HORIZONS and Drug-eluting Stent Usage in Acute Myocardial Infarction

Myocardial infarction (MI) is one of the few clinical presentations whereby percutaneous coronary intervention reduces the risk of death compared with medical therapy alone. However, treatment with drug-eluting stents (DES) – so-called ‘off-label’ use for patients with ST-segment-elevation MI (STEMI) – raises safety concerns with respect to the morbidity and mortality attributed to late stent thrombosis (LST). Pathology data clearly indicate delayed healing as the primary substrate in all cases of DES-related LST, where differences in lesion morphology invariably show a greater prevalence of uncovered struts, accumulated fibrin and inflammation in ruptures relative to stable plaques. The prolonged risk of LST appears to persist up to at least four years after DES implantation. Results from the recently published Harmonising Outcomes with Revascularisation and Stents – Acute Myocardial Infarction (HORIZONS-AMI) trial of 3,006 prospective patients presenting with STEMI, randomised to paclitaxel-eluting (PES) or identical bare-metal stents (BMS), show similar 12-month death and stent thrombosis rates. Despite a significant reduction in ischaemia-driven target lesion revascularisation, a sub-study analysis showed a greater incidence of malapposition in patients receiving PES. Along these same lines, other registry studies point towards inconsistencies in advocating the use of DES for AMI. Considering that arterial healing in response to DES is delayed for periods longer than one year, long-term follow-up beyond this point is required to confirm the results of the HORIZONS trial. However, despite the final outcome, the results may remain disputable since the trial may not have been sufficiently powered to address the relative risks of LST or mortality. Clearly, there remains a need for larger randomised controlled studies before the broader use of this technology in AMI patients is settled.