Cardiac Arrhythmias – abnormal electricity activity in the heart, such as irregular heartbeat. The heart may ad additional beats or the heart may skip beats; however not all arrhythmias are life threatening while other arrhythmias can cause cardiac arrest or even death.

People will sometimes feel a real strong heartbeat or feel their heart skip a beat. Actually this is normal.

Sinus arrhythmia is a condition where a normality of your heart beating faster or slowing down that can occur with breathing in and out. You usually see this in children and it does decrease as they get older... In doing meditation exercises and deep breathing is involved you may also see this in this type of exercise. 
The most common arrhythmia is a palpitation. This type of arrhythmia is more aggravating that dangerous. It is more noticeable in adults and generally happens after doing something strenuous.

Some arrhythmias do not have symptoms. However, some asymptomatic arrhythmias            have been associated with adverse results like a higher risk of stroke, heart attack or heart failure, embolisation and even death. This is due to a higher risk of blood clotting in the heart muscle and a higher risk of a weaker heartbeat that does not allow enough blood to get to the heart muscle.