Echocardiography: The Preeminent Front Line Screening and Diagnostic Tool for Cardiovascular Imaging and Physiological Assessmen
- Sat, 5/3/08 - 12:47pm
- 0 Comments
- 2363 reads
Cardiovascular imaging presents as a landscape of multiple maturing technologies, developed through billions of dollars of research and decades of dedication by both industry and clinicians to create diagnostic tools capable of revealing many of the elusive characteristics of cardiovascular disease. So powerful are these tools that they have become integral in the clinician s diagnostic armamentarium.1-7 For the uninitiated, echocardiography is the utilization of ultrasound to view cardiopulmonary and the major thoraco-abdominal vascular structures and obtain structural, hemodynamic and perfusion parameters of the heart and great vessels.
Ultrasound imaging is accomplished by transmitting ultrasound through the tissues and fluids of the body. At the core of this technology is the piezoelectric crystal (crystalline material that converts sound into an electrical signal), which enables the generation, sending and reception of ultrasound waves. The term two-dimensional imaging refers to the computer re-creation of reflected ultrasound waves into an image with height and width dimensions, thus the reference to two dimensions. Three-dimensional echo is in the early stages of clinical application and adds the third plane of depth. A computer-mediated rendition of the reflected signals produce still and moving images, and overlays of color Doppler images depict speed and direction of blood flow. Focused directional ultrasound, referred to as Doppler, enables the unique assessment of dynamic physiological characteristics and cardiovascular hemodynamics yielding a differentiation of etiologies for symptoms of heart failure.8-10
With this in mind, imagine the cardiac ultrasound exam as providing the ability to view thin slices (tomographic planes) of the beating heart. During the cardiac cycle, one can observe the expansion and contraction of the ventricles in concert with the opening and closing of the heart valves, which are driven by the rise and fall of pressures within the cardiac chambers. By selective interpretation of the reflected ultrasound, the speeds at which the structures move within the ultrasound beam are re-created into two- and three-dimensional images. This results in visualization of the relative slower moving tissue and valves, and non-visualization or darkening of areas of the image where blood is moving at a faster speed. In this manner, thrombus formations, changes in myocardial integrity due to myocardial infarction or disease infiltration, and delineation of non-myocardial structures such as tumors and cysts are readily discernable. With increased sophistication of the manipulation of the send/receive functionality of the ultrasound, advances in image quality, and the use of injectable non-radioactive microbubble agents, the imaging capabilities of ultrasound have dramatically advanced the ability to visualize cardiac structures and demonstrate perfusion within the myocardium.
1. Cheitlin MD, Alpert JS, Armstrong WF, et al. ACC/AHA Guidelines for the Clinical Application of Echocardiography: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Clinical Application of Echocardiography) Developed in Collaboration With the American Society of Echocardiography. Circulation 1997;95:1686-1744.
2. German Society of Pneumology. Recommendations for use of echocardiography in pneumologic diagnosis. Pneumologie 1998;52:519-521.
3. Stewart W, Douglas PS, Sagar K, et al. Echocardiography in Emergency Medicine: A Policy Statement by the American Society of Echocardiography and the American College of Cardiology. The Task Force on Echocardiography in Emergency Medicine of the American Society of Echocardiography and the Echocardiography TPEC Committees of the American College of Cardiology. J Am Soc Echocardiogr 1999;12:82-84.
4. Malergue MC, Abergel E, Bernard Y, et al. Recommendations of the French Society of Cardiology concerning indications for Doppler echocardiography. Arch Mal Coeur Vaiss 1999;92:1347-1379.
5. Zarnke KB, Levine M, McAlister FA, et al. The 2000 Canadian recommendations for the management of hypertension: Part two - diagnosis and assessment of people with high blood pressure. Can J Cardiol 2001;17:1249-1263.
6. Quiñones MA, Douglas PS, Foster E, et al. ACC/AHA clinical competence statement on echocardiography: A report of the American College of Cardiology/American Heart Association/American College of Physicians-American Society of Internal Medicine Task Force on clinical competence. J Am Soc Echocardiogr 2003;16:379-402.
7. Gottdiener JS, Bednarz J, Devereux R, et al. American Society of Echocardiography recommendations for use of echocardiography in clinical trials. J Am Soc Echocardiogr 2004;17:1086-1119.
8. Waggoner AD, Rovner A, de las Fuentes L, et al. Clinical outcomes after cardiac resynchronization therapy: Importance of left ventricular diastolic function and origin of heart failure. J Am Soc Echocardiogr 2006;19:307-313.
9. Bruch C, Rothenburger M, Gotzmann M, et al. Risk stratification in chronic heart failure: Independent and incremental prognostic value of echocardiography and brain natriuretic peptide and its N-terminal fragment. J Am Soc Echocardiogr 2006;19:522-528.
10. Kanzaki H, Nakatani S, Kawada T, et al. Right ventricular dP/dt/p(max), not dP/dt(max), noninvasively derived from tricuspid regurgitation velocity is a useful index of right ventricular contractility. J Am Soc Echocardiogr 2002;15:136-142.
11. Szili-Torok T, McFadden EP, Jordaens LJ, Roelandt JR. Visualization of elusive structures using intracardiac echocardiography: Insights from electrophysiology. Cardiovasc Ultrasound 2004;2:6.
12. Morton JB, Kalman JM. Intracardiac echocardiographic anatomy for the interventional electrophysiologist. J Interv Card Electrophysiol 2005;13(Suppl 1):11-16.
13. Hansen WH, Gilman G, Finnesgard SJ, et al. The transition from an analog to a digital echocardiography laboratory: the Mayo experience. J Am Soc Echocardiogr 2004;17:1214-1224.
14. Gilman G, Lutzi CA, Daniels BK, et al. The architecture of a mobile outreach echocardiography service. J Am Soc Echocardiogr 2006;19:1526-1528.
Post new comment