The palpitation (arrhythmia) is a result of over fatigue, nervous tension, smoking, defalcation of alcohol or coffee and many cardiac diseases. In a case of increasing of the cardiac frequency to more of 100 beats In a minute (adults) and constant correct cardiac rhythm we say that is a sinus tachycardia. When the cardiac rhythm is below 60 beats /minute, we say that there is a sinus bradicardia. The concept o sinus arrhythmia means the changes from slow to fast cardiac rhythm and reverse.