The case for pre-hospital thrombolysis for STEMI patients who cannot undergo timely percutaneous coronary intervention (PCI) has been bolstered with real world Australian data suggesting the strategy is associated with similar long-term survival to primary PCI.
The findings are based on the six-year follow up of NSW patients involved in a non-randomised parallel cohort study comparing mortality and morbidity outcomes in primary PCI patients and those who received pre-hospital thrombolysis.
Some 150 patients in the New England-Hunter rural region were administered pre-hospital thrombolysis and 334 underwent primary PCI during the study period.
At six year follow up all-cause mortality was 16% and 19%, respectively, and the incidence of recurrent myocardial infarction was 15% and 11% in the pre-hospital thrombolysis and primary PCI groups.
Writing in MJA, the study investigators say the comparable incidence of events is reassuring, and none of outcome differences reached statistical significance.
Professor Andrew Boyle from the John Hunter Hospital where the study was carried out told the limbic that for the many patients living in regional areas and a long way from a cath lab, it is an important study that shows outcomes for patients eligible to have thrombolysis in the field are as good those seen in patients undergoing primary angioplasty.
“The study is the result of an amazing collaboration between NSW Ambulance and the Hunter New England local health district. Working together we’ve been able to put in a really revolutionary protocol which is based on randomised controlled trials showing its effectiveness,” he says.
The protocol was introduced across the New England Hunter region – an area equivalent to the size of England but only serviced by one 24/7 cardiac catheterisation laboratory (CCL) – in 2008, as part of a pilot study to provide early reperfusion to eligible STEMI patients who would normally be forced to travel up to six hours for treatment.
It involves pre-hospital diagnosis and triage by paramedics using 12-lead electrocardiogram that is then transmitted to the reporting cardiologist.
Once diagnosis of STEMI is confirmed, a reperfusion strategy – pre-hospital thrombolysis with subsequent transport to a PCI capable hospital or primary PCI – is determined depending on whether patients can reach the CCL within 60 minutes of the first medical contact (FMC) or if there is any contraindication to fibrinolysis irrespective of the estimated FMC-to-CCL time.
Pointing out a number of exclusion criteria for pre-hospital thrombolysis such as high blood pressure, high bleeding risk or a history of previous bleeding Professor Boyle acknowledged that the group undergoing primary PCI was very different to the group eligible for pre-hospital thrombolysis.
Thus while outcomes between the two arms look similar, pre-hospital thrombolysis doesn’t show equivalence to primary PCI, which remains the gold standard for reperfusion.
“The populations are quite different – it is a very highly selected group who are able to have thrombolysis in the field but in terms of the observations made from the study, it’s very reassuring the we’re delivering a very safe therapy and that the long term outcomes are good,” he said.
Professor Boyle said the ‘excellent’ clinical outcomes reported in the pre-hospital thrombolysis group at 12 months led to a NSW state-wide adoption of the reperfusion protocol.
“Every regional ambulance in NSW can now deliver pre hospital thrombolysis,” he said, noting that the protocol has now also been taken up in regional Victoria, South Australia and Queensland.
“But the problem remains that there are not enough ambulances available to directly transport patients to the primary PCI centre and so some of those PHT-treated patients will get taken to a smaller hospital without PCI capabilities and that remains an ongoing issue of resourcing in regional Australia.”
According to Professor Boyle the use of aspirin, clopidogrel and enoxaparin along with tenecteplase was mandatory in the pre-hospital thrombolysis group.
All patients in the primary PCI group received aspirin in the ambulance, however a second antiplatelet agent and antithrombotic agents were administered in the CCL at the discretion of the interventional cardiologist.
Patients in the pre-hospital thrombolysis group underwent rescue PCI if there were ongoing ischaemic symptoms, less than 50% ST-segment resolution 90 minutes post fibrinolysis, or electrical or haemodynamic instability.
Pre-hospital thrombolysis patients with clinical and electrocardiographic evidence of reperfusion were taken to the CCL at the next available opportunity for routine PCI.