Researchers and scientists are continuously searching for ways to predict who is most likely to have a heart attack and who isn’t. French researchers report this could be as easy as measuring a person’s pulse rate three times.
The study looked at 7,746 French male civil servants. Their heart rates (measured by their pulse rates) were measured at rest (baseline), right before physical exercise (mild mental stress in anticipation of the exercise) and during exercise.
The results of the study show that “men whose heart rate increased the most during mild mental stress just before an exercise test had twice the risk of dying of a sudden heart attack in later life than men whose heart rate did not increase as much.”
The highest increase in heart rate during the mild mental stress was at least 12 beats a minute, the lowest, less than four beats per minute. The study participants who exhibited the highest increase in heart rate had twice the risk of sudden death due to a cardiac event compared to men who had the lowest increase.
However, those participants who had the highest increase in heart rate during the actual physical exercise had less 50% the risk of death compared with the men whose heart rate increased the least. The highest incidence of death due to a cardiac event occurred among the participants who increased their heart rate the most during mild mental stress and the least during exercise. There were none reported among those whose heart rate increased the least during mild mental stress and the most during the exercise test.
The authors think that the mechanism behind this effect lies with interaction between the autonomic (ANS) and sympathetic nervous systems (SNS). Vagus nerves are an important part of the ANS which controls the body’s autonomic functions including the heart beat. The SNS is responsible for increasing the heart rate and the dilation of blood vessels in the voluntary muscles and constriction of blood vessels in the skin and intestines during physical exercise.
According to lead researcher Professor Xavier Jouven
“There is a balance between the accelerator (sympathetic activation) and the brake (vagal activation). If vagal withdrawal occurs it is like releasing the brake. During an ischaemic episode, when blood flow to the heart is reduced, sympathetic activation occurs to counteract it. However, if there is no protection by the vagal tone (the brake), the activation can become uncontrolled and then it becomes dangerous. Our underlying assumption, which this study appears to have proved correct, is that the faster the vagal withdrawal in response to mental stress, the greater will be – during an ischaemic episode – the damaging effect of sympathetic activation unopposed by vagal activity.”
Heart attacks or myocardial infarctions are a major health problem in many developing countries. The US alone reports between 200,000 to 400,000 deaths due to heart attack each year. In 27 European countries, the mortality count is 486,000.
This method of predicting who is susceptible and who is not is easy, cheap, and non-invasive. However, it has only been tested for men. It still remains to be seen whether the same pulse rate readings can be a predictor of heart attack in women.