Boston, MA - For acute MI patients wondering if the next heart attack is the big one, maybe smoking marijuana relieves some of that stress and anxiety, but it isn't helping their chances of living any longer. New preliminary research suggests that marijuana use in acute MI survivors is associated with a threefold higher risk of mortality after infarction [1].

"For all the thousands and thousands of studies we've done on people who have had heart attacks, virtually nobody asks them about their marijuana use," said lead investigator Dr Kenneth Mukamal (Beth Israel Deaconess Medical Center, Boston, MA). "There is an extraordinary lack of data for exposure to something as common as marijuana. Every single study asks people if they smoke, if they drink alcohol, but we never ask about marijuana."

Speaking to heartwire about the study, which is published in the March 2008 issue of the American Heart Journal, Mukamal said that previous research has shown marijuana to have cardiovascular effects that might pose a risk, particularly to older adults and those with coronary disease, such as an increase in resting heart rate. Other studies have shown transient increases in MI risk, possibly due to carbon-monoxide exposure and an increase in heart rate, said Mukamal.

Oral cannabinoid therapy, however, has also been shown to stop atherosclerosis in a mouse model and to play other immunologic roles. With these differing effects of marijuana in mind, the group set out to study the relation between marijuana use and coronary heart disease in 1913 adults hospitalized with MI between 1989 and 1994. Of these, 52 patients reported marijuana use during the previous year, and 317 died during a mean follow-up of 3.8 years.

In an adjusted analysis, marijuana use was associated with a three times greater risk of all-cause, cardiovascular, and noncardiovascular death following acute MI, and there was a greater risk among those who smoked more frequently.

The investigators note that the study was small and they did not have a sufficient number of cases to evaluate cardiovascular and noncardiovascular deaths with accuracy. However, Mukamal told heartwire that they observed a particularly greater risk of noncardiovascular mortality associated with use among acute MI patients, which makes sense if patients are smoking to ease pain and discomfort from AIDS or other terminal illnesses.

The risk, however, was also doubled for cardiovascular mortality and, although not significantly, for cardiovascular disease. "We shouldn't see the increase in cardiovascular mortality if people are smoking marijuana only because they are dying of other things," he said. "This provides a hint that there is a true cardiovascular effect of marijuana here."

Mukamal, however, cautioned that the findings are exploratory and that further research is needed to identify the risks with precision.