Tie Your Mother Down was on the Billboard charts.
An ectopic pacemaker or ectopic focus is an excitable group of cells that causes a premature heart beat outside the normally functioning SA node of the heart .. SA node. SA node. heart. heart. ectopic. ectopia ( medicine ). It is thus a cardiac pacemaker that is ectopic , producing an ectopic beat .. cardiac pacemaker. cardiac pacemaker. ectopic. ectopia ( medicine ). ectopic beat. ectopic beat. Acute occurrence is usually non-life-threatening , but chronic occurrence can progress into tachycardia , bradycardia or ventricular fibrillation .. tachycardia. tachycardia. bradycardia. bradycardia. ventricular fibrillation. ventricular fibrillation. In a normal heart beat rhythm , the SA node usually suppresses the ectopic pacemaker activity due to the higher impulse rate of the SA node .. SA node. SA node. heart. heart. ectopic. ectopia ( medicine ). However , in the instance of either a malfunctioning SA node or an ectopic focus bearing an intrinsic rate superior to SA node rate , ectopic pacemaker activity may take over the natural heart rhythm .. SA node. SA node. heart. heart. ectopic. ectopia ( medicine ). This phenomenon -LRB- an intrinsically slower pacemaker activity being unmasked by failure of faster pacemaker tissue ` upstream ' -RRB- is called an escape rhythm , the lower rhythm having escaped from the dominance of the upper rhythm .. As a rule , premature ectopic beats -LRB- i.e. with a shorter than the prevailing preceding R-R ' interval -RRB- indicate increased myocyte or conducting tissue excitability , whereas late ectopic beats -LRB- i.e. with a prolonged preceding R-R ' interval -RRB- indicate proximal pacemaker or conduction failure with an escape ` ectopic ' beat .. ectopic. ectopia ( medicine )