Chapter 7: Dysrhythmia Interpretation and Management
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.
a. 0.06 to 0.10 seconds. c. 1.5 to 2.5 small boxes. 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 patient is in chronic junctional escape rhythm with no atrial activity noted. Studies have demonstrated normal AV node function. This patient may be a candidate for which type of pacing? a. Atrial pacing b. Ventricular pacing c. Dual-chamber pacing d. Transcutaneous pacing
a. Atrial pacing 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.
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
a. Calcium channel blocker medication b. Beta-blocker medication c. Athletic conditioning d. Hypothermia 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.
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
a. Hyperthyroidism b. Hypovolemia d. Heart Failure 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.
Because of the location of the AV node, 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
a. No P wave b. Inverted P wave c. Shortened PR interval d. P wave after the QRS complex ANS: A, B, C, D Because of the location of the AV nodein the center of the heartimpulses 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 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
a. Stroke c. Pulmonary emboli e. Decreased cardiac output 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.
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.
a. The heart rate varies, dependent on vagal tone and respiratory pattern. ANS: ASinus 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 nurse is reading the cardiac monitor and notes that the patient's heart rhythm is extremely irregular and 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.
a. atrial fibrillation. 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 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. If a P wave is present before the QRS complex, the PR interval is shortened less than 0.12 milliseconds. QRS complex is normal.
The patient has an irregular heart rhythm. To determine an accurate heart rate, the nurse first: a. identifies the markers on the ECG paper that indicate a 6-second strip. b. counts the number of large boxes between two consecutive P waves. c. counts the number of small boxes between two consecutive QRS complexes. d. divides the number of complexes in a 6-second strip by 10.
a. identifies the markers on the ECG paper that indicate a 6-second strip. ANS: A Six-second method: A quick and easy estimate of heart rate can be accomplished by counting the number of P waves or QRS waves within a 6-second strip to obtain atrial and ventricular heart rates per minute. This is the optimal method for irregular rhythms. Identify the lines above the ECG paper that represent 6 seconds, and count the number of P waves within the lines; then add a zero (multiply by 10) to identify the atrial heart rate estimate for 1 minute. Next, identify the number of QRS waves in the 6-second strip and again add a zero to identify the ventricular rate. Large box method: In this method, two consecutive P and QRS waves are located. The number of large boxes between the highest points of two consecutive P waves is counted, and that number of large boxes is divided into 300 to determine the atrial rate in beats per minute. The number of large boxes between the highest points of two consecutive QRS waves is counted, and that number of large boxes is divided into 300 to determine the ventricular rate. This method is accurate only if the rhythm is regular.Small box method: The small box method is used to calculate the exact rate of a regular rhythm. In this method, two consecutive P and QRS waves are located. The number of small boxes between the highest points of these consecutive P waves is counted, and that number is divided into 1500 to determine the atrial rate in beats per minute. The number of small boxes between the highest points of two consecutive QRS waves is counted, and that number is divided into 1500 to determine the ventricular rate. This method is accurate only if the rhythm is regular.
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 as a junctional escape rhythm, and understands that 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.
a. loss of sinus node activity. 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. An increased SA node rate would override the AV node.
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.
a. the fastest pacemaker cell in the heart. 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 patient has a permanent pacemaker inserted. The provider has set the pacemaker to the demand mode at a rate of 60 beats per minute. The nurse realizes that: a. the pacemaker will pace only if the patient's intrinsic heart rate is less than 60 beats per minute. b. the demand mode often competes with the patient's own rhythm. c. the demand mode places the patient at risk for the R-on-T phenomenon. d. the fixed rate mode is safer and is the mode of choice.
a. the pacemaker will pace only if the patient's intrinsic heart rate is less than 60 beats per minute. ANS: A Pacemakers can be operated in a demand mode or a fixed rate (asynchronous) mode. The demand mode paces the heart when no intrinsic or native beat is sensed. For example, if the rate control is set at 60 beats per minute, the pacemaker will only pace if the patients heart rate drops to less than 60. The fixed rate mode paces the heart at a set rate, independent of any activity the patients heart generates. The fixed rate mode may compete with the patients own rhythm and deliver an impulse on the T wave (R-on-T phenomenon), with the potential for producing ventricular tachycardia or fibrillation. The demand mode is safer and is the mode of choice.
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. if the number of PVCs are decreasing. d. if the PVCs are wider than 0.12 seconds.
a. the proximity of the R wave of the PVC to the T wave of a normal beat. 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 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 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.
a. transcutaneous pacemaker. c. temporary transvenous pacemaker. d. permanent pacemaker. 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.
Electrocardiogram (ECG) paper contains a standardized grid where the horizontal axis measures time and the vertical axis measures voltage or amplitude. The nurse must understand that each horizontal box 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.
b. 40 milliseconds or 0.04 seconds duration. ANS: BECG 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 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.
b. 60 to 100 beats per minute. 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 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
b. 75 beats/min ANS: BThe 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 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.
b. an accelerated junctional rhythm. 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 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 since it is benign.
b. begin cardiopulmonary resuscitation and advanced life support. 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 rhythm on the cardiac monitor is showing numerous pacemaker spikes, but no P waves or QRS complexes following the spikes. The nurse realizes this as: a. normal pacemaker function. b. failure to capture. c. failure to pace. d. failure to sense.
b. failure to capture. ANS: B When the pacemaker generates an electrical impulse (pacer spike) and no depolarization is noted, it is described 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). Common causes of failure to capture include output (milliamperes) set too low, or displacement of the pacing lead wire from the myocardium (transvenous or epicardial leads). Other causes of failure to capture include battery failure, fracture of the pacemaker wire, or increased pacing threshold as a result of medication or electrolyte imbalance. This is not normal pacemaker function. 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. Causes of failure to pace include battery or pulse generator failure, fracture or displacement of a pacemaker wire, or loose connections. When the pacemaker does not sense the patients 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 patients own rhythm, earlier than the programmed rate. The most common cause is displacement of the pacemaker electrode wire.
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 since 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.
b. from some area in the atria other than the SA node. ANS: BNormally 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.
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.
b. slow the impulse arriving from the SA node. 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.
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.
b. treatment to lower temperature. ANS: B Sinus tachycardia results when the SA node fires faster than 100 beats per minute. 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. Both atrial and ventricular rates are greater than 100 beats per minute, up to 160 beats per minute, but may be as high as 180 beats per minute. Sinus tachycardia 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. P waves are small and rounded. A P wave precedes every QRS complex, which is then followed by a T wave. The fast heart rhythm may cause a decrease in cardiac output because of the shorter filling time for the ventricles. Lowering cardiac out 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 infection or pain is treated appropriately.
The patient is scheduled to have a permanent pacemaker implanted. The patient asks the nurse, "How long will the battery in this thing last?" The nurse should answer, a. "Life expectancy is about 1 year. Then it will need to be replaced." b. "Pacemaker batteries can last up to 25 years with constant use." c. "Battery life varies depending on usage, but it can last up to 10 years." d. "Pacemakers are used to treat temporary problems so the batteries don't last long."
c. "Battery life varies depending on usage, but it can last up to 10 years." ANS: C Implanted permanent pacemakers are used to treat chronic conditions. These devices have a battery life of up to 10 years, which varies based on the manufacturers recommendations.
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.
c. a digitalis level would be ordered upon admission. 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 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.
c. assess the patient's medication profile. 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 has a permanent pacemaker in place with a demand rate set at 60 beats/min. The cardiac monitor is showing a heart rate of 44 beats/min with no pacemaker spikes. The nurse realizes this as: a. normal pacemaker function. b. failure to capture. c. failure to pace. d. failure to sense.
c. failure to pace. 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. Causes of failure to pace include battery or pulse generator failure, fracture or displacement of a pacemaker wire, or loose connections. This is not normal pacemaker function. When the pacemaker generates an electrical impulse (pacer spike) and no depolarization is noted, it is described 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). Common causes of failure to capture include output (milliamperes) set too low, or displacement of the pacing lead wire from the myocardium (transvenous or epicardial leads). Other causes of failure to capture include battery failure, fracture of the pacemaker wire, or increased pacing threshold as a result of medication or electrolyte imbalance. When the pacemaker does not sense the patients 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 patients own rhythm, earlier than the programmed rate. The most common cause is displacement of the pacemaker electrode wire.
The QT interval is the total time taken for ventricular depolarization and repolarization. Prolongation of the QT interval: a. decreases the risk of lethal dysrhythmias. b. usually occurs when heart rate increases. c. increases the risk of lethal dysrhythmias. d. can only be measured with irregular rhythms.
c. increases the risk of lethal dysrhythmias. ANS: CThe 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. Normally, the QT interval becomes longer with slower heart rates and shortens with faster heart rates, thus requiring a correction of the value (QTc). Generally, the QT interval is less than half the RR interval. QTc accuracy is based on a regular rhythm. In irregular rhythms such as atrial fibrillation, an average QTc may be necessary because the QT varies from beat to beat.
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.
c. monitor the rhythm and patient's condition. 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 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.
c. none of the P waves are conducted to the ventricles. ANS: C In first-degree AV block, a P wave precedes every QRS complex, which is followed by a T wave indicating complete conduction. It is represented on the ECG as a prolonged PR interval. Second-degree heart block refers to AV conduction that is intermittently blocked. Therefore, some P waves are conducted and some are not. Third-degree block is often called complete heart block because no atrial impulses are conducted through the AV node to the ventricles.
When assessing the 12-lead electrocardiogram (ECG) or a rhythm strip, it is helpful to understand that the electrical activity is viewed in relation to the positive electrode of that particular lead. 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.
c. upright. ANS: CWhen 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 is working on the night shift when she 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.
d. assess for hemodynamic instability. ANS: DSinus 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 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.
d. assess the patient and the electrical leads. 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 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.
d. clip chest hair if needed. ANS: DAdequate 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's heart rate is 165 beats per minute. His 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 to 78/30. His skin is cold and diaphoretic and he 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.
d. emergent cardioversion. ANS: DIf 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 patients 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.
