An ambulance drives at speed past the houses of parliament in Westminster.

HSIB highlights ‘time-critical’ delay to heart attack treatment

by Communications team

Our latest national report says that patients suffering from a heart attack face ambulance delays that could impact their ability to have life-saving treatment.

The report focuses on a form of heart attack known as an ST-elevated myocardial infarction (STEMI). The preferred course of treatment is a primary percutaneous coronary intervention (PPCI)*.

The procedure is most effective when the patient receives it within an hour and a half of being diagnosed.

Around 31,000 people have a STEMI each year and evidence suggests that patients across England could face delays in response.

National data shows that in November 2019, the average time from 999 call to PPCI procedure was 137 minutes with 10% of cases averaging at least 191 minutes. By February 2020, the average was 132 minutes with 10% of cases averaging at least 179 minutes.

Reference event

Our investigation involved a case which highlighted the risks related to the condition and the impact of delay.

Phil, a 61-year old male, suffered a STEMI while staying at a friend’s house. A delay in response to his condition meant that the time from the 999 call made by a friend to him receiving the PPCI was just under 4 hours (229 mins).

Phil survived and has mainly recovered, with some ongoing medical needs and reduced levels of physical activity.

The investigation examined the system-wide safety issues relating to the emergency response to heart attack and the treatment options available to those with a STEMI. Key findings broadly relate to:


  • The impact of delays. Ambulance delays impact on the ability to provide treatment and heightens the risk of death. The British Cardiovascular Intervention Society audit (2018) shared data which suggested that for every 15-minute delay in PPCI being provided beyond target timescales there were 6.3 more deaths per 1,000 patients suffering a STEMI.
  • The use and preference of treatment. Thrombolytic drugs (that dissolve blood clots) have been recommended as an alternative treatment to PPCI. However, HSIB identified that there is a lack of evidence to suggest which treatment is best when delays occur and that in fact thrombolysis is now rarely used as a pre-hospital STEMI treatment.
  • Ambulance service ability to administer treatment if needed. The investigation found that only 4 out of 10 English ambulance trusts now carry thrombolysis medication. Also, many paramedics are unlikely to encounter patients requiring thrombolysis.
  • Longer term impact on patients. There is a lack of evidence to show the impact on death rates in the longer term beyond 30 days, the effect on patients’ health in the longer term, and the impact on NHS resources.

The report concludes with three safety recommendations: two to NHS England and NHS Improvement and one to the Association of Ambulance Chief Executives (AACE). They focus on reviewing current guidance on timescales, clarifying information on STEMI treatment and addressing the system factors behind delays.

Dr Stephen Drage, Director of Investigations at HSIB says: said: “Delays in emergency response to STEMI’s and the impact this could have on treatment is a patient safety issue seen across England.

"Our investigation highlights that the reduced ability of the ambulance services to provide pre-hospital treatment places even more emphasis on patients arriving within a crucial time window to receive PPCI.

“Data cited in our report suggests that the longer the delay, the poorer the outcome could be even if patients survive the heart attack and the procedure that follows.

"Our safety recommendations focus on ensuring national clarity and consistency for paramedics dealing with STEMI transfers, and on building further understanding of the factors that influence ambulance response times and how this might contribute to delays.

"This work will aid in improving care for any patient that needs time-critical treatment, which will be particularly important to address as the NHS deals with the longer-term impact of COVID-19.”

Safety Recommendations

  • NHS England and NHS Improvement revise the Ambulance Clinical Quality Indicator: Clinical Outcomes for ST-elevation myocardial infarction to reflect each element of the call to balloon response and review this indicator alongside the critical time standards workstream.
  • Association of Ambulance Chief Executives, working with the College of Paramedics and cardiology specialists, produces a position statement on the use of pre-hospital thrombolysis by paramedics.
  • NHS England and NHS Improvement support the Joint Ambulance Improvement Programme to respond to emerging risks and research highlighting factors impacting on effective ambulance response.

*Primary percutaneous coronary intervention (PPCI) is a procedure which involves widening a blocked artery and inserting a stent to keep the artery open. It is the preferred model of care in the NHS in England to treat a STEMI.

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