"Sudden coital death" -- a fatal heart attack during sex -- is more common when a man is with his mistress than when he's with his wife, a new study has found.

Researchers at the University of Florence reviewed the available medical literature on the prevalence of infidelity and its effects.

"Unfaithfulness in men seems to be associated with a higher risk of major cardiovascular events," the researchers found.

Their analysis, which appeared in the Journal of Sexual Medicine, showed that cardiac arrest, both fatal and non-fatal, was relatively rare when a man was having sex with his wife at home, and more frequent when he was messing around with a paramour.

Some may call it karma, but the researchers suggest a guilty conscience, the demands of satisfying a younger woman and the strain of keeping the secret as possible explanations, as reported in the Telegraph.

"Several interpersonal, sexual, and biological factors are associated with having extramarital affairs," the researchers said.

They also found that unfaithful men display "better sexual functioning" and "larger testis volume."