A large and long term study of Frenchmen suggests there may be a simple way to establish if apparently healthy people have an elevated risk of sudden cardiac death by looking at how their heart responds under conditions of mild mental stress and during peak exercise.

The study was the work of Dr Xavier Jouven, a cardiologist at the European Georges Pompidou Hospital in Paris, and colleagues, and is published in the 2 July advance access issue of the European Heart Journal.

Sudden cardiac death is a major health problem and accounts for betwee 200,000 and 400,000 deaths every year in the US, wrote the authors.

They explained that the most common cause in adults is when fast heart rhythm (ventricular tachycardia) or erratic or uncoordinated contraction of muscle in a heart chamber (ventricular fibrillation) coincides with a loss of blood flow in the heart (ischaemic cardiac event).

Fewer than 5 per cent of people who experience this combination of heart events are successfully rescucitated, which is why finding out who might be at risk within the general population is a major public health challenge.

Jouven and colleagues had a hunch that people who respond to mild mental stress in preparation for an exercise test with the largest heart rate increases might be at highest risk of sudden cardiac arrest.

For this study they used data on nearly 8,000 male French civil servants who took part in the Paris Prospective Study I and were medically examined between 1967 and 1972.

The men underwent physical exams, gave blood samples, had electrocardiograms, and answered interview questions. They also had their resting heart rate measured, which was taken by measuring radial pulse for 1 minute after lying down for 5 minutes.

Data taken on the participants over a follow up period of 23 years allowed the researchers to compare heart rate changes between rest and mild mental stress (while the participants prepared for an exercise test) between those who experienced sudden cardiac death (81 participants), those who died from a non-sudden coronary event (129 participants), and those who died from any cause (1,306 participants).

In their analysis, Jouven and colleagues found that: The average heart rate increase during mild mental stress was 8.9 ± 10.8 beats per minute (bpm).
Risk of sudden cardiac death went up progressively with increase in heart rate during mental stress.
The 33 per cent of participants with the highest heart increase were more than twice as likely to suffer sudden cardiac death as the 33 per cent with the lowest heart rate increase (relative risk 2.09).
This relationship did not exist for non-sudden coronary deaths. The authors concluded that:

"An important heart rate increase produced by a mild mental stress predicts long-term risk for sudden cardiac death."

They suggested that a simple procedure that measures heart rate changes before an exercise test could be a valuable way to assess risk of sudden cardiac death in the general population.

"Excessive heart rate increase during mild mental stress in preparation for exercise predicts sudden death in the general population."
Xavier Jouven , Peter J. Schwartz , Sylvie Escolano , Céline Straczek , Muriel Tafflet , Michel Desnos , Jean Philippe Empana , and Pierre Ducimetière.
European Heart Journal, Advance Access published on July 2, 2009.
DOI 10.1093/eurheartj/ehp160
Eur Heart J 30: 1703-1710.

: Catharine Paddock, PhD

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