The findings of a nationwide heart research project have been presented by New Zealand cardiologist, Professor Ralph Stewart, in Paris this morning (2.40am NZT). The controversial findings could change the way we treat heart attack patients here and overseas.
The Heart Foundation study was the largest randomised trial undertaken in New Zealand and included 40,000 patients, from Northland to Southland, over two years.
Oxygen has been given to patients suffering a heart attack for more than 50 years, but so far there has been no evidence if this is helping or even harming the heart.
“It’s been a controversial subject. Some studies have suggested giving oxygen to people with normal oxygen blood levels could be harmful. On the other hand some patients having a heart attack have reduced oxygen levels in the blood and it is possible correcting this is beneficial. So this study was designed to determine whether the balance of routine oxygen was towards benefit or harm,” says Professor Stewart.
A heart attack is caused by a sudden blockage of an artery carrying blood to the heart, resulting in a lack of oxygen to keep the heart muscle alive, so oxygen therapy has been routinely given for many years for suspected benefit. However in recent years some small trials have suggested harm with oxygen therapy causing constriction to the arteries and worsening blood flow to heart muscle at risk,.
In the New Zealand study people suspected of, or suffering from a heart attack, were given either high flow oxygen routinely or oxygen only if their own levels were low.
“We found that high flow oxygen therapy neither improved or damaged the heart and as such believe giving oxygen routinely is not needed for most patients.
It’s really important to identify what works and what doesn’t. This is why these types of trials are so important. Results can also be very humbling, as they don’t always give the answer you expect.”
Associate Professor Gerry Devlin, Medical Director of the Heart Foundation and a Co-investigator of the study, highlights the real world design with involvement of all healthcare professionals a patient with a suspected heart attack encounters as a strength of the study.
The randomised trial was undertaken by St John and Wellington Free Ambulance first responders nationally, the National Cardiac and Emergency Medical Clinic Networks and hospitals all around New Zealand .
“The Heart Foundation is delighted to have been able to support this important work and are excited by the potential of the trial network Professor Stewart has established which can hopefully continue to work together to improve the heart health of New Zealanders,” says Devlin.
Created on: 5 September 2019