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Abstract
The projects in this thesis aimed to examine issues of management of patients with coronary heart disease undergoing percutaneous coronary intervention (PCI). In particular the following were examined: clinical outcomes following PCI with selective drug-eluting stent (DES) use; clinical outcomes after bare-metal stent (BMS) deployment in large infarct-related arteries (IRA); clinical outcomes following rescue angioplasty for ST-elevation myocardial infarction (STEMI) with high utilisation rates of glycoprotein IIb/IIIa inhibitors; troponin T (TnT) criteria for periprocedural myocardial infarction (MI) and its association with late clinical outcomes.
The introduction of DES has revolutionized interventional cardiology by reducing restenosis and thus target vessel revascularization (TVR) rates. Selective use of DES in those patients at highest risk of restenosis is a potentially attractive approach as it may allay concerns about the risk of late stent thrombosis (ST) and the need for compliance with dual anti-platelet therapy (DAPT), aspirin and clopidogrel for 1 year. Hence, clinical outcomes were examined after adoption of criteria for selective DES use at Liverpool Hospital, Sydney, Australia. Using these criteria which aimed for ~30% DES use in patients at high risk of restenosis, low TVR rates at 1 year of 4.9% were achieved, and rates of death and MI were comparable to those after BMS. Though the ST rate of 2% reflects 1st generation DES, whether similar findings occur with 2nd generation use remains to be determined.
In the emergent setting of STEMI, uncertainty about patients ability to comply with 1year DAPT after DES is common, and thus selective BMS deployment could be an attractive strategy if this achieved low TVR rates in large IRAs. BMS deployment in STEMI patients with IRAs ≥3.5mm was associated with low rates of TVR (2.2%). Their use in this setting warrants comparison with 2nd generation DES deployment in future randomised clinical trials.
Rescue PCI is guideline-recommended as it improves outcomes after failed fibrinolytic therapy. However, these recommendations are based on data from an earlier era of pharmacotherapy and procedural techniques. Clinical outcomes following rescue PCI, with high utilization rates of glycoprotein IIb/IIIa inhibitors and stenting, were examined. Mortality rates were comparable to rates for contemporary primary PCI in patients without pre-PCI shock (3.2%), especially in early presenters. Whether rates of bleeding can be reduced by different pharmacotherapies and interventional techniques, need clarification in future studies. Prospective studies of future pharmaco-invasive strategies in STEMI patients are warranted.
As peri-procedural MI is an important early clinical outcome, its diagnosis based on cardiac marker levels and their prognostic significance are important. Evaluation of TnT criteria for periprocedural MI were performed, and the association of both TnT and creatine kinase MB level elevations on death and/or MI were examined in both stable coronary heart disease and acute coronary syndrome; post-PCI TnT levels were associated with event-free survival at one year only in patients with stable coronary heart disease. In patients with acute coronary syndrome and elevated TnT levels undergoing PCI several days later, criteria of ≥20% increases in TnT were more common than absolute increments of > 3XURL in TnT or creatine kinase-MB levels. Elevations of ≥ 20% above elevated pre-PCI levels detects any small peri-procedural MIs of questionable prognostic significance though this criteria has not been revised in the recently published revision of the universal definition of MI.