Some people are literally bigger-hearted than others, a Kiwi researcher has found.
Despite a person’s heart size being critical in diagnosing heart disease and prescribing drugs, there was international uncertainty about what a normal size was. The study, led by Gillian Whalley of Unitec and published in the American College of Cardiology journal this month, aimed to correct this.
“We knew that heart size was correlated with how much body mass you have, generally bigger people have bigger hearts. And there was quite a lot of evidence emerging that it had nothing to do with fat.”
Although many doctors and medical researchers knew from experience ethnicity played a role, this was entirely anecdotal – a situation Whalley said was potentially dangerous.
“People start telling you stories about potential misdiagnosis or people not placing emphasis on abnormalities because the person is large and muscular, and that’s not safe,” she said.
“When you get heart disease, one of the things that happens is your heart enlarges, by the volume in size and the muscle around the main pumping chamber. And when you’re exposed to things like high blood pressure and diabetes it gets even thicker … It’s a measure of damage to your heart.”
Holding medical knowledge back was the cost of assessing the huge numbers of people needed to get robust data, but Whalley combined the data of 22,000 healthy individuals recruited for 43 different pieces of research.
Now freely available is her formula based on normal heart sizes for European, East Asian, South Asian, African American and African men and women – and each were distinctive enough from each other to even surprise Whalley herself.
She hoped the numbers would be put to immediate use worldwide, especially when it came to prescribing medicines that can cause heart damage, like breast and gastric cancer drug Herceptin.
“Some treatments you can only give when the heart is a certain size or a certain function,” she said. “The threshold [for not prescribing Herceptin] seemed to work for European women … but was low for an East Asian woman.”
After the study, there still remained a distinct lack of good data available for Maori and Pacific Islanders, Whalley said. A current Health Research Council-funded study will allow her to test 900 New Zealanders to find normal ranges for heart sizes for both ethnic groups.