Stress test with autoimmune conditions.

I have swelling and severe stiffness on my ankles and feet on both legs since January. I have palpitations and high Heart rate at resting issues. So the cardiologist ordered the stress test. I can walk slowly around the house at a slow pace. I don't know if I can walk fast or run on the treadmill for a stress test. The doctor's nurse said I have to do the treadmill while running considering my age for better evaluation. Are there any alternative tests for this? I have to finish this test to get the cardiac evaluation for my ankle swelling. Can we do stress test with inflammatory arthritis diagnosis. My rheumatologist diagnosis are possible Seronegative RA or psoriatic arthritis. No definite diagnosis yet because my labs are negative and I have symptoms. MRI feet showed inflammation. How to do stress test walking with this?