Echocardiography

Background

Echocardiography uses ultrasound imaging to visualize the structures of the heart. An ultrasound machine uses an electrical pulse that causes a sound wave that courses through tissue and results in an image based on the variable conductance through different parts of the body. There are two ways to obtain images in echocardiography, noninvasively and invasively. For the noninvasive approach, an ultrasound is placed externally on the chest, and this is referred to as a transthoracic echocardiogram (TTE). Alternatively, an ultrasound probe can be passed down the esophagus, and this invasive approach is referred to as a transesophageal echocardiogram (TEE). A TEE provides better resolution and improved image quality because the probe is in closer proximity to the heart; however, it carries the risk of being an invasive procedure. A TTE is noninvasive, easier to perform, carries little to no risk to the patient, and provides a great deal of useful information.

How to Use It

Transthoracic echocardiography is the initial imaging test of choice to evaluate a patient’s cardiac structure and function. The images obtained allow the cardiologist to evaluate :

• 1.

  Left ventricular systolic function and diastolic function.

• 2.

  Left ventricular structure.

• 3.

  Right ventricular structure and function.

• 4.

  Aortic, pulmonic, mitral, and tricuspid valves for evidence of valvular pathology including stenosis, regurgitation, or structural deformities.

• 5.

  Prosthetic valves.

• 6.

  Diseases of the pericardium and proximal aorta.

• 7.

  Pulmonary hypertension.

• 8.

  Structure of the atria and congenital defects of the heart.

Transesophageal echocardiography is performed if the TTE is either nondiagnostic or if it identified an abnormality that requires further evaluation. In addition, a TEE may be performed during surgery, both in cardiac and noncardiac cases, and during percutaneous transcatheter procedures to guide the placement of the intervention device (such as in transcatheter aortic valve replacement [TAVR]). The most common indications for a TEE are:

• 1.

  Evaluation of the left atrial appendage for the presence of a blood clot (such as prior to cardioversion or atrial fibrillation ablation).

• 2.

  Further evaluation of prosthetic valves including assessments for valve endocarditis or paravalvular abscess.

• 3.

  For patients with low-quality or nondiagnostic TTE images including patients who are intubated and on mechanical ventilation.

• 4.

  During surgical procedures to evaluate cardiac structure/function.

Given that a TEE is an invasive procedure, it must not be performed if there is significant esophageal pathology such as esophageal trauma, perforation, tumor, prior esophageal surgery, or active or recent bleeding. Consultation by a gastroenterologist may be necessary for evaluation of the esophagus via esophagogastroduodenoscopy (EGD) prior to a TEE in some cases. See Chapter 32: Gastrointestinal Endoscopy - Upper for more details.

A stress TTE is performed to evaluate a patient’s left ventricular systolic function in order to deduce if exercise or a pharmacologic agent can lead to inducible ischemia from underlying coronary artery disease. This is particularly useful for patients with symptoms that are concerning for coronary artery disease. These may include exertional chest discomfort or shortness of breath. The cardiologist will consider the patient’s history, physical examination, and baseline electrocardiogram (EKG) to determine if a stress TTE is appropriate. See Chapter 53: Stress Tests for more details.

How It Is Done