Please consider adding the term
ventricular premature beat
def - an extra heartbeat resulting from abnormal electrical activation originating in the ventricles before a normal heartbeat would occur
source - Merck Manual Online Medical Dictionary
syn - ventricular ectopic beat, premature ventricular contraction
in J:151367 and existing annotations under irregular heartbeat and abnormal heartbeat
child of - irregular heartbeat
Also, sinus arrhythmia is currently a child of abnormal heart rate but arrhythmia is a synonym for irregular heartbeat so shouldn't sinus arrhythmia be a child of irregular heartbeat?