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Adult II: Assessment of Cardiac Rythm.

Terms in this set (57)

Resting Membrane Potential
Called the isoelectric line, resting cardiac cell is negatively charged and when there is a change in the charge an action potential is produced.
Intracellular Electrolyte
Potassium
Extracellular Electrolyte
Sodium and Calcium
Phases of an Action Potential
0- Depolarization (sodium moves into cell)
1- Early repolarization (closure of sodium channels)
2- Plateau (calcium moves into cell)
3- Repolarization (potassium moves into cell)
4- Resting membrane potential (gradient returned to normal)
Heart's Pacemaker
Sinoatrial Node
P Wave
Atrial depolarization stimulated by firing of SA node
PR Interval
Atrial conduction from SA node to AV node
0.12-0.20 seconds
QRS Complex
Ventricular depolarization and atrial repolarization
<0.10 seconds
ST Segment
Ventricular conduction, should be isoelectric. Deflection indicates ventricular muscle injury.
T Wave
Ventricular repolarization and is affected by ventricular muscle injury
QT Interval
Represents ventricular depolarization and repolarization
<0.40 seconds
Dysrythmias: Hypokalemia
Longer PR interval
Flattened T wave
Longer QT interval
Extra waves (U waves)
PVC
Dyrythmias: Hyperkalemia
Tall, peaked T waves
Shortened QT interval
PR interval lengthens
Wide QRS
May lead asystole
Dysrythmias: Hypercalcemia
Strenghtens contractility
Shortens QT interval
Dysrythmias: Hypocalcemia
Prolonged QT intervals
Dyrythmias: Hypomagnesemia
Inc. irritability of nervous system
Prominent U waves
Flattened T wave
Prolonged QT interval
Torsades de Pointes
Dysrythmias: Hypermagnesemia
Prolonged PR interval
Wide QRS complex
Bradycardia
Tall, peaked T waves
Hypothermia & Hypoxemia
Decreases electrical activity of the heart
Bradycardia
Prolonged PR intervals
Prolonged QT interval
Wide QRS complex
Increase in excitability
Sinus Bradycardia
<60bpm, Originates from SA node
S/S: syncope, hypotension, and angina
Treatment for Bradycardia
Atropine
Sinus Tachycardia
HR 100-150bpm
Caused by sympathetic nervous system stimulation
S/S of Tachycardia
Fluttering in chest, SOB, lightheadedness, angina, rapid rate causes decreased ventricular filling time and stroke volume
Treatment for Tachycardia
Relieving cause, sedatives, tranqulizers, antianxiety agents, analgesics, antipyretics.
Supraventricular Tachycardia (SVT)
HR 100-250bpm
Rythm is regular but P waves non-distinguishable
QRS is normal
SVT Treatment
Valsalva's maneuver, adenosine x2 PRN, CCB, Digitalis, Propranolol, quinidine. If no response to drugs then cardioversion
Atrial Flutter
Atrial rate >250bpm
Sawtooth pattern
Atrial Flutter Treatment
Cardioversion, CCB, BB, and digitalis
Atrial Fibrillation
Most common heart disturbance.
Atria contracting sporadically, unable to refill before ejection --> ventricles are inadequately filled and SV diminishes
A Fib ECG Characteristics
Absent P waves
Irregular QRS complexes
A Fib Treatment
Control ventricular rate: digoxin, beta-adrenergic blockers, calcium channel blockers, cardioversion, and coumadin to prevent clot formation.
Junctional ECG Pattern
40-60bpm
QRS complex is normal
P wave can occur anywhere but generally not seen
Not treated if asymptomatic otherwise, atropine, and pacemaker.
Junctional Tachycardia (Accelerated Junctional Rythm)
rate >100bpm, Inverted or absent P waves
Not treated if asymptomatic otherwise pacemaker.
Premature Atrial Contractions (PACs)
Abnormal P wave
Irregular rythm
Normal QRS
PAC Treatment
Digitalis and BB
Premature Ventricular Contractions (PVCs)
Originate in ventricle, does not stimulate atria
Absent P wave
Irregular Rythm
Wide QRS
May be unifocal or multifocal
Causes of PVCs
Ischemia, hypoxia, acidosis, hypokalemia, digitalis toxicity
PVC Treatment
Not all treated, esp. if rate is too slow
Tx: lidocaine, amiodarone, and procainamide
Ventricular Tachycardia
Classified as 3+ PVCs occurring at a rapid rate
>100bpm
Non-identifiable P wave
QRS >0.12 sec
Ventricular Tachycardia S/S
Patients may be alert with a carotid pulse
Loss of consciousness will occur
Ventricular Tachycardia Treatment
Cardioversion
Meds: amiodarone, lidocaine, and magnesium (esp. with Torsades de Pointes)
Ventricular Fibrillation
Most common cause of sudden death
ECG is chaotic and irregular
Ventricular Fibrillation S/S
Unresponsive with no pulse
Ventricular Fibrillation Treatment
CPR, defibrillation, vasopressin or epinephrine
Meds: amiodarone, procainamide, lidocaine, and magnesium
AV Blocks (2 Types)
1st degree
2nd degree (Mobitz I and Mobitz II)
1st Degree Heart Block
Prolonged PR interval (>0.20 sec)
Treat only if symptomatic with atropine or temporary pacing
2nd Degree Heart Block
Mobitz 1/Wenckebach: progressive lengthening of PR interval until QRS is dropped
Mobitz 2: worse, can progress to complete heart block, P waves are blocked so no QRS is generated.
Treatment: pacemaker, atropine, dopamine, or epinephrine
Complete Heart Block/3rd Degree
Atria and ventricles are contracting independently of each other, CO is diminished, no relationship between P and QRS
3rd Degree S/S
Alterations in mental status, syncope, and may progress to ventricular fibrillation
Bundle Branch Block
Impaired conduction through the right and left bundle of his branches
QRS complex is prolonged
No treatment required for the block itself
Class IA, IB, IC Antiarrythmics
Sodium Channel Blockers- slowing of conduction, suppresses automaticity
Norpace, lidocaine, and flecainide
Class II Antiarrythmics
Beta Blockers- reduce automaticity, blocks sympathetic mediation to reduce HR and BP
Inderal and Esmolol
Class III
Potassium Channel Blockers- prolong action potential without affecting resting membrane potential
Amiodaroe and Covert
Class IV
Calcium Channel Blockers- reduce automaticity and slows conduction through AV node.
Cardizem, digoxin (SVT, A Fib, A flutter), and adenosine (only SVT)
Cardioversion
Synchronized.
Used to treat SVT, atrial fibrillation, atrial flutter, and ventricular tachycardia in unstable patients
Defibrillation
Unsynchronized (200J or more)
Pacemaker (Types of pacing)
Ventricular Stimulation (spike before QRS), Atrial stimulation (spike before P), and ventricular and atrial stimulation (spike before P and QRS)
Pacemaker Problems
Failure to sense: pacemaker competes with pts own impulse
Failure to capture: intiaties impulse but stimulus is not strong enough to produce depolarization
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