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HOW TO ENHANCE THE QUALITY OF THE FETAL ECHOCARDIOGRAPHIC DIAGNOSE Insights of fetal echocardiography 20-55% of infants with CHD are not diagnosed until after hospital discharge Most (50 - 90%) cardiac defects occur in low rish patients In a large nationwide study with 1,374 infants who had heart surgery at age six months or younger In only 34% of cases was the heart defect detected before birth, although rates increased each year from 26% in 2006 to 42% in 2012 With rates ranging from a low of 11.8% to a high of 53.4% across geographic regions There was also significant variation of prenatal CHD detection rates by type of defect (p 20 – 25 frames/s are perceived by the human eye as “real time” Optimizing the use of the velocity scale, the wall filter, the persistence, the gain, color line density Figure : A large color box is chosen (65 degrees), which results in a slow frame rate of 11 Hz (11 frames/s) A slow frame rate impedes visualization of the fetal heart on color Doppler Figure 12.3: An appropriate size color box is chosen (30 degrees), wide enough to cover the fetal heart This results in an improved frame rate of 39 Hz (39 frames/s) Abuhamad, A (2010) A Practical Guide to Fetal Echocardiography Philadenphia, PA: Lippincott Williams and Wilkins Velocity scale Velicity scale/pulse repetition frequency is use to determine the range of mean velocities in the region of interest or within the color box For color doppler interrogation of the atrioventricular valves, the semilunar valves, and the great vessels, high-velocity range (>±30 cm/s) is selected Figure : Apical four-chamber view of the fetal heart with color Doppler showing the effect of velocity scale (pulse repetition frequency [PRF]) on the display of color Doppler In A, a low color Doppler velocity scale is chosen (18 cm/s), resulting in color aliasing of blood flow across the atrioventricular valves, thus mimicking flow turbulence (open arrow) In B, the color velocity scale is appropriately chosen (44 cm/s), resulting in optimal display of blood flow across the atrioventricular valves in diastole Abuhamad, A (2010) A Practical Guide to Fetal Echocardiography Philadenphia, PA: Lippincott Williams and Wilkins Color filter Color filter allows for the elimination of signals from wall motion and other low velocities A high filter should therefore be selected for the color evaluation of the atrioventricular valves and flow across the great vessels A low color filter should be used for the evaluation of the pulmonary and systemic veins given their lower flow settings Color persistence Low color persistence settings should be generally selected for fetal cardiac assessment Color Doppler image resolution A compromise should therefore be sought between the color image quality and frame rate We opt for a high color resolution when peripheral pulmonary vessels are imaged or in fetal echocardiography in early gestation in which the region of interest (color box) is usually small The smallest color box is chosen in both these conditions in order to get the highest frame rate possible Abuhamad, A (2010) A Practical Guide to Fetal Echocardiography Philadenphia, PA: Lippincott Williams and Wilkins Color gain • Color gain demonstrates the amount of color exhibited on the screen, similar to the grayscale gain function Artifacts occur when the color gain setting is too high in fetal cardiac imaging (fig 12.5A and B) Gain settings in the midrange may also lead to superimposition of color over the border of a structure of interest, particularly when the atrioventricular valves are examined, giving the false impression of a septal defect The color gain in cardiac imaging should therefore be initially set on low and gradually increased until the color information is optimized Figure 12.5: Apical four-chamber view of the fetal heart with color Doppler showing the effect of color gain on the display of color Doppler In A, a high-gain setting is chosen, resulting in color overlap over the septum, mimicking the presence of an atrioventricular septal defect (star) In B, an appropriate color gain setting is chosen, resulting in optimal display of color flow across the atrioventricular valves during diastole Abuhamad, A (2010) A Practical Guide to Fetal Echocardiography Philadenphia, PA: Lippincott Williams and Wilkins Adjust PW Doppler Any area of abnormal color flow should be further evaluated with PW doppler Pulsed-wave doppler interrogation should be attempted from near degrees to the direction of flow in order to help ensure the most accurate doppler velocities and flow profiles are obtained Although degrees is ideal, the doppler angle should be sampled within 15-20 degrees of the direction of flow and angle correction capabilities should be utilized Evaluation can be made for normal forward flow, reversed or regurgitant flow, stenotic highvelocity flow, and/or absent flow Peak systolic velocity is commonly measured during a fetal echocardiogram PSV is obtained when the sample volume is placed distal to the cardiac valve Proximal placement will show regurgitant or reversed flow Abuhamad, A (2010) A Practical Guide to Fetal Echocardiography Philadenphia, PA: Lippincott Williams and Wilkins Required knowledge base for core levels of expertise Knowledge Knowledge of the indications for transthoracic echocardiography in pediatric patients Knowledge of common congenital heart defects and surgical interventions Knowledge of Doppler methods and their application for assessment of blood flow and prediction of intracardiac pressures Knowledge of the limitations of echocardiography and Doppler techniques Knowledge of alternative diagnostic imaging techniques Knowledge of standard acoustic windows and transducer positions Knowledge of image display and orientation used in fetal echocardiography Ability to recognize normal and abnormal cardiovascular structures by 2-dimensional imaging and to correlate the cross- sectional images with anatomic structures Familiarity with standard echocardiographic methods of ventricular function assessment 10 Familiarity with major developments in the field of noninvasive diagnostic imaging Method of screening Detection rate Minimum exam: 4C 40 – 50% Extended exam: 4C, RVOT, LVOT 60 – 80% Extended exam: 10C >90% Fig Standardized transverse views Fig Sagittal views 0.92 0.89 0.90 0.65 0.92 1.00 1.00 1.00 Fig Short axis views Pediatric Council of the American Society of Echocardiography LIMITATIONS OF FE IN DIAGNOSIS Examples of major lession on “ 4CV “ of fetal heart Hypoplastic left heart syndrome Severe coarctation of the aorta Critical aortic stenosis Tricuspid atresia Pulmonary atresia with intact ventricular septum Atrioventricular septal defect Double inlet ventricles Examples of major lesions where the four chamber view of the heart is typically normal / near normal and for which views of the outflow tracts are required Transposition of the great arteries Tetralogy of Fallot + / - pulmonary atresia Common arterial trunk Some forms of coarctation of the aorta Examples of lesions that are difficult to detect even in experienced hands Total anomalous pulmonary venous drainage Coarctation of the aorta (milder forms) Some types of ventricular septal defect Milder forms of aortic and pulmonary valve stenosis Lesions that cannot be predicted from prenatal cardiac imaging Patent arterial duct Secundum atrial septal defects Assessing size • Normal size: what is normal size (mean +/- 2SD, growth parameters (gestational period, body weight, head circumference, height,… heart parameters (dimension, area, volume) • Large heart: Right/left/both sides; Causes (cardiac malformation, Valvular/ventricular dysfunction, secondary to fetal diseases; Effects on fetus, long – term effects • Small heart: Anatomic definition: diameter/area below -2SD; functional definition: too small to be a ventricle; growth parameters: body weight> gestational age; any potential of catch up growth? Z Score 17 cardiac dimensions TAKE HOME MASSAGE Extended fetal echo is very effective, high sensitive, high specific method in fetal cardiac abnomaities screening Device capacity, operator ‘ skill, “Imagability” of the patient are both affected to the quality of fetal echocardiographic diagnose With the deplopment of device, knowlegde in fetal cardiological field, we are having more facilitation in improving the detection of fetal echocardiogrphy However, still existence of some limitations without resolving in foetus, so postnatal screening is necessary Thanh you for your attention ! ... hiccups, fetal movement Unable to time acquisition to cardiac cycle No representative cardiac STIC Entire cardiac cycle represented can see valvular movement Timing of acquisition unnecessary... as high as possible Frame rates > 20 – 25 frames/s are perceived by the human eye as “real time” Optimizing the use of the velocity scale, the wall filter, the persistence, the gain, color line... is difficult, as in cases of maternal obesity, overabundance or lack of amniotic fluid, or suboptimal fetal positioning, observations should be made with the frequency set between 2.5 and 3.5
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