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The echocardiographic examination should be conducted in a systematic matter.
The examiner must be able to perform two-dimensional, pulsed-wave Doppler,
and continuous wave Doppler examinations of the heart. The availability
of color Doppler is valuable but not essential for most examinations. The
echocardiographic examination should be performed and interpreted by individuals
with advanced training in cardiac diagnosis.
Board certification by the American College of Veterinary Internal Medicine, Specialty of Cardiology is considered by the American College of Veterinary Medical Association as the benchmark of clinical proficiency for veterinarians in clinical cardiology, and examination by a Diplomate of this Specialty Board is recommended. Other veterinarians may be able to perform these examinations provided they have appropriate equipment and have received advanced training in echocardiography.
The pericardial space, both atria, both ventricles, the great vessels, and the four cardiac valves should be imaged using long axis, short axis, apical, and angled image planes as necessary to perform a complete examination of the heart. Nomenclature should follow that recommended by the American College of Veterinary Internal Medicine Specialty of Cardiology. An anatomic diagnosis may be possible based on two-dimensional imaging; however, the origin of cardiac murmurs should also be evaluated using Doppler methods.
Doppler examination of all cardiac valves should be performed and recorded. Abnormal flow should be quantified using pulsed wave or continuous wave Doppler techniques. Values obtained should be compared to reference values. The depressant effects of any tranquilizers or sedative must be considered when measuring peak flow velocities. Color Doppler echocardiography should be employed if available to assess normal and abnormal blood flow patterns. Identification of abnormal flow across the cardiac septa or shunts at the level of the great vessels is best done by a combination of color and pulsed wave Doppler techniques. Typical echocardiographic features of common congenital heart defects are indicated in table one.
Special attention should be directed to the assessment of flow patterns and velocities in the left ventricular outlet and descending aorta. Optimal alignment with blood flow should be sought for accurate velocities to be reported. This may require the use of sub-xiphoid (subcostal) transducer positions as well as left apical (caudal parasternal) transducer placements. In addition to measurement of peak velocity using pulsed or color wave Doppler, the pulsed wave sample volume should be gradually advanced from the subaortic area into the ascending aorta in order to identify sudden accelerations in flow velocity, turbulence, or aortic regurgitation.
Echocardiographic studies should be reported on videotape for subsequent analysis and a written record of abnormal findings should be entered into the medical record.
|Congenital Defect||Typical Auscultatory Features||Diagnostic Echocardiographic and Doppler Echocardiographic Features|
|Patent ductus arteriosus||Continuous heart murmur with maximal intensity over the left cranial dorsal cardiac base||Continuous retrograde flow from the patent ductus arteriosus into the pulmonary artery|
|Ventricular septal defect||Systolic murmur with maximal intensity over the right ventral precordium; less often maximal intensity is over the pulmonic valve area and pulmonary artery||The septal defect can often be imaged in multiple imaging planes. Abnormal, generally high velocity, systolic flow across the septal defect is evident.|
|Atrial septal defect||Systolic murmur with maximal intensity over the pulmonic valve area and pulmonary artery. The second heart sound may be widely split||The septal defect can generally be imaged in multiple imaging planes. Abnormal blood flow may be identified across the septal defect into the right atrium.|
|Pulmonic stenosis||Systolic murmur with maximal intensity over the pulmonic valve area and pulmonary artery||Abnormal pulmonary valve and /or subvalvular anatomy. Sudden acceleration of blood flow in the right ventricular outlet with turbulent, high velocity systolic flow across the pulmonary valve and into the main pulmonary artery.|
|Valvular and subvalvular aortic stenosis||Systolic murmur with maximal intensity over the subaortic or aortic valve area and radiating into the ascending aorta. The murmur may also be prominent over the right cranial thorax.||Abnormal subvalvular or aortic valvular anatomy may be evident. Sudden acceleration of blood flow into the left ventricular outflow tract with turbulent, high velocity systolic flow across the aortic valve and into the ascending aorta. Concurrent aortic regurgitation is usually present.|
|Mitral valve dysplasia||Systolic murmur with maximal intensity over the left apex and mitral area||Abnormal anatomy of the mitral valve apparatus. High velocity retrograde systolic flow across the mitral valve into the left atrium. Concurrent mitral valve stenosis may be present.|
|Tricuspid valve dysplasia||Systolic murmur with maximal intensity over the tricuspid valve area||Abnormal anatomy of the tricuspid valve apparatus. High velocity retrograde systolic flow across the tricuspid valve into the right atrium. Concurrent tricuspid valve stenosis may be present.|
|Right to left cardiac shunt||Variablea systolic murmur at the left base is often detected; cyanosis is an important clinical sign||Abnormal anatomy related to the cardiac malformations examples include: tetralogy of Fallot, patent ductus arteriosus with pulmonary hypertension, pulmonary or tricuspid valves stenosis with atrial septal defect. Right to left shunting may be documented by Doppler techniques and/or by contrast echocardiography.|