Although nicotine replacement therapy via patch or gum was linked to a risk of a rapid or irregular heartbeat, the researchers said the heart symptoms were minor and temporary.

"These more minor risks are well known to clinicians and usually pass with time," Mills said. "They occur most often when people are taking nicotine replacement therapy and smoking at the same time, which is a bad idea."

Previous research found that combination nicotine replacement therapy, wearing a patch and using nicotine gum when there is the urge to smoke, may be more effective but lead to more side effects than the gum or patch alone.

But Mills said most patients in the analysis were relatively healthy, so the results may not be true for everyone.

"It's possible that the risk factors might be different in people with multiple diseases," Mills said. "Patients should discuss with their healthcare provider any potential risk factors that they may have developed from their smoking history. For patients who have chronic lung disease or other associated cardiovascular risks, clinicians should determine which smoking cessation aid to use by their risk profiles."