Vivid scans reveal blood flows differently in men's and women's hearts

Blood flows differently through the hearts of men and women, according to new research.

Scans have identified dramatic variations in its movement through the left ventricle – the organ’s main pumping chamber.

Men’s hearts have to work harder and exert more energy there in order to move blood through the organ, whereas women’s blood swirled more violently and the ventricle’s wall showed more signs of strain – patterns scientist think are linked. 

The finding could shed light on gender inequalities in cardiovascular disease care that are costing lives, the University of Wisconsin, Madison authors believe.  

Heart disease is the leading of death for American men and women alike, but the exact types of cardiac conditions affect each group differently. 

And from their observations, doctors believe these differences are explicable not just by the differences in the size and shape of male and female human hearts, but in their structural mechanics, and how blood moves through them.  

Kinetic energy, for instance, the force spent during contraction and filling of the muscle, was significantly higher in the left ventricles of men.

Vorticity, on the other hand, a measure of regions of rotating flow that form during different points of the cardiac cycle, was greater in women.

There was also more strain – an indicator of left ventricular function, reports Radiology: Cardiothoracic Imaging.

The study used a sophisticated technique called 4D flow MRI (magnetic resonance imaging).

It offered striking visuals of blood flow in the heart and vessels of 20 men and 19 women.

When these were compared with cardiac function there were significant differences between the sexes.

The results could be used to help create quantitative standards that adjust for gender to provide improved assessment of heart performance.

Differences in the hearts of men and women have long been known. Women’s are smaller in size and beat faster than men’s, on average.

But much less is known about the way that blood flows through the hearts of men and women – and how that relates to cardiac health.

Lead author Dr David Rutkowski, of the University of Wisconsin, Madison, said: ‘Using the MRI data, we found differences in how the heart contracts in men and women.

‘There was greater strain in the left ventricle wall of women and a higher vorticity in the blood volume.We hypothesize these two things are related.’

The study and the methods it employed have a number of potential applications,he said.

These include improved understanding of why the hearts of men and women respond differently to physiological stresses and disease.

The results also add information that might one day improve clinical assessment of the heart.

Dr Rutkowski said: ‘These blood flow metrics would be useful as reference standards because they are derived from healthy people, so we could use these to compare with someone who is unhealthy.’

The ability of 4D flow MRI to provide numbers for various blood flow parameters is especially important.

He said: ‘There’s been a push in the last couple of decades to make MRI more quantitative.

‘So instead of looking at something and saying it looks normal or different, we can get a number to go with that visual information.’

The researchers are currently using 4D flow MRI to look at patients with atrial fibrillation (AF) – an irregular heartbeat that can lead to serious complications.

It is the most common heart rhythm disturbance, affecting around 1 million people in the UK.

Mainly diagnosed in older people, it blights the lives of seven percent of over 65s, causing them to get out of breath performing the lightest of tasks.Men are more prone than women.

The hope is MRI will help detect patterns and relationships in the atria, the upper chambers of the heart, similar to those found in the ventricles.

Dr Rutkowski added: ‘The goal of our work in general is to move from qualitative MRI to more quantitative MRI.

‘Getting blood flow and velocity information is just one more metric that is being developed to make MRI more quantitative.’

In September a British Heart Foundation report found more than 8,000 women in England and Wales died unnecessarily after a heart attack during the last decade.Experts say there are inequalities in diagnosis, treatment and aftercare.

Some commonly held myths – such as heart disease and heart attacks only affecting men – meant women were unaware of their risk, and slow to seek medical help.

There is also a misperception that men and women experience completely different heart attack symptoms.

But studies suggest that although symptoms can vary from person to person, chest pain is the most common symptom in both men and women.

Cardiovascular disease is the UK’s number one killer, claiming 170,000 lives a year.It affects around seven million Britons, and is responsible for one in four premature deaths.