Echocardiography is a valuable non-invasive tool for imaging the heart and surrounding intrathoracic structures and is an essential component in the diagnostic armamentarium of the veterinary cardiologist. A wide variety of cardiac diseases can be diagnosed echocardiographically, the severity of the disease ascertained and a prognosis for life and performance derived. It is important to recognize, however, that the echocardiographic examination is only a part of the complete cardiac work-up. The signalment, historical information, physical examination findings, electrocardiogram, thoracic radiographs and clinical laboratory findings must be integrated with the echocardiographic findings to arrive at the correct diagnosis and develop an optimal therapeutic plan for each patient.
Echocardiography is used to evaluate cardiac chamber size, wall thickness, wall motion, valvular anatomy, valve motion, the proximal great vessels and the pericardium. Anatomic relationships can be determined and cardiac function can be assessed. This technique is a sensitive tool for detecting pericardial and pleural fluid, identifying mass lesions within and adjacent to the heart, characterizing congenital cardiac defects and diagnosing valvular and myocardial pathology. Most examinations should be completed without chemical restraint because many of the common tranquilizers have a negative inotropic effect on the myocardium.
Technical expertise in performing and interpreting the echocardiographic examination are prerequisites to the valid use of this clinical tool. Good quality images are essential to obtain the maximal amount of diagnostic information from this valuable technique. A complete echocardiographic examination should be performed on all patients so that no diagnostic information is missed. Air-filled structures such as the lung and bone are excellent reflectors of ultrasound and prevent transmission of the ultrasound beam to the deeper structures. Therefore, the intercostal spaces in the axillary region at the cardiac notch are used as the cardiac windows. Air-free contact between the transducer and body wall is necessary and is achieved by the use of ultrasound coupling gel and clipping the hair of the patient in this region if the hair coat is dense. The ultrasound transducer must be positioned so that the ultrasound beam is perpendicular to the intracardiac structures for optimal image quality while the ultrasound beam must be as parallel as possible to flow disturbances to accurately quantify the flow abnormality with Doppler echocardiography. Correct placement of the ultrasound cursor within the particular view is essential for obtaining accurate and reproducible measurements. The equipment settings also affect the quality of images obtained.
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