Cannabis consumption in a systemic form such as smoking has been associated with heart palpitations and fast heart rhythms. Smoked cannabis should likely be avoided if you have atrial fibrillation for this reason. Some studies suggest the negative cardiovascular effects of smoked cannabis are related to THC. There has not been enough research on CBD extract products to determine if they are safe for those with atrial fibrillation. There have not been any studies associating localized forms of cannabis with harmful heart rhythms. It is likely safe, from a cardiovascular standpoint, to use topical cannabis infused patches, balms, salves, massage oils, etc. in limited quantities for localized pain control.
You should discuss your particular case closely with your cardiologist and cannabis-recommending physician before use.
A growing number of case reports have demonstrated an association between smoked cannabis consumption and adverse cardiacvascular effects. This includes cardiac dysrythmia including atrial fibrillation and increased cardiac work, which can precipitate cardiac chest pain and even heart attacks. Smoked cannabis has also been associated with low blood pressure upon standing which can increase the risk of fainting. These effects are likely mediated by an effect in which THC triggers the sympathetic nervous system in intermittent users. Chronic users appear to develop tolerance to triggering of the sympathetic nervous system; however, they may suffer from microscopic damage to the arteries that supply the heart.
Interestingly, a recent large case-control study from Denmark demonstrated that NSAID type medications (Ibuprofen/Advil and Naproxen/Aleve etc) are also associated with increased incidence of atrial fibrillation. This is in addition to prior literature that shows NSAIDs can aggravate hypertension. A series of two studies published in 2015 additionally show that opiates are likely associated with a higher risk of heart attack and atrial fibrillation. Unfortunately, there is no ideal option for chronic pain control in the setting of atrial fibrillation. Depending on your reason for using cannabis products there may be safe options available.
Reference: Korantzopoulos P. Atrial fibrillation and Marijuana Smoking. Int J Clin Pract. 2008;62(2):308-313 Jones RT. Cardiovascular system effects of marijuana. J Clin Pharmacol 2002; 42 (11 Suppl.): 58S-63. Sidney S. Cardiovascular consequences of marijuana use. J Clin Pharmacol 2002; 42 (11 Suppl.): 64S-70. Rezkalla SH, Sharma P, Kloner RA. Coronary no-flow and ventricular tachycardia associated with habitual marijuana use. Ann Emerg Med 2003; 42: 365-9