Chapter 07: Dysrhythmia Interpretation and Management
ANS: A Atrial flutter arises from a single irritable focus in the atria. The atrial focus fires at an extremely rapid, regular rate, between 240 and 320 beats per minute. The P waves are called flutter waves and may have a sawtooth appearance. The ventricular response may be regular or irregular based on how many flutter waves are conducted through the AV node. Atrial flutter with RVR occurs when atrial impulses cause a ventricular response greater than 100 beats per minute. Atrial fibrillation arises from multiple ectopic foci in the atria, causing chaotic quivering of the atria and ineffectual atrial contraction.
Interpret the following rhythm: a. Atrial flutter with variable conduction b. Ventricular fibrillation c. Atrial fibrillation d. Atrial flutter with RVR (rapid ventricular response)
ANS: A Normal sinus rhythm (NSR) reflects normal conduction of the sinus impulse through the atria and ventricles. Atrial and ventricular rates are the same and range from 60 to 100 beats per minute. Rhythm is regular or essentially regular. PR interval is 0.12 to 0.20 seconds. QRS interval is 0.06 to 0.10 seconds. P and QRS waves are consistent in shape. Sinus tachycardia results when the SA node fires faster than 100 beats per minute. Bradycardia is defined as a heart rate less than 60 beats per minute. Sinus arrhythmia is a cyclical change in heart rate that is associated with respiration. The heart rate slightly increases during inspiration and slightly slows during exhalation because of changes in vagal tone.
Interpret the following rhythm: a. Normal sinus rhythm b. Sinus bradycardia c. Sinus tachycardia d. Sinus arrhythmia
ANS: C AV nodal blocking medications (such as beta blockers, calcium channel blockers, and digoxin) and increased vagal tone may cause sinus exit block. Causes are explored, and prescribed medications may need to be adjusted or discontinued. If patients are symptomatic, significant numbers of pauses may require treatment, including temporary (including transcutaneous) and permanent implantation of a pacemaker.
The patient is admitted with sinus pauses causing periods of loss of consciousness. The patient is asymptomatic, awake and alert, but fatigued. He answers questions appropriately. When admitting this patient, the nurse should first a. prepare the patient for temporary pacemaker insertion. b. prepare the patient for permanent pacemaker insertion. c. assess the patient's medication profile. d. apply transcutaneous pacemaker paddles.
ANS: A, B, D Common causes of sinus tachycardia include hyperthyroidism, hypovolemia, heart failure, anemia, exercise, use of stimulants, fever, and sympathetic response to fear or pain and anxiety. Hypothyroidism and sleep tend to slow the heart rate.
Which of the following are common causes of sinus tachycardia? (Select all that apply.) a. Hyperthyroidism b. Hypovolemia c. Hypothyroidism d. Heart Failure e. Sleep
ANS: A Sinus arrhythmia is a cyclical change in heart rate that is associated with respiration. The heart rate increases slightly during inspiration and slows slightly during exhalation because of changes in vagal tone. The ECG tracing demonstrates an alternating pattern of faster and slower heart rate that changes with the respiratory cycle. Interval measurements are normal. This rhythm is tolerated well, and no treatment is required. The PR and QRS intervals are normal.
Which of the following is true about a patient diagnosed with sinus arrhythmia? a. The heart rate varies, dependent on vagal tone and respiratory pattern. b. Immediate treatment is essential to prevent death. c. Sinus arrhythmia is not well tolerated by most patients. d. PR and QRS interval measurements are prolonged.
ANS: A The normal intrinsic rate for the AV node and junctional tissue is 40 to 60 beats per minute, but rates can accelerate. An accelerated junctional rhythm has a rate between 60 and 100 beats per minute, and the rate for junctional tachycardia is greater than 100 beats per minute. If a P wave precedes QRS, it is inverted or upside down; the P wave may not be visible, or it may follow the QRS. If a P wave is present before the QRS, the PR interval is shortened to less than 0.12 milliseconds. Atrial fibrillation arises from multiple ectopic foci in the atria, causing chaotic quivering of the atria and ineffectual atrial contraction. The AV node is bombarded with hundreds of atrial impulses and conducts these impulses in an unpredictable manner to the ventricles.
Interpret the following rhythm: a. Junctional rhythm b. An accelerated junctional rhythm c. A junctional tachycardia d. Atrial fibrillation
ANS: C Failure to pace or fire occurs when the pacemaker fails to initiate an electrical stimulus when it should fire. The problem is noted by absence of pacer spikes on the rhythm strip. Note that after the 3-second mark, the pacemaker failed to fire. When the pacemaker generates an electrical impulse (pacer spike) and no depolarization is noted, it is described as a failure to capture. On the ECG, a pacer spike is noted, but it is not followed by a P wave (atrial pacemaker) or a QRS complex (ventricular pacemaker) within the appropriate time frame. When the pacemaker does not sense the patient's own cardiac rhythm and initiates an electrical impulse, it is called failure to sense. Failure to sense manifests as pacer spikes that fall too closely to the patient's own rhythm, earlier than the programmed rate. This is not normal pacemaker function.
Interpret the following rhythm: a. Normal pacemaker function b. Failure to capture c. Failure to pace d. Failure to sense
ANS: A A single ectopic focus produces PVC waveforms that look alike, called unifocal PVCs. Waveforms of PVCs arising from multiple foci are not identical and are called multifocal PVCs. PVCs may occur in a predictable pattern, such as every other beat (bigeminal), every third beat (trigeminal), or every fourth beat (quadrigeminal). PVCs can also occur sequentially. Two PVCs in a row are called a pair (or couplets), and three or more in a row are called nonsustained ventricular tachycardia.
Interpret the following rhythm: a. Sinus rhythm with multifocal premature ventricular contractions b. Sinus rhythm with unifocal premature ventricular contractions c. Sinus rhythm with bigeminal premature ventricular contractions d. Sinus rhythm with paired premature ventricular contractions (couplets)
ANS: A, C The waveform that initiates the QRS complex (whether it is a Q wave or an R wave) marks the beginning of the interval. The normal width of the QRS complex is 0.06 to 0.10 seconds. This width equals 1.5 to 2.5 small boxes. The normal PR interval is 0.12 to 0.20 seconds, three to five small boxes wide; not the QRS interval. A pathological Q wave has a width of 0.04 seconds and a depth that is greater than one fourth of the R wave amplitude; therefore, the QRS complex would be wider than that.
The normal width of the QRS complex is which of the following? (Select all that apply.) a. 0.06 to 0.10 seconds. b. 0.12 to 0.20 seconds. c. 1.5 to 2.5 small boxes. d. 3.0 to 5.0 small boxes. e. 0.04 seconds or greater.
ANS: B Normally a P wave indicates that the SA node initiated the impulse that depolarized the atrium. However, a change in the shape of the P wave may indicate that the impulse arose from a site in the atria other than the SA node. The P wave represents atrial depolarization. It is usually upright in leads I and II and has a rounded, symmetrical shape. The amplitude of the P wave is measured at the center of the waveform and normally does not exceed three boxes, or 3 millimeters, in height.
The nurse is examining the patient's cardiac rhythm strip in lead II and notices that all of the P waves are upright and look the same except one that has a different shape and is inverted. The nurse realizes that the P wave with the abnormal shape is probably a. from the SA node because all P waves come from the SA node. b. from some area in the atria other than the SA node. c. indicative of ventricular depolarization. d. normal even though it is inverted in lead II.
ANS: D Ventricular fibrillation (VF) is a chaotic rhythm characterized by a quivering of the ventricles, which results in total loss of cardiac output and pulse. VF is a life-threatening emergency, and the more immediate the treatment is, the better the survival will be. VF produces a wavy baseline without a PQRST complex. Because a loose lead or electrical interference can produce a waveform similar to VF, it is always important to immediately assess the patient for pulse and consciousness.
The nurse is talking with the patient when the monitor alarms and shows a wavy baseline without a PQRST complex. The nurse should a. defibrillate the patient immediately. b. initiate basic life support. c. initiate advanced life support. d. assess the patient and the electrical leads.
ANS: B ECG paper contains a standardized grid where the horizontal axis measures time and the vertical axis measures voltage or amplitude. Horizontally, the smaller boxes denote 0.04 seconds each or 40 milliseconds; the larger box contains five smaller boxes and thus equals 0.20 seconds or 200 milliseconds.
The nurse using cardiac monitoring understands that each horizontal box on the electrocardiogram (ECG) paper indicates a. 200 milliseconds or 0.20 seconds duration. b. 40 milliseconds or 0.04 seconds duration. c. 3 seconds duration. d. millivolts of amplitude.
ANS: C Digitalis toxicity is a major cause of this rhythm, and further digitalis doses should not be given until a digitalis level is obtained. Other causes of Mobitz I include AV nodal blocking drugs, acute inferior wall myocardial infarction or right ventricular infarction, ischemic heart disease, and excess vagal response. This type of block is usually well tolerated, and no treatment is indicated unless the dropped beats occur frequently.
The patient is asymptomatic but is diagnosed with second-degree heart block Mobitz I. The patient is on digitalis medication at home. The nurse should expect that a. the patient has had an anterior wall myocardial infarction. b. the physician will order the digitalis to be continued in the hospital. c. a digitalis level would be ordered upon admission. d. the patient will require a transcutaneous pacemaker.
ANS: A, B, C, D Because of the location of the AV node—in the center of the heart—impulses generated may be conducted forward, backward, or both. With the potential of forward, backward, or bidirectional impulse conduction, three different P waveforms may be associated with junctional rhythms: When the AV node impulse moves forward, P waves may be absent because the impulse enters the ventricle first. The atria receives the wave of depolarization at the same time as the ventricles; thus, because of the larger muscle mass of the ventricles, there is no P wave. When the AV node impulse is conducted backward, the impulse enters the atria first. When depolarization occurs backward, an inverted P wave is created. Once the atria have been depolarized, the impulse moves down the bundle of His and depolarizes both ventricles normally. A short PR interval (<0.12 second) is noted. When the impulse is conducted both forward and backward, P waves may be present after the QRS complex.
The possible P waveforms that are associated with junctional rhythms include which of the following? (Select all that apply.) a. No P wave b. Inverted P wave c. Shortened PR interval d. P wave after the QRS complex e. Normal P wave and PR interval
ANS: A Atrial fibrillation arises from multiple ectopic foci in the atria, causing chaotic quivering of the atria and ineffectual atrial contraction. The AV node is bombarded with hundreds of atrial impulses and conducts these impulses in an unpredictable manner to the ventricles. The atrial rate may be as high 700 and no discernible P waves can be identified, resulting in a wavy baseline and an extremely irregular ventricular response. Atrial flutter arises from a single irritable focus in the atria. The atrial focus fires at an extremely rapid, regular rate, between 240 and 320 beats per minute. The P waves are called flutter waves and may have a sawtooth appearance. The ventricular response may be regular or irregular based on how many flutter waves are conducted through the AV node. Atrial flutter with RVR occurs when atrial impulses cause a ventricular response greater than 100 beats per minute. A junctional escape rhythm is a ventricular rate between 40 and 60 beats per minute with a regular rhythm. P waves may be absent, inverted, or follow the QRS complex. If a P wave is present before the QRS complex, the PR interval is shortened to less than 0.12 milliseconds. QRS complex is normal.
Interpret the following rhythm: a. Atrial fibrillation b. Atrial flutter c. Atrial flutter with RVR d. Junctional escape rhythm
ANS: A Pacemakers may be used to stimulate the atrium, ventricle, or both chambers (dual-chamber pacemakers). Atrial pacing is used to mimic normal conduction and to produce atrial contraction, thus providing atrial kick. This is the case in the scenario provided. Ventricular pacing stimulates ventricular depolarization and is commonly used in emergency situations or when pacing is required infrequently. Dual-chamber pacing allows for stimulation of both atria and ventricles as needed to synchronize the chambers and mimic the normal cardiac cycle. However, with this patient, ventricular and AV function are normal. Transcutaneous pacing is delivered through the skin via external electrode pads connected to an external pacemaker.
Interpret the following rhythm: a. Atrial pacing b. Ventricular pacing c. Dual-chamber pacing d. Transcutaneous pacing
ANS: B Pacemakers may be used to stimulate the atrium, ventricle, or both chambers (dual-chamber pacemakers). Atrial pacing is used to mimic normal conduction and to produce atrial contraction, thus providing atrial kick. Ventricular pacing stimulates ventricular depolarization and is commonly used in emergency situations or when pacing is required infrequently. This patient's pacemaker is stimulating the ventricles. Dual-chamber pacing allows for stimulation of both atria and ventricles as needed to synchronize the chambers and mimic the normal cardiac cycle. There is no evidence of a dual pacemaker since the atrial spike is not seen on the ECG strip. Transcutaneous pacing is accomplished via skin electrodes.
Interpret the following rhythm: a. Atrial pacing b. Ventricular pacing c. Dual-chamber pacing d. Transcutaneous pacing
ANS: C Pacemakers may be used to stimulate the atrium, ventricle, or both chambers (dual-chamber pacemakers). Atrial pacing is used to mimic normal conduction and to produce atrial contraction, thus providing atrial kick. Ventricular pacing stimulates ventricular depolarization and is commonly used in emergency situations or when pacing is required infrequently. Dual-chamber pacing allows for stimulation of both atria and ventricles as needed to synchronize the chambers and mimic the normal cardiac cycle. This is the case in the scenario provided as seen by pacemaker spikes in both the atrial and ventricular position.
Interpret the following rhythm: a. Atrial pacing b. Ventricular pacing c. Dual-chamber pacing d. Transcutaneous pacing
ANS: B Also called a Mobitz I or Wenckebach phenomenon, second-degree AV block type I is represented on the ECG as a progressive lengthening of the PR interval until there is a P wave without a QRS complex. In first-degree AV block, a P wave precedes every QRS complex, and every P wave is followed by a QRS; however, the PR interval is >0.20 seconds. Second-degree AV block type II (Mobitz II) is a more critical type of heart block that requires early recognition and intervention. There is no progressive lengthening of the PR interval, which remains the same throughout with the exception of the dropped beat(s). Third-degree block is often called complete heart block because no atrial impulses are conducted through the AV node to the ventricles. In complete heart block, the atria and ventricles beat independently of each other because the AV node is completely blocked to the sinus impulse and it is not conducted to the ventricles. One hallmark of third-degree heart block is that the P waves have no association with the QRS complexes and appear throughout the QRS waveform.
Interpret the following rhythm: a. First-degree AV block b. Second-degree AV block Mobitz I (Wenckebach phenomenon) c. Second-degree AV block Mobitz II d. Third-degree AV block (complete heart block)
ANS: C Second-degree AV block type II (Mobitz II) is a more critical type of heart block that requires early recognition and intervention. There is no progressive lengthening of the PR interval, which remains the same throughout with the exception of the dropped beat(s). Also called a Mobitz I or Wenckebach phenomenon, second-degree AV block type I is represented on the ECG as a progressive lengthening of the PR interval until there is a P wave without a QRS complex. In first-degree AV block, a P wave precedes every QRS complex, and every P wave is followed by a QRS. Third-degree block is often called complete heart block because no atrial impulses are conducted through the AV node to the ventricles. In complete heart block, the atria and ventricles beat independently of each other because the AV node is completely blocked to the sinus impulse and it is not conducted to the ventricles. One hallmark of third-degree heart block is that the P waves have no association with the QRS complexes and appear throughout the QRS waveform.
Interpret the following rhythm: a. First-degree AV block b. Second-degree AV block Mobitz I (Wenckebach phenomenon) c. Second-degree AV block Mobitz II d. Third-degree AV block (complete heart block)
ANS: D Third-degree block is often called complete heart block because no atrial impulses are conducted through the AV node to the ventricles. In complete heart block, the atria and ventricles beat independently of each other because the AV node is completely blocked to the sinus impulse and it is not conducted to the ventricles. One hallmark of third-degree heart block is that the P waves have no association with the QRS complexes and appear throughout the QRS waveform. Second-degree AV block type II (Mobitz II) is a more critical type of heart block that requires early recognition and intervention. There is no progressive lengthening of the PR interval, which remains the same throughout with the exception of the dropped beat(s). Also called a Mobitz I or Wenckebach phenomenon, second-degree AV block type I is represented on the ECG as a progressive lengthening of the PR interval until there is a P wave without a QRS complex. In first-degree AV block, a P wave precedes every QRS complex, and every P wave is followed by a QRS.
Interpret the following rhythm: a. First-degree AV block b. Second-degree AV block Mobitz I (Wenckebach phenomenon) c. Second-degree AV block Mobitz II d. Third-degree AV block (complete heart block)
ANS: A Idioventricular rhythm is an escape rhythm that is generated by the Purkinje fibers. This rhythm emerges only when the SA and AV nodes fail to initiate an impulse. The Purkinje fibers are capable of an intrinsic rate of 20 to 40 beats per minute. Because this last pacemaker is located in the ventricles, the QRS complex appears wide and bizarre with a slow rate. No P waves are present. If the rate is between 40 and 100 beats per minute, this rhythm is called accelerated idioventricular rhythm (AIVR). Ventricular tachycardia (VT) is a rapid, life-threatening dysrhythmia originating from a single ectopic focus in the ventricles. It is characterized by at least three PVCs in a row. VT occurs at a rate greater than 100 beats per minute, but the rate is usually around 150 beats per minute and may be up to 250 beats per minute. VF produces a wavy baseline without a PQRST complex. Because a loose lead or electrical interference can produce a waveform similar to VF, it is always important to immediately assess the patient for pulse and consciousness.
Interpret the following rhythm: a. Idioventricular rhythm b. Accelerated idioventricular rhythm c. Ventricular tachycardia d. Ventricular fibrillation
ANS: D When the pacemaker does not sense the patient's own cardiac rhythm and initiates an inappropriate electrical impulse, it is called failure to sense. Failure to sense manifests as pacer spikes that fall too closely to the patient's own rhythm, earlier than the programmed rate. This is not normal pacemaker function. When the pacemaker generates an electrical impulse (pacer spike) and no depolarization is noted, it is described as a failure to capture. On the ECG, a pacer spike is noted, but it is not followed by a P wave (atrial pacemaker) or a QRS complex (ventricular pacemaker). Failure to pace or fire occurs when the pacemaker fails to initiate an electrical stimulus when it should fire. The problem is noted by absence of pacer spikes on the rhythm strip. When the pacemaker does not sense the patient's own cardiac rhythm and initiates an electrical impulse, it is called failure to sense.
Interpret the following rhythm: a. Normal pacemaker function b. Failure to capture c. Failure to pace d. Failure to sense
ANS: D In first-degree block, P and QRS waves are consistent in shape. P waves are small and rounded. A P wave precedes every QRS complex, which is followed by a T wave. PR interval is prolonged and is greater than 0.20 seconds. QRS complex and QT/QTc measurements are normal. Normal sinus rhythm (NSR) reflects normal conduction of the sinus impulse through the atria and ventricles. Atrial and ventricular rates are the same and range from 60 to 100 beats per minute. Rhythm is regular or essentially regular. PR interval is 0.12 to 0.20 seconds. In a complete heart block, the atria and ventricles beat independently of each other. A first-degree AV block means the PR interval is greater than 0.20 seconds
Interpret the following rhythm: a. Normal sinus rhythm b. Sinus rhythm with second-degree AV block c. Complete heart block d. Sinus rhythm with first-degree AV block
ANS: A The peak of the T wave through the downslope of the T wave is considered the vulnerable period, which coincides with partial repolarization of the ventricles. If a PVC occurs during the T wave, ventricular tachycardia may occur. When the R wave of a PVC falls on the T wave of a normal beat, it is referred to as the R-on-T phenomenon. This strip does not show sinus rhythm, multi-focal PVCs (PVCs that are from different places in the heart and therefore look different), non-sustained ventricular tachycardia, or bigeminal premature ventricular contractions (where every other beat is a PVC).
Interpret the following rhythm: a. R-on-T phenomenon leading to ventricular fibrillation b. Sinus rhythm with multifocal premature ventricular contractions c. Nonsustained ventricular tachycardia d. Sinus rhythm with bigeminal premature ventricular contractions
ANS: C A single ectopic focus produces PVC waveforms that look alike, called unifocal PVCs. Waveforms of PVCs arising from multiple foci are not identical and are called multifocal PVCs. PVCs may occur in a predictable pattern, such as every other beat (bigeminal), every third beat (trigeminal), or every fourth beat (quadrigeminal). PVCs can also occur sequentially. Two PVCs in a row are called a pair (couplet), and three or more in a row are called nonsustained ventricular tachycardia.
Interpret the following rhythm: a. Sinus rhythm with multifocal premature ventricular contractions b. Sinus rhythm with unifocal premature ventricular contractions c. Sinus rhythm with bigeminal premature ventricular contractions d. Sinus rhythm with paired premature ventricular contractions (couplets)
ANS: D A single ectopic focus produces PVC waveforms that look alike, called unifocal PVCs. Waveforms of PVCs arising from multiple foci are not identical and are called multifocal PVCs. PVCs may occur in a predictable pattern, such as every other beat (bigeminal), every third beat (trigeminal), or every fourth beat (quadrigeminal). PVCs can also occur sequentially. Two PVCs in a row are called a pair (couplet), and three or more in a row are called nonsustained ventricular tachycardia.
Interpret the following rhythm: a. Sinus rhythm with multifocal premature ventricular contractions b. Sinus rhythm with unifocal premature ventricular contractions c. Sinus rhythm with bigeminal premature ventricular contractions d. Sinus rhythm with paired premature ventricular contractions (couplets)
ANS: B A single ectopic focus produces PVC waveforms that look alike, called unifocal PVCs. Waveforms of PVCs arising from multiple foci are not identical and are called multifocal PVCs. PVCs may occur in a predictable pattern, such as every other beat (bigeminal), every third beat (trigeminal), or every fourth beat (quadrigeminal). PVCs also can occur sequentially. Two PVCs in a row are called a pair, and three or more in a row are called nonsustained ventricular tachycardia.
Interpret the following rhythm: a. Sinus rhythm with multifocal premature ventricular contractions b. Sinus rhythm with unifocal premature ventricular contractions c. Sinus rhythm with trigeminal premature ventricular contractions d. Sinus rhythm with paired premature ventricular contractions (couplets)
ANS: B Normal sinus rhythm (NSR) reflects normal conduction of the sinus impulse through the atria and ventricles. Atrial and ventricular rates are the same and range from 60 to 100 beats per minute. Rhythm is regular or essentially regular. PR interval is 0.12 to 0.20 seconds. QRS interval is 0.06 to 0.10 seconds. P and QRS waves are consistent in shape. Sinus tachycardia results when the SA node fires faster than 100 beats per minute. Bradycardia is defined as a heart rate less than 60 beats per minute. Sinus arrhythmia is a cyclical change in heart rate that is associated with respiration. The heart rate increases slightly during inspiration and slows slightly during exhalation because of changes in vagal tone.
Interpret the following rhythm: a. Normal sinus rhythm b. Sinus bradycardia c. Sinus tachycardia d. Sinus arrhythmia
ANS: C Normal sinus rhythm (NSR) reflects normal conduction of the sinus impulse through the atria and ventricles. Atrial and ventricular rates are the same and range from 60 to 100 beats per minute. Rhythm is regular or essentially regular. PR interval is 0.12 to 0.20 seconds. QRS interval is 0.06 to 0.10 seconds. P and QRS waves are consistent in shape. Sinus tachycardia results when the SA node fires faster than 100 beats per minute. Bradycardia is defined as a heart rate less than 60 beats per minute. Sinus arrhythmia is a cyclical change in heart rate that is associated with respiration. The heart rate slightly increases during inspiration and slightly slows during exhalation because of changes in vagal tone.
Interpret the following rhythm: a. Normal sinus rhythm b. Sinus bradycardia c. Sinus tachycardia d. Sinus arrhythmia
ANS: A The underlying rhythm is identified first. Following this step, the dysrhythmia that is occurring to disrupt the underlying rhythm is then determined. A premature atrial contraction (PAC) is a single ectopic beat arising from atrial tissue, not the sinus node. The PAC occurs earlier than the next normal beat and interrupts the regularity of the underlying rhythm. The P wave of the PAC has a different shape than the sinus P wave because it arises from a different area in the atria; it may follow or be in the T wave of the preceding normal beat. If the early P wave is in the T wave, this T wave will look different from the T wave of a normal beat. Normal sinus rhythm (NSR) reflects normal conduction of the sinus impulse through the atria and ventricles. Atrial and ventricular rates are the same and range from 60 to 100 beats per minute. Rhythm is regular or essentially regular. PR interval is 0.12 to 0.20 seconds. QRS interval is 0.06 to 0.10 seconds. P and QRS waves are consistent in shape. Sinus tachycardia results when the SA node fires faster than 100 beats per minute. Bradycardia is defined as a heart rate less than 60 beats per minute.
Interpret the following rhythm: a. Sinus rhythm with PACs b. Normal sinus rhythm c. Sinus tachycardia d. Sinus bradycardia
ANS: B The impulse from the SA node quickly reaches the atrioventricular (AV) node located in the area called the AV junction, between the atria and the ventricles. Here the impulse is slowed to allow time for ventricular filling during relaxation or ventricular diastole. The AV node has pacemaker properties and can discharge an impulse if the SA node (not the ventricle) fails. The electrical impulse is then rapidly conducted through the bundle of His to the ventricles (not the SA node) via the left and right bundle branches.
One of the functions of the atrioventricular (AV) node is to a. pace the heart if the ventricles fail. b. slow the impulse arriving from the SA node. c. send the impulse to the SA node. d. allow for ventricular filling during systole.
ANS: A, B, C, D Vasovagal response; medications such as digoxin or AV nodal blocking agents, including calcium channel blockers and beta blockers; myocardial infarction; normal physiological variant in the athlete; disease of the sinus node; increased intracranial pressure; hypoxemia; and hypothermia may cause sinus bradycardia. Hyperthyroidism is a cause of sinus tachycardia.
Sinus bradycardia is a symptom of which of the following? (Select all that apply.) a. Calcium channel blocker medication b. Beta blocker medication c. Athletic conditioning d. Hypothermia e. Hyperthyroidism
ANS: B The sinus node reaches threshold at a rate of 60 to 100 times per minute. Because this is the fastest pacemaker in the heart, the SA node is the dominant pacemaker of the heart. The AV node has an inherent rate of 40 to 60 beats per minute and the His-Purkinje system can fire at a rate of 20 to 40 beats per minute. Sinus tachycardia results when the SA node fires faster than 100 beats per minute.
The normal rate for the SA node when the patient is at rest is a. 40 to 60 beats per minute. b. 60 to 100 beats per minute. c. 20 to 40 beats per minute. d. more than100 beats per minute.
ANS: C The QT interval is measured from the beginning of the QRS complex to the end of the T wave. This interval measures the total time taken for ventricular depolarization and repolarization. Abnormal prolongation of the QT interval increases vulnerability to lethal dysrhythmias, such as ventricular tachycardia and fibrillation. The nurse monitors the patient for the development of these rhythms and is prepared to intervene should they occur. A prolonged QT is not associated with bradycardias, hypokalemia, or blood pressure irregularities.
The nurse caring for patients on cardiac monitors assesses the patient with a prolonged QT interval for a. electrolyte disturbances such as hypokalemia. b. symptomatic bradycardias. c. the development of lethal dysrhythmias. d. difficulty maintaining the blood pressure.
ANS: C When an electrical signal is aimed directly at the positive electrode, an upright inflection is visualized. If the impulse is going away from the positive electrode, a negative deflection is seen; and if the signal is perpendicular to the imaginary line between the positive and negative poles of the lead, the tracing is equiphasic, with equally positive and negative deflection.
The nurse caring for patients with cardiac monitoring understands that when an electrical signal is aimed directly at the positive electrode, the inflection will be: a. negative. b. upside down. c. upright. d. equally positive and negative.
ANS: B The rule of 1500 is used to calculate the exact rate of a regular rhythm. The number of small boxes between the highest points of two consecutive R waves is counted, and that number of small boxes is divided into 1500 to determine the ventricular rate. 1500/20 = 75 beats/min. This method is accurate only if the rhythm is regular.
The nurse is calculating the rate for a regular rhythm. There are 20 small boxes between each P wave and 20 small boxes between each R wave. What is the ventricular rate? a. 50 beats/min b. 75 beats/min c. 85 beats/min d. 100 beats/min
ANS: A, C, E One complication of atrial fibrillation is thromboembolism. The blood that collects in the atria is agitated by fibrillation, and normal clotting is accelerated. Small thrombi, called mural thrombi, begin to form along the walls of the atria. These clots may dislodge, resulting in pulmonary embolism or stroke. The ineffectual contraction of the atria results in loss of "atrial kick." If too many impulses conduct to the ventricles, atrial fibrillation with rapid ventricular response may result and compromise cardiac output. Ashman beats are not clinically significant. No recognizable or discernible P waves are present; therefore, PR interval is absent.
The nurse is caring for a patient who has atrial fibrillation. Sequelae that place the patient at greater risk for mortality/morbidity include which of the following? (Select all that apply.) a. Stroke b. Ashman beats c. Pulmonary emboli d. Prolonged PR interval e. Decreased cardiac output
ANS: A The cardiac cycle begins with an impulse that is generated from a small concentrated area of pacemaker cells high in the right atria called the sinoatrial node (sinus node or SA node). The SA node has the fastest rate of discharge and thus is the dominant pacemaker of the heart. The AV node has pacemaker properties and can discharge an impulse if the SA node fails. The ventricles have pacemaker capabilities if the sinus node or the AV node ceases to generate impulses.
The nurse is caring for a patient who is on a cardiac monitor. The nurse realizes that the sinus node is the pacemaker of the heart because it is a. the fastest pacemaker cell in the heart. b. the only pacemaker cell in the heart. c. the only cell that does not affect the cardiac cycle. d. located in the left side of the heart
ANS: A Atrial fibrillation arises from multiple ectopic foci in the atria, causing chaotic quivering of the atria and ineffectual atrial contraction. No discernible P waves can be identified, resulting in a wavy baseline and an extremely irregular ventricular response. Atrial flutter arises from a single irritable focus in the atria. The atrial focus fires at an extremely rapid, regular rate, between 240 and 320 beats per minute. The P waves are called flutter waves and may have a sawtooth appearance. Atrial flutter with rapid ventricular response occurs when atrial impulses cause a ventricular response greater than 100 beats per minute. A junctional escape rhythm is a ventricular rate between 40 and 60 beats per minute with a regular rhythm. P waves may be absent, inverted, or follow the QRS complex. QRS complex is normal.
The nurse is reading the cardiac monitor and notes that the patient's heart rhythm is extremely irregular and that there are no discernible P waves. The ventricular rate is 90 beats per minute, and the patient is hemodynamically stable. The nurse realizes that the patient's rhythm is a. atrial fibrillation. b. atrial flutter. c. atrial flutter with rapid ventricular response. d. junctional escape rhythm.
ANS: B Ventricular fibrillation (VF) is a chaotic rhythm characterized by a quivering of the ventricles, which results in total loss of cardiac output and pulse. VF is a life-threatening emergency, and the more immediate the treatment, the better the survival will be. VF produces a wavy baseline without a PQRST complex. Because a loose lead or electrical interference can produce a waveform similar to VF, it is always important to immediately assess the patient for pulse and consciousness. If no pulse is present, provide emergent basic and advanced life-support interventions, including defibrillation. IV medications can be used as part of advanced life support. Cardioversion is not warranted since the patient is pulseless. This rhythm is not benign and cannot be ignored.
The nurse notes the following rhythm on the heart monitor. The patient is unresponsive and not breathing. The nurse should a. treat with intravenous amiodarone or lidocaine. b. provide emergent basic and advanced life support. c. provide electrical cardioversion. d. ignore the rhythm because it is benign.
ANS: D Sinus bradycardia may be a normal heart rhythm for some individuals such as athletes, or it may occur during sleep. Assess for hemodynamic instability related to the bradycardia. If the patient is symptomatic, interventions include administration of atropine. If atropine is not effective in increasing heart rate, then transcutaneous pacing, dopamine infusion, or epinephrine infusion may be administered. Atropine is avoided for treatment of bradycardia associated with hypothermia.
The nurse notices sinus bradycardia on the patient's cardiac monitor. The nurse should a. give atropine to increase heart rate. b. begin transcutaneous pacing of the patient. c. start a dopamine infusion to stimulate heart function. d. assess for hemodynamic instability.
ANS: C First-degree AV block is a common dysrhythmia in the elderly and in patients with cardiac disease. As the normal conduction pathway ages or becomes diseased, impulse conduction becomes slower than normal. It is well tolerated. No treatment is required. Continue to monitor the patient and the rhythm.
The nurse notices that the patient has a first-degree AV block. Everything else about the rhythm is normal. The nurse should a. prepare to place the patient on a transcutaneous pacemaker. b. give the patient atropine to shorten the PR interval. c. monitor the rhythm and patient's condition. d. give the patient an antiarrhythmic medication.
ANS: B Ventricular tachycardia (VT) is a rapid, life-threatening dysrhythmia originating from a single ectopic focus in the ventricles. Determine whether the patient has a pulse. If no pulse is present, provide emergent basic and advanced life-support interventions, including defibrillation. If a pulse is present and the blood pressure is stable, the patient can be treated with intravenous amiodarone or lidocaine. Cardioversion is used as an emergency measure in patients who become hemodynamically unstable but continue to have a pulse. It also may be used in nonemergency situations, such as when a patient has asymptomatic VT.
The nurse notices ventricular tachycardia on the heart monitor. When the patient is assessed, the patient is found to be unresponsive with no pulse. The nurse should a. treat with intravenous amiodarone or lidocaine. b. begin cardiopulmonary resuscitation and advanced life support. c. provide electrical cardioversion. d. ignore the rhythm because it is benign.
ANS: C Third-degree block is often called complete heart block because no atrial impulses are conducted through the AV node to the ventricles. Normally every P wave is conducted to the ventricles. If some of the P waves are conducted but others are not, further assessment is needed to determine the type of block present. A prolonged PR interval is a first-degree AV block, and is well tolerated and requires no treatment.
The nurse understands that in a third-degree AV block a. every P wave is conducted to the ventricles. b. some P waves are conducted to the ventricles. c. none of the P waves are conducted to the ventricles. d. the PR interval is prolonged.
ANS: A The optimal method of determining a heart rate from an ECG strip when the patient has an irregular heart rate is to count the number of P waves or QRS waves within a 6-second strip to obtain both atrial and ventricular heart rates per minute. In order to do this accurately, the nurse first much identify the markers on the ECG paper that indicate a 6-second strip. The other methods are not as accurate with an irregular heart rate.
The patient has an irregular heart rhythm. To determine an accurate heart rate, the nurse would first a. identify the markers on the ECG paper that indicate a 6-second strip. b. count the number of small boxes between two consecutive P waves. c. count the number of small boxes between two consecutive QRS complexes. d. divides the number of complexes in a 6-second strip by 10.
ANS: D Adequate skin preparation of electrode sites requires clipping the hair, cleansing the skin, and drying vigorously (moisture gels are not applied). Cleansing includes washing with soap and water, or alcohol, to remove skin debris and oils. Before application, the electrodes are checked to ensure that the gel is moist. It is difficult for electrodes to adhere to the chest in the presence of chest hair. Clipping, not shaving, is recommended since shaving may create small nicks that can become a portal for infection.
The patient is admitted with a condition that requires cardiac rhythm monitoring. To apply the monitoring electrodes, the nurse must first a. apply a moist gel to the chest. b. make certain that the electrode gel is dry. c. avoid soaps to avoid skin irritation. d. clip chest hair if needed.
ANS: B Sinus tachycardia results when the SA node fires faster than 100 beats per minute. All other components of the ECG are normal. Sinus tachycardia is a normal response to stimulation of the sympathetic nervous system. Sinus tachycardia is also a normal finding in children younger than 6 years. The fast heart rhythm may cause a decrease in cardiac output because of the shorter filling time for the ventricles. Lowering cardiac output further may complicate the situation. The dysrhythmia itself is not treated, but the cause is identified and treated appropriately. For example, if the patient has a fever or is in pain, the fever (and infection) or pain is treated appropriately.
The patient is admitted with a fever and rapid heart rate. The patient's temperature is 103° F (39.4° C). The nurse places the patient on a cardiac monitor and finds the patient's atrial and ventricular rates are above 105 beats per minute. P waves are clearly seen and appear normal in configuration. QRS complexes are normal in appearance and 0.08 seconds wide. The rhythm is regular, and blood pressure is normal. The nurse should focus on providing: a. medications to lower heart rate. b. treatment to lower temperature. c. treatment to lower cardiac output. d. treatment to reduce heart rate.
ANS: D Ventricular tachycardia (VT) is a rapid, life-threatening dysrhythmia originating from a single ectopic focus in the ventricles. It is characterized by at least three PVCs in a row. VT occurs at a rate greater than 100 beats per minute, but the rate is usually around 150 beats per minute and may be up to 250 beats per minute. Depolarization of the ventricles is abnormal and produces a widened QRS complex. The patient may or may not have a pulse. Determine whether the patient has a pulse. If no pulse is present, provide emergent basic and advanced life-support interventions, including defibrillation. If a pulse is present and the blood pressure is stable, the patient can be treated with intravenous amiodarone or lidocaine.
The patient is alert and talking when the nurse notices the following rhythm. The patient's blood pressure is 90/44 mm Hg. The nurse should a. defibrillate immediately. b. begin basic life support. c. begin advanced life support. d. treat with intravenous amiodarone or lidocaine.
ANS: A The peak of the T wave through the downslope of the T wave is considered the vulnerable period, which coincides with partial repolarization of the ventricles. If a PVC occurs during the T wave, ventricular tachycardia may occur. When the R wave of PVC falls on the T wave of a normal beat, it is referred to as the R-on-T phenomenon. PVCs may occur in healthy individuals and usually do not require treatment. The nurse must determine if PVCs are increasing in number by evaluating the trend. If PVCs are increasing, the nurse should evaluate for potential causes, such as electrolyte imbalances, myocardial ischemia or injury, and hypoxemia. Runs of nonsustained ventricular tachycardia may be a precursor to the development of sustained ventricular tachycardia. Because the stimulus depolarizes the ventricles in a slower, abnormal way, the QRS complex appears widened and has a bizarre shape. The QRS complex is wider than 0.12 seconds and often wider than 0.16 seconds.
The patient is having premature ventricular contractions (PVCs). The nurse's greatest concern should be: a. the proximity of the R wave of the PVC to the T wave of a normal beat. b. the fact that PVCs are occurring, because they are so rare. c. whether the number of PVCs is decreasing. d. whether the PVCs are wider than 0.12 seconds.
ANS: A, C, D Treatments include transcutaneous or transvenous pacing and implanting a permanent pacemaker. Atropine reduces vagal tone, but that is not a cause of complete heart block and will produce more P waves, but the P waves will still not be associated with the QRS complexes. It is important to note that the only treatment is pacing. Amiodarone IV is used to suppress ventricular dysrhythmia and is not used to treat third-degree heart block.
The patient is in third-degree heart block (complete heart block) and is symptomatic. The treatment for this patient is which of the following? (Select all that apply.) a. Transcutaneous pacemaker b. Atropine IV c. Temporary transvenous pacemaker d. Permanent pacemaker e. Amiodarone IV
ANS: D If an abnormal P wave cannot be visualized on the ECG but the QRS complex is narrow, the term supraventricular tachycardia (SVT) is often used. This is a generic term that describes any tachycardia that is not ventricular in origin; it is also used when the source above the ventricles cannot be identified, usually because the rate is too fast. Treatment is directed at assessing the patient's tolerance of the tachycardia. If the rate is higher than 150 beats per minute and the patient is symptomatic, emergent cardioversion is considered. Cardioversion is the delivery of a synchronized electrical shock to the heart by an external defibrillator. Beta blockers are a possibility if the patient is not symptomatic. Atropine is used in the treatment of bradycardia. If atropine is not effective in increasing heart rate, then transcutaneous pacing is implemented.
The patient's heart rate is 165 beats per minute. The cardiac monitor shows a rapid rate with narrow QRS complexes. The P waves cannot be seen, but the rhythm is regular. The patient's blood pressure has dropped from 124/62 mm Hg to 78/30 mm Hg. The patient's skin is cold and diaphoretic, and the patient is complaining of nausea. The nurse prepares the patient for a. administration of beta blockers. b. administration of atropine. c. transcutaneous pacemaker insertion. d. emergent cardioversion.
ANS: B The normal intrinsic rate for the AV node and junctional tissue is 40 to 60 beats per minute, but rates can accelerate. An accelerated junctional rhythm has a rate between 60 and 100 beats per minute, and the rate for junctional tachycardia is greater than 100 beats per minute. If P wave precedes QRS, it is inverted or upside down; the P wave may not be visible, or it may follow the QRS. If a P wave is present before the QRS, the PR interval is shortened less than 0.12 milliseconds. Atrial fibrillation arises from multiple ectopic foci in the atria, causing chaotic quivering of the atria and ineffectual atrial contraction. The AV node is bombarded with hundreds of atrial impulses and conducts these impulses in an unpredictable manner to the ventricles.
The patient's heart rate is 70 beats per minute, but the P waves come after the QRS complex. The nurse correctly determines that the patient's heart rhythm is a. a normal junctional rhythm. b. an accelerated junctional rhythm. c. a junctional tachycardia. d. atrial fibrillation.
ANS: A Junctional escape rhythm occurs when the dominant pacemaker, the SA node, fails to fire. The normal heart rate of the AV node is 40 to 60 beats per minute, so the AV node rate has neither increased nor decreased. P waves may be inverted. An increased SA node rate would override the AV node.
The patient's heart rhythm shows an inverted P wave with a PR interval of 0.06 seconds. The heart rate is 54 beats per minute. The nurse recognizes the rhythm is due to the a. loss of sinus node activity. b. increased rate of the AV node. c. increased rate of the SA node. d. decreased rate of the AV node.
