Acute Cardiac Dysfunction in Critical Illnes

Overview

The overall aim of the study is to establish the clinical importance of cardiac dysfunction, by estimating its incidence and impact on short- and long-term outcomes, in a mixed population of critically ill patients with multi-organ failure. Pathogenesis of cardiac dysfunction in critical illness and key molecules linked to this will be explored.

During critical illness, the heart is exposed to extreme external stressors, which may contribute to heart failure. There is a lack of knowledge of what happens to the heart over the course of critical illness. The few studies available suggest that LV dysfunction is common in critical illness, with a prevalence of 10-30%. Notably, LV regional hypokinesia is a frequent pattern of LV dysfunction among these patients and is associated with a higher risk of death. LV regional hypokinesia during critical illness may have several possible aetiologies, including ischemic, inflammatory or other/mixed processes. Of these, acute coronary artery obstruction is probably most important. Patients with sepsis, for example, and acute ST elevation myocardial infarction have twice the risk of death. Type II myocardial infarction can also lead to LV dysfunction due to insufficient coronary artery flow e.g., from tachycardia, hypotension and hypoxia, resulting in myocardial ischemia. In the absence of CAD, LV regional hypokinesia could also result from myocardial inflammation secondary to systemic inflammatory response, direct toxic effects of cytokines or pathogenic infiltration. Another possible aetiology is Takotsubo syndrome, an acute cardiac condition characterised by reversible regional hypokinesia, usually in the apical portion of the LV. The current paradigm suggests that Takotsubo syndrome is triggered by the overstimulation of the myocardium by catecholamines and is closely correlated to events involving severe emotional or physical stress. Cardiac dysfunction in critical illness is likely a phenotype of Takotsubo syndrome since patients in the ICU undergo extreme stress and are exposed to both endogenously-released and exogenously-administered catecholamines. In critical illness, accurate diagnosis of LV dysfunction is challenging due to the similar clinical presentation of potential aetiologies. However, diagnosing the underlying aetiology of LV dysfunction is essential to provide appropriate treatment and optimise outcomes. CAD can be diagnosed with coronary angiography and cardiac computed tomography (CCT). In the absence of CAD, cMRI is useful. cMRI can differentiate between myocardial ischemia, and inflammation, as well as between an acute or past event. In this study, patients are examined with echocardiography to identify those with cardiac dysfunction. In a sub-set of patients with LV dysfunction, patients will be examined with coronary CT (if no angiography performed) and cardiac MRI. Blood samples are collected for storage in biobank.