According to French researchers men whose heart rate increased the most in the period prior to an exercise test had double the risk of sudden cardiac death (SCD) in later life than those whose heart rate did not increase to the same extent. They further explained that slight mental stress prior to the exercise is usually associated with an increase in heart rate by just a few beats per minute (bpm). They also noted that previous association was between SCD and heart-rate which increased during physical stress and that an insufficient increase in heart rate during strenuous exercise is predictive of SCD, but this is first time an association of this kind has been seen. They concluded that taking a pulse during this time period could provide a simple tool for identifying people who may be at increased risk of SCD. The researchers analyzed data from 7746 French policemen participating in the Paris Prospective Study, who were aged 42 to 53. The men were examined between 1967 and 1972 and given ECGs and physical examinations, and their resting heart rate was measured. Heart rate was measured again in the few minutes before they took an exercise stress test, during the test, and afterward during the recovery period. Complete data on the exercise stress test were available for 6456 men; 388 of these were excluded from the analysis because of an ischemic response to exercise or an impaired chronotropic response. During an average 23 years of follow-up, there were 1516 deaths including 81 sudden cardiac deaths and 129 non–sudden cardiac deaths and 355 men were lost to follow-up. The risk of SCD rose progressively with heart-rate increase during the mild-mental-stress period before the exercise test (p for trend=0.02). After multifactorial adjustment, men who had the highest increase in heart rate during this period (an increase of more than 12 bpm) had twice the risk of SCD of those who had the lowest increase in heart rate (increase of less than 4 bpm), a relative risk of 2.09. No such relationship was observed for non–sudden cardiac death. There were no SCDs among the 440 men who increased their heart rate the least during this period and the most during the exercise test. The highest proportion of SCDs was among the 471 men who increased their heart rate the most during mild mental stress and the least during exercise. Jouven et al noted that the findings showed different neural responses to different types of stress give a differential impact on arrhythmic risk. He explained that the 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. Jouven and his team also found that the risk of SCD was influenced strongly by genetic predisposition. It increased nearly threefold in men whose mothers had died suddenly and nearly 10-fold when both parents had died suddenly when compared with those whose parents had not died in this way. The researchers reported that this will raise the intriguing possibility of a genetic predisposition to the autonomic responses associated with higher or lower risk for SCD. Jouven noted that the study shows that a person's pulse can be used as a prognostic marker. The results will support toward a better understanding of the mechanisms of cardiac death. He concluded that people who showed a higher heart-rate increase with mild mental stress could be considered for additional investigations and for tailored preventive strategies, aimed in the first place at reducing the probability of heart disease. The study was conducted on men only so it is possible that findings in women may be different.