Like with many things, keto has its range (variations). Originally it was developed to control seizures and it is good for that, but some more extreme forms are not sustainable, if seizures are not your problem. I remember during my Mayo Clinic Wellness Coach Training program, that keto diet was not recommended as a long-term dietary option.

I agree with @gloaming that you should not rule out all the carbs, as all carbs are not created equal and they also contribute to your gut biome. You may consider getting and reading "The 30-day Heart Tune-Up" by Steven Masley, MD who has a gentle, middle-of-the-road approach to heart healthy diet.

It is important to include in your meals both soluble and insoluble fiber (begin with a fruit, apple or berries), protein, healthy fats, but having up to 1/2 cup cooked minimally processed carbs is beneficial to your long-term health. The order of various foods that I just described, also helps with controlling your blood sugar spikes.

As far as movement goes, apart from exercise you may consider non-exercise physical activity every hour. 2-3 minutes of walking, sit-ups (if not too weird at the office :), bending forward and backward to stretch your spine a bit.

Try various things, in consultation with your cardiologist. Little lifestyle experiments and adjustments can go a long way. Observe how you feel and take what works for you.

Be healthy!
J.