Non-elevation acute myocardial infarction (NSTEMI) is one of the commonest phenotype of acute coronary syndrome (ACS) and associated with significant morbidity and mortality at the short and long term. An invasive strategy in the form of coronary angiography (CA) or percutaneous coronary intervention (PCI) allows an early assessment of coronary anatomy, identify culprit lesions and plan further management. While the effectiveness of the invasive strategy is well documented in clinical trials, there is limited data regarding the changes in demographics, risk profile and comorbidity burden of patients receiving invasive strategy in contemporary practice. Furthermore, the opinion is divided regarding the optimal timing of invasive strategy in this cohort and it is unclear how risk stratification guides the utilisation of invasive strategy in a real world setting.
Consequently, this thesis was designed to determine, 1) changes in characteristics, risk profile and comorbidity burden of patients admitted with a diagnosis of an NSTEMI and how this relates to the use of an invasive strategy in different subgroups of patients 2) optimal timing of invasive strategy in different subgroups of patients 3) guidelines recommended risk stratification and how this translates into the use of invasive strategy 4) availability of cardiac catheter laboratory facilities, use of invasive strategy and clinical outcomes and 5) optimal access site practice to perform invasive strategy.
This thesis addresses the aforementioned aims in mainly three parts. Part 1 relates to results in chapter 4 and 5 which systematically looked at the use of an invasive strategy in different subgroups of patients. Chapter 4 demonstrates a temporal increase in the utilisation of invasive strategy albeit slower adoption was noted in older, women and more comorbid patients. Furthermore, the results from chapter 5 showed that despite the increase in the use of early invasive strategy within 24hours, there were significant disparities in utilisation of an early invasive strategy in Women, African Americans, admission day and older patients. Part 2 of the thesis shows that an invasive strategy for management of NSTEMI is not delivered according to international guidelines recommendations. Specifically, the disconnect between baseline risk and utility of invasive strategy increases with increasing risk and women achieve even slower access than men to the invasive strategy, so that overall their care is even more discrepant with the guidelines. Chapter 7 highlights important differences in both the utilisation of invasive strategy and subsequent management of NSTEMI patients according to admitting hospital cardiac catheter laboratory facilities. These variations are important particularly in the high-risk NSTEMI where patients admitted to ‘diagnostic’ hospitals had a greater risk of in-hospital mortality. Finally, part 3 of the thesis showed that left radial access offers a very safe and effective alternative access site route for performing invasive strategy and may also help to reduce procedure related stroke complications.
Overall, this thesis has demonstrated that there are significant inequalities in the use of invasive strategy in clinical practice in that elderly, women, ethnic minorities, and more comorbid patients. Furthermore, there is a significant disconnect between guidelines recommended risk stratification criteria and use of invasive strategy. There are also significant institutional variations in the adoption of an invasive strategy which may be associated with poor outcomes in high-risk patients. Clinical implications and further areas of research are discussed in detail.