What could cause stomach pain and an irregular heart beat?

Irregular heart beat. Pain sensors on the heart are often inaccurate. Occasionally heart irritation can tell your brain that you're experiencing pain in the abdomen, or even the neck, back, arms, or part of the chest away from the heart itself. Also, similar nerves that feed heart regulation, also send signals to the abdomen and stomach. Get a thorough history & physical examination with your doctor or cardiologist.