Chapter 35: Dysrhythmias Practice Questions

Chapter 35: Dysrhythmias Practice Questions

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tenzinzompaPreview Chest Pain 108 terms Alake_MyersPreview Dysrhy 79 terms bor When computing a heart rate from the ECG tracing, the nurse counts 15 of the small blocks between the R waves of a patient whose rhythm is regular. From these data, the nurse calculates the patient's heart rate to be 60 beats/min.75 beats/min.100 beats/min.150 beats/min.100 beats/min.Since each small block on the ECG paper represents 0.04 seconds, 1500 of these blocks represents 1 minute. By dividing the number of small blocks (15, in this case) into 1500, the nurse can calculate the heart rate in a patient whose rhythm is regular (in this case, 100).

Which statement best describes the electrical activity of the heart represented by measuring the PR interval on the ECG?

• The length of time it takes to depolarize the atrium
• The length of time it takes for the atria to depolarize and repolarize
• The length of time for the electrical impulse to travel from the SA node to the Purkinje fibers
• The length of time it takes for the electrical impulse to travel from the SA node to the AV node
• The length of time for the electrical impulse to travel from the SA node to the Purkinje fibers

The electrical impulse in the heart must travel from the SA node through the AV node and into the Purkinje fibers in order for synchronous atrial and ventricular contraction to occur. When measuring the PR interval (the time from the beginning of the P wave to the beginning of the QRS), the nurse is identifying the length of time it takes for the electrical impulse to travel from the SA node to the Purkinje fibers. The P wave represents the length of time it takes for the impulse to travel from the SA node through the atrium causing depolarization of the atria (atrial contraction). Atrial repolarization occurs during ventricular depolarization and is hidden by the QRS complex. The length of time it takes for the electrical impulse to travel from the SA node to the AV node is the flat line between the end of the P wave and the beginning of the Q wave on the ECG and is not usually measured.

The nurse obtains a 6-second rhythm strip and charts the following analysis:

Tab 1 Atrial data

Rate: 70, regular

Variable PR interval Independent beats Tab 2 Ventricular data

Rate: 40, regular

Isolated escape beats Tab 3 Additional data

QRS: 0.04 sec

P wave and QRS complexes unrelated What is the correct interpretation of this rhythm strip?

• Sinus arrhythmias
• Third-degree heart block
• Wenckebach phenomenon
• Premature ventricular contractions
• Third-degree heart block

Third-degree heart block represents a loss of communication between the atrium and ventricles from AV node dissociation. This is depicted on the rhythm strip as no relationship between the P waves (representing atrial contraction) and QRS complexes (representing ventricular contraction). The atria are beating totally on their own at 70 beats/min, whereas the ventricles are pacing themselves at 40 beats/min.Sinus dysrhythmia is seen with a slower heart rate with exhalation and an increased heart rate with inhalation.In Wenckebach heart block, there is a gradual lengthening of the PR interval until an atrial impulse is nonconducted and a QRS complex is blocked or missing.Premature ventricular contractions (PVCs) are the early occurrence of a wide, distorted QRS complex.

The nurse is caring for a patient who is 24 hours postpacemaker insertion. Which nursing intervention is most appropriate at this time?

• Reinforcing the pressure dressing as needed
• Encouraging range-of-motion exercises of the involved arm
• Assessing the incision for any redness, swelling, or discharge
• Applying wet-to-dry dressings every 4 hours to the insertion site
• Assessing the incision for any redness, swelling, or discharge

After pacemaker insertion, it is important for the nurse to observe signs of infection by assessing for any redness, swelling, or discharge from the incision site. The nonpressure dressing is kept dry until removed, usually 24 hours postoperatively. It is important for the patient to limit activity of the involved arm to minimize pacemaker lead displacement.The nurse is watching the cardiac monitor, and a patient's rhythm suddenly changes. There are no P waves. Instead there are fine, wavy lines between the QRS complexes. The QRS complexes measure 0.08 sec (narrow), but they occur irregularly with a rate of 120 beats/min. The nurse correctly interprets this rhythm as what?Sinus tachycardia Atrial fibrillation Ventricular fibrillation Ventricular tachycardia Atrial fibrillation Atrial fibrillation is represented on the cardiac monitor by irregular R-R intervals and small fibrillatory (f) waves. There are no normal P waves because the atria are not truly contracting, just fibrillating. Sinus tachycardia is a sinus rate above 100 beats/minute with normal P waves.Ventricular fibrillation is seen on the ECG without a visible P wave; an unmeasurable heart rate, PR or QRS; and the rhythm is irregular and chaotic. Ventricular tachycardia is seen as three or more premature ventricular contractions (PVCs) that have distorted QRS complexes with regular or irregular rhythm, and the P wave is usually buried in the QRS complex without a measurable PR interval.A patient has sought care following a syncopal episode of unknown etiology. Which nursing action should the nurse prioritize in the patient's subsequent diagnostic workup?Preparing to assist with a head-up tilt-test Preparing an IV dose of a β-adrenergic blocker Assessing the patient's knowledge of pacemakers Teaching the patient about the role of antiplatelet aggregators Preparing to assist with a head-up tilt-test In patients without structural heart disease, the head-up tilt-test is a common component of the diagnostic workup following episodes of syncope. IV β-blockers are not indicated although an IV infusion of low-dose isoproterenol may be started in an attempt to provoke a response if the head-up tilt-test did not have a response. Addressing pacemakers is premature and inappropriate at this stage of diagnosis. Patient teaching surrounding antiplatelet aggregators is not directly relevant to the patient's syncope at this time.