Cardiac Stress in Septic Shock - Biomarkers, Echocardiography and Outcome

Overview

Septic shock is a major cause of death in intensive care. Septic shock is often dominated by profound changes in organ functions, of which cardiac failure is one of the most severe. In septic shock, biological markers of cardiac stress are often elevated. It is not known to what extent this indicates structural damage to the heart, or in what way they correlate to echocardiographic signs of heart failure. Here, cardiac failure in ICU patients with septic shock is studied, using biological markers of cardiac stress, inflammatory parameters and echocardiography. Investigators hypothesize that biomarkers of cardiac stress correlate with echocardiographic signs of heart failure, and that they can predict an increased risk of death.

Sepsis and septic shock are major health concerns worldwide. Sepsis is the consequence of inflammatory processes and humoral and cellular reactions to severe infection. Its clinical presentation is variable, with a continuum from a systemic response to infection to fulminant disease refractory to resuscitation and with multiple organ failure. Septic shock is the most severe form of sepsis and the leading cause of death in intensive care patients with a high mortality despite modern resuscitation and treatment. Septic shock is dominated clinically by circulatory changes presenting with profound vasodilatation and hypotension. Cardiac output values are often seemingly normal, or even enhanced, when compared with the physiological range. However, relative to the vasodilatation, cardiac output is often not adequately enhanced. Thus, the degree of myocardial depression in sepsis is often underestimated by the clinician, albeit a factor that markedly increases mortality. Septic cardiomyopathy typically engages both ventricles globally, and involves diminished cardiac response to volume and circulating catecholamines. It is not primarily hypoxic, but rather has a multifactorial origin. In survivors, it is typically reversible, but long-term consequences are not known. Cardiac biomarkers, i.e. troponins and natriuretic peptides, are all associated with worse outcome in septic shock. Cardiac troponins are frequently elevated and correlate to the duration of hypotension and the intensity of vasopressor support. Elevated natriuretic peptides predict adverse outcome, and values are often markedly elevated even in seemingly normal echocardiographic findings. It is not clear whether this indicates structural myocardial damage, or rather demonstrate a global septic membrane leakage. Thus, with the complexity of sepsis, combinations of cardiac biomarkers and markers of global inflammation may provide a more robust tool for stratification and prognostication and for evaluation of septic organ dysfunction. In clinical cardiology, combinations of biomarkers of myocardial stress are used for stratification and prognostication of myocardial failure, but the role of such multimarker panels in septic cardiomyopathy has not been studied. Echocardiography is used clinically, and has been the focus of several studies, to characterize septic cardiomyopathy. Echocardiographic signs of systolic dysfunction has been the main focus of previous investigations, and the systolic component is the focus of modern guidelines of clinical management in septic cardiomyopathy. The role of diastolic dysfunction is gaining interest, with data suggesting higher mortality in patients with diastolic dysfunction than in those with systolic dysfunction. To date, the correlation of echocardiographic signs of systolic or diastolic dysfunction myocardial stress biomarker panels, and the dynamics of any correlation, has not been studied. The hypothesis of this study is that biological markers of cardiac stress correlate with echocardiographic signs of cardiac failure, that they can predict outcome, and that they correlate to conventional methods of outcome prediction.