What is Cardiac Imaging?

Cardiac imaging refers to methods of visualizing the heart, its internal anatomy, functioning, blood vessels, and surrounding structures.

What is cardiac imaging used for?

Cardiac imaging is used for several purposes. It provides the ability to confirm the presence of any physical abnormality or verify changes to the physiology of the cardiovascular components. Several modalities of cardiac imaging are used for different indications and symptoms.

Here are a few of the questions that can be answered using cardiac imaging.

  • Is the heart or a part of the heart the wrong size?
  • Does the heart have a congenital anomaly?
  • Is the heart beating correctly?
  • Is the blood flow normal?
  • Is there anything blocking or pressing on the heart or any blood vessels?

Types of cardiac imaging

There are several types of cardiac imaging that allow healthcare providers like cardiologists to diagnose and treat conditions of the heart. Here are six of the most common types of cardiac imaging.

1. Chest X-Ray

Chest X-Rays (CXR) are the oldest form of cardiac imaging and differentiate structures based on their density. High-density structures appear white, and those of low density appear black, while fluids, such as blood, may appear somewhere in between. Although more useful when diagnosing diseases of the lungs and other thoracic pathologies, chest x-rays play an essential role in cardiology.

Chest X-Rays provide an overall image of the structure of the chest as they visualize the heart’s location, orientation, and overall size and shape. They can be used to calculate the cardiac ratio, which measures what percentage of the chest the heart takes up.

Common reasons Chest X-Rays are ordered include:

  • Cardiomegaly (abnormal enlargement of the heart muscle).
  • Lung manifestations of heart disease, such as pleural effusion or pulmonary emboli in heart failure patients.
  • Confirm the positioning of cardiac devices after implantation procedures.
  • After trauma to the chest.
  • Evaluation for the presence of ballooning (aneurysm) of large blood vessels associated with the heart.

As Chest X-Rays are less costly, take less time to do and get necessary results, they are often used as an initial exam for symptoms that may be heart-related, thereby providing a window view of the patient’s cardiovascular system. Because Chest X-Rays cannot be used to view fine details or see inside the heart, additional testing is usually needed.

2. Echocardiography

Echocardiography is a form of ultrasound that emits high-frequency sound waves that penetrate the body and record the waves as they bounce off the internal structures. The receiver on the machine detects these recordings and creates a visual representation. Structures that reflect the waves appear white, muscle tissues appear gray, and fluid appears black. Unlike X-rays, which provide a picture of a specific moment, echocardiograms can show the movements of the structures in real-time.

There are three main types of echocardiography:

  1. Transthoracic echocardiography (TTE), during which the transducer is placed on the chest wall, ****is used most often. Point of care ultrasonography (POCUS) may be used at the bedside for patients who cannot be moved because of urgency or if they are critically ill. This type of echocardiogram does not require fasting, anesthesia, or a sterilized operating room, making it more readily available in the clinic and significantly less costly.
  2. Transesophageal echocardiography (TEE) involves attaching the transducer to an endoscope and introducing it into the esophagus, through which it emits and receives the wave pattern. TEE provides better images as the muscles and ribs of the chest are no longer in the way. It is also used to rule out the presence of a thrombus (blood clot) within the heart.
  3. Intracardiac echocardiography (ICE), requires attaching a transducer to the tip of a catheter. The catheter is introduced through the femoral vein and guided to the heart. It is used to identify complex abnormalities and during cardiac procedures when better visualization is needed.

Indications for echocardiograms include:

  • Using the doppler function to identify areas of abnormal blood flow, assess the function of the heart valves, measure the blood flow to evaluate the functioning of the different parts of the heart, and quantify key measurements such as the ejection fraction (EF).
  • Evaluating the presence of possible pleural effusion or pulmonary emboli.
  • Visualizing the ventricular walls and cavity structure to assess muscle function, size of the cardiac chambers, and any wall motion abnormalities, such as mitral valve regurgitation.
  • Congenital defects, such as septal wall defects.
  • Assessment of major vessels in suspected anomalies and dissections.
  • In combination with a stress test to assess the heart function under greater physical demands to identify problems that may have been missed during a regular exam.

While an echocardiogram can take anywhere from one to several hours to complete, depending on the indication, it provides a wealth of information to cardiologists about a vast amount of cardiac diseases. However, the resolution and clarity it provides is limited, thus, there can be poor visualization of the structures in some patients due to obesity or the presence of lung diseases.

3. Cardiac MRI

Magnetic Resonance Imaging (MRI) uses strong magnets and radio frequency waves to induce minute changes within the body which are detected by the sensors of the MRI and used to create an image of the part of the body being imaged.

Cardiac MRIs help assess heart muscle function, structural abnormalities, the volume of blood being pumped by the heart, and the characterization of the tissues. It can also reveal the extent of damage sustained by heart tissue from heart attacks and other diseases.

As Cardiac MRIs provide a substantial amount of information, they are often used for:

  • Assessing cardiac masses, such as tumors.
  • Establishing prognosis of various heart diseases, such as abnormal heart rhythms, cardiomyopathy, infiltrative diseases, and heart failure.
  • Diagnosing myocarditis (infection of the heart muscle) by confirming the presence of inflammation and edema in the tissue.
  • Assessing response to medication treatment.
  • Assessing potential adverse events from medical interventions during clinical trials.
  • The diagnosis and assessment of aortic diseases, such as aneurysms and dissection.

Despite the versatility of Cardiac MRIs, there are some disadvantages. They can take 45 minutes to an hour to perform and require that the patient stay still and are asked to hold their breath several times during the procedure to get accurate images. They are also expensive and have limited availability. Cardiac MRIs may not be suitable for some patients who have kidney disease, are allergic to contrast, or have certain metal implants.

4. Cardiac CT

Cardiac computed tomography (CT) involves a series of x-rays taken at different angles and combined to provide a 3D image of the heart. Contrast is used to better differentiate the chambers of the heart from blood vessels.

While a Cardiac CT can provide information about structural abnormalities of the heart, it is used only for specific indications because of the amount of radiation exposure. Contrast given during the CT may be contraindicated in some patients and has a risk of causing kidney damage.

CT angiography with contrast provides direct visualization of the coronary arteries and is used in symptomatic patients, usually with the complaint of chest pain, to confirm or deny a myocardial infarction. It is especially useful in understanding the extent of blockage of the coronary arteries and is less invasive than traditional catheterization.

Calcium scoring using CT detects the presence and extent of coronary artery calcification, which helps predict future risk of cardiovascular diseases and guides preventative treatment. A Cardiac CT also provides visualization of the thoracic aorta and is used to assess acute aortic syndromes.

5. Catheterization

Cardiac catheterization, specifically left-heart catheterization, involves inserting a catheter into a peripheral artery and threading it to the heart to visualize the coronary arteries. Contrast is injected through the catheter, and the blood flow can be viewed through x-rays during a cardiac procedure.

Indications for cardiac catheterization include:

  • Evaluation of narrowing or blockages of the coronary arteries and opening them, as indicated, through a percutaneous coronary intervention (PCI).
  • Assessment of valvular disorders.
  • Assessment and closure of congenital heart defects.

Due to its invasive nature, although minimal, there is a risk of bleeding, infection, kidney damage from contrast exposure, stroke, and heart attack.

6. Nuclear Cardiac Imaging

Also known as radionuclide imaging, nuclear imaging refers to imaging techniques during which small amounts of radioactive material is injected into the blood and used to visualize the blood flow to the heart using a gamma camera. Unlike other imaging modalities, nuclear imaging provides a visual representation of organ function rather than structure.

There are two main types of nuclear imaging modalities used in cardiology:

1. Myocardial perfusion imaging (MPI) is used with stress tests that involve exercising or taking a medication that increases the heart rate, thus, the need for oxygen. This imaging technique shows how much of the radioactive material is being taken up by the heart tissue, which estimates the amount of blood reaching that tissue. Areas with decreased uptake represent parts of the tissue not getting enough blood supply. MPI can also identify areas of previous heart attacks where the scar tissue will not take up any of the radioactive tracers.

2. Multigated Acquisition (MUGA) Scan is an older non-invasive imaging technique used to assess changes in heart function. It involves serial imaging through several cardiac cycles synchronized with an electrocardiograph (ECG), using different views. A composite is made using these images and may be used to assess different parts of the heart. A MUGA scan may be done at rest or as part of a stress test.

MUGA can be used for:

  • Calculating the left ventricle ejection fraction (LVEF)
  • Identifying systolic or diastolic dysfunction.
  • Assess cardiac valvular function.
  • Quantifying the size of a congenital shunt.

Although other imaging modalities have largely replaced MUGA, it is still often used to monitor cardiac function in patients receiving cardiotoxic chemotherapy.

Emerging Cardiac Imaging Through Clinical Trials

Whether for routine examination or following a cardiac event, there are several modalities for which to evaluate the heart. The resolution, measurements, and diagnostic capabilities of each imaging technique vary to provide an option for each indication. Cardiac imaging has many possibilities, such as accurately identifying trends in structure measurements, determining the diagnosis of heart disease, or detecting an urgent cardiac event to ensure timely and lifesaving therapies are provided.

Cardiac imaging also plays a large role in cardiology clinical trials, helping scientists to further advance medical discoveries and develop new drugs, treatments, and medical devices for various heart diseases and conditions. Scientists are always looking to discover new noninvasive tools to further advance how we can view and treat the heart. If you’re looking to sponsor a cardiology or cardiac imaging clinical trial to improve upon existing cardiac imaging tools or to create new emerging tools, make sure you work with a trusted contract research organization (CRO) to deliver high-quality trial results.

Vial supports cardiology clinical trials across multiple indications. We are a tech-enabled CRO providing next-generation clinical trial management services that deliver faster, more efficient trials for biotech sponsors at up to 50% less cost. The Vial Cardiology CRO distinguishes itself by leveraging digital technology, such as its Vial Technology Platform, which brings together eSourceEDC, and ePRO in one connected system to streamline site processes. These best-in-class CRO services help accelerate the development of new therapies and devices for biotech companies. Connect with us for more information on how to run faster, better, and cheaper cardiology clinical trials.

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