Certain arrhythmias may increase the risk of developing conditions such as a stroke, when the heart quivers it's unable to pump blood effectively, which can cause blood to accumulate and may result in the formation of blood clots. If a clot breaks loose, it can travel and obstruct a brain artery, causing a stroke and can lead to death. It can also lead to a heart failure. Sometimes, controlling the rate of an arrhythmia that's causing heart failure can improve the heart's function.
Attribution: Straight Talk Foundation