Copyright @ 2006 by the Shock Society. Unauthorized reproduction of this article is prohibited. MYOCARDIAL STRUCTURAL CHANGES IN LONG-TERM HUMAN SEVERE SEPSIS/SEPTIC SHOCK MAY BE RESPONSIBLE FOR CARDIAC DYSFUNCTION Marcos A. Rossi, Mara R. N. Celes, Cibele M. Prado, and Fabiano P. Saggioro Department of Pathology, Faculty of Medicine of Ribeira ˜ o Preto, University of Sa ˜ o Paulo, Ribeira ˜ o Preto, Sa ˜ o Paulo, Brazil Received 6 Jun 2006; first review completed 23 Jun 2006; accepted in final form 24 Jul 2006 ABSTRACT—The present investigation sought to determine the cellular mechanisms directly dependent on long-term severe sepsis/septic shock that could lead to myocardial structural changes in humans. Human hearts from eight cases of long-term severe sepsis/septic shock arising from infection, as defined by the ACCP/SCCM Consensus Conference; eight cases of acute necrotizing pancreatitis and acute lung injury, a noninfectious pathologic cause of systemic inflammatory response; and three cases of accidental death without thoracic injury selected from autopsies were studied. Transmural blocks of myocardial tissue were excised from the middle portion of the left ventricular free wall and were fixed in formalin or were frozen. Histochemical and immunohistochemical methods were used to evaluate the cross-striations of the myocardial cells, the number and size of interstitial macrophages, the intracardiomyocyte accumulation of lipid, the actin/ myosin contractile apparatus, and the expression of iNOS, nitrotyrosine, and TNF-! in the myocardia of septic and control hearts. Greater interstitial cellular infiltration composed of larger and elongated macrophages and TNF-! protein expression in myofibers, interstitial macrophage cell types, and smooth muscle cells and endothelial cell in the vessels; intracardiomyocyte lipid accumulation; scattered foci of actin/myosin contractile apparatus disruption; and increased expression for iNOS and nitrotyrosine in myocytes and interstitial macrophage cell types could be observed in long-term human septic myocardium as compared with normal and acute pancreatitis control myocardia. These findings give support to an opinion that structural changes could be responsible for long-term sepsis-induced myocardial dysfunction. The higher number of macrophages, most of them with morphological features of ‘‘activation,’’ and TNF-! protein expression could favor the reduction of cardiac function in septic hearts. The intramyocyte lipid accumulation in these hearts very likely reflects myocardium ventricular contractile dysfunction. In addition, the increased expression of iNOS and the evidence for the significant presence of peroxynitrite in cardiomyocytes and interstitial macrophage cell types suggest that oxidative damage may play a role in actin/myosin disruption in the hearts of septic patients. KEYWORDS—Sepsis, septic shock, myocardial cell injury, myocardial dysfunction, macrophage, lipid accumulation, actin, myosin, iNOS, nitrotyrosine INTRODUCTION Clinical studies have shown that myocardial contractility is reduced in severe sepsis and septic shock in the absence of changes of ventricular preload or afterload (1). This myocar- dial dysfunction is recognized as an important factor con- tributing to the high mortality of septic patients (2). Although cardiac function is depressed, it remains controversial whether the myocardial contractile dysfunction is secondary to structural changes. Clinically unrecognized myocardial injury as revealed by elevated levels of cardiac troponins I and T has been reported in critically ill patients (3Y7). However, the exact mechanism of the increased troponin levels in patients with sepsis remains unknown. Possible mechanisms are diffuse necrosis, cardiac troponin proteolysis, or leakage of cytoplasmic cardiac troponins with reversible damage to the contractile complex of heart muscle cells. Previous experi- mental studies have shown either an association between sepsis and structural myocardial changes (8Y15), such as tissue and mitochondrial edema and myocyte necrosis, or an impairment of myocardial contractility in the absence of tissue injury (16, 17). No study, however, has sought to determine the cellular mechanisms directly dependent on sepsis/septic shock that could lead to myocardial structural changes in humans. Previous retrospective study evaluated 71 autopsies of septic patients using morphologic criteria of inclusion: inflammation reaction in two or more organs; acute splenitis; bilateral acute pyelonephritis; fibrin thrombi in the lungs, liver, and glomeruli; and neutrophils sequestration in pulmonary capil- laries (18). The authors described a typical infectious myocarditis: 19 cases (27%) of interstitial myocarditis with an exudate mainly composed of neutrophils, sometimes forming microabscesses, 8 cases (11%) of bacterial coloniza- tion, and 5 cases (7%) of fiber necrosis. Seventy-one age- and sex-matched cases served as controls. The evaluation was made in formalin-fixed myocardial tissue (with no reference to the specific area of the myocardium) and hematoxylin and eosinYstained sections. Although the authors described a typical bacterial myocarditis, they proposed that these myo- cardial changes were likely induced by blood-borne mediators and were responsible for the myocardial dysfunction in human 10 SHOCK, Vol. 27, No. 1, pp. 10Y18, 2007 Address reprint requests to Marcos A. Rossi, Professor of Pathology, Depart- ment of Pathology, Faculty of Medicine of Ribeira ˜o Preto, University of Sa ˜o Paulo, 14049-900 Ribeira ˜o Preto, Sa ˜o Paulo, Brazil. E-mail: marossi@fmrp.usp.br. This work has been supported by grants from the Funda0a ˜o de Amparo a ` Pesquisa do Estado de Sa ˜o Paulo (04/01777-0 and 04/14578-5) and the Conselho Nacional de Desenvolvimento Cientı ´fico e Tecnolo ´gico (CNPq). DOI: 10.1097/01.shk.0000235141.05528.47 Copyright Ó 2006 by the Shock Society