There is no clinical term for sudden heart rhythm, so I guess it should be sinus rhythm. Sinus rhythm is a heart rhythm in which the sinus node issues impulses that control the heart and cause it to contract. Sinus rhythm is the normal heart rhythm of the human body. It is usually between 60-100 beats per minute under normal conditions. If the heart rate level is below 60 beats, it is considered sinus bradycardia, while more than 100 beats is considered sinus tachycardia. Normally, everyone should be in sinus rhythm, and as long as they are within the above range, there is no problem. Sinus rhythm is a normal phenomenon that does not require treatment. Any rhythm that is formed by the sinus node issuing impulses that control the heart is called sinus rhythm.