Any medical complications? Can perfusion scan cause coughing?

Shouldn't. A myocardial perfusion scan shouldn't cause a cough. Perhaps a mild allergy is present but this is extremely rare. A ventilation-perfusion scan may cause a cough primarily due to the ventilation scan component. People who get these tests often have underlying medical problems associated with cough, and that would be the primary reason for the cough, not the scan.
Usually not. Usually it shouldn't unless you have an allergy. If it occurs each time then certainly possible.