I take (took) a betablocker when I started Atkins. I didn't lose but it was because I also had low thyroid. I have irregular heartbeat also and doing the lowcarb was the best thing in the world. It got rid of about 70% of arrythmias I had and decreased the severity to the point that I don't usually take it anymore.

The betablocker works on the beta cell in your pancreas and causes you to release more insulin. I think the effect on your weight loss is dependent on your dose and how reactive your pancreas is.

Be careful when you start atkins, you lose a lot of fluids in the beginning and that can trigger arrythmias. I do better gradually lowering my carbs than jumping down to 20.

good luck Nancy