By Dennis Thompson
Marijuana users who have suffered a heart attack had about the same risk as nonusers of a rapid and irregular rhythm in the lower chambers of the heart, known as the ventricles, the researchers found.
"We found no difference in the two populations," said senior researcher Dr. Christine Tompkins, a cardiologist with the University of Colorado School of Medicine.
Further, marijuana users appeared to have lower rates of atrial fibrillation, an irregular rhythm in the upper chambers of the heart (the atria).
Don't feel free to get baked just yet, though. Both the researchers and a heart expert stressed that the jury is still out on exactly what the heart risks of smoking pot might be.
In fact, earlier research in the same group of patients found that marijuana use appears to increase the chances of having an earlier heart attack, Tompkins added.
The average age of a first heart attack was about 57 for the straight-laced, but 47 for cannabis users, Tompkins said.
"At this point, I have to say we don't know the full cardiac effects of marijuana use," Tompkins said. "We need to do additional studies."
Colorado was one of the first states in the nation to legalize recreational marijuana, in 2012. At this point, a total of nine states have approved recreational pot use.
Given the wave of legalization, Tompkins and her colleagues decided this was the perfect time to assess the heart effects of marijuana use.
"We felt an obligation to look at the cardiac effects of cannabis use," Tompkins said. "We still don't know the long-term impact it has on one's heart health."
There's strong evidence that weed has become more popular among people in late middle age and senior citizens. Federal data shows a 455 percent increase in marijuana use among U.S. adults aged 55 to 64 and a 333 percent jump in those aged 65 and older between 2002 and 2014.
The researchers reviewed medical records for nearly 1.3 million patients treated for heart attack between 1994 and 2013. Pot users were identified because they either admitted to use or had a positive toxicology screen for marijuana, Tompkins said.
There was no difference in risk for either an irregular or rapid heart rhythm in the ventricles between pot users and nonusers, and there was a decreased risk for atrial fibrillation in users, researchers found.
The findings were to be presented Thursday at the Heart Rhythm Society's annual meeting, in Boston. Such research is considered preliminary until it is published in a peer-reviewed journal.
Animal studies have found cannabinoid receptors reduce the risk of abnormal heart rhythm, Tompkins said. Pot also has been shown to alter the autonomic nervous system, which oversees the stability of heart rhythm.
On the other hand, the chemicals in marijuana also have been shown to promote clotting and cause blood vessels to constrict in some patients, two factors that increase heart attack risk, Tompkins said.
And other studies also have linked pot use to higher blood pressure and increased heart rate, said Dr. Mark Estes, director of the New England Cardiac Arrhythmia Center at Tufts University Medical Center in Boston.
"The information on the cardiovascular effects of marijuana is very, very limited, but the best evidence available would indicate there's the potential for harm," Estes said. "I don't think people should be reassured by any means that smoking marijuana is safe."