Cardiovascular imaging plays an essential role in the practice of cardiology. Two-dimensional (2D) echocardiography is able to visualize the heart directly in real time using ultrasound, providing instantaneous assessment of the myocardium, cardiac chambers, valves, pericardium, and great vessels. Doppler echocardiography measures the velocity of moving red blood cells and has become a noninvasive alternative to cardiac catheterization for assessment of hemodynamics. Transesophageal echocardiography (TEE) provides a unique window for high-resolution imaging of posterior structures of the heart, particularly the left atrium, mitral valve, and aorta. Nuclear cardiology uses radioactive tracers to provide assessment of myocardial perfusion and metabolism, along with ventricular function, and is applied primarily to the evaluation of patients with ischemic heart disease. Cardiac MRI and CT can delineate cardiac structure and function with high resolution. They are particularly useful in the examination of cardiac masses, the pericardium, the great vessels, and ventricular function and perfusion. Gadolinium enhancement during cardiac MRI adds information on myocardial perfusion. Detection of coronary calcification by CT as well as direct visualization of coronary arteries by CT angiography (CTA) may be useful in selected patients with suspected coronary artery disease (CAD). This chapter provides an overview of the basic concepts of these cardiac imaging modalities as well as the clinical indications for each procedure.
2D echocardiography uses the principle of ultrasound reflection off cardiac structures to produce images of the heart (Table 229-1). For a transthoracic echocardiogram (TTE), the imaging is performed with a handheld transducer placed directly on the chest wall. In selected patients, a TEE may be performed, in which an ultrasound transducer is mounted on the tip of an endoscope placed in the esophagus and directed toward the cardiac structures.
Table 229–1. Clinical Uses of Echocardiography |Favorite Table|Download (.pdf)
Table 229–1. Clinical Uses of Echocardiography
|Left ventricular hypertrophy|
|Regional wall motion abnormalities|
|Morphology and motion|
|Intracardiac pressures |
|Inadequate transthoracic images|
|Aortic disease Infective endocarditis|
|Source of embolism|
Current echocardiographic machines are portable and can be wheeled directly to the patient's bedside. Thus, a major advantage of echocardiography over other imaging modalities is the ability to obtain instantaneous images of the cardiac structures for immediate interpretation. Thus, echocardiography has become an ideal imaging modality for cardiac emergencies. A limitation of TTE is the inability to obtain high-quality images in all patients, especially those with a thick chest wall or severe lung disease, as ultrasound waves are poorly transmitted through lung parenchyma. Technology such as harmonic imaging and IV contrast agents (which traverse the pulmonary circulation) can be used to enhance endocardial ...