Advanced - Dysrhythmias
Excitability - ANSthe ability of non-pacemaker heart cells to respond to an electrical impulse that
begins in pacemaker cells.
Depolarization - ANSoccurs when the normally negatively charged cells within the heart muscle
develop a positive charge.
Conductivity - ANSthe 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 - ANSthe 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 - ANSwhere 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 - ANSthe 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 - ANScomposed 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 - ANSWhile obtaining a 12-lead ECG, remind the patient be as as still as
possible in a ________________________ position, breathing normally.
Clea, Dry, Moist - ANSFor 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 - ANSa 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 - ANSthe 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.
PR Interval - ANSmeasured form the beginning of the P wave to the end of the PR segment.
Represents the time required for atrial depolarization, the impulse delay in the AV node, and the
travel time to the Purkinje files. Normally measures from 0.12-0.20 seconds (five small blocks).
QRS Complex - ANSrepresents ventricular depolarization on ECG lead.
ST Segment - ANSan isoelectric line and represents early ventricular repolarization. Changes
may be a result of myocardial injury, ischemia, infarction, conduction abnormalities or
medications.
T wave - ANSventricular repolarization, usually positive, rounded, and slightly asymmetric. May
change as a result of myocardial ischemia, potassium/calcium imbalances, medications, or ANS
effects.
U wave - ANSif this is present, it follows the T wave a may result from slow depolarization of
ventricular Purkinje fibers. An abnormal U wave may suggest an electrolyte abnormality
(Hypokalemia).
QT Interval - ANSrepresent the total time required for ventricular depolarization and
depolarization. Measured from the beginning of the Q wave to the end of the T wave. Varies
with the patient's age and gender and changes with the heart rate, lengthening with slower heart
rates and shortening with faster rates.
Artifact - ANSan interference seen on the monitor or rhythm strip, which may look like a
wandering or fuzzy baseline. It can be caused by patient movements, loose or defective
electrodes, improper grounding, or faulty ECG equipment such as broken worse or cables.
Some can mimic lethal dysrhythmias such as ventricular tachycardia or ventricular fibrillation.
ASSESS PATIENT TO DIFFERENTIATE ARTIFACT FROM ACTUAL LETHAL RHYTHMS. DO
NOT RELY ONLY ON THE ECG MONITOR.
Normal Sinus Rhythm - ANSthe rhythm originating from the SA node that meets these ECG
criteria:
-Rate: 60-100bpm
-Rhythm: atrial and ventricular rhythms regular
-P waves: present, consistent configuration, one P wave before each QRS complex
-PR Interval: 0.12-0.20 seconds and constant
-QRS Duration: 0.04-0.10 second and constant
60-100, normal, one, 0.12-0.20, .04-.10 - ANSNormal Sinus Rhythm is the rhythm originating
from the SA node that meets these ECG criteria:
Rate: _______________ bpm