Women may be missing a diagnosis of a potentially deadly heart condition due to guidelines that don't account for natural differences in sex and body size, according to a new study led by UCL researchers.
The research, published in the Journal of the American College of Cardiology and funded by the British Heart Foundation, details how current guidelines might be changed after showing a new personalised approach improves diagnosis accuracy.
When they tested their updated approach in 1,600 patients with clinically diagnosed hypertrophic cardiomyopathy (HCM), the researchers found that it was particularly beneficial for women, increasing identification by 20 percentage points.
The new method takes people's age, sex and size into account to determine whether their heart muscle is dangerously large. As well as preventing people being missed, it could also reduce the number of people mis-diagnosed with HCM.
Around one in 500 people in the UK have HCM, a genetic condition where the muscular wall of the heart becomes thickened, making it harder for the heart to pump blood around the body. It can cause life-threatening problems like abnormal heart rhythms, which can lead to cardiac arrest and sudden death.
Typically, two-thirds of people currently diagnosed with HCM are men, but researchers say women are just as likely to have the condition. There is no single gold standard test used to diagnose HCM. Doctors review a variety of tests and scan results. The most important of these involves measuring the thickness of the wall of the left ventricle, the heart's main pumping chamber.
For 50 years the threshold for diagnosing HCM this way has been 15 millimetres for everyone - if the muscle is thicker than this, a patient is considered likely to have HCM.
Dr Hunain Shiwani (UCL Institute of Cardiovascular Science and St Bartholomew's Hospital), who led the research, said: "It is clear that this threshold, which is based on the results of studies from the 1970s, needs to be reconsidered. Having the same cut off for everyone regardless of age, sex or size completely ignores the fact that heart wall thickness is strongly influenced by these factors.
"Our research provides a long-overdue update, showing that a personalised approach improves the accuracy of diagnosis. Effective treatments for HCM are starting to be used for the first time, making it more important than ever that we can correctly identify those who need them."
The team used an AI tool they developed to analyse MRI heart scans with greater precision and in much less time than a human can. The tool was given 5,000 MRI scans of healthy hearts and measured the thickness of the left ventricle wall in each. From these data, the researchers were able to determine what normal ventricle wall thickness is for people of different ages, sexes, and sizes - measured by body surface area.
This allowed them to set thresholds for abnormal wall thickness, indicating HCM, depending on a person's age, sex and size. The threshold was set higher if the person was older, larger or a man, and lower if they were younger, smaller or a woman.
After testing the accuracy of the new thresholds in the group of HCM patients, the researchers applied them, as well as the current 15 mm cut-off, to a group of over 43,000 participants in the UK Biobank.
For every eight people identified with possible HCM using the current threshold, only one was a woman. People identified were also much taller, heavier and older than the population average.
When the new personalised thresholds were applied instead, the overall number of people identified was lower, suggesting fewer misdiagnoses. Importantly, there was a much more even split between men and women - with women making up 44% of those identified - a much more realistic finding since HCM should affect men and women equally.
By incorporating other key factors, including ethnicity, and ensuring the new thresholds work with echocardiogram scans, which are more commonly used clinically, the team hope to ensure personalised guidelines can be adopted as soon as possible by doctors throughout Europe and America.
Dr Sonya Babu-Narayan, Clinical Director at the British Heart Foundation and clinical cardiologist, said: "Hypertrophic cardiomyopathy is a severe, potentially life-threatening condition, and missed diagnosis means people that might benefit from new and effective treatments could slip through the net. At the same time, a diagnosis is itself a life changing event and we should be making every effort to prevent misdiagnosing people.
"By updating the traditional one-size-fits-all approach, this study redefines abnormal heart wall thickness, a key contributor to the diagnosis of hypertrophic cardiomyopathy. As a result, more women and small individuals were identified who would otherwise be underdiagnosed.
"Whilst other diagnostic factors are also important, this more personalised approach to defining abnormal heart muscle thickness heralds a new era for accurate diagnosis for patients and families affected by hypertrophic cardiomyopathy."
MRI heart scan. Credit: iStock / mr.suphachai praserdumrongchai
