where do you get that they tested for blocked arteries? It appears all that was performed was an ecg and a stress ecg. Neither of which tests for blocked arteries. Imaging tests are the only tests that will "test" for a blockage.
Especially since the autopsy provided no evidence of occlusion of any veins/arteries of the heart that would have been considered as causation of death, their cause of death is "cardiac arrhythmia" which in itself, can be adequate to cause death. There was nothing, either in their tests nor in the autopsy, that would suggest there was any real concern of a blockage.
and I can assure you that angina is not the only cause for pain, either in the chest in general or specific to the heart. Some types of arrhythmia itself can be the cause of considerable pain.

