Hello, Fever such as this and when spiking needs a thorough investigation especially given the history of a procedure done 48 hours before. Endocarditis is a possibility and MUST be excluded given the serious consequences this can have. A full clinical check, bloods such as hemogram, LFTs, infection screen with blood c/s, CRP, Chest X Ray, ECG, 2D-ECHO are minimum investigations to start with. Control the temperature with plain paracetamol 1g upto twice daily 12 hrs apart and wait for the infection screen results. Costochondritis especially viral ones can cause high temperatures, chest pains with non-specific ECG changes but the important thing to exclude is pericarditis (lining of the heart inflamed). Best Wishes.