The Mail Online reports on a new heart operation that could save the lives of thousands of people who have heart attacks every year.
When someone has a heart attack caused by a blocked artery, the standard procedure is to unblock the artery that supplies blood to the heart using a tube called a stent.
Researchers examined whether inserting stents in other narrowed arteries during the operation as a preventive measure reduced the risk of a future heart attack.
They found that patients who had the preventive procedure were about two-thirds less likely to have another heart attack than those who only had surgery on the blocked artery.
Overall, the results from this well-designed study are likely to be of interest to heart doctors as they consider what the best preventive treatment is for their patients.
It is important to note that the study results do not apply to all patients who have had a heart attack, also called myocardial infarction (MI). The study only looked at patients with one kind of MI called ST-segment elevation myocardial infarction (STEMI) who could be treated with stenting. The results would not apply to patients with non-STEMI or those who need a different type of heart operation.
Where did the story come from?
The study was carried out by researchers from the Wolfson Institute of Preventive Medicine, Barts and the London School of Medicine and Dentistry, in collaboration with five regional centres across the UK, and was funded by Barts and the London Charity.
It was published in the peer-reviewed New England Journal of Medicine.
The Mail Online reported this study reasonably accurately, but did not indicate that this surgery would not be applicable to a large number of patients who have had heart attacks but are not suitable candidates for this type of emergency operation.
What kind of research was this?
This was a single-blind, randomised trial to test a preventive surgical intervention in people who are already having emergency surgical treatment for a heart attack caused by blocked coronary arteries (the arteries that supply the heart muscle with oxygen).
Current UK guidelines advise that patients who have a blocked coronary artery that causes a heart attack should have the artery widened with an emergency angioplasty, where a short wire-mesh tube called a stent is inserted. The stent acts as “scaffolding”, holding the artery open. The procedure is sometimes also known as percutaneous coronary intervention (PCI).
Some people who have this operation also have other arteries that are narrowed but not yet blocked. These arteries could become blocked in future and cause another heart attack. This study aimed to determine whether inserting stents into other narrowed coronary arteries during the same operation would reduce the risk of a further heart attack. This was referred to as a “preventive” PCI.
This study design is the best way of comparing two different interventions, as the groups should be well balanced at the start of the trial. This means any differences at the end of the trial can be attributed to the intervention received.
What did the research involve?
The researchers enrolled 465 consecutive patients who had had a specific type of heart attack called an ST-segment elevated myocardial infarction (STEMI). They enrolled these patients at five coronary care centres in the UK from 2008-13. The patients were of any age and had to have at least one other coronary artery that was narrowed by at least 50%.
Patients were not eligible if they:
- were unable to respond and give consent
- had undergone another kind of heart surgery previously called coronary-artery bypass grafting (CABG)
- had more severe artery stenosis needing a different kind of surgery (CABG) rather than PCI or which was unlikely to be successfully treated with PCI
They were randomly allocated by a computer into two groups. One group only received PCI on the blocked artery. The other group had PCI on the blocked artery and PCI on the other narrowed arteries (preventive PCI).
The researchers followed the participants up after six weeks and then every year to see who had a further non-fatal or fatal heart attack, or a type of chest pain that indicated narrowed coronary arteries and had not responded to treatment (refractory angina).
They then analysed whether the preventive PCI reduced the risk of these outcomes. They also compared other factors between the two groups, such as age, sex, the presence or absence of diabetes, the location of the blocked coronary artery and the number of narrowed coronary arteries, to see if these factors may have influenced the results.
What were the basic results?
After following up the participants for an average of 23 months, there were 74 cases of further non-fatal heart attack or death from cardiac causes or refractory angina. This included 21 cases in the 234 people in the preventive PCI group and 53 cases in 231 people in the group receiving PCI just for the blocked artery.
This meant that preventive PCI reduced the rate of non-fatal or fatal heart attack or refractory angina from 23 per 100 people in the non-preventive PCI group to 9 per 100 people in the preventive PCI group, which is about 65% lower (hazard ratio 0.35, 95% confidence interval 0.21 to 0.58).
The results were not affected by age, sex, the presence or absence of diabetes, the location of the blocked coronary artery, or the number of narrowed coronary arteries.
Preventive PCI was not possible in 11 patients allocated to this group:
- there was insufficient time for emergency surgery for three patients because other patients needed emergency PCI
- five preventive PCIs failed
- three patients had other complications
The rates of complications related to the surgery (procedure-related stroke, bleeding requiring transfusion or surgery, and contrast-induced nephropathy requiring dialysis) were similar in the two groups.
How did the researchers interpret the results?
The researchers concluded that preventive PCI in other coronary arteries with major narrowing reduces the risk of future cardiovascular events in patients with acute STEMI heart attack and narrowing of multiple coronary arteries who needed PCI for the blocked artery.
This was a well-designed study which showed that over the course of two years, the risk of another non-fatal or fatal heart attack is reduced in heart attack patients who have preventive stents inserted in narrowed arteries at the same time as a procedure to insert stents into the blocked coronary artery that caused their heart attack.
However, an important point to note is that the study results do not apply to all patients who have had a heart attack. The study only looked at the group of patients who had a specific type of heart attack – a STEMI – and needed an emergency stent placement operation.
STEMI shows a different pattern of electrical activity in the heart to other forms of heart attack called non-ST-segment elevation MI or non-STEMI, and the artery causing the heart attack is usually easier to identify.
Further studies would be needed to test the procedure in patients who have had a non-STEMI heart attack. The results also do not apply to patients with more severe coronary artery disease who need a coronary artery bypass graft (CABG), or those who have had this surgery in the past.
The researchers rightly point out that although preventive PCI has been shown to reduce future risk, the study was not able to indicate whether the procedure would be safer or more successful if it was performed after the initial emergency surgery, rather than at the same time.