If there are some ECG changes, they will indicate that the blood supply to the heart(part of it) is reduced. TMT test will tell you whather you have any such ischemia
But in your case, because of back problem, TMT can not be adviced. Only way out is coronary angiogram, which is a safe procedure and will give definitive results.
Before undergoing spinal surgery
the cardiologist opinion and clearance(fitness) is better.