Many conditions can be potential irritants to the potential ectopic pacemakers of the heart, such as drugs, stimulants or hypoxia. In such irritable state certain focus may start to fire impulses regardless of the work of the dominant pacemaker. Those impulses are going to depolarise certain parts of the heart and these parts will contract, but that actually represents an extracontraction of the heart, because at the same time the SA Node fires impulses regularly. These exctracontractions are called the premature beats, because they appear earlier than expected. Now, in situations where we have a highly irritable focus, this focus can start to release more impulses than one and thus multiple extrasystoles or multiple premature beats occur. These extrasystoles may occur one after the other or be interrupted by normal beats generated in the SA node. For all of them we have characteristic patterns named bigeminy, trigeminy, quadrigeminy, couplets, triplets and etc. To learn more about this topic go to my YouTube channel linked in the bio. #ecg #medicine #medical #medicalstudent #medstudent #doctor #nurse #medico