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CH. 4. Cardiac dysrhythmias Questions and Answers
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CH. 4. Cardiac dysrhythmias
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CH. 4. Cardiac dysrhythmiasTachycardias may be classified as narrow QRS complex or wide QRS complex or wide
QRS complex. What are some examples of each type and how do the electrical
pathways differ? - answerAn electrocardiogram (ECG) is used to determine narrow and
wide complex tachycardia which is based on the QRS complex.
- Narrow complex is when the QRS is less than 0.12 seconds (120 ms). Examples
include sinus tachycardia, atrial fibrillation, atrial flutter, supraventricular tachycardia.
- Wide complex is when the QRS is greater than or equal to 0.12 seconds (120 msec).
Examples include ventricular tachycardia, a narrow complex tachycardia with an
aberrant conduction system, pacemaker- tracked or mediated tachycardia.
What is the development of atrial fibrillation significant for a patient? - answerMost
patients have an underlying cardiac problem such as a valvular disease or electrolyte
imbalance. Also, they may be unable to tolerate the rapid rhythm that occurs at the
onset of AF.
Why is anticoagulation important for a patient in atrial fibrillation? - answerPatients with
AF are at high risk for embolic strokes.
What are the common treatment modalities for atrial fibrillation? - answera. Rate control
with chronic anticoagulation is recommended for most AF patients.
b. Coumadin (warfarin) is used unless the patients are in a low-risk group or have
contraindications to its use.
c. Beta blockers (atenolol, metoprolol) and ca. ch blockers (diltiazem, verapamil) are
recommended for rate control as an outpatient; digoxin should be considered as
second-line therapy for patients who do not respond to these medications.
d. For patients requesting cardioversion, either synchronized cardioversion or
pharmacological conversion is appropriate.
e. To minimize the risk of embolic stroke in patients electing cardioversion, either
transesophageal echocardiogram (TEE) or 3 weeks of anticoagulation prior to
cardioversion is acceptable. Both strategies are followed by 3 to 4 weeks of
anticoagulation.
What are the characteristics of third-degree heart block? - answerThird-degree heart
block, also known as complete heart block, occurs when the impulses from the atria are
not conducted through the AV junction. Therefore, there is no relationship between the
atria (P waves) and the ventricles (QRS waves). The PR interval varies and the QRS is
usually wide and the heart rate slow (less than 40 to 60).
Amiodarone is indicated to treat both supraventricular tachycardias and ventricular
tachycardias.
, Which tachycardias may be treated with amiodarone, and what is its mechanism of
action? - answer- Amiodarone is an antiarrhythmic agent. It has actions similar to
calcium channel blockers on slowing conduction and prolonging refractoriness at the AV
node. Amiodarone also prolongs the duration of cardiac action potential via the sodium
and potassium channels, raising the threshold for SVT and ventricular fibrillation, and
may prevent its recurrence.
- Amiodarone is indicated in
(a) stable irregular narrow complex tachycardia, such as atrial fibrillation,
(b) stable regular narrow-complex tachycardia,
(c) to control rapid ventricular rate due to accessory pathway conduction in pre-excited
atrial arrhythmias,
(d) hemodynamically stable monomorp. VT
(e) polymorphic VT with normal QT interval.
What are four ways in which pacemakers can malfunction? - answerPacemakers can
fail by failing to pace or capture as well as by oversensing and undersensing.
As you enter the ICU for your oncoming shift, you are told to go immediately to your
assigned room because your patient, a 55-year-old male, is in full cardiac arrest. You
quickly learn that your patient had open heart surgery 2 days ago for a coronary bypass
graft and mitral valve repair. He is on the ventilator and has a central line for IV
medications. You enter the cardiac room and find the code team performing CPR and
charging the monitor for another defibrillation. You see ventricular tachycardia on the
monitor; however, the patient has no pulse and no blood pressure. The team leader tells
you that this is the second shock and no medications have been given yet.The team
leader asks you to be the medication nurse for the code.
What medication do you assume will be given first? - answerEpinephrine 1 mg IV,
repeated every 3 to 5 minutes.
What is the implication of giving this/ these medication(s)? - answerEpinephrine is a
peripheral vasoconstrictor; therefore, the implication is that this drug may increase
coronary
and cerebral perfusion pressure during CPR.
After a second defibrillation, the monitor reveals sinus brady with a rate of 48, what
should be done next? - answerAssess the patient for a pulse, as it appears his
dysrhythmia may have converted to a sinus rhythm.
What meds should be given next? - answerAnantidysrhythmic will be important to
prevent a return of the ventricular dysrhythmia; amiodarone 150 mg IV bolus followed
by a 1 mg/min infusion for 6 hours then a 0.5 mg/min maintenance infusion over 18
hours.
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