Stress and heart attacks: the brain is the key player.


How might stress lead to a heart attack? One way might be through an unhealthy lifestyle and poor dietary choices. There is another way that is more direct and possibly even more important.

The heart is a little like a national army of a peaceful country. During peacetime, it carries out its daily practice at a relatively slow and gentle pace. The second the country is at war, the army is expected to rapidly rise to the challenge of defending the country, working at maximal intensity.

If you are asleep one moment and attacked by a lion the next, your heart should be able to rapidly adapt to the change in demand and go from beating slowly to beating rapidly. This feature of adaptability is known as ‘Heart Rate Variability’ or HRV.

This adaptability is conferred to the heart largely via input from the prefrontal cortex of the brain. High adaptability is suggestive of a strong prefrontal cortex input. The adaptability is the net result of both the ‘tense’ signal and the ‘relaxation’ signal coming from the brain. (The sympathetic and parasympathetic signal input ratio). The prefrontal cortex (logical brain) increases the adaptability of the heart by enhancing the relaxation signal. Stress enhances the tense signal and chronic stress leads to detrimental changes in the prefrontal cortex. As a result, stress reduces this adaptability. For good adaptability, we want a healthy prefrontal cortex.

How does poor adaptability lead to a heart attack? If the heart suddenly has to work at maximal intensity and it is not very adaptable, it will struggle to deliver. This ‘struggle’ may result in abnormal heart rhythms and a diminished oxygen supply to parts of the body, the brain and muscles of the heart. This 'struggle' can result in a heart attack.

It is the signal coming down from the brain to the heart that affects the heart's resistance to a heart attack. The region of the brain from where this signal originates also plays a role in rational thinking, concentration and problem solving. The prefrontal cortex is the part of the brain we use to 'think'. It also, amazingly, protects the heart!

The fascinating feature of this route is that stress is not increasing the risk of a heart attack through its direct effect on the heart or through its direct effect on blood vessels, cholesterol, etc. Here, stress is increasing the risk of a heart attack through its effects on the brain.

Here, we come to another extraordinary finding. We all know that fish is good for our hearts. Most of us think that fish (and the omega 3 within fish) brings benefits through its effects on cholesterol profile, preventing atherosclerosis, etc. These things do play an important role. However, fish might be bringing benefits to our heart through a completely different pathway, one that has nothing to do with cholesterol or plaque formation.

That pathway is through the prefrontal cortex. Recent studies suggest that a diet containing fatty fish(or omega 3 fatty acids) may act on the prefrontal cortex to raise the adaptability of the heart. This effect is directly opposite to the effect of stress. Peculiar as it may sound, fatty fish may confer its protection from heart attacks, not through its direct effects on the cardiovascular system, but through its effects on the brain!

We know that parts of the prefrontal cortex can ‘shrink’ in depression and through chronic stress and patients with depression have a higher risk of cardiac events. We think this is because of the brain’s influence on the adaptability of the heart.

If you want to take steps towards improving your prefrontal cortex activity and overall state of calmness and possibly protect yourself from a heart attack at the same time, then eat more fatty fish...!

References

Thayer JF, Lane RD (2009) Claude Bernard and the heart-brain connection: further elaboration of a model of neurovisceral integration. Neurosci Biobehav R 33: 81–88.

Thayer JF, Ahs F, Fredrikson M, Sollers JJ, Wager TD (2012) A meta-analysis of heart rate variability and neuroimaging studies: implications for heart rate variability as a marker of stress and health. Neurosci Biobehav R 36: 747–756.

Hansen AL, Dahl L, Bakke L, Frøyland L, Thayer JF (2010) Fish consumption and heart rate variability. J Psychophysiol 24: 41–47.

Villa B, Calabresi L, Chiesa G, Rise P, Galli C, et al. (2002) Omega-3 fatty acid ethyl esters increase heart rate variability in patients with coronary disease. Pharmacol Res 45: 475.

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