Urden Chapter 13 - Cardivascular Diagnostic Procedures
A patient's arterial line waveform has become damped. What action should the nurse take to correct the situation? a. Check for kinks, blood, and air bubbles in the pressure tubing. b. Prepare for a normal saline fluid challenge for hypotension. c. Discontinue the arterial line as it has become nonfunctional. d. Check the patient's lung sounds for a change in patient condition.
ANS: A A damped waveform occurs when communication from the artery to the transducer is interrupted and produces false values on the monitor and oscilloscope. Damping is caused by a fibrin "sleeve" that partially occludes the tip of the catheter, by kinks in the catheter or tubing, or by air bubbles in the system.
Which statement made by a patient would indicate the need for further education before an electrophysiology procedure? a. "I need to take all my heart medications the morning of the procedure." b. "The doctor is going to make my heart beat wrong on purpose." c. "I will be awake but relaxed during the procedure." d. "I will be x-rayed during the procedure."
ANS: A All antidysrhythmic medications are discontinued several days before the study so that any ventricular dysrhythmias may be readily induced during the electrophysiology procedure (EPS). Anticoagulants, especially warfarin, are also stopped before EPS. Premedication is administered before the study to induce a relaxed state, and during the procedure, the patient is conscious but receives sedative agents (midazolam) at regular intervals.
Which diagnostic tool can be used to detect structural heart abnormalities? a. Echocardiogram b. Electrocardiogram (ECG) c. Exercise stress test d. 24-hour Holter monitor
ANS: A Echocardiography is used to detect structural heart abnormalities such as mitral valve stenosis and regurgitation, prolapse of mitral valve leaflets, aortic stenosis and insufficiency, hypertrophic cardiomyopathy, atrial septal defect, thoracic aortic dissection, cardiac tamponade, and pericardial effusion.
Which statement regarding the use of cuff blood pressures is true? a. Cuff pressures may be unreliable when a patient is in shock. b. Cuff pressures are more accurate than arterial line pressures. c. Cuff pressures and arterial line pressures should be nearly identical. d. Cuff pressures should not be compared to arterial line pressures.
ANS: A If the arterial line becomes unreliable or dislodged, a cuff pressure can be used as a reserve system. In the normotensive, normovolemic patient, little difference exists between the arm cuff blood pressure and the intravascular catheter pressure, and differences of 5 to 10 mm Hg do not generally alter clinical management. The situation is different if the patient has a low cardiac output (CO) or is in shock. The concern is that the cuff pressure may be unreliable because of peripheral vasoconstriction, and an arterial line is generally required. It is usual practice to compare a cuff pressure after the arterial line is inserted.
When assessing a patient with PVCs, the nurse knows that the ectopic beat is multifocal because it appears in what way? a. In various shapes in the same lead b. With increasing frequency c. Wider than a normal QRS d. On the T wave
ANS: A If the ventricular ectopic beats are of various shapes in the same lead, they are multifocal. Multifocal ventricular ectopics are more serious than unifocal ventricular ectopics because they indicate a greater area of irritable myocardial tissue and are more likely to deteriorate into ventricular tachycardia or fibrillation.
Why is a new-onset of atrial fibrillation serious? a. It increases the patient's risk for a stroke. b. It increases the patient's risk for a deep venous thrombosis. c. It may increase cardiac output to dangerous levels. d. It indicates the patient is about to have a myocardial infarction.
ANS: A In atrial fibrillation the atria do not contract normally; they quiver. This increases the chance of the blood clotting in the atria because of a lack of complete emptying of the atria. These clots can break free and cause embolic strokes and pulmonary emboli. Atrial fibrillation does not indicate impending myocardial infarction or an increased risk of deep venous thrombosis. Atrial fibrillation decreases cardiac output from the loss of atrial kick.
Pulsus paradoxus may be noted on the bedside monitor when what is observed? a. A decrease of more than 10 mm Hg in the arterial waveform during inhalation b. A single, nonperfused beat on the electrocardiogram (ECG) waveform c. Tall, tented T waves on the ECG waveform d. An increase in pulse pressure greater than 20 mm Hg on exhalation
ANS: A Pulsus paradoxus is a decrease of more than 10 mm Hg in the arterial waveform that occurs during inhalation. It is caused by a fall in cardiac output (CO) as a result of increased negative intrathoracic pressure during inhalation.
A physician orders removal of the central venous catheter (CVC) line. The patient has a diagnosis of heart failure with chronic obstructive pulmonary disease. The nurse would place the patient in what position for this procedure? a. Supine in bed b. Supine in a chair c. Flat in bed d. Reverse Trendelenburg position
ANS: A Recommended techniques to avoid air embolus during central venous catheter (CVC) removal include removing the catheter when the patient is supine in bed (not in a chair) and placing the patient flat or in the reverse Trendelenburg position if the patient's clinical condition permits this maneuver. Patients with heart failure, pulmonary disease, and neurologic conditions with raised intracranial pressure should not be placed flat.
Why is the Allen test performed before placement of a radial arterial line placement? a. To evaluate collateral circulation to the hand b. To estimate patency of the radial artery c. To appraise the neurologic function of the hand d. To assess the sensitivity of the insertion point
ANS: A The Allen test involves occluding the radial or ulnar artery after blanching the hand. If the hand turns pink, then the nonoccluded artery provides enough circulation to the hand. If the hand remains blanched, then no collateral circulation exists, and that wrist should not be used for arterial line placement.
A patient's bedside electrocardiogram (ECG) strips show the following changes: increased PR interval; increased QRS width; and tall, peaked T waves. Vital signs are temperature 98.2° F; heart rate 118 beats/min; blood pressure 146/90 mm Hg; and respiratory rate 18 breaths/min. The patient is receiving the following medications: digoxin 0.125 mg PO every day; D51/2 normal saline with 40 mEq potassium chloride at 125 mL/hr; Cardizem at 30 mg PO q8h; and aldosterone at 300 mg PO q12h. The practitioner is notified of the ECG changes. What orders should the nurse expect to receive? a. Change IV fluid to D51/2 normal saline and draw blood chemistry. b. Give normal saline with 40 mEq of potassium chloride over a 6-hour period. c. Hold digoxin and draw serum digoxin level. d. Hold Cardizem and give 500 mL normal saline fluid challenge over a 2-hour period.
ANS: A The electrocardiographic (ECG) changes are most consistent with hyperkalemia. Removing the potassium from the intravenous line and drawing laboratory values to check the potassium level is the best choice with the least chance of further harm. Digoxin toxicity can be suspected related to the prolonged PR interval, but hyperkalemia explains all the ECG changes. The patient is not hypotensive or bradycardic, so holding the Cardizem is not indicated.
Zeroing the pressure transducer on hemodynamic monitoring equipment occurs when the displays reads which number? a. 0 b. 250 c. 600 d. 760
ANS: A The monitor is adjusted so that "0" is displayed, which equals atmospheric pressure. Atmospheric pressure is not zero; it is 760 mm Hg at sea level. Using zero to represent current atmospheric pressure provides a convenient baseline for hemodynamic measurement purposes.
Patient education for a patient with a Holter monitor should include which instruction? a. Keep a diary of activities, symptoms, and any medications that are taken. b. Do not drink coffee while the recorder is on. c. Do not take a bath but a shower is alright. d. Carry the monitor in a purse or backpack.
ANS: A The patient should be instructed to keep a diary of activities, symptoms, and any medications that are taken and to carry the monitor by a shoulder strap or clipped to a belt or pocket. The only activities that are restricted while wearing a Holter monitor are those that would get the chest electrodes or monitor wet, eliminating swimming and taking a shower or tub bath. The patient can drink coffee during the test.
Which lead is best to monitor a patient? a. Varies based on the patient's clinical condition and recent clinical history b. Lead aVF c. Lead V1 d. Lead II
ANS: A The selection of an electrocardiographic monitoring lead is not a decision to be made casually or according to habit. The monitoring lead should be chosen with consideration of the patient's clinical condition and recent clinical history. Lead II is recommended for monitoring of atrial dysrhythmias. Lead V1 is recommended for monitoring of ventricular dysrhythmias. Leads I and aVF are selected to detect a sudden change in ventricular axis.
The physician is going to place a central venous catheter. Which anatomic site is associated with a lower risk of infection? a. Subclavian vein b. External jugular vein c. Internal jugular vein d. Femoral vein
ANS: A The subclavian site should be used for insertion rather than jugular or femoral insertion sites to minimize infection risk.
The patient is admitted with a diagnosis of cardiogenic shock. The patient's heart rate (HR) is 135 beats/min with weak peripheral pulses. The patient has bilaterally crackles in the bases of the lungs. O2 saturation is 90% on 4L/NC. The practitioner orders diuretics and vasodilators. What response should the nurse expect after starting the medications? a. Decreased preload and afterload b. Increased preload and afterload c. Decreased preload and increased afterload d. Increased preload and decreased afterload
ANS: A Vasodilators are used to decrease afterload, and diuretics are used to decrease preload.
The patient's admitting 12-lead ECG shows wide, M-shaped P waves. What diagnosis could be responsible for this finding? a. Mitral stenosis b. Chronic pulmonary disease c. Hypotension d. Pericarditis
ANS: A Wide, M-shaped P waves are seen in left atrial hypertrophy and are called P mitrale because left atrial hypertrophy is often caused by mitral stenosis.
A positive signal-averaged electrocardiogram (ECG) indicates that a patient is at risk for what problem? a. Myocardial infarction b. Sudden cardiac death c. Coronary artery disease d. Stroke
ANS: B A positive signal-averaged electrocardiogram (ECG)—in combination with other specific indicators—is a predictor of increased risk for sudden cardiac death. Many patients with a positive signal-averaged ECG (abnormal) display a normal signal-averaged ECG when placed on antidysrhythmic medications. The signal-averaged ECG is not analyzed in isolation. It is used in conjunction with other cardiac diagnostic tests, including the electrophysiology study (EPS). It is a helpful adjunct to the EPS but does not replace it.
A patient asks why he had to take a deep breath when the radiology technician took his chest radiograph. Which statement is the best response? a. "Deep breaths get the chest wall closer to the machine." b. "When the lungs are filled with air, you get a clearer picture." c. "Taking a deep breath decreases the error caused by motion." d. "Holding your breath makes the heart appear larger."
ANS: B A radiograph is taken when the patient has taken a deep breath (inspiration). During exhalation, the lungs are less full of air, which can make the lung tissue appear "cloudy" as if there is additional lung water. The heart also appears larger during exhalation. This could lead to an erroneous diagnosis of heart failure.
On returning from the cardiac catheterization laboratory, the patient asks if he can get up in the chair. What should the nurse tell the patient? a. "You cannot get up because you may pass out." b. "You cannot get up because you may start bleeding." c. "You cannot get up because you may fall." d. "You cannot get up until you urinate."
ANS: B After catheterization, the patient remains flat for up to 6 hours (varies by institutional protocol and catheter size) to allow the femoral arterial puncture site to form a stable clot. Most bleeding occurs within the first 2 to 3 hours after the procedure.
What is the physiologic effect of left ventricular afterload reduction? a. Decreased left atrial tension b. Decreased systemic vascular resistance c. Increased filling pressures d. Decreased cardiac output
ANS: B Afterload is defined as the pressure the ventricle generates to overcome the resistance to ejection created by the arteries and arterioles. After a decrease in afterload, wall tension is lowered. The technical name for afterload is systemic vascular resistance (SVR). Resistance to ejection from the right side of the heart is estimated by calculating the pulmonary vascular resistance (PVR). The PVR value is normally one-sixth of the SVR.
Which serum lipid value is a significant predictor of future acute myocardial infarction (MI) in persons with established coronary artery atherosclerosis? a. High-density lipoprotein (HDL) b. Low-density lipoprotein (LDL) c. Triglycerides d. Very-low-density lipoprotein
ANS: B Both the LDL-C and total serum cholesterol levels are directly correlated with risk for coronary artery disease, and high levels of each are significant predictors of future acute myocardial infarction in persons with established coronary artery atherosclerosis. LDL-C is the major atherogenic lipoprotein and thus is the primary target for cholesterol-lowering efforts.
Why is mixed venous oxygen saturation (SVO2) monitoring helpful in the management of the critically ill patient? a. It facilitates oxygen saturation monitoring at the capillary level. b. It can detect an imbalance between oxygen supply and metabolic tissue demand. c. It assesses the diffusion of gases at the alveolar capillary membrane. d. It estimates myocardial workload during heart failure and acute pulmonary edema.
ANS: B Continuous venous oxygen monitoring permits a calculation of the balance achieved between arterial oxygen supply ( ) and oxygen demand at the tissue level by sampling desaturated venous blood from the PA catheter distal tip.
Mechanical contraction of the heart occurs during which phase of the cardiac cycle? a. Phase 0 b. Phase 2 c. Phase 3 d. Phase 4
ANS: B During phases 1 and 2, an electrical plateau is created, and during this plateau, mechanical contraction occurs. Because there is no significant electrical change, no waveform appears on the electrocardiogram (ECG). During phase 0 (depolarization), the electrical potential changes rapidly from a baseline of -90 mV to +20 mV and stabilizes at about 0 mV. Because this is a significant electrical change, it appears as a wave on the ECG as the QRS. During phase 3 (repolarization), the electrical potential again changes, this time a little more slowly, from 0 mV back to -90 mV. This is another major electrical event and is reflected on the ECG as a T wave. During phase 4 (resting period), the chemical balance is restored by the sodium pump, but because positively charged ions are exchanged on a one-for-one basis, no electrical activity is generated, and no visible change occurs on the ECG tracing.
When assessing the pulmonary arterial waveform, the nurse notices dampening. After tightening the stopcocks and flushing the line, the nurse decides to calibrate the transducer. What are two essential components included in calibration? a. Obtaining a baseline blood pressure and closing the transducer to air b. Leveling the air-fluid interface to the phlebostatic axis and opening the transducer to air c. Having the patient lay flat and closing the transducer to air d. Obtaining blood return on line and closing all stopcocks
ANS: B Ensuring accuracy of waveform calibration of the system includes opening the transducer to air and leveling the air-fluid interface of the transducer to the phlebostatic axis.
A patient with heart failure may be at risk for hypomagnesemia as a result of which factor? a. Pump failure b. Diuretic use c. Fluid overload d. Hemodilution
ANS: B Hypomagnesemia can be caused by diuresis. Diuretic use with heart failure often contributes to low serum magnesium levels.
What type of atrioventricular (AV) block can be described as a gradually lengthening PR interval until ultimately the final P wave in the group fails to conduct? a. First-degree AV block b. Second-degree AV block, type I c. Second-degree AV block, type II d. Third-degree AV block
ANS: B In Mobitz type I block, the atrioventricular (AV) conduction times progressively lengthen until a P wave is not conducted. This typically occurs in a pattern of grouped beats and is observed on the electrocardiogram (ECG) by a gradually lengthening PR interval until ultimately the final P wave in the group fails to conduct. When all atrial impulses are conducted to the ventricles but the PR interval is greater than 0.20 second, a condition known as first-degree AV block exists. Mobitz type II block is always anatomically located below the AV node in the bundle of His in the bundle branches or even in the Purkinje fibers. This results in an all-or-nothing situation with respect to AV conduction. Sinus P waves are or are not conducted. When conduction does occur, all PR intervals are the same. Because of the anatomic location of the block, on the surface, ECG the PR interval is constant and the QRS complexes are wide. Third-degree, or complete, AV block is a condition in which no atrial impulses can conduct from the atria to the ventricles. This is also described by the term complete heart block.
What is the most common complication of a central venous catheter (CVC)? a. Air embolus b. Infection c. Thrombus formation d. Pneumothorax
ANS: B Infection related to the use of central venous catheters (CVCs) is a major problem. The incidence of infection strongly correlates with the length of time the CVC has been inserted, with longer insertion times leading to a higher infection rate. The risk of air embolus, although uncommon, is always present for a patient with a central venous line in place. Air can enter during insertion through a disconnected or broken catheter by means of an open stopcock, or air can enter along the path of a removed CVC. Unfortunately, clot formation (thrombus) at the CVC site is common. Thrombus formation is not uniform; it may involve development of a fibrin sleeve around the catheter, or the thrombus may be attached directly to the vessel wall. Pneumothorax has a higher occurrence during placement of a CVC than during removal.
A patient with a serum potassium level of 6.8 mEq/L may exhibit what type of electrocardiographic changes? a. A prominent U wave b. Tall, peaked T waves c. A narrowed QRS d. Sudden ventricular dysrhythmias
ANS: B Normal serum potassium levels are 3.5 to 4.5 mEq/L. Tall, narrow peaked T waves are usually, although not uniquely, associated with early hyperkalemia and are followed by prolongation of the PR interval, loss of the P wave, widening of the QRS complex, heart block, and asystole. Severely elevated serum potassium (greater than 8 mEq/L) causes a wide QRS tachycardia.
Which of the following is most indicative of decreased left ventricular preload? a. Increased pulmonary artery occlusion pressure (PAOP) b. Decreased pulmonary artery occlusion pressure (PAOP) c. Increased central venous pressure (CVP) d. Decreased central venous pressure (CVP)
ANS: B Pulmonary artery occlusion pressure (PAOP) normally reflect the pressure in the left ventricle at the end of diastole. Left ventricular end-diastolic pressure is preload, and so an increase in preload will first increase the PAOP measurements and vice versa. Central venous pressure changes are reflective of right ventricular preload.
What is the initial intervention in a patient with sinus tachycardia with the following vital signs: heart rate, 136 beats/min; blood pressure, 102/60 mm Hg; respiratory rate, 24 breaths/min; temperature, 99.2° F; SpO2, 94% on oxygen 2 L/min by nasal cannula? a. Administer adenosine IV push. b. Identify the cause. c. Administer nitroglycerine 0.4 mg sublingual. d. Administer lidocaine 75 mg IV push.
ANS: B Sinus tachycardia can be caused by a wide variety of factors, such as exercise, emotion, pain, fever, hemorrhage, shock, heart failure, and thyrotoxicosis. Many medications used in critical care can also cause sinus tachycardia; common culprits are aminophylline, dopamine, hydralazine, atropine, and catecholamines such as epinephrine. This patient has a stable heart rate and SpO2; therefore, there is time to identify the cause of the sinus tachycardia. Lidocaine is indicated for ventricular dysrhythmias. Nitroglycerine is not indicated because the patient is not having chest pain at this time. Adenosine is usually not indicated unless the heart rate is greater than 150 beats/min.
What effect does ventricular tachycardia have on cardiac output? a. Increases cardiac output due to an increase in ventricular filling time b. Decreases cardiac output due to a decrease in stroke volume c. Increases cardiac output due to an increase in preload d. Decreases cardiac output due to a decrease in afterload
ANS: B Tachycardia is detrimental to anyone with ischemic heart disease because it decreases the time for ventricular filling, decreases stroke volume, and compromises cardiac output. Tachycardia increases heart work and myocardial oxygen demand while decreasing oxygen supply by decreasing coronary artery filling time.
The patient's admitting 12-lead ECG shows tall, peaked P waves. What diagnosis could be responsible for this finding? a. Mitral stenosis b. Pulmonary edema c. Ischemia d. Pericarditis
ANS: B Tall, peaked P waves occur in right atrial hypertrophy and are referred to as P pulmonale because this condition is often the result of chronic pulmonary disease. Ischemia occurs when the delivery of oxygen to the tissues is insufficient to meet metabolic demand. Cardiac ischemia in an unstable form occurs because of a sudden decrease in supply, such as when the artery is blocked by a thrombus or when coronary artery spasm occurs. If the pulmonary edema is caused by heart failure, sometimes described as hydrostatic pulmonary edema, the fluid may be in a "bat-wing" distribution, with the white areas concentrated in the hilar region (origin of the major pulmonary vessels). However, as the heart failure progresses, the quantity of fluid in the alveolar spaces increases, and the white, fluffy appearance is seen throughout the lung. Pericarditis is inflammation of the sac around the heart.
What does the P wave component of the electrocardiographic waveform represent? a. Atrial contraction b. Atrial depolarization c. Sinus node discharge d. Ventricular contraction
ANS: B The P wave is an electrical event and represents atrial depolarization. Atrial contraction should accompany the P wave but does not always. The sinus node discharge is too faint to be recorded on the surface electrocardiogram. Ventricular contraction usually accompanies the QRS complex.
Which portion of the electrocardiogram (ECG) is most valuable in diagnosing atrioventricular (AV) conduction disturbances? a. P wave b. PR interval c. QRS complex d. QT interval
ANS: B The PR interval is an indicator of atrioventricular nodal function. The P wave represents atrial depolarization. The QRS complex represents ventricular depolarization, corresponding to phase 0 of the ventricular action potential. The QT interval is measured from the beginning of the QRS complex to the end of the T wave and indicates the total time interval from the onset of depolarization to the completion of repolarization.
A patient presents with atrial flutter with an atrial rate of 280 beats/min and a ventricular rate of 70 beats/min. Which statement best explains this discrepancy in rates? a. The ventricles are too tired to respond to all the atrial signals. b. The atrioventricular (AV) node does not conduct all the atrial signals to the ventricles. c. Some of the atrial beats are blocked before reaching the AV node. d. The ventricles are responding to a ventricular ectopic pacemaker.
ANS: B The atrioventricular (AV) node does not allow conduction of all these impulses to the ventricles. In this case, the rhythm would be described as atrial flutter with a 4:1 AV block, indicating that only one of every four atrial signals is conducted to the ventricles.
Which statement expresses the correct order when working with an invasive pressure monitor? a. Level the transducer, locate the phlebostatic axis, zero the transducer, and take the reading. b. Locate the phlebostatic axis, level the transducer, zero the transducer, and take the reading. c. Take the reading, level the transducer, locate the phlebostatic axis, and zero the transducer. d. Locate the phlebostatic axis, zero the transducer, level the transducer, and take the reading.
ANS: B The correct order is locate the phlebostatic axis, level the transducer, zero the transducer, and take the reading. The transducer cannot be zeroed before it is leveled. Readings cannot be taken before the transducer is zeroed, and leveling the transducer cannot occur until the phlebostatic axis has been identified.
What is the major factor influencing the patient's response to atrial flutter? a. Atrial rate b. Ventricular response rate c. PR interval d. QRS duration
ANS: B The major factor underlying atrial flutter symptoms is the ventricular response rate. If the atrial rate is 300 and the atrioventricular (AV) conduction ratio is 4:1, the ventricular response rate is 75 beats/min and should be well tolerated. If, on the other hand, the atrial rate is 300 beats/min but the AV conduction ratio is 2:1, the corresponding ventricular rate of 150 beats/min may cause angina, acute heart failure, or other signs of cardiac decompensation.
Which criteria are representative of the patient in normal sinus rhythm? a. Heart rate, 64 beats/min; rhythm regular; PR interval, 0.10 second; QRS, 0.04 second b. Heart rate, 88 beats/min; rhythm regular; PR interval, 0.18 second; QRS, 0.06 second c. Heart rate, 54 beats/min; rhythm regular; PR interval, 0.16 second; QRS, 0.08 second d. Heart rate, 92 beats/min; rhythm irregular; PR interval, 0.16 second; QRS, 0.04 second
ANS: B The parameters for normal sinus rhythm are heart rate, 60 to 100 beats/min; rhythm, regular; PR interval, 0.12 to 0.20 second; and QRS, 0.06 to 0.10 second.
A patient with a potassium level of 2.8 mEq/L is given 60 mEq over a 12-hour period. A repeat potassium level is obtained, and the current potassium level is 3.2 mEq/L. In addition to administering additional potassium supplements, what intervention should now be considered? a. Discontinue spironolactone b. Drawing a serum magnesium level c. Rechecking the potassium level d. Monitoring the patient's urinary output
ANS: B The patient should have serum magnesium level drawn. Hypomagnesemia is commonly associated with other electrolyte imbalances, most notably alterations in potassium, calcium, and phosphorus. Low serum magnesium levels can result from many causes.
A patient reports that he has been having "indigestion" for the last few hours. Upon further review the nurse suspects the patient is having of chest pain. Cardiac biomarkers and a 12-lead electrocardiogram (ECG) are done. What finding is most significant in diagnosing an acute coronary syndrome (ACS) within the first 3 hours? a. Inverted T waves b. Elevated troponin I c. Elevated B-type natriuretic peptide (BNP) d. Indigestion and chest pain
ANS: B The troponins are biomarkers for myocardial damage. The elevation of Troponin I and troponin T occurs 3 to 6 hours after acute myocardial damage. Because troponin I is found only in cardiac muscle, it is a highly specific biomarker for myocardial damage. B-type natriuretic peptide (BNP) are usually drawn when heart failure is suspected, not acute coronary syndrome (ACS). Usually within 4 to 24 hours from the onset of the infarction, abnormal Q waves begin to develop in the affected leads, and T waves begin to invert.
Which electrocardiographic (ECG) abnormality is most often found in ventricular dysrhythmias? a. Retrograde P waves b. Wide QRS complexes c. No P waves d. An inverted T wave
ANS: B Ventricular dysrhythmias result from an ectopic focus in any portion of the ventricular myocardium. The usual conduction pathway through the ventricles is not used, and the wave of depolarization must spread from cell to cell. As a result, the QRS complex is prolonged and is always greater than 0.12 second. It is the width of the QRS, not the height that is important in the diagnosis of ventricular ectopy.
Why is the measurement of the QT interval important? a. It facilitates rhythm identification and is best assessed in Lead II. b. It helps differentiate myocardial ischemia from infarction. c. An increasing QT interval increases the risk of torsades de pointes. d. A decreasing QT interval increases the risk of torsades de pointes.
ANS: C A prolonged QT interval is significant because it can predispose the patient to the development of polymorphic ventricular tachycardia, known also as torsades de pointes. A long QT interval can be congenital, as a result of genetic inheritance, or it can be acquired from an electrolyte imbalance or medications.
Which of the electrocardiogram (ECG) findings would be positive for an inferior wall myocardial infarction (MI)? a. ST segment depression in leads I, aVL, and V2 to V4 b. Q waves in leads V1 to V2 c. Q waves in leads II, III, and aVF d. T-wave inversion in leads V4 to V6, I, and aVL
ANS: C Abnormal Q waves develop in leads overlying the affected area. An inferior wall infarction is seen with changes in leads II, III, and aVF. Leads I and aVF are selected to detect a sudden change in ventricular axis. If ST segment monitoring is required, the lead is selected according to the area of ischemia. If the ischemic area is not known, leads V3 and III are recommended to detect ST segment ischemia.
What is the effect of preload on cardiac output? a. As preload increases, cardiac output increases. b. As preload increases, cardiac output decreases. c. As preload increases, cardiac output increases until it overstretches the ventricle and cardiac output decreases. d. Increased preload has no effect on cardiac output.
ANS: C According to the Frank-Starling law of the heart, if preload increases stroke volume, then cardiac output may increase. If, however, preload causes excessive left ventricular stretch, it can actually decrease cardiac output and may result in congestive heart failure.
After a myocardial infarction, a patient presents with an increasing frequency of premature ventricular contractions (PVCs). The patient's heart rate is 110 beats/min, and electrocardiogram (ECG) indicates a sinus rhythm with up to five unifocal PVCs per minute. The patient is alert and responsive and denies any chest pain or dyspnea. What action should the nurse take next? a. Administer lidocaine 100 mg bolus IV push stat. b. Administer Cardizem 20 mg IV push stat. c. Notify the physician and monitor the patient closely. d. Nothing; PVCs are expected in this patient.
ANS: C Although premature ventricular contractions (PVCs) are frequently present after myocardial infarction, they are not always benign. In individuals with underlying heart disease, PVCs or episodes of self-terminating ventricular tachycardia (VT) are potentially malignant. Nonsustained VT is defined as three or more consecutive premature ventricular beats at a rate faster than 110 beats/min lasting less than 30 seconds. The patient does not appear symptomatic from the PVCs at this time; therefore, lidocaine is not indicated. Cardizem is not prescribed for ventricular ectopy.
To accurately measure the heart rate of a patient in normal sinus rhythm, which technique would be the most accurate? a. The number of R waves in a 6-second strip b. The number of large boxes in a 6-second strip c. The number of small boxes between QRS complexes divided into 1500 d. The number of large boxes between consecutive R waves divided into 300
ANS: C Calculation of heart rate if the rhythm is regular may be done using the following methods. Method 1: number of RR intervals in 6 seconds multiplied by 10 (eg, 8 10 = 80/min). Method 2: number of large boxes between QRS complexes divided into 300 (eg, 300 4 = 75/min). Method 3: number of small boxes between QRS complexes divided into 1500 (eg, 1500 18 = 84/min).
What characteristic is associated with junctional escape rhythms? a. Irregular rhythm b. Rate greater than 100 beats/min c. P wave may be present or absent d. QRS greater than 0.10 seconds
ANS: C Characteristics of a junctional escape rhythm include a rate of 40 to 60 beats/min, regular rhythm, present or absent P waves, PR less than 0.12 seconds, and QRS between 0.06 and 0.10 seconds.
Which diagnostic test is most effective for measuring overall heart size? a. 12-lead electrocardiography b. Echocardiography c. Chest radiography d. Vectorcardiography
ANS: C Chest radiography is the oldest noninvasive method for visualizing images of the heart, and it remains a frequently used and valuable diagnostic tool. Information about cardiac anatomy and physiology can be obtained with ease and safety at a relatively low cost. Radiographs of the chest are used to estimate the cardiothoracic ratio and measure overall heart size.
What is the rationale for giving the patient additional fluids after a cardiac catheterization? a. Fluids help keep the femoral vein from clotting at the puncture site. b. The patient had a nothing-by-mouth order before the procedure. c. The radiopaque contrast acts as an osmotic diuretic. d. Fluids increase cardiac output.
ANS: C Fluid is given for rehydration because the radiopaque contrast acts as an osmotic diuretic. Fluid is also used to prevent contrast-induced nephropathy or damage to the kidney from the contrast dye used to visualize the heart structures.
A patient becomes unresponsive. The patient's heart rate is 32 beats/min in an idioventricular rhythm; blood pressure is 60/32 mm Hg; SpO2 is 90%; and respiratory rate is 14 breaths/min. Which intervention would the nurse do first? a. Notify the physician and hang normal saline wide open. b. Notify the physician and obtain the defibrillator. c. Notify the physician and obtain a temporary pacemaker. d. Notify the physician and obtain a 12-lead ECG.
ANS: C If the sinus node and the atrioventricular (AV) junction fail, the ventricles depolarize at their own intrinsic rate of 20 to 40 times per minute. This is called an idioventricular rhythm and is naturally protective mechanism. Rather than trying to abolish the ventricular beats, the aim of treatment is to increase the effective heart rate (HR) and reestablish dominance of a higher pacing site such as the sinus node or the AV junction. Usually, a temporary pacemaker is used to increase the HR until the underlying problems that caused failure of the other pacing sites can be resolved.
Most chest radiographs of critically ill patients are obtained using a portable chest radiograph machine. What is the difference between a chest radiograph taken in the radiology department and one taken in the critical care unit? a. Portable chest radiographs are usually clearer. b. Only posterior views can be obtained in the critical care unit. c. The sharpness of the structures is decreased with a portable chest radiograph. d. Chest radiographs taken in radiology enlarge some thoracic structures.
ANS: C In the supine radiograph with the patient lying flat on the bed, the x-ray tube can be only approximately 36 inches from the patient's chest because of ceiling height and x-ray equipment construction. This results in a lower quality film from a diagnostic standpoint because the images of the heart and great vessels are magnified and are not as sharply defined.
Which noninvasive imaging technique is useful in diagnosing complications of a myocardial infarction (MI)? a. 12-lead ECG b. CT c. MRI d. Echocardiography
ANS: C Magnetic resonance imaging is useful in diagnosing complications of myocardial infarction, such as pericarditis or pericardial effusion, valvular dysfunction, ventricular septal rupture, aneurysm, and intracardiac thrombus. Computed tomography is used to calculate the coronary artery calcium score. Echocardiography uses ultrasound reflected best at interfaces between tissues that have different densities. In the heart, these are the blood, cardiac valves, myocardium, and pericardium. Because all these structures differ in density, their borders can be seen on the echocardiogram. The standard 12-lead electrocardiogram provides a picture of electrical activity in the heart using 10 different electrode positions to create 12 unique views of electrical activity occurring within the heart.
A 55-year-old patient is scheduled for a stress test. What is the estimation of the patient's maximal predicted heart rate? a. 65 beats/min b. 155 beats/min c. 165 beats/min d. 265 beats/min
ANS: C The maximal predicted heart rate is estimated using the formula: 220 - Patient's age: 220 - 55 = 165.
What is the formula for calculating mean arterial pressure (MAP)? a. Averaging three of the patient's blood pressure readings over a 6-hour period b. Dividing the systolic pressure by the diastolic pressure c. Adding the systolic pressure and two diastolic pressures and then dividing by 3 d. Dividing the diastolic pressure by the pulse pressure
ANS: C The mean arterial pressure is one-third systole and two-thirds diastole.
When performing a 12-lead electrocardiogram (ECG), how many wires are connected to the patient? a. 3 b. 5 c. 10 d. 12
ANS: C The standard 12-lead electrocardiogram provides a picture of electrical activity in the heart using 10 different electrode positions to create 12 unique views of electrical activity occurring within the heart. Fours wires are applied to the extremities to produce leads I, II, III, aVR, aVL, and aVF. Six wires are attached to the V1 to V6 chest lead positions.
What is the target range for an international normalized ratio (INR)? a. 1.0 to 2.0 b. 1.5 to 3.0 c. 1.5 to 2.5 d. 2.0 to 3.0
ANS: D A target international normalized ratio of 2.5 (range, 2.0 to 3.0) is desirable.
A new-onset myocardial infarction (MI) can be recognized by what electrocardiogram (ECG) change? a. Q waves b. Smaller R waves c. Widened QRS d. ST segment elevation
ANS: D Any change from baseline is expressed in millimeters and may indicate myocardial ischemia (one small box equals 1 mm). ST segment elevation of 1 to 2 mm is associated with acute myocardial injury, preinfarction, and pericarditis. ST segment depression (decrease from baseline more of 1 to 2 mm) is associated with myocardial ischemia. Widened QRS complexes are indicative of ventricular depolarization abnormalities such as bundle branch blocks and ventricular dysrhythmias. Q waves and smaller R waves are indications usually present 24 hours to 1 week after the myocardial infarction is completely evolved; they represent necrosis.
ST segment monitoring for ischemia has gained increasing importance with the advent of thrombolytic therapy. What is the most accurate method for monitoring the existence of true ischemic changes? a. Biomarkers b. Echocardiogram c. 5-lead ECG d. 12-lead ECG
ANS: D Cardiac biomarkers are proteins that are released from damaged myocardial cells. The initial elevation of cTnI, cTnT, and CK-MB occurs 3 to 6 hours after the acute myocardial damage. This means that if an individual comes to the emergency department as soon as chest pain is experienced, the biomarkers will not have risen. For this reason, it is clinical practice to diagnose an acute myocardial infarction by 12-lead electrocardiography and clinical symptoms without waiting for elevation of cardiac biomarkers.
The patient has a heart rate (HR) of 84 beats/min and a stroke volume (SV) of 65 mL. Calculate the cardiac output (CO). a. 149 mL b. 500 mL c. 4650 mL d. 5460 mL
ANS: D Cardiac output (CO) is the product of heart rate (HR) multiplied by stroke volume (SV). SV is the volume of blood ejected by the heart during each beat (reported in milliliters). 84 65 = 5460 mL.
What parameter is used to assess the contractility of the left side of the heart? a. Pulmonary artery occlusion pressure b. Left atrial pressure c. Systemic vascular resistance d. Left ventricular stroke work index
ANS: D Contractility of the left side of the heart is measured by the left ventricular stroke work index.
Which condition can cause an artificial increase in the pulmonary artery occlusion pressure (PAOP)? a. Aortic regurgitation b. Aortic stenosis c. Mitral stenosis d. Mitral regurgitation
ANS: D If mitral regurgitation is present, the mean pulmonary artery occlusion pressure reading is artificially elevated because of abnormal backflow of blood from the left ventricle to the left atrium during systole.
A patient's central venous pressure (CVP) reading suddenly increased from 10 to 48 mm Hg. His lungs are clear except for fine rales at the bases. What should the nurse do next? a. Nothing as this reading is still within normal limits. b. Place a STAT call into the physician. c. Administer ordered prn Lasix. d. Check the level of the transducer.
ANS: D If the transducer falls below the correct level, the reading would be falsely elevated. This rise is consistent with a transducer having fallen from the correct level on the bed to the floor. Lasix is not indicated. Central venous pressure (CVP) of 45 mm Hg, if true, is severely elevated. Not enough information has been provided to call the physician. If the CVP value is true and the patient's condition is poor, a call to the physician would be appropriate after assessment.
Which cardiac biomarker is elevated in decompensated heart failure? a. Triglycerides b. Troponin I c. Troponin T d. B-type natriuretic peptide (BNP)
ANS: D In decompensated heart failure, ventricular distension from volume overload or pressure overload causes myocytes in the ventricle to release B-type natriuretic peptide (BNP). With greater ventricular wall stress, more natriuretic peptide is released from the myocardium, reflected as an elevated BNP level. The BNP value is combined with the physical examination, the 12-lead ECG, and a chest radiograph to increase the accuracy of heart failure diagnosis. Troponins are elevated with acute coronary syndrome. Triglycerides are not a biomarker and are reflective of lipids in the bloodstream.
What major clinical finding present in a patient with ventricular fibrillation (VF)? a. Hypertension b. Bradycardia c. Diaphoresis d. Pulselessness
ANS: D In ventricular fibrillation (VF), the patient does not have a pulse, no blood is being pumped forward, and defibrillation is the only definitive therapy. No forward flow of blood or palpable pulse is present in VF.
A nurse is obtaining the history of a patient who reveals that he had an myocardial infarction (MI) 5 years ago. When the admission 12-lead electrocardiogram (ECG) is reviewed, Q waves are noted in leads V3 and V4 only. Which conclusion is most consistent with this situation? a. The patient may have had a posterior wall MI. b. The patient must have had a right ventricular MI. c. The admission 12-lead ECG was done incorrectly. d. The patient may have had an anterior MI.
ANS: D Not every acute myocardial infarction (MI) results in a pathologic Q wave on the 12-lead electrocardiogram (ECG). When the typical ECG changes are not present, the diagnosis depends on symptomatic clinical presentation, specific cardiac biomarkers (eg, cTnI, cTnT, CK-MB), and non-ECG diagnostic tests such as cardiac catheterization. Anterior and posterior wall MIs have ST changes, not Q wave changes.
Which findings would be reasons to abort an exercise stress test? a. Ventricular axis of +90 degrees b. Increase in blood pressure c. Inverted U wave d. ST segment depression or elevation
ANS: D Signs that can alert the nurse to stop the test include ST segment elevation equal to or greater than 1.0 mm (one small box) or ST depression equal to or greater than 2.0 mm (2 small boxes). Blood pressure is expected to rise during exercise, but a systolic blood pressure greater than 250 mm Hg or a diastolic blood pressure greater than 115 mm Hg is considered high enough to stop the test. Parameters for ventricular axis in degrees are -30 to +90. Left-axis deviation is present if the axis falls between -30 and -90 degrees.
Which blood test standardizes prothrombin time (PT) results among worldwide clinical laboratories? a. aPTT b. ACT c. HDL d. INR
ANS: D The international normalized ratio (INR) was developed by the World Health Organization in 1982 to standardize prothrombin time results among clinical laboratories worldwide. High-density lipoproteins (HDLs) are particles of the total serum cholesterol. Activated coagulation time (ACT) is also known as the activated clotting time. The ACT is a point of care test that is performed outside of the laboratory setting in areas such as the cardiac catheterization laboratory, the operating room, or critical care units. The activated partial thromboplastin time (aPTT) is used to measure the effectiveness of intravenous or subcutaneous ultrafractionated heparin therapy.
A patient returns from the cardiac catheterization laboratory after angioplasty and stent placement (ECG changes had indicated an inferior wall myocardial infarction in progress). Which lead would best monitor this patient? a. Varies based on the patient's clinical condition and recent clinical history b. Lead V3 c. Lead V1 d. Lead II
ANS: D The selection of an electrocardiographic monitoring lead is not a decision to be made casually or according to habit. The monitoring lead should be chosen with consideration of the patient's clinical condition and recent clinical history. Lead II is recommended for monitoring of atrial dysrhythmias and would be appropriate in this case as due to inferior wall injuries. Lead V1 is recommended for monitoring of ventricular dysrhythmias. Leads I and aVF are selected to detect a sudden change in ventricular axis.
Which intervention should be strictly followed to ensure accurate cardiac output readings? a. Inject 5 mL of iced injectate at the beginning of exhalation over 30 seconds. b. Inject 10 mL of warmed injectate into the pulmonary artery port three times. c. Ensure at least 5° C difference between injectate and the patient temperature. d. Administer the injectate within 4 seconds during inspiration.`
ANS: D To ensure accurate readings, the difference between injectate temperature and body temperature must be at least 10° C, and the injectate must be delivered within 4 seconds, with minimal handling of the syringe to prevent warming of the solution. This is particularly important when iced injectate is used.
