(1) Infective endocarditis is a severe inflammatory disease associated with substantial mortality and morbidity. Alkaline phosphatase (AP) levels have been shown to change significantly during sepsis additionally we previously found higher initial AP drop after cardiac surgery is associat-ed with unfavorable outcomes. Therefore, the course of AP after surgery for endocarditis is of special interest. (2) 314 patients with active isolated left-sided infective endocarditis at the De-partment of Cardiac Surgery (Medical University of Vienna, Austria) between 2009 and 2018 were enrolled in this retrospective analysis. Blood samples were analyzed at different time points (baseline, postoperative day 1-7, postoperative days 14, and 30). Patients were categorized ac-cording to relative alkaline phosphatase drop (≥30% vs. <30%). (3) The rate of postoperative renal replacement therapy with or without prior renal replacement therapy (7.4 vs. 21.8%; p=0.001 and 6.7 vs. 15.6%; p=0.015, respectively) and extracorporeal membrane oxygenation (2.2 vs. 19.0%; p=0.000) was observed after a higher initial alkaline phosphatase drop. Short-term (30-day mor-tality 3.0 vs. 10.6%; p=0.010) and long-term mortality (p=0.008) were significantly impaired after a higher initial alkaline phosphatase drop. (4) The higher initial alkaline phosphatase drop was accompanied by impaired short and long-term outcomes after cardiac surgery for endocarditis. Future risk assessment scores for cardiac surgery should consider alkaline phosphatase.

Microvascular integrity is a critical factor in myocardial fluid homeostasis. The subtle equilibrium between capillary filtration and lymphatic fluid removal is disturbed during pathological processes leading to inflammation, but also in hypoxia or due to alterations in vascular perfusion and coagulability. The degradation of the glycocalyx as the main component of the endothelial filtration barrier as well as pericyte disintegration result in accumulation of interstitial and intracellular water. Moreover, lymphatic dysfunction evokes an increase in metabolic waste products, cytokines and inflammatory cells in the interstitial space contributing to myocardial oedema formation. This leads to myocardial stiffness and impaired contractility eventually resulting in cardiomyocyte apoptosis, myocardial remodelling and fibrosis. The following article reviews pathophysiological inflammatory processes leading to myocardial oedema including myocarditis, ischaemia-reperfusion injury and viral infections with a special focus on the pathomechanisms evoked by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In addition, clinical implications including potential long-term effects due to viral persistence (long-COVID), as well as treatment options are discussed.