under contract means there is an offer on it already and the buyer and seller are negotiating back and forth to come to an agreement. if ya need any more help just e-mail me. Lori lspalletta Â· 1 decade ago
Premature atrial complexes are caused by abnormal electrical impulses transmitted by the atria (either of the upper chambers of the heart). The abnormal electrical impulses cause contractions of the upper chamber of the heart earlier than expected. Such premature beats are generally harmless. slide 1 of 7.
Ventricular Arrhythmias. Premature ventricular contractions (PVCs) are the most common cause of irregular heart rhythms. The heartbeat is created by an electrical signal that originates in an area of specialized cells in the heartâs upper right chamber, the right atrium. premature ventricular contraction (PVC) is a too-early heartbeat that originates in the ventricles and disrupts the heartâs normal rhythm.