Cardiac Imaging


Article Author:
Rameez Rehman


Article Editor:
Amgad Makaryus


Editors In Chief:
Susan Johnson
Alexandra Caley


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Kyle Blair
Trevor Nezwek
Radia Jamil
Erin Hughes
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Navid Mahabadi
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Abbey Smiley
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Daniyal Ameen
Altif Muneeb
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes
Komal Shaheen
Sandeep Sekhon


Updated:
4/9/2019 8:59:41 PM

Introduction

As innovative technology has progressed throughout the field of medicine, so too has the ability to visualize the heart and its vasculature noninvasively. Several cardiac imaging modalities have become essential in the practice of modern cardiovascular medicine not only in diagnosis but also in the management of various cardiovascular diseases as well as in the guidance of invasive procedures. These modalities include echocardiography, myocardial perfusion imaging via nuclear scintigraphy, magnetic resonance imaging (MRI), and computed tomography (CT). The gold standard imaging modality for the visualization of the coronary arteries remains the invasive technique of coronary angiography via coronary catheterization. Each modality can be used individually or in combination depending on desired diagnostic needs. These studies are now routinely used together with history taking, physical examination, laboratory testing and have come to define the practice of modern cardiovascular medicine. Additionally, appropriateness guidelines for the use of these imaging techniques are now standard in the assessment of the ideal imaging modality to be used in specific patient situations to optimize diagnostic and cost efficiency as well as minimize risk to the patient.[1][2][3][4]

Equipment

Echocardiography uses high-frequency sound waves, essentially ultrasound, to penetrate the body and bounce off structures of interest to produce an image. Transducers emit sound waves that are sensed by the receiver up to one hundred frames per second making it possible to generate moving images in real time. Fluid or blood appears black. Reflective surfaces such as calcified structures appear white while muscle tissue appears gray. Transthoracic echocardiography involves the combination of multiple images from various scanning locations on the chest wall. A variation of transthoracic echo is the transesophageal echo in which the transducer is placed on an endoscope that is inserted into the esophagus. This allows for better visualization of cardiac structures with less obstruction from the chest wall, muscles, and ribs. The need for less penetration allows for better image quality and spatial resolution of various cardiac structures. Transesophageal echocardiography requires both topical anesthetics of the oropharynx and sedation of the patient. The procedure is usually performed under conscious sedation. Consent is required, and the patient needs continuous monitoring during as well as following the procedure in the recovery period.[5][6]

In addition to imaging, echocardiography can determine the velocity of blood flow through the heart and vessels via its Doppler function. Pressure differences between chambers and even valves can be determined using the velocity. Doppler helps visualize not only blood flow but also identifies turbulent regions of accelerated flow. This can be used to determine valvular insufficiency. Stress (either exercise or pharmacologic) echocardiography is routinely used to evaluate cardiac function in the setting of exercise. Three-dimensional echocardiography is a newer echocardiographic technique that allows for the acquisition of three-dimensional datasets that can be analyzed and can specifically assess chamber volumes, valvular abnormalities, and other structural pathology. Additionally, strain rate imaging is a method used for measuring a regional or global deformation of the heart muscle to assess the change in shape and dimensions during the cardiac cycle.

Classical echocardiographic equipment has been large and confined to special rooms dedicated to performing tests. Over the last several years, smaller portable ultrasound equipment has become available to be used at the bedside and can even be carried during medical rounds. Although most handheld devices lack all the functionality of their larger counterparts, they are often able to provide crucial information rapidly and efficiently.    

Nuclear imaging involves the injection of intravenous radioactive tracers that become trapped in the myocytes after traveling through the vasculature surrounding the myocardium. Various tracers are used depending on their half-life and the diagnostic purpose of the study.  These radioactive tracers emit radioactive rays that can be detected by specialized scanners that can convert the rays into perfusion images of the heart. Like with echocardiography, nuclear imaging can be performed during stress (either exercise or pharmacologic) to assess for evidence of ischemia.

Cardiac computed tomography uses multiple x-ray beams from a CT scanner at various angles to create cross-sectional images. The x-ray beams pass through the body and are collected by a detector array that can generate an image. Depending on the path of the beam through tissues of varying densities, a gray scale is created. Bone appears white; the air is black, blood and muscle are various shades of gray. To better differentiate the cardiac chambers from the vascular structures, contrast is often used. These images can also be used to produce a three-dimensional image of the heart. CT coronary angiography uses contrast dye to produce a three-dimensional image of the heart vasculature without the need for invasive coronary catheterization.[7]

Cardiac magnetic resonance imaging (CMR) takes advantage of protons in hydrogen molecules to create an image. The human body is made up of a majority of water. Therefore hydrogen molecules are plentiful. An MRI machine creates a magnetic field and alters the spin of the protons. Depending on the surroundings, the frequencies of the spins change. These frequencies are detected, and an image is reconstructed. The cardiac structure is very well-visualized with MRI. The contrast between tissue and vasculature is more pronounced than cardiac CT.

Invasive cardiac catheterization is an invasive technique utilizing a fluoroscopic technique that allows for the assessment of coronary anatomy and remains the gold standard in cardiac imaging. It involves gaining direct access to the coronary arteries via the peripheral anatomy usually through the wrist or the groin vessels. Percutaneous access is gained with a flexible sheath inserted into the vessel that allows for catheters to be advanced towards the heart. The catheter has diagnostic value and can be used to measure hemodynamic pressure changes in the right and left ventricle. The main diagnostic value of catheterization remains with its use for coronary angiography. With the use of contrast agents, direct visualization of the coronaries in real time during the cardiac cycle is possible. Cardiac catheterization is both diagnostic as well as therapeutic with options available for reperfusion of the myocardium with the use of balloon angioplasty and stent placement.[8]

Complications

The technique and the need for sedation during transesophageal echocardiography expose the patient to a variety of risks. These may include damage to the esophagus such as perforation, aspiration, and complications related to anesthesia. These complications are very rare, especially at experienced centers.

Cardiac CT leads to exposure to ionizing radiation, which is well-known to have harmful side effects. The risk for malignancy following exposure is difficult to determine and likely small, nonetheless remains a possibility. Risk versus benefit must be discussed when considering these imaging modalities, and consideration of cumulative exposure should also be ascertained especially with repeat imaging studies and in performing these tests in patients at a young age.

The use of contrast agents has a substantial impact on the diagnostic value of radiologic imaging and is commonly used for cardiac CT, cardiac catheterization, and CMR. The most feared complication remains contrast-induced nephropathy. In those with normal renal function, it is a self-limiting side effect. However, in those with baseline renal abnormality, especially with those that are diabetic; progression to chronic kidney disease remains high.

Cardiac magnetic resonance imaging uses a magnetic field to generate an image. As a result, the presence of metallic hardware remains a major risk during testing. In 2011, the first CMR compatible pacemaker became available, however, at this time a permanent pacemaker remains a contraindication to CMR. The same goes for implantable defibrillators.

Cardiac catheterization remains the most invasive modality and has the most potential for harmful side effects. These include as mentioned renal injury and possible renal failure from contrast exposure, myocardial infarction, stroke, induction of arrhythmias and vascular complications such as bleeding. There are no absolute contraindications to cardiac catheterization. However, relative contraindications do exist. They include decompensated heart failure, bacteremia, acute stroke, and acute renal failure.

Clinical Significance

Echocardiography allows for direct visualization of the heart including the size of the chambers, the thickness of the ventricular walls, and any structural abnormalities. It also allows for an assessment of contractility and left ventricular ejection fraction. Transesophageal echocardiography has become the test of choice for detecting valvular vegetations and thrombi within the heart. Transesophageal echo also allows visualization of the left atrial appendage, which is often too difficult to visualize with standard transthoracic echocardiography. In the setting of renal dysfunction, transesophageal echo has become the modality of choice for evaluation of aortic dissection. Stress echocardiography is routinely used to evaluate cardiac function in the setting of exercise and can determine myocardial ischemia. For those able to exercise, echocardiography is performed during the use of a treadmill or bicycle. For those unable to exercise, pharmacologic stimulation is used to simulate exercise as an echocardiogram is performed. Wall motion abnormalities are used to signify areas of possible ischemia. Echocardiography is unique in that it can provide a great deal of clinical data and remain safe without any exposure to radiation.

Radionuclide imaging is most often used for evaluation in those patients with known or suspected coronary artery disease. Nuclear imaging allows for not only diagnosis but also for risk stratification and can be used for the assessment of myocardial viability before revascularization. Radioactive tracers mark areas where blood can reach the capillaries, a sign of myocardial perfusion. Areas with hypoperfusion are indicative of regions of myocardial ischemia. Nuclear imaging can also be used as a stress test with imaging before and after stress again precisely marking areas of decreased perfusion as areas of ischemia.[9]

Cardiac CT allows for direct visualization of coronary vasculature in three dimensions without the need for an invasive procedure like coronary catheterization. CT also allows for calcium scoring which is the ability to detect the presence of coronary artery calcification; calcification has been associated with atherosclerosis and mortality. CT angiography has emerged as imaging study of choice for rapid assessment of cardiac vasculature especially in the setting of suspected aortic dissection given normal renal function.  Newer applications utilizing cardiac CT for perfusion and fractional flow reserve are on the horizon and are set to expand the diagnostic armamentarium of cardiac CT.

Cardiovascular MRI is mainly used to assess cardiac structure as well as function. The contrast between cardiac tissue and vasculature is better visualized leading to a sharper definition when compared to cardiac CT. CMR perfusion utilizing first pass gadolinium imaging is also employed to test for myocardial ischemia and has been compared with other imaging modalities. Late gadolinium enhancement CMR is used for the identification of infarcted myocardial tissue. This technique is routinely used along with perfusion CMR to assess whether a territory in question is ischemic or infarcted (scar). Additionally, phase contrast and myocardial tagging sequences utilizing CMR allow for valvular and flow assessment as well as myocardial performance assessment in patients. CMR has a wide range of diagnostic capability. However, it requires attention to detail especially in the proper acquisition sequences used, and analysis of these images is reserved to be performed in centers with clinical training and expertise in this imaging modality.[10]

Coronary angiography via cardiac catheterization allows for the comprehensive evaluation of coronary anatomy and severity of cardiac disease. Not only does it allow for visualization but also allows for interventions to reperfuse the myocardium. Cardiac catheterization is the treatment of choice in emergency situations such as acute myocardial infarction and therefore remains the gold standard for assessment of coronary anatomy.  Intravascular ultrasound is an invasive technique utilized during cardiac catheterization that uses ultrasound to visualize the lumen and the wall of blood vessels. This can be especially useful in the assessment of plaques in the arteries that may be significant but are not causing major stenosis to blood flow. Another complementary technique used during cardiac catheterization is fractional flow reserve assessment. Fractional flow reserve determines the ratio between the achieved blood flow in a stenosed coronary artery and the expected maximum flow in a normal coronary artery.  By this measurement, a luminal stenosis which may be borderline (approximately 40% to 60%) can be functionally assessed to determine its clinical hemodynamic significance. Finally, transcatheter structural invasive procedures are now performed (for example, transcatheter aortic valve replacement or transcatheter mitral valve repair). These procedures are generally guided by noninvasive cardiac imaging both before the procedure for patient evaluation and selection (transthoracic and transesophageal echocardiography, cardiac CT, cardiac MRI), during the procedure for direct guidance (transesophageal echocardiography), and after the procedure for survey of the procedure results and possible complications (echocardiography).

Enhancing Healthcare Team Outcomes

When patients present with symptoms of heart disease, the primary care provider, nurse practitioner, internist and the emergency department physician have available numerous imaging methods to assess heart function. In order to avoid redundancy or duplication, it is important to consult with the cardiologist to confirm the best imaging test. The type of cardiac imaging test depends on the urgency of the problem and the symptoms.[11][12][13]


  • Image 5713 Not availableImage 5713 Not available
    Contributed by A. Makaryus MD
Attributed To: Contributed by A. Makaryus MD

Interested in Participating?

We are looking for contributors to author, edit, and peer review our vast library of review articles and multiple choice questions. In as little as 2-3 hours you can make a significant contribution to your specialty. In return for a small amount of your time, you will receive free access to all content and you will be published as an author or editor in eBooks, apps, online CME/CE activities, and an online Learning Management System for students, teachers, and program directors that allows access to review materials in over 500 specialties.

Improve Content - Become an Author or Editor

This is an academic project designed to provide inexpensive peer-reviewed Apps, eBooks, and very soon an online CME/CE system to help students identify weaknesses and improve knowledge. We would like you to consider being an author or editor. Please click here to learn more. Thank you for you for your interest, the StatPearls Publishing Editorial Team.

Cardiac Imaging - Questions

Take a quiz of the questions on this article.

Take Quiz
On a chest radiograph, the anterior border of the heart is made up of which of the following?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which of the following radiopharmaceuticals is not used in cardiac imaging?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Cardiac MRI is performed in such a way as to eliminate as much as possible the motion artifacts stemming from the pulsatile flow. How is this accomplished?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
A time-activity curve over the left ventricle is being obtained during a cardiac cycle imaging with labeled red blood cells. The trough represents which of the following?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
A cardiac positron emission tomography (PET) exam is being performed using both an 18-F fluorodeoxyglucose (FDG) and 13-N ammonia. The scan shows diminished N-13 ammonia activity in the inferoapical area. This same area on 18-F FDG imaging shows normal to increased uptake. How is this interpreted?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
A National Medical Response Team member is being tested as to his knowledge of cardiac radiopharmaceuticals. He is asked which of the following choices are not used in cardiac imaging? Which of the following must he choose in order to pass the test?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which of the following exams should use a high-resolution collimator?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
The National Medical Response Team gets a request for a STAT myocardial infarct-avid study with Tc99m-pyrophosphate. It is 10 AM and he is told the patient's symptoms began at 8 AM, 2 hours earlier. When should this study be performed?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
When assessing the significance of cardiac uptake on a Tc99m-pyrophosphate exam, internal standards of comparison include which of the following?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
A 77-year-old male with a history of hypertension, diabetes mellitus type 2, and chronic kidney disease presents with sudden onset shortness of breath and substernal chest pain radiating to the back. The patient is tachycardic but otherwise hemodynamically stable. EKG reveals sinus tachycardia with nonspecific ST wave abnormalities. Given the scenario which of the following is the best diagnostic test to determine a diagnosis?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which of the following is not a contraindication for a cardiac magnetic resonance imaging?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
A 52-year-old male with a history of hypertension is seen by his primary care physician for an annual checkup. The physician notices a new grade III/IV systolic murmur at the apex radiating to the left axilla. The patient is asymptomatic with a benign physical exam. What would be the best initial imaging modality for further workup of the murmur?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up

Cardiac Imaging - References

References

Guglielmo M,Baggiano A,Muscogiuri G,Fusini L,Andreini D,Mushtaq S,Conte E,Annoni A,Formenti A,Mancini EM,Gripari P,Guaricci AI,Rabbat MG,Pepi M,Pontone G, Multimodality imaging of left atrium in patients with atrial fibrillation. Journal of cardiovascular computed tomography. 2019 Mar 30;     [PubMed]
Williams MC,Newby DE,Nicol ED, Coronary atherosclerosis imaging by CT to improve clinical outcomes. Journal of cardiovascular computed tomography. 2019 Mar 29;     [PubMed]
Antoniades C,Kotanidis CP,Berman DS, State-of-the-art review article. Atherosclerosis affecting fat: What can we learn by imaging perivascular adipose tissue? Journal of cardiovascular computed tomography. 2019 Mar 29;     [PubMed]
Singh M,Sporn ZA,Schaff HV,Pellikka PA, ACC/AHA Versus ESC Guidelines on Prosthetic Heart Valve Management: JACC Guideline Comparison. Journal of the American College of Cardiology. 2019 Apr 9;     [PubMed]
Pettemerides V,Turner TJ,Steele C,Macnab A, Does stress echocardiography still have a role in the rapid access chest pain clinic post NICE CG95? Echo research and practice. 2019 Mar 1;     [PubMed]
Calogero E,Fabiani I,Pugliese NR,Santini V,Ghiadoni L,Di Stefano R,Galetta F,Sartucci F,Penno G,Berchiolli R,Ferrari M,Cioni D,Napoli V,De Caterina R,Di Bello V,Caramella D, Three-Dimensional Echographic Evaluation of Carotid Artery Disease. Journal of cardiovascular echography. 2018 Oct-Dec;     [PubMed]
Rischpler C,Woodard PK, PET/MR Imaging in Cardiovascular Imaging. PET clinics. 2019 Apr;     [PubMed]
Yannopoulos D,Bartos JA,Aufderheide TP,Callaway CW,Deo R,Garcia S,Halperin HR,Kern KB,Kudenchuk PJ,Neumar RW,Raveendran G, The Evolving Role of the Cardiac Catheterization Laboratory in the Management of Patients With Out-of-Hospital Cardiac Arrest: A Scientific Statement From the American Heart Association. Circulation. 2019 Mar 19;     [PubMed]
Wu J,Liu C, Recent advances in cardiac SPECT instrumentation and imaging methods. Physics in medicine and biology. 2019 Mar 13;     [PubMed]
Bhatia S,Anstine C,Jaffe AS,Gersh BJ,Chandrasekaran K,Foley TA,Hodge D,Anavekar NS, Cardiac magnetic resonance in patients with elevated troponin and normal coronary angiography. Heart (British Cardiac Society). 2019 Apr 4;     [PubMed]
Misra A,Sriram C,Gupta P,Humes R, The Adult with Post-operative Congenital Heart Disease: a Systematic Echocardiographic Approach. Current cardiology reports. 2019 Mar 18;     [PubMed]
Zoghbi WA,Asch FM,Bruce C,Gillam LD,Grayburn PA,Hahn RT,Inglessis I,Islam AM,Lerakis S,Little SH,Siegel RJ,Skubas N,Slesnick TC,Stewart WJ,Thavendiranathan P,Weissman NJ,Yasukochi S,Zimmerman KG, Guidelines for the Evaluation of Valvular Regurgitation After Percutaneous Valve Repair or Replacement: A Report from the American Society of Echocardiography Developed in Collaboration with the Society for Cardiovascular Angiography and Interventions, Japanese Society of Echocardiography, and Society for Cardiovascular Magnetic Resonance. Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography. 2019 Feb 20;     [PubMed]
Gill EA,Blaha MJ,Guyton JR, JCL roundtable: Coronary artery calcium scoring and other vascular imaging for risk assessment. Journal of clinical lipidology. 2019 Jan - Feb;     [PubMed]

Disclaimer

The intent of StatPearls is to provide practice questions and explanations to assist you in identifying and resolving knowledge deficits. These questions and explanations are not intended to be a source of the knowledge base of all of medicine, nor is it intended to be a board or certification review of CNS-Adult-Gerontology. The authors or editors do not warrant the information is complete or accurate. The reader is encouraged to verify each answer and explanation in several references. All drug indications and dosages should be verified before administration.

StatPearls offers the most comprehensive database of free multiple-choice questions with explanations and short review chapters ever developed. This system helps physicians, medical students, dentists, nurses, pharmacists, and allied health professionals identify education deficits and learn new concepts. StatPearls is not a board or certification review system for CNS-Adult-Gerontology, it is a learning system that you can use to help improve your knowledge base of medicine for life-long learning. StatPearls will help you identify your weaknesses so that when you are ready to study for a board or certification exam in CNS-Adult-Gerontology, you will already be prepared.

Our content is updated continuously through a multi-step peer review process that will help you be prepared and review for a thorough knowledge of CNS-Adult-Gerontology. When it is time for the CNS-Adult-Gerontology board and certification exam, you will already be ready. Besides online study quizzes, we also publish our peer-reviewed content in eBooks and mobile Apps. We also offer inexpensive CME/CE, so our content can be used to attain education credits while you study CNS-Adult-Gerontology.