“…They contained a heterogenous mix of patients, procedures and locations, commonly found in these studies [6,22,23]. Twenty studies reported on all operations performed [2, [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42], 11 reported on aortic valve replacements with or without coronary artery bypass grafts (CABG) [43][44][45][46][47][48][49][50][51][52][53], 8 CABG only [54][55][56][57][58][59][60][61], 2 on mitral valve repair/replacement [62,63], 2 on unspecified valvular operations [64,65] and 1 on thoracic aortic [66] operations. A total of 23 were based in Europe [2, 24, 25, 28, 31, 35-39, 42, 46, 48-50, 53-57, 59, 62, 67], 5 in North America (NA)…”