2 Research recommendations
- 2.1 Primary PCI and fibrinolysis in people with acute STEMI who present very early
- 2.2 Primary PCI and fibrinolysis in people with acute STEMI who have a long anticipated transfer time for primary PCI
- 2.3 Radial arterial access primary PCI versus femoral arterial access primary PCI
- 2.4 Culprit vessel primary PCI versus multivessel PCI
- 2.5 Relationship between volume of procedures and clinical outcomes
The Guideline Development Group has made the following recommendations for research, based on its review of evidence, to improve NICE guidance and patient care in the future.
If a person with acute STEMI presents within 1 hour of the onset of symptoms, is it better for that person to be given fibrinolysis with a short call to needle time rather than to be transferred to a centre that carries out primary PCI for primary PCI with a delay of up to 120 minutes?
Fibrinolytic drugs are administered intravenously and can be given out of hospital by an ambulance crew or in the emergency department of a hospital. Benefit from fibrinolysis declines significantly with time from onset of symptoms. Primary PCI, on the other hand, requires transfer to an interventional cardiology service, which inevitably delays the start of reperfusion treatment. Regardless of the reperfusion method used, delays to treatment are associated with an increased risk of impaired left ventricular systolic function and death.
It is unclear whether people with acute STEMI with a very short presentation delay would benefit more from immediate fibrinolysis (usually pre-hospital for people who do not self-present to hospital emergency departments) compared with transfer to a centre that carries out primary PCI.
To answer this question, a randomised controlled trial of pre-hospital fibrinolysis versus primary PCI in people with acute STEMI who have a short presentation delay of 1 hour or less is needed. Primary end points would include cardiovascular and all-cause mortality and other major adverse cardiovascular events. The STREAM study has recruited people who present early (less than 3 hours from onset of symptoms), and those presenting very early (less than 1 hour) could be analysed as a subgroup. However, it is not known whether this cohort will be big enough to allow a statistically significant conclusion to be drawn.
2.2 Primary PCI and fibrinolysis in people with acute STEMI who have a long anticipated transfer time for primary PCI
In people with acute STEMI who present more than 1 hour after the onset of symptoms, is a primary PCI-related delay of 120–180 minutes associated with outcomes similar to, better or worse than pre-hospital administered fibrinolysis?
Primary PCI is the preferred coronary reperfusion therapy provided it can be delivered 'in a timely fashion'. It is suggested that primary PCI is the preferred reperfusion strategy for primary PCI-related delays of at least up to 2 hours. However, there is inadequate evidence to conclude whether primary PCI is still preferable at primary PCI-related time delays of more than 2 hours.
No specifically designed randomised controlled trial or observational study has addressed the issue of the extent to which primary PCI-related time delay (and other factors such as presentation delay and a person's risk profile) diminishes the advantages of primary PCI over fibrinolysis. For example, in more geographically remote areas, a short presentation delay together with an anticipated long primary PCI-related delay could favour a strategy of pre-hospital fibrinolysis.
To answer this question, a randomised controlled trial of pre-hospital fibrinolysis versus primary PCI in people with acute STEMI who have a primary PCI-related time delay of 2 hours or more is needed. Primary end points would include cardiovascular and all-cause mortality and other major adverse cardiovascular events.
What is the clinical and cost effectiveness of radial arterial access compared with femoral arterial access for coronary angiography or primary PCI in people with acute STEMI managed by primary PCI?
There is no current evidence that demonstrates if there is a mortality difference between radial arterial access primary PCI compared with femoral arterial access primary PCI. It is unclear if operator experience has influenced current evidence. Operators may need additional training if 1 approach was shown to be superior. A randomised controlled trial comparing the 2 interventions for longer-term outcomes of all-cause mortality and major adverse cardiovascular events would answer the question. The trial would need to address the impact of operator expertise on the clinical outcomes. In addition, the need for operator training could be informed by an observational study that looked at the effectiveness and impact on clinical outcomes of experienced radial operators primarily using the radial approach versus experienced femoral operators primarily using the femoral approach including closure devices. The study would need a sufficient number of participants to enable differences in outcomes to be detected.
Does multivessel PCI, at the time of presentation of people with acute STEMI, confer an advantage over a strategy of 'culprit vessel only' primary PCI, followed by further elective revascularisation driven by symptoms and evidence of ischaemia?
One-third of people presenting with STEMI have multivessel coronary artery disease at the time of presentation. Currently, there is uncertainty about whether to initially treat only the vessel likely to have caused the presentation or whether to treat all significant lesions. Most of the current evidence that examines 'culprit vessel only' primary PCI versus multivessel PCI in these people comes from studies that are underpowered or non-randomised. Answering this question would clarify the appropriate revascularisation strategy for this patient group. A randomised controlled trial powered to examine all-cause mortality and major adverse cardiovascular events with a 5-year follow-up would be the optimum design.
What is the relationship between hospital volume of primary PCI procedures and optimal outcomes in people with acute STEMI?
There is a suggestion that outcomes may be better in larger-volume primary PCI units, and some retrospective registries have reported data to support this. However, the quality of the data is poor and still leaves the question open. In the UK, primary PCI is provided by units that vary greatly in the number of cases per year. The development of services has been ad hoc and not designed specifically around the provision of primary PCI. If it was possible to conclusively show that people were or were not better off being treated in larger volume units, then it would have important implications for the national provision of primary PCI.