Chapter 13: Cardiovascular Diagnostic Procedures Flashcards

Question

Which cardiac biomarker is elevated in decompensated heart failure? a. Triglycerides b. Troponin I c. Troponin T d. B-type natriuretic peptide (BNP)

Answer 1

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.

Answer 2

ANS: A The subclavian site should be used for insertion rather than jugular or femoral insertion sites to minimize infection risk.

Answer 3

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.

Answer 4

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.

Answer 5

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.

Answer 6

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.

Answer 7

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

Answer 8

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.

Answer 9

ANS: C A prolonged QT interval is significant because it can predispose the patient to the development of polymorphic ventricular tachycardia, also known 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.

Answer 10

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.

Answer 11

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. Four 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.

Answer 12

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.

Answer 13

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.

Answer 14

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 (e.g., 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.

Answer 15

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.

Answer 16

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 (e.g., 8  10 = 80/min). Method 2: number of large boxes between QRS complexes divided into 300 (e.g., 300 ÷ 4 = 75/min). Method 3: number of small boxes between QRS complexes divided into 1500 (e.g., 1500 ÷ 18 = 84/min).

Answer 17

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 SpO 2 ; 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.

Answer 18

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.

Answer 19

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.

Answer 20

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

Answer 21

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.

Answer 22

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

Answer 23

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.

Answer 24

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.

Answer 25

ANS: A Vasodilators are used to decrease afterload, and diuretics are used to decrease preload.

Answer 26

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.

Answer 27

ANS: D A target international normalized ratio of 2.5 (range, 2.0 to 3.0) is desirable.

Answer 28

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.

Answer 29

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.

Answer 30

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.

Answer 31

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.

Answer 32

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.

Answer 33

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.

Answer 34

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.

Answer 35

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.

Answer 36

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.

Answer 37

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 mmHg 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.

Answer 38

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.

Answer 39

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.

Answer 40

ANS: C The maximal predicted heart rate is estimated using the formula: 220 – Patient’s age: 220 – 55 = 165.

Answer 41

ANS: B Pulmonary artery occlusion pressure (PAOP) normally reflects 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.

Answer 42

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.

Answer 43

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.

Answer 44

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.

Answer 45

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.