Using Echocardiography in Critical Care

Achikam Oren-Grinberg, MD, MS*
Beth Israel Deaconess Medical Center
Boston, Massachusetts, USA

Sajid Shahul, MD**
Beth Israel Deaconess Medical Center
Boston, Massachusetts, USA

Echocardiography was introduced to the operating suite in the 1970s, with epicardial echocardiography as its initial application. Transesophageal echocardiography (TEE ) during surgery was first described in 1980 but did not become commonplace until the middle of that decade. Since then, TEE has evolved into a widely used and versatile modality for diagnosis and monitoring of critically ill patients. As such, its use has expanded into the perioperative period and the intensive care unit (ICU). Currently, echocardiography is the only imaging modality that provides real-time information on cardiac anatomy and function at the bedside.

History in the ICU
Echocardiography in the ICU was first performed only by board-certified cardiologists who were called to assist in the diagnosis of cardiovascular diseases. This practice started to change in Europe during the mid-1980s, when intensivists in France and Denmark extended the use of ultrasound to a more global and comprehensive assessment of hemodynamics.(1) The ICU use of echocardiography spread fairly slowly until the end of the 1990s. Recent increasing interest among intensivists may be explained by a number of factors(1):

• A significant decrease in the use of the pulmonary artery catheter after several negative trials evaluating its impact on prognosis

• An accumulation of clinical evidence documenting the additional value of echocardiography compared to traditional invasive hemodynamic assessment

• An improvement in ultrasound technology, leading to portable machines producing high-quality images

• An increasing number of publications on clinical applications of echocardiography

• The design of specific courses dedicated to the education and training of the intensivist

Initially, some cardiologists raised concerns that intensivists would not be able to perform echocardiographic exams and interpret results adequately and accurately. Despite these early concerns, studies have shown that intensivists and in-training physicians can perform these tasks even with minimal echocardiographic training.(2-4) These and other studies demonstrated that intensivists were able to perform their own examinations and thus were able to provide 24-hour availability of immediate echocardiography without the cardiologist.

Despite utilizing the same technology, cardiologist’s and intensivist’s applications of echocardiography are very different. The cardiology echocardiographic examination typically is obtained by sonographers and interpreted by cardiologists. In contrast, intensivists perform their own examinations. The cardiologist’s examination is comprehensive, emphasizing cardiac disease conditions, whereas the intensivist typically focuses the examination to address a specific physiological question: “Is my patient’s hypotension a result of a cardiac pathology, and if yes, what is it?” Cardiologists interpret echocardiographic examinations in the laboratory with limited knowledge of the patient’s hemodynamic status. Intensivists interpret the examination at the bedside, taking into consideration the patient’s hemodynamic status, response to supportive medications and heart-lung physiology interaction in assessment of fluid responsiveness. The role of the intensivist performing echocardiography in the ICU for hemodynamically unstable patients is gaining acceptance, but many still believe that this modality should be kept in the hands of the cardiologists.

Diagnosing Hemodynamic Instability and Shock
Quick diagnosis of the etiology of shock in the critically ill patient is vital to guide timely and appropriate management. Echocardiography is the diagnostic modality of choice in such patients because of its portability, safety, ability to provide immediate diagnosis, and increased availability with regard to size and price. Advances in echocardiography allow for sophisticated understanding of myocardial structure and function. The modality provides both anatomic and functional information about the heart, systolic and diastolic function, cavity size, valvular function and fluid status.(5) It also allows for noninvasive estimation of central venous pressure (CVP), systolic and diastolic pulmonary artery pressures (PAP), pulmonary artery occlusion pressure (PAOP) and left atrial pressure. For these reasons, information obtained from echocardiography may be more comprehensive and valuable than that derived from invasive modes of hemodynamic monitoring. Thus, it is not surprising that echocardiography is becoming an indispensable tool in the management of critically ill patients.

Early identification of the underlying cause of hemodynamic instability is a crucial component of modern critical care management. Echocardiography allows for rapid and accurate bedside diagnosis in patients with hemodynamic compromise and is the diagnostic modality of choice in such circumstances.(6) Examples of lifesaving diagnoses in these settings include pericardial tamponade (Figure 1), pulmonary embolism (Figure 2), aortic dissection (Figure 3) and systolic ventricular failure. Other important conditions contributing to hemodynamic instability can be easily diagnosed by echocardiography. These include right ventricular failure, hypovolemia, valvular abnormalities – most commonly acute valvular regurgitation and systolic anterior motion (SAM) of the mitral valve leaflet, leading to dynamic left ventricular outflow obstruction. Finally, cardiac output can be easily calculated noninvasively with echocardiography.

Echocardiography for Hemodynamically Unstable ICU Patients
Managing the hemodynamically unstable patient in the ICU remains a challenging and time-consuming exercise. Echocardiography can be used as an effective monitoring tool in these complex patients. Several echocardiographic protocols have been developed by clinicians to allow fast diagnosis; the Focused Assessed Transthoracic Echocardiography (FATE) protocol is one example.

The FATE protocol is easy to use to efficiently assess and monitor patients in the ICU.(7) The FATE examination is a rapid echocardiographic assessment performed to screen for significant pathology and to obtain information about the volume and contractility of the heart. Steps of the protocol include(7):

• Excluding obvious pathology

• Assessing wall thickness and chamber dimensions

• Assessing contractility

• Visualizing the pleura on both sides

• Relating the information to the clinical context

The examination can be performed by physicians with only limited training in echocardiography. It requires imaging the heart and pleura in the most favorable sequence from one or more tomographic planes.(7) Different Doppler modalities can be used as needed to calculate cardiac output, assess valvular pathologies, and measure a variety of hemodynamic variables. This systematic approach allows for a rapid assessment of myocardial load conditions, dimensions and contractility; it facilitates proper diagnosis and expeditious intervention. The protocol has been shown to be a practical and useful hemodynamic monitoring tool in ICU patients. A study of the FATE protocol evaluated the feasibility of an abbreviated focused transthoracic echocardiogram in visualizing hemodynamic determinants, including significant pathology, and demonstrated that it added new information in 37.3% of patients and contributed decisive information in 24.5%. Only in 2.6% of the examinations performed was the information too limited to aid in patient management.(7) These findings and other reports support the benefit of a focused echocardiographic examination when performed by a non-cardiologist in the ICU.

Educational Program and Echocardiographic Training
Although the use of echocardiography by intensivists is gaining acceptance, formal training and certification programs are emerging only now. Educational and training programs in echocardiography cater to sonographers and cardiologists but usually are not suitable for intensivists. Board certification is designed to produce practitioners specializing in a comprehensive assessment of cardiac physiology, function and disease condition and is intended for cardiologists or cardiac anesthesiologists.

Because of intensivists’ growing interest in implementing this modality in the ICU setting, the Society of Critical Care Medicine has developed the highly successful Fundamentals of Critical Care Ultrasound course, which incorporates training in echocardiography targeted to intensivists. The course dedicates considerable time for hands-on skill sessions, allowing clinicians to practice ultrasound skills in general, and echocardiography specifically for the management of hemodynamically unstable patients. With a focus on a comprehensive approach of heart–lung interactions in ventilated patients and expeditious diagnosis of gross cardiovascular pathologies, such educational sessions are an important step in enhancing and improving the use of echocardiography in the ICU.

References:

1. Vieillard-Baron A, et al. Echocardiography in the intensive care unit: from evolution to revolution? Intensive Care Med. 2008;34:243–249.

2. Kimura BJ, et al. Usefulness of a hand-held ultrasound device for bedside examination of left ventricular function. Am J Cardiol. 2002;90:1038-1039.

3. Manasia AR, et al. Feasibility and potential clinical utility of goal-directed transthoracic echocardiography performed by noncardiologist intensivists using a small hand-carried device (SonoHeart) in critically ill patients. J Cardiothorac Vasc Anesth. 2005;19:155-159.

4. Colreavy FB, et al. Transesophageal echocardiography in critically ill patients. Crit Care Med. 2002;30:989-996.

5. Cahalan MK, et al. Advances in noninvasive cardiovascular imaging: implications for the anesthesiologist. Anesthesiology. 1987;66:356-372.

6. Thys DM, et al. Practice guidelines for perioperative transesophageal echocardiography: A report by the American Society of Anesthesiologists and the Society of Cardiovascular Anesthesiologists Task Force on Transesophageal Echocardiography. Anesthesiology. 1996;84:986-1006.

7. Jensen MB, et al. Transthoracic echocardiography for cardiopulmonary monitoring in intensive care. Eur J Anaesthesiol. 2004;21:700-707.