I'm sorry for your troubles. I needed cardiac clearance several times. One was prior to my neck dissection in 2011, and another before starting chemo in 2013. Although it delays matters, it's in your best interest. The cardiologist gave me clearance after an EKG, and echocardiogram to start chemo since the stress test would be done at a later date, due to scheduling, and after I needed to start treatment in a few days, and agreed to go back. I didn't go back until I finished treatment. Maybe there are other cardiologists in your area that can accommodate you faster.

Good luck