Is there a basement or crawl space underneath the kitchen floor? If yes then you may be able to install a radiant heat system. It would tap into your current hot water heating system.

The other option is to replace the cast iron radiator with a base board radiator. It would free up some wall space. There are manufacturers which make radiators which are very stylish looking in various colors and shapes. Perhaps you can mount the new radiator high on the wall so you could use the space below it. It is not optimum, but it could work in your situation. I think you can also get a toe kick size radiator, but I am not sure if these are effective.

Use electric resistance heating is an option, but it is going to be much more expensive to operate compared to the gas furnace. This would be the least attractive option for me.

Thank you Mike. We love the cast iron radiators and have them in all rooms of the house but we know it is not ideal to have the radiator next to the sliding door. Yes, there is a crawl space under the kitchen which is easily accessible from the basement. I thought the installation of the electric pad under the floor would be so much cheaper and if you read on their web sites, fairly economical to run although utilities are never cheap!

I agree installation of a electric radiant system could be cheaper. The problem is resistive heating is the most expensive way to heat a room. Price out both options and estimate the additional cost of operating the resistive heat. You should be able to calcualte how many years it will take to offset the additional cost of the hot water radiant system.