mechanical and electrical activity
correlation between the electrical and mechanical functions of the heart
electrical activity stimulates the heart to
... [Show More] contract
ECG shows both functions
electrical pulse = action potential
videos
https://www.youtube.com/watch?v=nGIsS6c7pBA
https://www.youtube.com/watch?v=nGIsS6c7pBA
what's the difference between telemetry and ECG?
ECG is diagnostic while telemetry monitors rhythm changes
Cardiac monitoring is used to diagnose dysrhythmias, chamber enlargement, Mycoardial ischemia or infarction, monitor effects of electrolye imbalances of medication administration. Cardiac electrical activity can be monitored by an ECG. 12 - lead, ambulatory (Holter monitoring), or telemetry. For continuous monitoring or telemetry most monitors use 2-4 electrodes. These electrodes create an imaginary line, called a lead, that serves a reference point from which the electrical activity is viewed. A lead is like an eye of a camera - it has a narrow peripheral view, looking only at the electrical activity directly in front of it.
The electrical impulse that travels through the heart can be viewed by means of electrocardiography, the end product of which is an electrocardiogram. Each phase of the cardiac cycle is reflected by specific waveforms on the screen of a cardiac monitor or on a strip of ECG graph paper. In other words, it represents the function of the heart's conduction system.
ECG can show ischemia, infarction, enlarged cardiac chambers, electrolyte imbalances, drug toxicity.
placing telemetry leads
white goes on right
black opposite white
"grass under snow" (green)
"fire under smoke" (red)
brown in the middle
changes leads for shower (remove old, shower, add new)
placing EKG electrodes
12-lead EKG, we only put on 10 leads
4 limb
2 saddle the sternum
4 on the left side of the chest
client needs to remain still and breathe normally
properties of cardiac cells
conductivity
contractility
automaticity
excitability
refractoriness
Conductivity: transmit electrical impulses across cell membranes and from cell to cell.
Contractility: A/V muscle cells shorten fiber lengths to propel blood forward during contraction.
Automaticity: Ability of cardiac cells to initiate an impulse (primary pacemaker cells).
Excitability: Ability to respond to stimulus and then depolarize.
Refractoriness: Cells unable to respond to stimulus until recovered from previous stimulus (repolarization).
Although the SA node and AV node ordinarily initiate the pacing of the heart, all of the cells have the capability of doing so.
Depolarization: normally negatively charge cells developing a positive charge. Depolarization produces mechanical contractions.
arrhythmia
no rhythm
dysrhythmia
abnormal rhythm
classified by the site of origin:
-SA node
-Atrial
-AV node
-ventricular
PQRST complex
one heart beat
P wave
SA node fires at the beginning
the wave itself shows the atria contracting
P wave: atrial depolarization (contraction);
PR interval
conduction from SA to AV
normal is 0.12-0.20 sec (3-5 dots)
PR interval: beginning of P wave to end of PR interval: atrial depolarization, AV delay and travel time to purkinje fibers. 0.12 - 0.20.
QRS complex
conduction from AV node to Purkinje fibers
ventricular contraction
normal is < 0.10 sec (2.5 dots)
QRS complex: ventricular depolarization (contraction). Time required for depolarization of both ventricles: 0.04-0.10.
QT interval
QT interval: ventricular depolarization + repolarization. QT may be prolonged with some medications; can be a dangerous sign.
ST segment
ST segment: early ventricular repolarization. Should not be elevated more than 1 mm or 1 line above or depressed more than 0.5 mm (1/2 line below). Elevated ST segment indicates an MI: STEMI or NSTEMI. Depressed means ischemia.
T wave
ventricles are relaxed and filling
during this time, they won't respond to stimulation
we want a wide T wave, but not one that's too tall
T wave: ventricular repolarization: resting and cannot respond to a stimulus.
Rhythm Strip Analysis
1. Determine Regularity (of R waves):
-determine underlying rhythm (regular or irregular)
-"March it across" (calipers) and make sure the spacing between each QRS peak is equal
2. Calculate the (ventricular) rate:
-dots = 0.04 sec
-boxes = 0.2 sec
-hashtags = 3 sec
-if patient has a regular rhythm, count the peaks between 3 hashmarks (6 seconds) and multiply by 10 to get a rough estimate of the heart rate
OR
-count # of small squares between 2 consecutive R ways and divide this number into 1500 (1500/23 boxes = 65 bpm)
3. Assess the P waves:
-present?
-P for every QRS (1:1)?
-are they all the same?
4. Measure the PR interval:
-normal (0.12-0.20)?
-consistent?
-pattern?
5. Measure the QRS complex:
-normal (<0.10)?
-are they all the same?
normal sinus rhythm
HR 60-100bpm
regular rhythm
P waves are identical and present before each QRS
PR interval 0.12-0.20
QRS <0.12
when rhythms are NOT normal
Cardiac dysthrmias are heartbeat disturbances (beat formation, beat conduction). The terms dysrhythmias and arrhythmias are used interchangeably. In reality, dysrhythmia means abnormal rhythm and arrhythmia means absent rhythm.
Dysrhythmias are classified by the site of origin: SA node, Atrial, AV node, ventricular.
ectopy
FLB (funny little beats)
causes of dysrhythmia
cardiac:
-valve issues
-cardiomyopathy
-heart failure
-MI
-conduction defects
pulmonary:
-hypoxia
-acidosis
other:
-electrolyte imbalance (K+)
-blunt trauma
-drugs
-caffeine
-electrical shock
-hypoglycemia
-hypothermia
-clots [Show Less]