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Ectopic Focus (ectopic pacemaker)



An ectopic pacemaker occurs when an excitable group of cells outside the normally functioning SA node causes a premature heartbeat. When an electrical signal is generated from this group of cells, it is called ectopic. The term ectopic focus means: (1). ectopic, the electrical signal originates from a different location other than the SA node, and (2). focus, the site where the electrical signal originates from. This ectopic pacemaker can self-generate an electrical signal that can either cause an early beat or can continually pace the heart. The focus can be in the atria, junction (the AV Nodal area) or from the ventricles. Typically, this condition will simply cause an early contraction (PAC, PVC or PJC). Other times it can take over pacing the heart. If it paces the heart from the Junctional area or ventricles, it is called an escape rhythm, i.e. junctional escape or ventricular escape. if it paces from within the atria, it will generate a rhythm such as A-fib., A-flutter, wondering atrial pacemaker (WAP) or multifocal atrial tachycardia (MAT). Many times we use the term ectopy to describe a rhythm having PACs, PVCs or PJCs, because they all have an ectopic focal point (ectopic focus). See below.



 What is a ventricular escape beat?
It is a self-generated electrical discharge initiated by, and causing contraction of the ventricles (PVC). Normally, the heart rhythm is paced from the SA node and follows the normal pathway down to the ventricles. With a ventricular escape beat, there is no P-wave because the atrium does not contract. The pacing signal fires from within the ventricle before the SA node can generate its signal. This is a ventricular ectopic focus

 What is a junctional escape rhythm?
When a junctional rhythm happens, it typically has a rate of 40-60 bpm. Junctional rhythm (escape rhythm) functions as a built in safety mechanism, or like a backup feature that kicks in whenever the SA node (primary pacemaker) fails, or the AV node blocks the atrial impulse. The junction jumps in and takes over pacing the heart.

 What is atrial ectopic focus?
Atrial ectopic focus can simply be a premature atrial contraction (PAC). Or the atria can have multiple excitable groups of cells that take over pacing the heart from within the atria such as A-fib, A-flutter, wandering atrial pacemaker (WAP) or multifocal atrial tachycardia (MAT). The focal point is in the atria.


(A) "Sinus rhythm with ectopy" means a patient in sinus rhythm is also having:
  1. Premature ventricular contractions (PVCs).
  2. Premature atrial contractions (PACs).
  3. Both PACs and PVCs (and sometimes PJCs).
(B) Atrial ectopic focus happens when:
  1. A group of excitable cells in the atria conducts an early beat.
  2. The atria stops contracting for a moment , so the ventricles take over pacing.
  3. When you study cardiac rhythms, the topic focuses on the atria.
(C) An escape rhythm results from:
  1. The Bundle Branches do not repolarize on time, so a junctional rhythm occurs.
  2. The EKG machine keeps printing and won't stop.
  3. The SA node fails to pace, so either the atria, junction or ventricles pace the heart.


Answers:
A = 3
B = 1
C = 3
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