Climate change: How worsening heatwaves could hurt your heart in NZ

In a new project, supported with a Marsden Fund grant, University of Auckland research fellow Dr Amelia Power and colleagues are examining how the powerhouses of our heart cells are likely to fare in extra-hot weather.

Mitochondria are responsible for converting the food we eat into usable energy, in the form of a molecule called adenosine triphosphate, or ATP.

Power said the heart happened to be a particularly energy-hungry organ, and its muscle cells relied heavily on mitochondria for ATP production.

“Mitochondria make up about 30% of the volume of heart muscle cells and are absolutely crucial for maintaining the heart’s constant contraction and relaxation.”

Earlier work by Power and others has suggested that, at temperatures between 40-43C, mitochondria in healthy hearts can start to “uncouple” – continuing to consume oxygen but no longer producing ATP at the same rate.

That could lead to the heart losing its main energy source, with potentially dire consequences.

“If the heart can’t maintain its ATP supply, it’s going to struggle to pump blood effectively,” she said.

“This could lead to impaired contractility, irregular heartbeats, and ultimately, heart failure.”

She hypothesised that mitochondria in diseased hearts may have disrupted membranes that become “leakier” at lower temperatures compared to healthy hearts.

This could further impair the heart’s ability to maintain contractility and keep beating efficiently.

To test this, she and colleagues will use specialised techniques to measure heart mitochondria functions in real-time from heart tissue biopsies, at both normal and increasing temperatures.

They also plan to test a drug called elamipretide, which can stabilise a key mitochondrial membrane lipid called cardiolipin.

She said that might ultimately improve the temperature tolerance of mitochondria in diseased hearts, helping them maintain ATP output even as the mercury rises.

“It might be something that could be given to people who are experiencing heat stress, or are just having a high fever, so they can keep up with their ATP supply,” Power said.

“Going forward, understanding how temperature affects people’s health is going to be increasingly important – particularly among people with heart disease that might be more susceptible.”

NZ lags behind in heatwave planning – study

Power’s project comes as separate new review has set out how rising temperatures pose a growing health risk to New Zealand’s most vulnerable populations – underscoring an urgent need for stronger adaptation measures.

The just published review, by a team of researchers from Malaysia and New Zealand, noted the northern half of the North Island already experienced temperatures over 25C and higher humidity for an average 45 to 55 days each year.

As climate change continued to increase ambient temperatures, much of northern New Zealand would see extreme heat-related risks more rapidly.

Yet the researchers found our preparedness for this warmer future lagged behind other temperate regions like southern Australia, Ireland and parts of the US, where more comprehensive measures were in place.

Measures here could include encouraging people to adjust daily routines to avoid peak heat exposure, using cooling technologies, or enhancing social support networks, they said.

While the researchers singled out those likely to be hit hardest – including the elderly, children, pregnant women, and those with health conditions or living in deprivation – they said there was pressing need to understand more.

“Identifying these at-risk groups further stresses the urgency of targeted strategies to protect those most vulnerable and mitigate the effects of rising temperatures.”

MetService has recently begun issuing heat alerts for nearly 50 centres, with specific conditions set for each location.

When triggered, an alert banner will appear on MetService’s website and app.

Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.

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