Heart rate?

Hi all.

Newbie here, so please excuse the potentially dumb and obvious question! I’m assuming heart rate is tied to metabolic rate? I ask because I have bradycardia and I’m desperately trying to reverse that. Full disclosure, I’m recovering from an eating disorder. I am at a BMI of 19 and am about 5-10 pounds away from my weight goal. I feel like I’m not terribly underweight, but I’m still plagued by bradycardia and orthostatic hypotension.

I am gaining on pretty low calorie amounts, and my temps are about 98 and 98.2 upon waking. I’m thinking my metabolism is still suppressed, since I’m gaining on low amounts. Any thoughts?

Also, is there any macronutrient that would help with the bradycardia (protein to rebuild heart muscle?) or will it basically improve with better nutrition / higher calories? I’m so ready to get on with my life, and am concerned I’ve “ruined” my metabolism forever by dieting for most of my life.

Any recommendations for where to begin to add calories? Carbs? Protein? Does it matter?

Thanks. Any help would be so helpful.
PS – I used to be a marathon runner and fitness instructor, so I’d expect a lower heart rate. But every doctor I’ve seen says it’s too low and directly tied to my history with ED.