Advanced – Dysrhythmias 2023 Review Update
Excitability - the ability of non-pacemaker heart cells to respond to an electrical impulse
that begins in
... [Show More] pacemaker cells.
Depolarization - occurs when the normally negatively charged cells within the heart
muscle develop a positive charge.
Conductivity - the ability to send an electrical stimulus from cell membrane to cell
membrane. As a result, excitable cells depolarize in rapid succession from cell to cell
until all cells have depolarized. Ex: the wave of depolarization causes the deflections in
the ECG waveforms that are recognized as the P wave and QRS complex.
Contractility - the ability of atrial and ventricular muscle cells to shorten their fiber length
in response to electrical stimulation, causing sufficient pressure to push blood forward
through the heart. In other words, this is the mechanical activity of the heart.
AV Node - where impulses slow down or are delayed before proceeding to the
ventricles. This delay is reflected in the PR segment on the ECG. This slow conduction
provides a short delay, allowing the atria to contract and the ventricles to fill.
SA Node - the heart's primary pacemaker. It can spontaneously and rhythmically
generate electrical impulses at a rate of 60-100 beats per min and therefore has the
greatest degree of automaticity.
Purkinje Cells - composed of the bundle of HIS, bundle branches, and these fibers.
Responsible for the rapid conduction of electrical impulses throughout the ventricles,
leading to ventricular depolarization and the subsequent ventricular muscle contraction.
Semi-Reclined - While obtaining a 12-lead ECG, remind the patient be as as still as
possible in a ________________________ position, breathing normally.
Clea, Dry, Moist - For continous ECG monitoring, be sure to __________________ skin
and clip hairs/shave. Ensure that the electrode placement is _____________ and the
gel on each electrode is ______________ and fresh.
P Wave - a deflection on an ECG representing atrial depolarization. When the electrical
impulse is consistently generated form the SA node, this wave has a consistent shape
in a given lead. If an impulse is then generated from a different (ectopic) focus, such as
atrial tissue, the shape of this wave changes in the lead, indicating that an ectopic focus
has fired.
PR Segment - the isoelectric line from the end of the P wave to the beginning of the
QRS complex, when the electrical impulse is traveling through the AV node, where it is
delayed.
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