NUR 145 Pharmacology - Ch. 24 (Dysrhythmias) Questions and Correct Answers
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Module
NUR 145
Institution
NUR 145
Dysrhythmia (sometimes called arrhythmia) occurs when there is a disturbance of the normal electrical conduction, resulting in an abnormal heart muscle contraction or heart rate.
Conduction system or electrical system, of the heart is the anatomic structure that controls the sequence of muscle con...
NUR 145 Pharmacology - Ch. 24
(Dysrhythmias) Questions and Correct
Answers
Dysrhythmia ✅(sometimes called arrhythmia) occurs when there is a disturbance of
the normal electrical conduction, resulting in an abnormal heart muscle contraction or
heart rate.
Conduction system ✅or electrical system, of the heart is the anatomic structure that
controls the sequence of muscle contractions so that an optimal volume of blood is
pumped from the heart with each beat. See Fig 24-1, pg. 387
The normal electrical conduction pathway in the heart starts with the firing of which
component?
A. Atrioventricular (AV) node
B. Internodal pathway
C. Sinoatrial (SA) node
D. Atria ✅Answer: C
Rationale: The firing of the SA node is the initiation of normal cardiac rhythm. The
electrical impulse goes from the SA node through the internodal pathways, to the AV
node, to the bundle of His, to the bundle branches, to the Purkinje fibers in the
ventricles. Then the process is repeated.
Electrical impulses ✅are conducted by sodium, calcium, and potassium ions.
Dysrhythmias ✅- Stress, ischemia, and heart failure can cause irregular
muscular contraction
- Normal conduction pathway could be partially
obstructed, causing an irregular flow of electrical
impulses, resulting in an irregular pattern of muscle
contractions
Classification of Dysrhythmias ✅Supraventricular
-Develop above the bundle of His
-Atrial flutter, atrial fibrillation
-Premature atrial contractions
-Sinus tachycardia, sinus bradycardia
-Paroxysmal supraventricular tachycardia
Ventricular
-Develop below the bundle of His
-Premature ventricular contractions
*Dysrhythmias can be the result of blocked pathways and are classified by degree of
block. First degree is partial block with delayed response, second degree is occasional
blockage, and third degree is complete block.
Drug Therapy for Dysrhythmias ✅Class I: myocardial depressant inhibits sodium ion
movement
-Class Ia agents—prolong duration of electrical
stimulation
-Class Ib agents—shorten duration of electrical
stimulation
-Class Ic agents—potent myocardial depressants, slow
conduction rate
Class II: beta-adrenergic blocking agents
Class III: slow rate of electrical conduction
Class IV: block calcium ion flow
* Antidysrhythmic agents classified according to effects on the heart's electrical
conduction system.
Assessment of Patients
with Dysrhythmias ✅*Initially monitor with ECG
*Past medication history
*Presence of six cardinal signs of cardiovascular disease
*Basic mental status
*Baseline vital signs
-Blood pressure, pulse, respirations, temperature, O2 sat
*Auscultation and percussion of heart and lung sounds
*Laboratory tests: electrolytes, blood gases
Six cardinal signs of cardiovascular disease: ✅1. dyspnea 4. edema
2. chest pain 5. syncope
3. fatigue 6. palpitations
Drug Class:
Class III Antidysrhythmic Agents ✅Drugs: amiodarone hydrochloride (Cordarone,
Pacerone): Table 24-1, pg. 388
**Successful in treating many dysrhythmias where other antidysrhythmics fail, but have
many adverse effects, some of which are severe and potentially fatal.
Drug Class:
Class III Antidysrhythmic Agents - Actions ✅Prolong the action potential of atrial and
ventricular tissue by increasing the refractory period
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