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Ch 36 med surg definitions
definitions for "care of patients with dysrhythmias" med surg luther college
57
Nursing
Undergraduate 3
02/19/2012

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Term
cardiac dysrhythmias
Definition
abnormal rhythms of the heart's electrical system that can affect its ability to effectively pump oxygenated blood throughout the body
Term

Automaticity

 

Definition
(pacing fxn) is the ability of cardiac cells to generate an electrical impulse spontaneously and repetitively
Term
excitability
Definition
the ability of non-pacemaker heart cells to respond to an electrical impulse generated from pacemaker cells and to depolarize
Term
depolarization
Definition
occurs when the normally negatively charged cells within the heart muscle develop a positive charge
Term
depolarization
Definition
occurs when the normally negatively charged cells within the heart muscle develop a positive charge
Term
conductivity
Definition
the ability to transmit an electrical stimulus from cell membrane to cell membrane
Term
contractility
Definition
  • the ability of atrial and ventricular muscle cells to shorten their fiber length in response to electrical stimulation, generating sufficient pressure to propel blood forward
  • the mechanical activity of the heart
Term
Sinoatrial (SA) node
Definition
  • conduction system of the heart begins here
  • located close to the surface of the right atrium near its junction with the superior vena cava
  • the heart's primary pacemaker
  • has the greatest degree of automaticity
Term
Atrioventricular (AV) junctional area
Definition

consists of a transitional cell zone, the AV node itself, and the bundle of His

 

Term
AV node
Definition

lies just beneath the right atrial endocardium, between the tricuspid valve and the ostium of the coronary sinus

 

Term
Purkinje Cells
Definition
  • make up the bundle of His, bundle branches, and terminal Purkinje fibers.
  • responsible for the rapid conduction of electrical impulses throughout the ventricles, leading to ventricular depolarization and the subsequent ventricular muscle contraction
Term
Electrocardiogram (ECG)
Definition
provides a graphic representation (picture) of cardiac electrical activity
Term
P wave
Definition

deflection representing atrial depolarization

the shape may be a positive, negative, or a biphasic (both) deflection, depending on the lead selected.[image]

Term
PR segment
Definition
the isoelectric line from the end of the P wave to the beginning of the QRS complex, when the lectrical impulse is traveling through the atrioventricular node, where it is delayed[image]
Term
PR interval
Definition

measured from the beginning of the P wave to the end of the PR segment.

it represents the time required for atrial depolarization as well as the impulse delay in the AV node and the travel time to the purkinje fibers

[image]

Term
QRS complex
Definition

represents ventricular depolarization

the shape depends on the lead selected

[image]

Term
Q Wave
Definition

the first negative deflection and is not present in all leads

when present, it is small and represents initial ventricular septal depolarization.

when it is abnormally present in a lead, it represents myocardial necrosis

[image]

Term
R wave
Definition

the first positive deflection

it may be small, large, or absent, depending on the lead.

[image]

Term
S wave
Definition

a negative deflection following the R wave

is not present in all leads

[image]

Term
QRS duration
Definition

represents the time required for depolarization of both ventricles

it is measured from the beginning of the QRS complex to the J point (the junction where the QRS complex ends and the ST segment begins)

[image]

Term
ST segment
Definition
  • normally an isoelectric line and represents early ventricular repolarization.
  • its length varies with changes in the heart rate, the administration of medications, and electrolyte disturbances.
  • elevation or depression can be caused by myocardial injury, ischemia or infarction, conduction abnormalities, or the administration of meds

[image]

Term
T wave
Definition

follows the ST segment and represents ventricular repolarization

usually positive, rounded, and slightly asymmetric

if an ectopic stimulus excites the ventricles during this time, it may cause ventricular irritability, lethal dysrhythmias, and possible cardiac arrest in the vulnerable heart

[image]

Term
R-on-T phenomenon
Definition
T waves may become tall and peaked, inverted (negative), or flat as a result of MI, K or Ca imbalances, meds, or autonomic nervous system effects
Term
U wave
Definition

represents late ventricular repolarization

follows the T wave and may result from slow repolarization of ventricular Purkinje fibers

an abnormal U wave may suggest an electrolyte imbalance (hypokalemia)

[image]

Term
QT interval
Definition

represents the total time required for ventricular depolarization and repolarization.

measured from the beginning of QRS complex to the end of the T wave

[image]

Term
Normal Sinus Rhythm
Definition

the rhythm originating from the SA note (dominant pacemaker) that meets these ECG criteria

  1. Rate: 60-100bmp
  2. Rhythm: regular
  3. P waves: present, consistent configuration, one P wave before each QRS complex
  4. PR interval: 0.12 to 0.20 seconds and constant
  5. QRS duration: 0.04 to 0.10 seconds and constant
Term
Sinus Arrhythmia
Definition
  • variant of normal sinus rhythm (all the characteristics except for its irregularity)
  • results from changes in intrathoracic pressure during breathing
  • in this context, it does not mean absence of rhythm
  • the heart rate increase slightly during inspiration and decreases slightly during exhalation
  • irregular rhythm is freq observed in healthy children as well was adults
Term
Dysrhythmia
Definition

any disorder of the heartbeat

result from:

  • a disturbance in the relationship bt electrical conductivity and the mechanical response of the myocardium
  • a disturbance in impulse formation
  • a disturbance in impulse conduction
  • a combination of these
Term
premature complexes
Definition
  • early rhythm complexes
  • they occur when a cardiac cell or cell group, other than the SA node, becomes irritable and fires an impulse before the next sinus impulse is produced
Term
palpitations
Definition
"skipping" of the heartbeat
Term
Sinus Bradycardia
Definition

the sinus node discharge rate is less than 60 beats/min in adults

increases coronary perfusinon time

decreases coronary perfusion pressure

myocardial o2 demand decreases

Term
valsalva maneuver
Definition
bearing down for a bowel movement or gagging
Term
premature atrial complex (PAC)
Definition

occurs when atrial tissue becomes irritable

an atrial dysrhythmia

ectopic focus fiires an impuls before the next sinus impulse is due

Term
supraventricular tachycardia (SVT)
Definition

involves the rapid stimulation of atrial tissue at a rate of 100-280 beats/min in adults and 200-300bpm in children

an atrial dysrhythmia

Term
paroxysmal supraventriuclar tachycardia (PVST)
Definition

a term used when the rhythm is intermittent in a SVT

initiated suddenly by a premature complex such as a PAC and terminated suddenly with or w/o intervention

Term
atrial fibrillation
Definition

most common dysrhythmia seen in clinical practice

multiple rapid impulses from many atrial foci depolarize the atria in a totally disorganized manner at a rate of 350-600 times per minute

quivers

Term
atrial flutter
Definition

rapid atrial depolarization occurring at a rate of 250-350 times per minute

the AV node blocks the number of imulses that reach the ventricles as a portective mechanism

Term
idioventricular rhythm (ventricular escape rhythm)
Definition

the ventricular nodal cells pace the ventricles

rate is usually less than 40bpm

rhythm in a the dying heart, where downward displacement of the pacemaking has occurred

Term
Pulseless electrical activity (PEA)
Definition

characterized by no palpable pulse and therefore, no perfusion

electrical activity is displayed on the monitor

Term
Premature ventricular complexes (PVCs)
Definition

result from increased irritability of ventricular cells and are seen as early ventricular complexes followed by a pause

frequently occur in repetitive rhythms

Term
Nonsustained ventricular tachycardia (NSVT)
Definition
three or more successive PVCs
Term
Ventricular Tachycardia (VT)
Definition

"V Tach"

occurs with repetitive firing of an irritable ventricular ectopic focus

usually at a rate of 140 to 180bpm or more

 

Term
Ventricular Fibrillation (VF)
Definition

result of electrical chaos in the ventricles

life threatening

impulses from many irritable foci fire in a totally disorganized manner so that ventricular contraction cannot occur

Term
Ventricular Asystole
Definition

sometimes called ventricular standstill

complete absence of any ventricular rhythm

Term
Atrioventricular (AV) blocks
Definition
exists when supraventricular impulses are excessively delayed or totally blocked in the AV node or intraventricular conduction system
Term
Bundle Branch Block (BBB)
Definition

a conduction delay or block within one of the two main bundles of His branches

usually sinus in origin

may be a temorary or a permanent conduction disorder

Term
Vaughn-Williams Classification
Definition
commonly used to categorize drugs according to their effects on the action potential of cardiac cells (classes I through IV)
Term
Torsades de Pointes
Definition

life-threatening VT

magnesium sulfate can be used

Term
Vagal Maneuvers
Definition
induce vagal stimulation of the cardiac conduction system, specifically the SA and AV nodes
Term
carotid sinus massage
Definition

the physician massages over one carotid artery for a few seconds, observing for a change in cardiac rhythm

causes vagal stimulation, slowing SA and AV nodal conduction

Term
Temporary Pacing
Definition
nonsurgical intervention that provides at timed electrical stimulus to the heart when either the impulse initiation or the conduction system of the heart is defective
Term
Asynchronous (fixed-rate) pacing mode
Definition
is used when the patient is asystolic or profoundly bradycardic, which may occur after open-heart surgery
Term
Noninvasive temporary pacing (NTP)
Definition
accomplished through the application of two large external electrodes
Term
invasive temporary pacemaker
Definition

a system that consists of an external battery-operated pulse generator and pacing electrodes (leads)

the wires are attached to the generator on one end and are in contact with the heart on the other end

electrical impulses are emitted from the negative terminal of the generator and flow through the lead wire, and then stimulate the cardiac cells to depolarize

Term
cardioversion
Definition
a synchronized countershock that may be performed in emergencies for unstable ventricular or supraventricular tachydysrhythmias or electively for stable tachydysrhythmias that are resistant to medical therapies
Term
Defibrillation
Definition
an asynchronous counter shock, depolarizes a critical mass of myocardium simultaneously to stop the re-entry circuit, allowing the sinus node to regain control of the heart
Term
Radiofrequency catheter ablation
Definition
an invasive procedure that may be used to destroy an irritable focus causing a supraventricular or ventriular tachydysrhythmia
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