CARDIOLOGY Medical School Crash Course™
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Table of Contents Preface .............................................................................................................................................. i Chapter 1: Cardiac Imaging Techniques and Evaluations ......................................................................1 Electrocardiogram................................................................................................................................... 1 Holter Monitor ........................................................................................................................................ 3 Other Cardiac Event Recording Devices .................................................................................................. 4 Echocardiogram ...................................................................................................................................... 5 Cardiac Stress Test .................................................................................................................................. 6 Angiography ............................................................................................................................................ 8 Key Takeaways ........................................................................................................................................ 9 Quiz ......................................................................................................................................................... 9 Chapter 2: Heart Failure ................................................................................................................... 12 Types of Heart Failure ........................................................................................................................... 12 Left-sided Heart Failure ........................................................................................................................ 12 Causes of Heart Failure ......................................................................................................................... 13 Symptoms of Heart Failure ................................................................................................................... 14 Diagnosis of Heart Failure ..................................................................................................................... 15 Treatment of Heart Failure ................................................................................................................... 17 Key Takeaways ...................................................................................................................................... 18 Quiz ....................................................................................................................................................... 18 Chapter 3: Acute Myocardial Infarction ............................................................................................ 21 The Acute MI......................................................................................................................................... 21 Causes of an Acute MI .......................................................................................................................... 22 Signs and Symptoms of an Acute MI ..................................................................................................... 22 Diagnosis of an Acute MI ...................................................................................................................... 23 Treatment of an Acute MI ..................................................................................................................... 23 Treatment Interventions ....................................................................................................................... 25 Prevention of an Acute MI .................................................................................................................... 26 Key Takeaways ...................................................................................................................................... 26 Quiz ....................................................................................................................................................... 26 Chapter 4: Ventricular Cardiac Arrhythmias ...................................................................................... 29 Premature Ventricular Contractions ..................................................................................................... 29 Ventricular Tachycardia ........................................................................................................................ 29
Ventricular Fibrillation .......................................................................................................................... 32 Key Takeaways ...................................................................................................................................... 34 Quiz ....................................................................................................................................................... 34 Chapter 5: Atrial Cardiac Arrhythmias ............................................................................................... 37 Sinus Tachycardia.................................................................................................................................. 37 Paroxysmal Supraventricular Tachycardia ............................................................................................ 37 Atrial Flutter .......................................................................................................................................... 40 Sinus Bradycardia .................................................................................................................................. 42 Atrial Fibrillation ................................................................................................................................... 42 Key Takeaways ...................................................................................................................................... 43 Quiz ....................................................................................................................................................... 44 Chapter 6: Heart Block ..................................................................................................................... 46 Second Degree Heart Block-Mobitz I and Mobitz II .............................................................................. 46 Third Degree Heart Block ...................................................................................................................... 49 Key Takeaways ...................................................................................................................................... 51 Quiz ....................................................................................................................................................... 51 Chapter 7: Hypertension .................................................................................................................. 54 Hypertension Facts ............................................................................................................................... 54 Essential Hypertension ......................................................................................................................... 55 Secondary Hypertension ....................................................................................................................... 56 Treatment for Hypertension ................................................................................................................. 57 Key Takeaways ...................................................................................................................................... 60 Quiz ....................................................................................................................................................... 60 Chapter 8: Valvular Heart Disease .................................................................................................... 63 Valvular Disease Basics ......................................................................................................................... 63 Mitral Valve Stenosis ............................................................................................................................ 63 Mitral Valve Regurgitation .................................................................................................................... 65 Mitral Valve Prolapse ............................................................................................................................ 66 Aortic Stenosis ...................................................................................................................................... 67 Aortic Regurgitation .............................................................................................................................. 68 Tricuspid Stenosis ................................................................................................................................. 69 Tricuspid Regurgitation ......................................................................................................................... 69 Pulmonic Stenosis ................................................................................................................................. 70
Pulmonic Regurgitation......................................................................................................................... 70 The Treatment of Valvular Heart Disease ............................................................................................. 71 Key Takeaways ...................................................................................................................................... 71 Quiz ....................................................................................................................................................... 71 Chapter 9: Congenital Heart Disease ................................................................................................. 74 Simple Congenital Heart Defects .......................................................................................................... 74 Atrial Septal Defects.............................................................................................................................. 74 Ventricular Septal Defect ...................................................................................................................... 75 Patent Ductus Arteriosus ...................................................................................................................... 77 Valvular Congenital Heart Defects ........................................................................................................ 79 Complex Congenital Heart Defects ....................................................................................................... 79 Transposition of the Great Arteries ...................................................................................................... 81 Key Takeaways ...................................................................................................................................... 82 Quiz ....................................................................................................................................................... 82 Chapter 10: Pericarditis and Pericardial Diseases .............................................................................. 85 Pericarditis ............................................................................................................................................ 85 Cardiac Tamponade .............................................................................................................................. 89 Key Takeaways ...................................................................................................................................... 90 Quiz ....................................................................................................................................................... 90 Chapter 11: Endocarditis .................................................................................................................. 93 Bacterial Endocarditis ........................................................................................................................... 93 Key Takeaways ...................................................................................................................................... 95 Quiz ....................................................................................................................................................... 96 Chapter 12: Cardiomyopathy ............................................................................................................ 98 Types of Cardiomyopathy ..................................................................................................................... 98 Dilated Cardiomyopathy ....................................................................................................................... 98 Hypertrophic Cardiomyopathy (HCM) .................................................................................................. 99 Restrictive Cardiomyopathy ................................................................................................................ 100 Arrhythmogenic Right Ventricular Hyperplasia ................................................................................... 101 Diagnosing Cardiomyopathy ............................................................................................................... 101 General Treatment of Cardiomyopathy .............................................................................................. 102 Key Takeaways .................................................................................................................................... 102 Quiz ..................................................................................................................................................... 102
Summary ....................................................................................................................................... 105 Course Questions and Answers ...................................................................................................... 107
Preface The introduction to cardiology course is about the tests used to evaluate the heart, and diseases that adversely affect the heart and cardiovascular system. A person can be born with a heart condition (called a congenital heart defect), although many heart conditions are inherited, or may be secondary to living a sedentary lifestyle, eating poorly, or other diseases that affect the heart including diabetes mellitus and infectious processes that affect the heart function. This course covers the various ways the heart is evaluated clinically, and discusses several different heart conditions a person can develop. The first chapter in the course discusses the tests used to evaluate the heart in its well and sick state. Many patients are familiar with the electrocardiogram or ECG, which measures the electrical activity of the heart at rest. There are other, similar tests that measure the electrical activity of the heart over time. Stress tests measure the stressed heart and the echocardiogram evaluates the heart using ultrasound. Other imaging studies of the heart are discussed in this chapter. The purpose of chapter two is to understand the phenomenon of heart failure. Heart failure involves a failure of the pump function of the heart for several different reasons. A person can have left-sided heart failure, right-sided heart failure, congestive heart failure, or biventricular heart failure. There are many reasons behind heart failure, including damage to heart muscle, obstructive cardiac disease, and a generalized weakness of the heart muscle. The discussion will include the causes of heart failure, the symptoms of the disorder, the diagnosis, and the management of this problem. The acute myocardial infarction (MI) or “heart attack” is one of the more serious problems in cardiology and is discussed in chapter three of this course. An acute MI may cause cardiac muscle necrosis and occasionally sudden death. The causes of an acute myocardial infarction, the symptoms, the prevention, and the treatment of this problem will be the focus of this chapter. There are a variety of ventricular arrhythmias, which are the topic of chapter four in the course. They occur when there is abnormal electrical activity of the heart, which may cause a fast heartbeat, the absence of a perfusable heartbeat, or an irregularity of the heartbeat. A ventricular arrhythmia can cause a sudden decrease in cardiac output and other complications, including an episode of sudden cardiac death. The three main ventricular arrhythmias covered in this chapter include premature ventricular contractions (PVCs), ventricular tachycardia, and ventricular fibrillation. The focus of chapter five in the course is the different atrial arrhythmias that can affect the heart. In general, atrial arrhythmias are less serious when compared to ventricular arrhythmias. Many people experiencing chronic atrial arrhythmias that are stabilized with medications to control the heart rate and maximize the cardiac output. Typical atrial dysrhythmias include supraventricular tachycardia (SVT), atrial flutter, and atrial fibrillation. Chapter six discusses heart block, which is considered any dissociation between the SA node and the AV node. This type of dissociation is helpful in cases of atrial flutter, but not helpful in all other cases of heart block, as it usually involves an unacceptably low heart rate. The chapter will cover both types of second-degree and third-degree heart block. Chapter seven of the course focuses on the topic of hypertension, which is the most common cardiovascular disease in adults. Most patients with hypertension will have essential hypertension, i
which is considered idiopathic. There are other less common causes of hypertension including hypertension secondary to renovascular disease, pheochromocytoma, and other miscellaneous causes. The mechanisms and treatment of hypertension is also covered in this chapter. Chapter eight’s main topic is valvular heart disease. Valvular heart disease can involve any type of damage or dysfunction of the valves of the heart, including the mitral, aortic, pulmonic, or the tricuspid valve. The tricuspid and the mitral valve control the amount of blood travelling from the atria to the ventricles. The pulmonic valve controls the blood flow to the lungs, and the aortic valve controls the blood flow from the left ventricle to the aorta. The valves most likely to be affected by valvular disease are the mitral and aortic valve (left-sided valves). Each of the valves and their dysfunctions will be covered in this chapter. The purpose of chapter nine is to understand the pathophysiology of the various congenital heart diseases a child may be born with. These include a number of different structural lesions that affect the heart from birth, usually secondary to a failure in the development of the heart. Congenital heart disease can affect the inner walls, or septum, of the heart (septal holes), the valves of the heart (which can be misshapen or have an abnormal number of leaflets), or the blood vessels leading to and from the heart (such as transposition of the great vessels). Chapter ten is about pericardial diseases, such as pericarditis and cardiac tamponade. Pericarditis involves an inflammation of the sac that surrounds the heart. The main symptom of this condition is severe anterior chest pain that may confused for a myocardial infarction. It can be caused by a viral, fungal, or bacterial infection; or secondary to inflammation. Cardiac tamponade is a constriction of cardiac output caused by fluid or blood building up between the pericardial sac and the heart itself. Chapter eleven in the course focuses on endocarditis, which is most often bacterial in nature. Infective endocarditis, also referred to as bacterial endocarditis or BE because it is generally caused by a bacterial organism that settles in the inner lining of the heart and on heart valves. There are two types of the disorder, acute bacterial endocarditis and subacute (chronic) bacterial endocarditis. The most common organism that causes BE is Staphylococcus aureus. Less common bacterial causes include: Streptococcus viridans, coagulase negative Staphylococcus, other Streptococcal species, and Enterococcus. The twelfth and final chapter covers the topic of cardiomyopathy. Cardiomyopathy is a condition directly affecting the heart muscle. There are several types and etiologies of cardiomyopathy, but they often have similar symptoms. Most cases of cardiomyopathy involve thickening or rigidity of the heart muscle (but this is not always the case). Scar tissue can replace healthy muscle tissue in some cases of cardiomyopathy. The heart becomes week and prone to arrhythmias, and the valves may also be damaged as well.
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Chapter 1: Cardiac Imaging Techniques and Evaluations This chapter covers the important topic of the tests used to evaluate the heart in its well and sick state. Many patients are familiar with the electrocardiogram or ECG, which measures the electrical activity of the heart at rest. There are other, similar tests that measure the electrical activity of the heart over time. Stress tests measure the stressed heart, and the echocardiogram evaluates the heart using ultrasound. Other imaging studies of the heart are also discussed in this chapter.
Electrocardiogram The most commonly used assessment tool for evaluating the heart is an electrocardiogram or ECG. It is used to detect the rhythm and electrical activity of the heart, and to determine if there are abnormalities that may be affecting the cardiac rhythm. It can be performed in an outpatient or inpatient setting, and takes just a couple of minutes to perform. It is completely noninvasive and involves placing electrode (leads) on each of the four extremities, and in several locations on the chest. The device then measures the rhythm and electrical activity of the heart using 12 leads, causing it to commonly be referred to as a 12-lead ECG.
Figure 1 demonstrates an electrocardiogram being performed:
Figure 1 The electrodes are painlessly adhered to the skin and record the hearts electrical activity over a short period of time. The electrodes measure the rhythm of the heart as well as the depolarization and repolarization of the heart muscle during each beat. A total of ten electrodes are placed—four on the extremities and six on the precordium (chest). The test takes ten seconds to perform, during which several heartbeats are recorded on a rhythm strip in 12 leads. The test is completely non-invasive. The normal heart recognizes the depolarization of the heart, starting at the sinoatrial node or SA node, which is considered the pacemaker of the heart. The electrical activity spreads down the atrium, 1
reaches the AV (atrioventricular node) through the bundle of His, and into the Purkinje fibers, located in the ventricular wall. This pattern can be electrically recorded on the ECG. There are several reasons for performing an ECG. While it is often done to assess the heart prior to surgical procedures, it is also performed if a myocardial infarction or pulmonary embolism are suspected, a cardiac murmur is found, an abnormality in rhythm is detected, assessing a syncopal episode, and evaluating the effects of a drug or an electrolyte disturbance on the heart. Young people may have an ECG to screen for idiopathic hypertrophic cardiomyopathy; adults and kids may be tested during a surgical procedure; an ECG is used during cardiac stress testing (during exercise); and ECGs are done during CTA (CT angiography) or MRA (magnetic resonance angiography). In patients who are otherwise healthy, ECGs are not recommended as a standard screening tool for heart problems. There is a high rate of false positives, which will lead to unnecessary follow-up testing. The only time the ECG should be used as a screening tool is during physical exams for people in high-risk jobs, such as airline pilots. While there are 10 electrodes, there are a total of twelve different ECG “leads”. A lead is one of the electrical circuits inside the ECG machine. Some leads share the same electrodes but in a different pattern. The lead is a sort of vector that measures the electricity in one of several circuits. There are three sets of leads: augmented limb leads, limb leads, and precordial leads. There are three limb leads, three augmented limb leads, and six precordial leads. The electrodes are named RA (right arm), LA (left arm), RL (right leg), LL (left leg), and V1-V6 (the precordial electrodes). The leads include the three limb leads (Leads I, II, and III). The leads aVR, aVF, and aVL are the augmented leads, using the same electrode as the limb leads but with a different negative pole. The precordial leads are named after the precordial electrodes, including V1-V6. Sometimes an esophageal lead is placed into the esophagus to more accurately identify certain heart arrhythmias. An ICEG is an intracardiac ECG performed inside the heart with leads added through cardiac catheterization and the standard leads I, II, III, aVL, V1 and V6. The inferior leads, measuring the inferior of the heart are leads II, III, and aVF. The lateral leads are leads I, aVL, V5, and V6. The septal leads include V1 and V2 and the anterior leads are V3 and V5. V4 is an anterior lead and V5 is a lateral lead.
Figure 2 shows a typical electrocardiogram:
Figure 2 2
The ECG produces a heartbeat rhythm involving four electrical entities. The first is the P wave (which is representative of atrial depolarization, the QRS wave (which represents ventricular depolarization), the T wave (which represents ventricular repolarization), and the rarely-seen U wave (which represents purkinje fiber repolarization). The findings are reported on a grid with large and small boxes. Each small box is 1 mm by 1 mm, while each large box is 5 mm by 5 mm and represents 0.2 seconds. The ECG can detect ischemic changes and necrotic aspects of the heart. ST depression and non-ST segment myocardial infarctions represent ischemic changes in the heart. Inversion of the T waves can also indicate ischemia. ST elevation is characteristic of necrosis and can be seen in an ST-segment elevation myocardial infarction (STEMI). The first sign of an MI is hyperacute (peaked) T waves secondary to localized hyperkalemia in the heart. ST segment elevation happens next. After several hours, the ST segment will rise and, finally, the T wave inverts and a pathologic Q wave will develop. The ST segment elevation eventually resolves but the Q wave persists. Because the ECG only measures the function and rhythm of the heart at rest and only measures the heart for a couple of minutes, it may not detect an important arrhythmia of the heart. For this reason, there are several ways of detecting the heart rhythm over a period of time, such as the Holter Monitor and the implantable loop recorder.
Holter Monitor The Holter monitor is a technique that measures the rhythm of the heart over a 24-hour period of time. The patient wears a small device attached to the body by means of several electrodes on the chest itself. It continuously records the cardiac rhythm over a single day and is linked to the patient recording the time and nature of any symptoms they might have. The symptoms are evaluated along with the rhythm strip to see if the patient has any type of cardiac arrhythmia. Like the ECG, the Holter monitor evaluates the electrical activity of the heart but in a more portable way and over a longer period of time. It is used for as long as two weeks at a time. The main purpose of the Holter monitor is to detect occasional cardiac arrhythmias. For rarer symptoms, a cardiac event monitor is used (which is used for a month). Electrodes are attached to the bony parts of the chest, using between three and eight electrodes connected to a small device hung around the neck or placed in the pocket. The device records the heart’s electrical activity over the period of time the device is worn. Unlike the 12-lead ECG, there are only 2-3 leads in a standard Holter monitor, which is operated by battery. There are 12-lead/channel Holter monitors but these are uncommon. These types of monitors sometimes can detect ischemic changes in one of the leads. Newer models can sense the patient’s activity level as it records the electrical findings of the heart. Because there are fewer leads, the Holter monitor is not as good for detecting things like ST-segment changes.
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Figure 3 shows a Holter monitor as it is placed:
Figure 3 The process of reading the ECG recording would be time consuming for the physician as it records about 24-48 hours of material. For this reason, it is done using computer software. The automated results will give a summary of the heartbeat, including the heartbeat interval measure and the heartbeat morphology, the variability in heart rate, patient’s diary comments, and an overview of the rhythm. In general, it won’t record the patient’s activity level or ischemia unless an extremely modern-day device is utilized. Holter monitoring is completely painless and non-invasive. It can easily be worn for the 1-2 days necessary, record any event on the patient record, and match it to any cardiac rhythm finding. Patients are asked to participate in all normal activities, but should not bathe or shower with the monitor. The only thing the patient needs to do is make sure the electrodes are firmly attached and change the batteries as needed. If the patient has symptoms that do not occur every day, the Holter monitor might not be sufficient. For this reason, an event monitor might be worn. It is similar to a Holter monitor but only records the rhythm for a brief period of time when it detects an abnormality in the electrical activity of the heart. The rhythm strip can be sent wirelessly to the provider, who can assess the risk of the arrhythmia detected.
Other Cardiac Event Recording Devices An event monitor or “cardiac event monitor” will detect cardiac rhythm disturbances when the patient is having symptoms. Event monitors are similar to Holter monitors but it doesn’t record in a continuous way. It only starts to record when the patient is having symptoms. The device can also be worn for longer than a month. There are two event recording devices: symptom event monitors (which record the rhythm when the patient has symptoms) and the memory loop monitor (which records information from a few minutes before the activation and ends after the symptoms resolve). Each device records the ECG reading for a few minutes at a time. 4
The event recorder can evaluate uncommon symptoms, like palpitations and dizziness, which can be recorded when a button is pressed. Fainting spells can also be determined to be secondary to cardiac arrhythmias to something else. They are completely painless and noninvasive. The only preparation necessary is learning how to care for the device and learning how to record an event. After a few events have been documented, the device can be removed and the different arrhythmias that may have happened during the events are analyzed. Follow-up testing may be necessary if this test is abnormal and indicates something specific. An implantable loop recorder is uncommonly used to assess a patient for cardiac arrhythmias. It is implanted under the skin and records the heart rhythm on a continuous basis—day and night. It lasts in the body for up to three years and can help detect unusual or rare heart rhythm problems in the patient.
Echocardiogram An echocardiogram or “echo” is a specialized type of ultrasound designed to evaluate the heart. It uses sound waves that takes pictures of the heart muscle wall, the size of the heart’s chambers, the valves, the major blood vessels entering and leaving the heart, and the pericardium surrounding the heart. It can detect many different structural abnormalities of the heart but cannot necessarily detect coronary artery disease as these blood vessels are too small to see on an echocardiogram.
Figure 4 shows a typical echocardiography pattern:
Figure 4 5
The function and blood flow through the heart can be assessed with an echocardiogram. When an echocardiogram is performed after exercise, it can detect areas of decreased wall motion from cardiac ischemia and tell if a person is suffering from heart failure. An echocardiogram can also detect If there is an abnormal amount of fluid around the heart. Echocardiograms are more routinely used in the diagnosis and management of patients with coronary artery disease. It can detect the shape and size of the heart, the pumping capacity of the heart, and the location of various wall-motion abnormalities. Things like the cardiac output, diastolic function, and ejection fraction are also assessed. Hypertrophic cardiomyopathy, dilated cardiomyopathy, and valvular changes are assessible with an echocardiogram. It is completely non-invasive. Doppler echocardiography can detect the flow of blood through the heart, using color Doppler or spectral Doppler devices. Leakage or stenosis of valves can be seen as the flow is being assessed. Tissue motion is done by “tissue Doppler echocardiography”. IV contrast is used during “contrast echocardiography”. The usual echocardiography technique is transthoracic, which uses probes/transducers placed on the chest. A transesophageal echocardiogram is done with a transducer placed in the esophagus. This allows for imaging of the posterior aspect of the heart, and can be done when a more precise image of the heart is needed or when obtaining an external image may be difficult. Stress echocardiography measures the images of the heart prior to exercise and after exercise, looking for wall motion abnormalities after exercise that aren’t absent before exercise. It is not invasive and does not assess the patency of the coronary arteries. Three-dimensional echocardiography and four-dimensional echocardiography (using the movement of the heart as the fourth dimension) allows for the management and assessment of any pathology in the heart (especially cardiomyopathy and valvular disease). It takes computer technology and constructs a 3D image of the structures of the heart and is used during the placement of catheter-delivered valvular devices and various intraoperative assessments. Contrast-enhanced echocardiography can use IV contrast dye made of tiny bubbles that circulate during the test and which acts as a reflective surface for the ultrasound image. It is a good test for the evaluation of the global and regional wall motion function of the heart. It is the best test to evaluate LV thrombi and ventricular wall thickness. It can be used for the assessment of blood perfusion through the myocardial tissues (which might be abnormal in coronary artery disease).
Cardiac Stress Test A cardiac stress test is the best noninvasive way to determine whether a person has significant heart disease. It can detect arrhythmias that occur during physical activity and if the heart suffers from any kind of strain on the muscles during activity. Other names for this test include the “treadmill test”, the graded exercise test, the exercise electrocardiogram, or the stress EKG. In some cases, it can be combined with an echocardiogram performed immediately after exercise, and is an accurate way to detect early heart disease.
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Figure 5 depicts a typical cardiac stress test:
Figure 5 If a patient cannot exercise for physical reasons, a dobutamine or adenosine stress test can be done. The patient is hooked up to a cardiac monitoring device that measures the electrical activity of the heart. They are given intravenous adenosine or dobutamine—both of which stimulate the heart rate and mimic the effects of exercise on the heart. The blood pressure, heart rate, and ECG readings are measured to see if the elevated heart rate brings on ischemic changes in the heart muscle or a dangerous cardiac arrhythmia. A nuclear stress test is another way of detecting ischemic areas in the heart. The patient is injected with a radioactive uptake substance that is utilized by the heart muscle as part of heart muscle cell metabolism. Pictures of the radioactive uptake are taken of the heart at rest and again after exercising, looking for areas of decreased uptake after exercise. Areas of the heart muscle that are underperfused can be seen on the nuclear scan of the heart. Medications can also be used to elevate the heart rate among individual who can’t exercise. The cardiac stress test can compare the function of the coronary circulation before exercise and after maximal physical exertion, detecting abnormal blood flow to the rapidly beating heart. It is a good noninvasive way of screening for ischemic heart disease and assessing a patient’s heart function and prognosis after a heart attack. Heart simulation through exercise on a treadmill, pedaling a stationary bicycle, or turning a crank with their arms. Medications can also be used to mimic the effect of exercise. The test increases the heart rate gradually up to a heart rate near the patient’s maximal heart rate. Sometimes an echocardiogram or a nuclear test can be combined with an exercise test. In a stress echocardiogram, the stress test is combined with a before-and-after echocardiogram so wall motion differences between the resting and the exercise state can be determined. The test can also be done with dobutamine in patients who are unable to exercise. Obstructive coronary artery disease can also be assessed with this technique. The cardiac stress test is considered the first-line test to detect coronary artery disease in patients at a medium risk for CAD, including those with a family history of CAD, diabetes, hyperlipidemia, 7
hypertension, or a smoking history. Nuclear stress tests are used in patients who have an abnormal resting electrocardiogram, while an angiogram should be performed in high-risk patients. The treadmill test alone is 70-90 percent sensitive, and 50-75 percent specific in detecting CAD, while a nuclear test is 81 percent sensitive and 85-95 percent specific. In either test, the test should be interpreted based on a compilation of the patient’s other findings and is not necessarily the most accurate test when used alone. It is better in detecting true ischemic changes and narrowing of the coronary artery lumen rather than generalized thickening of the artery. The cardiac stress test cannot be used in cases of recent MI (within 48 hours), unstable angina, uncontrolled heart arrhythmia, other certain heart diseases (valvular disease, pericarditis, or PE), multivessel disease that might precipitate an MI during testing, and decompensated congestive heart failure. Patients with severe hypertension (greater than 200/110), aortic dissection, other illness, and severe pulmonary hypertension cannot have a stress test. The test should be stopped if ST segment elevation occurs, the patient becomes extremely fatigued, there is evidence of hypoperfusion (cyanosis), the patient has moderate or severe chest pain, the patient develops dizziness or syncope, or the systolic blood pressure decreases instead of increases during exercise. Anyone with sustained ventricular tachycardia should not complete the test.
Angiography An angiogram is a more invasive test of the heart and directly evaluates the coronary arteries in suspected cases of coronary artery disease. The patient can also have this test done to look at the pulmonary vasculature, the peripheral vasculature, or the cerebral vasculature. The aorta and carotid arterial blood flow can be assessed with an angiogram.
Figure 6 describes a left coronary angiography picture:
Figure 6 8
In a coronary angiogram, a catheter is placed in the femoral artery or vein (or less commonly, in the brachial artery or vein). The catheter is guided to the heart and radiocontrast dye is injected into the coronary arterial system. Any narrowing or blockages of the heart are evaluated through fluoroscopy of the heart while the dye is being injected. There are two specialized angiographic tests that can be done instead of a conventional angiogram. The first is known as a magnetic resonance angiogram or MRA. It uses a standard MRI machine and dye that can highlight the coronary vessels. The second is called a CT angiogram or CTA. It involves injecting a contrast dye that flows through the coronary arteries. The dye is picked up with a standard CT scanner with 3-dimensional and cross-sectional pictures taken of the heart vessels. These tests are slightly less invasive than a typical angiogram as a catheter is not required. The femoral artery is the most commonly-used access point for an angiogram of the heart. Using guide wires, contrast agents, and catheters, the inside of the arterial system can be detected. The test can be done using still images or moving images of the heart. A DSA (digital subtraction angiography) is used for all structures except the heart. It takes several pictures a second in order to evaluate the blood flow through the vessels, subtracting x-ray images of the organs and bones so only the vessels are seen. Images of the heart are done at 15-30 frames per second (without subtraction). DSA can only be used on non-moving blood vessels (and thus not the heart). A coronary angiogram assesses flow through the coronary arteries. A catheter is passed through an artery in the forearm or groin and is advanced so it reaches the main coronary artery. X-ray images are taken as dye is injected into the arteries, with the blood flow measured through the heart. This technique does not always detect atheroma or generalized atherosclerosis. Non-coronary angiography can be done to look at the vessels of the brain (and can detect aneurysms), the vessels of the legs or arms (peripheral angiography), and CT angiography during autopsies. Complications of this type of testing include having an allergy to contrast dye, having pain at the catheter insertion site, and damage to blood vessels near the puncture site.
Key Takeaways • • • •
There are several ways to measure the heart’s electrical activity, most commonly the ECG. An echocardiogram uses sound waves to visualize the structures of the heart. One of the best ways to measure the health of the heart is to perform an exercise stress test. An angiogram can be used on the vessels of the body to delineate the flow through the vessels.
Quiz 1. You are attempting to assess the heart in an asymptomatic patient. What is considered the most common assessment technique or tool in evaluating the health of the heart? a. Exercise stress test b. Holter monitor c. Electrocardiogram d. Echocardiogram 9
Answer: c. The electrocardiogram is by far the most commonly used assessment tool for evaluating the health of the heart in asymptomatic individuals. 2. What is the best way to screen a patient for asymptomatic heart disease? a. Stress electrocardiogram b. Stress echocardiogram c. Resting electrocardiogram d. Resting echocardiogram Answer: b. The stress echocardiogram is an effective way of detecting asymptomatic heart disease. It combines exercise, ECG readings, and an echocardiogram to look for stress on the heart and wall motion abnormalities brought on by exercise-induced ischemic changes in the heart muscle. 3. Which area of the body is least likely to be assessed by doing an angiogram? a. Cerebral blood vessels b. Carotid artery c. Coronary arteries d. Abdominal vasculature Answer: d. All of the listed areas are commonly assessed by using an angiogram. While the abdominal vasculature can technically be assessed with an angiogram, this is an uncommon test procedure. 4. Where is the “pacemaker” in the normal heart? a. The sinoatrial node b. The atrioventricular node c. The bundle of His d. The Purkinje fibers Answer: a. The sinoatrial node or SA node is the normal pacemaker of the heart, starting the electrical activity of each beat. 5. Which situation is least likely to require an ECG? a. Preoperative evaluation of the heart b. Evaluation of palpitations c. Evaluation of syncope d. Screening test in a healthy person Answer: d. ECGs are not recommended as a screening test in healthy people. 6. For what reason are ECGs not used as a screening tool? a. They are invasive and therefore not worth the risk. b. There is a high rate of false-positives. c. There is a high rate of false-negatives. d. It does not detect any previous heart problems. Answer: b. There is a high risk of false-positives in an ECG, leading to expensive and unnecessary followup testing. 7. Which test measures the electrical activity of the heart for the longest period of time? 10
a. Electrocardiogram b. Holter monitor c. Implantable loop recorder d. Cardiac event monitor Answer: c. The implantable loop recorder measures the electrical activity of the heart for as long as three years. 8. About how many leads/channels are there in the standard Holter monitor? a. One b. Three c. Seven d. Twelve Answer: b. There usually about 2-3 leads/channels in the standard Holter monitor. 9. What is the Holter monitor’s primary purpose? a. To detect cardiac arrhythmias b. To evaluate the heart while a patient is exercising c. To look for coronary artery ischemia d. To evaluate the valves of the heart Answer: a. The primary purpose of the Holter monitor is to evaluate the heart for cardiac arrhythmias. 10. Which is considered the best evaluation test for LV thrombi? a. Stress echocardiogram b. Three-dimensional echocardiogram c. Contrast echocardiogram d. Holter monitor Answer: c. The contrast echocardiogram can detect left ventricular thrombi with the greatest degree of accuracy.
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