Multivariable prediction models for atrial fibrillation after cardiac surgery: a systematic review protocol oleh Rui Providência, Gregory Y H Lip, Gary S Collins, Oliver C Redfern, Tatjana Petrinic, Peter J Watkinson, David A Clifton, Jie Ma, Jochen D Muehlschlegel, Kara G Fields, Hassan Alhassan, Anthony Eze, Ankith Reddy, Mona Hedayat, Jonathan P Bedford, Benjamin O’Brien