First-Trimester Fetal Echocardiography

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4 First-Trimester Fetal Echocardiography

Lisa K. Hornberger

I. HISTORICAL BACKGROUND

A. Normal first-trimester heart

1. Fetal cardiac anatomy was initially documented by Dolkart and Reimers in 1991, who assessed 52 fetuses ranging in gestational age from 10 to 14.9 weeks.

2. Normal first-trimester Doppler flow patterns were initially documented by Wladimiroff and colleagues in 1991. They assessed left and right ventricular inflow and outflow velocities in 30 fetuses ranging in gestational age from 11 to 13 weeks.

B. First early diagnosis of fetal heart disease

1. In 1990, Gembruch and colleagues described a case of left atrial isomerism with atrioventricular (AV) septal defect and AV block at 12 weeks of gestation.

2. Also in 1990, Bronshtein and colleagues diagnosed tetralogy of Fallot at 14 weeks of gestation.

C. Transvaginal versus transabdominal approaches

1. Earlier data suggested that transabdominal imaging was less useful than transvaginal imaging for first-trimester screening.

a. Transabdominal fetal ultrasound allowed assessment of the four chambers in less than 20% at 13 to 14 weeks (Catanzarite and Quirk, 1990).

b. Transvaginal ultrasound at 13 to 14 weeks (Dolkart and Reimers, 1990; Johnson et al, 1992; Hornberger and Benacerraf, 1995).

    (1) A four-chamber view was seen in more than 75%.
    (2) Great arteries were documented in more than 50%.

2. More recent data suggest that transabdominal and transvaginal approaches complement each other.

a. Haak and colleagues (1992) attempted a full cardiac assessment, including a four-chamber view, aortic root, long axis of the aorta, pulmonary trunk, and great artery crossover.

    (1) At 11 to 12 weeks’ gestation, they had 20% success.
    (2) At 13 to 14 weeks’ gestation, they had 92% success.

b. Huggon and colleagues, 2002.

    (1) Successful fetal heart assessment when crown-to-rump length was more than 60 mm.
    (2) Maternal body size was also important for transabdominal imaging.
       (a) At body mass index (BMI) of 23.6 kg/m2, imaging was successful.
       (b) At a mean BMI of 26 kg/m2, imaging was not successful.

3. Doppler assessment.

a. Hornberger and Benacerraf (1995) studied the frequency with which Doppler flow can be demonstrated and found significant improvement with gestational age.

b. Leiva and colleagues (1999) studied first-trimester changes in flow patterns.

    (1) They studied 48 pregnancies at 6 to 12 weeks.
    (2) The inflow signal was monophasic until 10 weeks, then biphasic with an increasing E wave.
    (3) Isovolumic contraction was 20% of the cycle at 6 weeks, then decreased to 0 after 12 weeks.
    (4) Isovolumic relaxation time was 16% throughout early gestational age.

II. LIMITATIONS

A. Reduced image resolution

1. Fetal size is a critical factor. Because this is a rapid period of general fetal growth, every week helps.

2. Fetal distance from the transducer significantly limits resolution. Transvaginal imaging should not be considered unless the fetus is less than 7 cm from the cervix.

3. Uterine anatomy can interfere with image resolution, particularly for the transvaginal approach.

4. As a result of such limitations, ventricular septal defects, AV septal defects, and more subtle conditions such as tetralogy of Fallot with milder pulmonary outflow obstruction may be missed.

B. Greater fetal activity at earlier gestational ages

C. Fetal position

1. Fetal position is still an important factor, particularly with transvaginal imaging, given limited range of motion of the transducer.

2. Mobility of the fetus helps with the early assessment because the fetus can change position significantly several times during the examination.

D. Potential for progression or development of lesions later in gestation

1. Left and right heart obstructive lesions.

a. Pulmonary and aortic valve stenosis.

b. Coarctation of the aorta.

2. Cardiomyopathy.

3. Rhabdomyomas.

4. Dysrhythmia.

E. Safety issues

1. The operator must be aware of the acoustic output of instruments used.

a. Thermal and mechanical indices must be within recommended levels.

b. These indices provide relative risk of producing thermal or cavitation effects.

2. Risks may be greater during embryogenesis (<10 weeks; Campbell and Platt, 1999).

3. For late first-trimester assessments, use short duration of scans and limited duration of Doppler interrogation.

III. APPROACH

A. Transducer frequencies

Use transducer frequencies greater than 5 MHz, if possible, to resolve the diminutive cardiac structures.

B. Two-dimensional imaging at earlier than 14 weeks (Fig. 4-1)

1. Visceral and atrial situs.

2. Four-chamber assessment.

3. Sweep to the outlets.

4. Three-vessel view.

5. Arches.

image

Fig. 4-1 A, A sagittal image, obtained in a 13-week gestational age (GA) fetus, demonstrates the aortic arch and inferior vena cava in their long axes. B, A four-chamber view obtained in a 12-13 week GA fetus. At this early gestational age, the four chambers are very symmetrical and the tricuspid and mitral valves have less offset. Details of the chambers, including the presence of the moderator band in the right ventricle, can be appreciated. A, anterior; L, left; R, right; S, spine. C, Sweeping up toward the head, the three-vessel view demonstrates the main pulmonary artery positioned most leftward and anterior, the ascending aorta to the right and posterior, and the superior vena cava most posterior and rightward. D, A more detailed assessment of the aortic arch as shown in this image is not consistently possible due to limitations in image resolution.

C. Doppler assessment (Fig. 4-2)

1. Spectral Doppler.

a. Ventricular inflows.

b. Ventricular outflows.

c. Inferior vena cava.

d. Ductus venosus has been suggested as a marker for cardiac pathology in the fetus (Matias et al, 1999).

2. Color Doppler (Fig. 4-3).

a. Assessment of normal anatomy (patency of inflows and outflows).

b. Exclude abnormal flows (particularly AV valve regurgitation).

image

Fig. 4-2 Pulsed Doppler interrogation of the ventricular inflows and outflows as well as pulmonary and systemic veins is possible in the late first trimester. It is more difficult to fully assess Doppler flows through a transvaginal approach given the limitations in range of motion and having only a single acoustic window. A, Tricuspid valve inflow in a 13-14 week fetus is biphasic and includes an E wave (E) (period of early ventricular filling/diastole) and an A wave (A) (occurs during atrial contraction). The E/A wave ratio is significantly less in the first trimester than later in pregnancy. B, The inferior vena caval flow pattern is very similar in the late first trimester, with a very short, low-velocity period of A wave reversal (A), which occurs during atrial systole. C, In the late first trimester, the ductus venosus flow is usually continuous and without cessation or reversal of flow, as is true later in gestation. This is a flow pattern observed in a fetus with increased nuchal translucency in which there was flow reversal during atrial systole. D, The inferior vena caval flow in the same fetus showed significant A wave (A) reversal as well, suggesting high ventricular filling pressures. E, Pulmonary vein flow can be documented in the later first trimester, and the flow pattern is very similar to that observed later in pregnancy, as is shown here.

image

Fig. 4-3 Color flow map images that demonstrate (A) patency of both ventricular inflows in a 12-week fetus and (B) patency of the aortic ouflow in a 14-week fetus. See also color version of figure (2A and 2B) in color insert.

D. Serial assessment

Reassessment is recommended in the second trimester given the image resolution issues in the first trimester and the potential for progression.

IV. CARDIAC PATHOLOGIES THAT CAN BE DETECTED IN THE FIRST TRIMESTER

A. Bronshtein and colleagues (1993)

1. Study included 36,323 TVG examinations in high-risk and low-risk pregnancies.

2. Isolated cardiac defect was found in 44%.

3. Extracardiac defects were found in 56% (27 of 72 karyotyped had a chromosomal abnormality).

4. Study limitations included:

a. Incomplete ascertainment of false negatives.

b. Confirmation in 90 of 173.

c. Ten had different cardiac pathology at postmortem examination or delivery.

B. Achiron and colleagues (1994)

1. Study examined 660 low-risk pregnancies.

2. Six cardiac defects were detected and three were missed.

3. Missed defects included small ventricular septal defects and rhabdomyoma.

C. Huggon and colleagues (2002)

1. Adequate transabdominal images were obtained in 402 of 478 assessed first-trimester pregnancies.

2. A normal heart was seen in 286.

a. A normal heart was verified in 189.

b. Seven had new findings later in gestation or at birth (including right aortic arch, ventricular septal defect, arch pathology, ventricular disproportion).

c. Abnormal heart was not verified in 90.

3. A definite heart defect was found in 60.

a. A defect was confirmed in 34.

b. A major lesion was identified in 33 of the 34 with a confirmed defect.

    (1) AV septal defect.
    (2) Hypoplastic left heart syndrome.
    (3) Ventricular septal defect.
    (4) Tricuspid valve disease.
    (5) Truncus arteriosus.
    (6) Pulmonary atresia with intact ventricular septum.
    (7) Cardiomyopathy.

c. Important lesions were missed in 18%, including double outlet right ventricle and arch obstruction.

4. The heart abnormality was of uncertain importance in 49.

5. Twenty had a possible heart defect.

V. CURRENT INDICATIONS: HIGHEST-RISK PREGNANCIES

A. Family history

1. Maternal or paternal heart disease.

2. Previously affected child or fetus.

B. Maternal disease

1. Consider early echocardiography in women with diabetes and phenylketonuria.

2. Consider early echocardiography particularly if maternal habitus will limit transabdominal imaging at later gestational ages.

C. Suspected extracardiac pathology

1. Structural abnormalities such as omphalocele or ectopia cordis.

2. Increased nuchal translucency.

D. In vitro fertilization pregnancies

VI. VI. TAKE-HOME MESSAGE

A. Limitations

1. First-trimester fetal echocardiography is possible, particularly by 13 to 14 weeks.

2. Fetal echocardiography in the first trimester is limited by reduced image resolution and should at this stage, when possible, be followed up with an assessment in the second trimester.

3. Given that the first and early second trimesters are periods of rapid fetal cardiovascular growth, there is potential for significant change in chamber and great artery size and function, thus warranting reassessment in the second trimester to exclude more progressive lesions.

B. Approach

1. The transvaginal approach for fetal echocardiography is warranted in pregnancies less than 12 to 13 weeks and in patients in whom image resolution is not sufficient transabdominally at 13 to 15 weeks.

2. Transabdominal imaging might provide sufficient images in the majority of pregnancies at 14 weeks of gestation.

REFERENCES

Achiron R, Weissman A, Rotstein Z, et al. Transvaginal echocardiographc examination of the fetal heart between 13 and 15 weeks’ gestation in a low-risk population. J Ultrasound Med. 1994;13:783-789.

Bronshtein M, Siegler E, Yoffe N, Zimmer EZ. Prenatal diagnosis of ventricular septal defect and overriding aorta at 14 weeks of gestation using transvaginal sonography. Prenat Diagn. 1990;10:697-702.

Bronshtein M, Zimmer EZ, Gerlis LM, et al. Early ultrasound diagnosis of fetal congenital heart effects in high and low-risk pregnancies. Obstet Gynecol. 1993;82:225-229.

Campbell S, Platt L. The publishing of papers on first trimester Doppler. Ultrasound Obstet Gynecol. 1999;14:159-160.

Carvahlo JS. Fetal heart scanning in the first trimester. Prenat Diagn. 2004;24:1060-1067.

Catanzarite V, Quirk JG. Second-trimester ultrasonography: Determinants of visualization of fetal anatomic structures. Am J Obstet Gynecol. 1990;163(4 Pt 1):1191-1195.

Dolkart LA, Reimers FT. Transvaginal fetal echocardiography in early pregnancy: Normative data. Am J Obstet Gynecol. 1991;165(3):688-689.

Gembruch U, Knopfle G, Chatterjee M, et al. First trimester diagnosis of fetal congenital heart disease by transvaginal 2-dimensional and Doppler echocardiography. Obstet Gynecol. 1990;78:496-498.

Haak MC, Twisk JW, Van Vugt JM. How successful is fetal echocardiographic examination in the first trimester of pregnancy? Ultrasound Obstet Gynecol. 2002;20:9-13.

Hornberger LK, Benacerraf BR. Blood flow velocities in the 10-20 weeks gestational age fetus. Circulation. 1996;94:1-236.

Hornberger LK, Benacerraf BR. Transvaginal fetal echocardiography in the delineation of cardiac anatomy and Doppler velocities at 10-14 weeks of gestation. Circulation. 1995;92:1-647.

Huggon IC, Ghi T, Cook AC, Zosmer N, et al. Fetal cardiac abnormalities identified prior to 14 weeks gestation. Ultrasound Obstet Gynecol. 2002;20:22-29.

Johnson P, Sharland G, Maxwell D, Allan L. The role of transvaginal fetal echocardiography in the early detection of congenital heart disease. Ultrasound Obstet Gynecol. 1992;3:248-251.

Leiva MC, Tolosa JE, Binotto CN, et al. Fetal cardiac development and hemodynamics in the first trimester. Ultrasound Obstet Gynecol. 1999;14(3):169-174.

Matias A, Huggon I, Areias JC, et al. Cardiac defects in chromosomally normal fetuses with abnormal ductus venosus blood flow at 10-14 weeks. Ultrasound Obstet Gynecol. 1999;14:307-310.

McAuliffe FM, Hornberger LK, Winsor S, et al. Fetal cardiac defects and increased nuchal translucency thickness: A prospective study. Am J Obstet Gynecol. 2004;191(4):1486-1490.

Wladimiroff JW, Huisman TW, Stewart PA. Fetal cardiac flow velocities in the late 1st trimester of pregnancy: A transvaginal Doppler study. J Am Coll Cardiol. 1991;17(6):1357-1359.

Yagel S, Weissman A, Rotstein Z, et al. Congenital heart defects: natural course and in utero development. Circulation. 1997;96(2):550-555.

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