Pulse Test Could Predict Sudden Death from Heart Attack

A new study suggests a simple and inexpensive test for identifying people who are at greater risk of dying suddenly and unexpectedly from a heart attack.

Researchers from the Hopital Européen Georges Pompidou (Paris, France) examined data from the Paris Prospective Study-1 of 7,746 Frenchmen, aged 42-53, employed by the Paris Civil Service as policemen. The men were given health examinations between 1967-1972, including electrocardiograms (ECGs) and physical examinations. Their resting heart rate was measured, and was measured again a few minutes just before they took part in a bicycle exercise test, while they were sitting on the bike; this was the time when the researchers considered the men to be under mild mental stress in preparation for the exercise test. Their heart rate was also measured during the exercise and afterwards, during the recovery period. During an average 23 years of follow-up there were 1,516 deaths among the participants, including 81 sudden deaths as a result of a heart attack.

The researchers found that the risk of sudden death from a heart attack increased with an increase in heart rate during mild mental stress. After adjusting for confounding factors such as smoking, age, weight, physical exercise, cholesterol levels, and diabetes, the researchers found that men who had the highest increase in heart rate during mild mental stress (increasing by more than 12 beats a minute) had twice the risk of death compared to men who had the lowest increase in heart rate (an increase of less than four beats a minute). Conversely, men who had the highest increase in heart rate during the exercise test itself had less than half the risk of sudden death, compared with the men whose heart rate increased the least during the exercise test.

Further analysis showed that, in fact, there were no sudden deaths from heart attack among the 440 men who increased their heart rate the least during mild mental stress and the most during the exercise test. In addition, the researchers found that the risk of dying suddenly from a heart attack was influenced strongly by genetic predisposition: the risk of sudden death increased nearly three-fold in men whose mothers had died suddenly, and nearly ten-fold when both parents had died suddenly, compared to men with parents who had not died in this way. The study was published in the April 29, 2009, issue of the European Heart Journal.

The researchers believe that the mechanism behind this effect is related to the interaction between the vagus nerves (which are an important part of the autonomic nervous system that controls the body's unconscious functions such as the heart beat) and sympathetic activation (activation of the sympathetic nervous system, which is one half of the autonomic nervous system and is responsible for increasing the heart rate, widening blood vessels in the muscles, and constricting them in the skin and intestines).

"During an ischemic 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 activation can become uncontrolled and then it becomes dangerous," explained lead author Prof. Xavier Jouven, M.D. "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 ischemic episode] the damaging effect of sympathetic activation unopposed by vagal activity."

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Hopital Européen Georges Pompidou