will also work to:

  • Improve and normalize the patient’s vital signs, cardiovascular system and bowel function; heart rates normalize with refeeding as their weight moves near 85% ideal body weight  (IBW)
  • Resolve serum electrolyte and chemistry abnormalities;
  • Restore levels of key electrolytes including phosphorus, potassium, magnesium and calcium.

Once the patient has achieved medical stability, he or she can transition to a 24-hour care facility where they can continue to work on recovery from their eating disorder through intensive psychotherapy, ongoing weight restoration and other evidence-based interventions. It is worth noting that although severe bradycardia often results in the placement of cardiac pacemaker in non-eating disordered patients, this is rarely needed in this population.


Get Help for Bradycardia

While proper medical treatment can reverse cardiovascular complications associated with eating disorders, when left untreated, bradycardia can lead to sudden cardiac arrest or sudden death. If you or someone you care about is experiencing cardiac complications like bradycardia due to an eating disorder, we can help. Reach out to us today to learn more about medical intervention for severe and extreme eating disorders with our experienced experts at ACUTE. With proper care provided by experienced experts, we can help you restore your weight and regain your health once again.




Written by

Philip S. Mehler, MD, FACP, FAED, CEDS

Dr. Philip Mehler, MD, FACP, FED, CEDS founded ACUTE at Denver Health, the country’s only designated Center of Excellence for those with the most extreme forms of eating disorders and…

ACUTE Earns Prestigious Center of Excellence Designation from Anthem
In 2018, the ACUTE Center for Eating Disorders & Severe Malnutrition at Denver Health was honored by Anthem Health as a Center of Excellence for Medical Treatment of Severe and Extreme Eating Disorders. ACUTE is the first medical unit ever to achieve this designation in the field of eating disorders. It comes after a rigorous review process.

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