King's College London

Left main coronary artery (LMCA) disease can lead to what’s known as a ‘widowmaker’ heart attack, so-called because of the low odds of survival. But this can be avoided if someone is given a stent to open up the narrowed LMCA, or heart bypass surgery.

However, research funded by the British Heart Foundation and published in the journal Circulation: Cardiovascular Interventions reveals how doctors may be missing up to 28 per cent of people with LMCA disease because current clinical guidelines on how to interpret test results may need to be updated.

When testing for LMCA disease, doctors typically look for the same blood pressure reduction in both branches of the left main coronary artery. But the new study results overturn this approach – by showing one branch often has lower blood pressure than the other.

This knowledge could in future help doctors better judge whether people have LMCA disease and could benefit from urgent treatment.

He added: “That means doctors can correctly diagnose LMCA disease, and consider a stent or bypass surgery, or carry out further investigations of the LMCA, rather than ignoring potentially important disease in a major artery of the heart.”

The left main coronary artery is the heart’s largest and most critical artery, supplying most of the heart muscle with blood. If the artery becomes substantially narrowed - as seen in people with LMCA disease - this can result in a major heart attack.

Doctors typically diagnose LMCA disease using a thin wire inserted through the wrist and guided to the heart. They are searching for reduced blood pressure in the two branches leading from the LMCA, which indicate it has been significantly narrowed by a build-up of cholesterol.

But doctors follow guidelines which suggest a blood pressure ‘score’ below 0.8 is significant and requires immediate treatment.

So, when one branch of the LMCA produces a ‘safer’ score above 0.8 - even if the other does not - doctors following the guidance might rule out LMCA disease.

The researchers say the new findings suggest guidelines should perhaps be updated, so that doctors do not look for the same blood pressure reduction above 0.8 in both branches - the left anterior descending (LAD) artery and the left circumflex artery.

The study involved 80 people undergoing tests on their coronary arteries. All of them had apparently conflicting blood pressure results from the two branches of the LMCA, including the 47 who had a diagnosis of LMCA disease.

The LAD may have lower blood pressure than the LCx, as seen in the study, partly because it supplies more of the heart muscle with blood than the other artery. As a result, it could have greater capacity to maintain its blood supply.

Ruling out LMCA disease because of a normal blood pressure reading in someone’s left circumflex artery and an apparently abnormal lower one in the LAD - which researchers say doctors do routinely - would result in up to 28 per cent of cases being missed, the study calculates.

However, the researchers highlight that more evidence is needed as the study was only conducted in 80 patients. In the meantime, researchers urge doctors to think carefully and conduct further in-depth investigations of blood vessels when faced with conflicting test results.

“This small study suggests that apparently conflicting results in both branches of this artery may be completely normal. More research is needed to confirm the results in more patients, but this may help doctors to more accurately interpret their results in future.”