Coronary plaques are blockages that cause narrowing and hardening of the heart's blood vessels, often causing angina (chest pain). When plaques rupture, they can lead to blood clot formation which blocks off the blood supply to the heart or brain, resulting in a heart attack or stroke. The reason why plaques rupture is unknown, but if doctors could accurately identify when plaques are about to rupture, patients could be managed and treated accordingly, potentially preventing substantial numbers of heart attacks and other serious coronary events.
A team of researchers led by Dr Nikhil Joshi, at the British Heart Foundation Centre for Cardiovascular Science in Edinburgh, UK, investigated the use of two radioactive tracers, 18F-NaF and 18F-fluorodeoxyglucose (18F-FDG). These simple and relatively inexpensive tracers are injected into patients' veins, and then patients undergo PET-CT, a type of scan that is commonly used in cancer diagnosis and is widely available in the UK. Earlier research has suggested that 18F-NaF and 18F-FDG might be able help doctors to identify characteristic features in the hearts of patients at high risk of serious coronary events, but this is the first systematic investigation into whether they can be used in this way.
Dr Joshi and colleagues investigated 18F-NaF and 18F-FDG in 40 patients who had recently had a heart attack (myocardial infarction), and 40 further patients who had stable angina. In nearly all (37, or 93%) of the heart attack patients, the highest coronary uptake of 18F-NaF (as revealed by the PET-CT scan) was seen in the area of the recently-ruptured plaque which had led to the heart attack. 18F-FDG did not exhibit the same effect, with no significant difference in uptake between 'innocent' and 'culprit' plaques.
In the group of patients with angina, the researchers identified increased uptake of 18F-NaF in the plaques of nearly half (18, or 45%) of the patients. More detailed and invasive intravascular ultrasound imaging confirmed that the areas of increased 18F-NaF uptake were associated in most cases with high-risk features that often lead to rupture and serious coronary events.
According to Dr Joshi, "Until now, there have been no non-invasive imaging techniques available which can identify high-risk and ruptured coronary plaques in patients with heart disease. For the first time, we have shown that this is possible, and given the ability of this new, non-invasive imaging technique to identify high-risk or ruptured coronary plaques, it has the potential to transform how we identify, manage, and treat patients with stable and unstable heart disease. The next step will be to conduct larger-scale trials of 18F-NaF imaging to assess whether increased coronary 18F-NaF activity is ultimately predictive of future adverse effects."*
According to Dr Gregory Thomas, of the Long Beach Memorial, Long Beach, USA, co-author of a linked Comment, "Ischaemic heart disease resulting from rupture of atherosclerotic plaques is a major cause of death worldwide. Precisely why a plaque ruptures remains a mystery, but this landmark article suggests that we are close to being able to detect when rupture is about to occur. Although many questions are still to be answered―including whether the findings apply to women, in whom plaque erosion is a much more common mechanism of myocardial infarction than in men, and whether high ¹⁸F-NaF plaques in the carotid and other cerebrovascular vessels might predict stroke and transient ischaemic attack―Joshi and colleagues and earlier pioneers have identified a new and hopefully fruitful frontier in nuclear cardiology and atherosclerotic coronary imaging."*
NOTES TO EDITORS:
*Quote direct from authors and cannot be found in text of Article / Comment
Journal
The Lancet