Since 1933, studies have explored the concept of trauma induced secondary cardiac injury (TISCI), yet till 2012, it had not been defined as the incidence of cardiac events and rise in cardiac biomarkers following traumatic injury. Despite, improvements in early outcomes, trauma patients have reduced long-term mortality with cardiac disease being the major contributor. Although many putative mechanisms have been suggested for TISCI, the underpinning pathophysiology still remains unclear. In this thesis, a prospective study of 290 critically injured patients identifies a 13% incidence of adverse cardiac events (ACE) with consistently raised serum h-FABP levels in these patients. H-FABP was found to be a good predictor of ACE through ROC analysis and a h-FABP of 16.8 ng/ml used to define trauma induced secondary cardiac injury (TISCI). TISCI was associated with longer hospital stay and higher mortality. Patients who developed ACE had higher plasma levels of adrenaline and noradrenaline with a correlating increase in plasma h-FABP. On multivariate analysis, hypertension was the only independent risk factors for ACE. The increase in serum cardiac biomarkers was reflected by an increase in serum h- FABP in our group's trauma hemorrhage murine models. The hearts of these models were used in the experiments that form the last experimental chapter of this thesis. Protein expression studies confirm this increase in serum h-FABP by evidence of concurrent leaching in the cardiac tissue, along with Troponin I. Myocardial injury was evident on electron microscopy with evidence of interstitial and organelle oedema, myofibrillar degeneration, nuclear condensation and changes in mitochondrial morphology. Immunohistochemistry and western blotting protein studies demonstrate the translocation of the mitochondrial death-related protein AIF to the cytosol and nucleus, where it becomes its active pro-apoptotic form. This thesis propositions the utility of the cardiac biomarker h-FABP in predicting ACE and outcomes in critically injured patients. Although increasing serum noradrenaline and adrenaline levels are associated with higher incidence of ACE and biochemical evidence of cardiac injury with rising h-FABP levels, multivariate analysis negates their value as independent predictors of ACE. Leaching out of the proteins h-FABP and Troponin I in the murine cardiac tissue confirmed the value of serum measurements of these proteins as markers of cardiac injury. This was associated with widespread ultrastructural myocardial damage in the TH mice with changes in mitochondrial morphology. The mitochondrial damage seen is associated with the translocation of the mitochondrial death-related protein AIF to the cytosol and the nucleus where I propose its canonical signaling leading to nuclear degradation and cell death is the driver of cardiac dysfunction.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:766268 |
| Date | January 2018 |
| Creators | Naganathar, Sriveena |
| Publisher | Queen Mary, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://qmro.qmul.ac.uk/xmlui/handle/123456789/54467 |
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