Yes, caffeine can stimulate your heart into arrythmias. The diagnosis of arrythmias can be made by wearing a 24-hour Holter Monitor, which is a portable device that records your heat beats for 24 hours. There are many types of arrythmias and yours has to be identified, the majoriy are benign but some could be dangerous. There are many types of heart murmors too, some are harmless but others may indicate some type of heart disease. You certainly need to visit a cardiologist for a complete check up.