high cardiac output

I recently had a stress echo which found that with exercise my heart did not squeeze properly which looked like balanced cardiac disease to my cardiologist. I was able to do 12 min on the treadmill. I am 48yrs old @ have always been in great shape until last yr when I had foot surg @ could not work out.When I started to exercise again I was having lightheadedness @ some chest pain which I could put my finger on with pushing myself in exercise or stress over the summer which prompted me tho visit my Dr. I have strong family hx so I had a cath done which was normal with clean arteries,normal pressures,ef 55% but my cardiac output was 10L/min. My thyroid function is normal @ i am already on supplement,I do not have tachycardia,I am anemic @ 10 which has improved since I am taking Fe. Is this something to worry about or just the way my heart operates?

[Cleveland Clinic]

Hi cardiac output could be caused by vitamin deficiencies, thyroid problems,  multiple myeloma, paget's disease, arterio-venous fistulas and some other rare causes.  It sounds you have symptoms and therefore should be worked up further.  

[happy101]

what is an a-v fistula??