Hi there,
Thanks for writing in.
I am a medical specialist with an additional degree in cardiology.
I read your mail with diligence.
Some researchers believe that electrolyte imbalance in this condition leads to low heart rate.
Electrolyte Imbalances - electrolytes are essential to the production of the body's "natural electricity" that ensures healthy teeth, joints and bones, nerve and muscle impulses, kidneys and heart, blood sugar levels and the delivery of oxygen to the cells. Bad Circulation, Slowed or Irregular Heartbeat, Arrhythmias, Angina, Heart Attack - There are many factors associated with having an Eating Disorder that can lead to heart problems or a heart attack. Sudden cardiac arrest can cause permanent damage to the heart, or instant death. Electrolyte imbalances (especially potassium deficiency), dehydration, malnutrition, low blood pressure, extreme orthostatic hypotension, abnormally slow heart rate, electrolyte imbalances, and hormonal imbalances call all cause serious problems with the heart.
Whereas a more scientific data from National Institute of Health, Journal of Endocrinology concludes that while there may be decrease in heart rate there is no change in heart rate variability (HRV).:

Changes in body composition, hormone secretions, and heart function with increased risk of sudden death occur in eating disorders. In this observational clinical study, we evaluated sympathovagal modulation of heart rate variability (HRV) and cardiovascular changes in response to lying-to-standing in patients with anorexia (AN) or bulimia nervosa (BN) to analyze: a) differences in autonomic activity between AN, BN, and healthy subjects; b) relationships between autonomic and cardiovascular parameters, clinical data and leptin levels in patients with eating disorders. HRV, assessed by power spectral analysis of heart rate variability beat to beat, blood pressure (BP) and heart rate (HR) were studied by tilt-table test in 34 patients with AN, 16 with BN and 30 healthy controls. Autonomic and cardiovascular findings were correlated with clinical data, and serum leptin levels. Leptin levels were lowered in AN vs BN and healthy subjects.

But both AN and BN patients showed unbalanced sympathovagal control of heart rate variability (HRV) due to relative sympathetic failure, prevalent vagal activity, impaired sympathetic activation after tilting, independently from their actual body weight and leptin levels. No significant correlations were obtained between HRV data vs clinical data, BP and HR findings, and leptin levels in eating disorders. Body mass indices (BMI) (p<0.02), and leptin levels (p<0.04) correlated directly with BP values. Our data showed alterations of sympathovagal control of HRV in eating disorders. These changes were unrelated to body weight and BMI, diagnosis of AN or BN, and leptin levels despite the reported effects of leptin on the sympathetic activity.

Personally, I believe in mild cases of eating disorders there is hardly any electrolyte imbalance thus no harmful effect on heart though slow pulse may be there. But in severe cases, there is an efect on heart whether there is effect on heart rate variability is yet under investigation. Medically, fear of sudden cardiac death is there whether disease is mild or severe but slow heart rate is NOT a precursor for it. Regards. If you have any more questions you may ask, I will be happy to answer those.


With Best Wishes
Dr Anil Grover,
Cardiologist
M.B.;B.S, M.D. (Internal Medicine) D.M.(Cardiology)
http://www/ WWW.WWWW.WW

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