Cardiac Ultrasonography in Structural Abnormalities and Arrhythmias

15 Pages·2007·6.69 MB·English

Cardiac Ultrasonography in Structural
Abnormalities and Arrhythmias
Recognition and Treatment
MICHAEL M. BROOK, MD; NORMAN H. SILVERMAN, MD, DSc (Med); and
MARIAVILLEGAS, San Francisco, California
Fetal cardiac ultrasonography has become an important tool in the evaluation of fetuses at risk
for cardiac anomalies. It can both guide prenatal treatment and assist the management and
timing of delivery. We recommend that a fetal echocardiogram be done when there is a family
history of congenital heart disease; maternal disease that may affect the fetus; a history of ma-
ternal drug use, either therapeutic or illegal; evidence of other fetal abnormalities; or evidence
offetal hydrops. The optimal timing of evaluation is 18 to 22 weeks' gestation. An entire range
of structural cardiac defects can be visualized prenatally, including atrioventricular septal de-
fect, ventricular septal defect, cardiomyopathy, ventricular outlet obstruction, and complex
car-
diac defects. The outcome for a fetus with a recognized abnormality is unfavorable, with less
than 50% surviving the neonatal period. Fetal cardiac arrhythmias are also a common occur-
rence, 15% in the series described here. Premature atrial or ventricular contractions are most
commonly seen and usually require no treatment. Supraventricular tachycardia can result in hy-
drops and require in utero treatment to prevent fetal demise. Complete heart block, particu-
larly in association with structural heart disease, has a poor prognosis forfetal survival.
(Brook MM, Silverman NH, Villegas M: Cardiac ultrasonography in structural abnormalities and arrhythmias-Recog-
nition and treatment, In Fetal Medicine [Special Issue]. Westj Med 1993; 159:286-300)
Cardiac ultrasonographyinfetusesatriskhasassumed Methods
amajorroleinthediagnosisandtreatmentofprena- IndicationsforFetalCardiac Ultrasonography
tal disorders. Structural defects occurin about 8 of 1,000
We use the following indications for fetal echocar-
live newborns"2 and morefrequently in other situations,
diography"5:
makingcardiacdefects oneofthemorecommonfetalab-
normalities. The development of high-resolution ultra- * Previousoccurrence ofcongenitalheartdisease in
sound scanners that provide two-dimensional imaging, siblingsorparents. Ifmorethanonechildhasbeenaffect-
real-time directed M mode, Doppler, and color Doppler edpreviously, orifthe motherorfatheralsohascongeni-
capabilities3 has enabled structural defects,4-'7 arrhyth- talheartdisease, thentherateofrecurrenceincreases.33-35
mias,"8-4 and abnormal cardiac function25-29 to be recog- * Maternaldiseasesknowntoaffectthefetus, suchas
nizedinfetuses as early as 16to 18 weeks. Thepresence diabetes mellitus orconnective tissuedisease, areimpor-
ofsubstantial cardiac defects may determine the site and tantindications forfetal echocardiography. Forinstance,
routeofdeliverythatisbestforbothfetus andmother. In euglycemic control atthetimeofconception andinearly
addition, the availability ofhigh-resolution cardiac ultra- pregnancy may reduce the risk of cardiac maldevelop-
sonography adds to the scope ofgenetic counseling, in- mentandoffetaldiabetic cardiomyopathy, whichcanbe
cluding the possibility oftherapeutic abortion in certain recognized beforeorafterbirth.
patients, andallowsthemonitoring ofarrhythmias during * Maternal drug use. Many drugs give rise to fetal
the administration ofantiarrhythmic agents, eithertrans- abnormalities, including cardiac abnormalities, whenin-
placentally or directly. As advances in cardiac surgical gestedduring pregnancy. These include alcohol, lithium
procedures presentthepossibility offetal cardiac opera- carbonate, antitumordrugs, certain anticonvulsants, and
tions, prenatal cardiac ultrasonography will be of even warfarin sodium.36
greaterimportance.A32 * Abnormalities ofotherfetalsystems, such as chro-
FromtheDepartmentofPediatrics,DivisionofPediatricCardiology,UniversityofCalifornia,SanFrancisco,SchoolofMedicine.
ReprintrequeststoMichaelM.Brook,MD,DeptofPediatrics,DivisionofPediatricCardiology,UCSFSchoolofMedicine,M342A,SanFrancisco,CA94143-0214.
,~~~~~~~~
THEWESTERN JOURNALOF MEDICINE o SEPTEMBER 1993 * 159 * 3 287
1993 159 * 3 287
mosomal abnormalities, diaphragmatic hernia, ompha- associates reported fatalities in seven of seven cases of
locele, polyhydramnios or oligohydramnios, and other nonimmunehydropswithcardiac disease.A
systemic anomalies, areindications forfetalechocardiog- * Abnormalitiesoffetalheartrhythm: tachycardiaor
raphy. When otherfetal abnormalities havebeendetected
by obstetric ultrasound examination,37 especially nonim-
A\
mune hydrops, omphalocele, or diaphragmatic hernia,
structural cardiac defects are more frequently detected.
Information derived from fetal echocardiography has a
direct bearing on care during the pregnancy. In acohort
of3,016pregnancies, Smythe andco-workers found 170
fetuses with heartdisease, ofwhich 55 (32%) hadextra-
cardiac abnormalities and 45 (28%) had chromosomal
disease.8
0 Hydrops, nonimmune hydrops. Many fetuses re-
ferred for nonimmune hydrops (16.5% to 22.0%) have
cardiac diseaseaswell.2539'0Hydropshas alowincidence
ofsurvival, particularly withcardiacdisease; Smytheand
Li ; -
a
A
Figure 2.-The drawing schematically represents various views
usedtoimagethefetalheart.Theheartisorientedmorehorizon-
tallythan after birth (center). Although all viewsshow imaging
through the abdomen, this is possible from the back. A, A 4-
chamberviewshows both atria andventricles andtheatrioven-
tricular valves. B, The long-axis view shows the left ventricular
outflowtract. C, Sagittal viewsshowthe pulmonarybifurcation,
theaorticarch, andtheductal arch. D, Short-axis imagesallow
visualization oftherightventricularoutflowtract. E,Apicalshort-
axisplanesshowtheventricularstructureandthepapillarymus-
clesoftheleftventricle (from Schmidtand Silverman, reprinted
with permission48).
Figure 1.-Top, An unmagnified sonographicviewisshown of
thefetus lying within the uterine cavityat 18weeks' gestation.
Thehead, legs, and bodycan beseenclearly, andtheorientation
oftheheartisestablished inthethoraxbyreferringtoitsposition
with regardtothefetal lie. Bottom,Amagnifiedtransverseultra-
sonographic view through the fetal heart (four chambers) and
thorax isshown in afetuswith nonimmunehydropsand pleural
effusions (Eff) surrounding the rightlung (RL)and leftlung (LL).
The right ventricle (RV) is seen close to the anterior chestwall Figure3.-Thisfetal4-chamberviewissimilartotheplaneofFig-
(ACW), whereas the leftatrium lies more posteriorly in frontof ure 2-A and demonstrates the cardiac chambers and the eu-
thedescendingaorta(DAo)andthespine(Sp).Therightatrium stachianvalve (EV) withinthe rightatrium (RA)andtheseptum
(RA) lies behindthe rightventricle (RV). Inthisand mostsubse- primum (SP) withintheleftatrium (LA)(from Schmidtand Sil-
quent echocardiographic images, a centimeter scale marker is verman, reprinted with permission49). LV= left ventricle, RV=
showntotherightofthefigure. rightventricle
288 CARDIAC ULTRASONOGRAPHY
bradycardia. Congenital heartblock is likely in thepres-
enceofaslow fetal heartrate (<80beatsperminute). To
evaluate the arrhythmia and to detect structural cardiac
defects, ifpresent, fetal echocardiography shouldbeper-
formed. In association with structural cardiac defects,
complete heart block has an extremely poor prognosis,
presumably because ofthe adverse interaction of struc-
turaldefectsandbradycardia.Themothersoffetuseswith
complete heart block, but without structural cardiac de-
fects,frequently areafflicted withaconnective tissuedis-
order, either overt or covert clinically.24'41,42 This can be
substantiated by obtaining matemal serum specimensfor
anti-Ro and anti-La antibodies or anti-DNA antibodies,
which have been found in a variety ofcollagen vascular
diseases thatproducecongenital heartblock. Inourexpe-
rience, otherarrhythmiashave nohigherassociation with
any structural abnormality ofthe heart.24Tachycardias in
utero are associated with heart failure, nonimmune hy-
drops, andfetal loss. Thetransplacental administration of
antiarrhythmic drugs has proved to be of substantive
valueforthe survival ofthese fetuses.
Figure4.-These images representa sweep in thesagittal plane
from left to right. Top, The most leftward cut shows the right
ventricle (RV) connected to the main pulmonary artery (MPA)
and the proximal left pulmonary artery (LPA). The left atrium
(LA), leftventricle (LV), and a portion ofthe aortic arch (AoA)
can beseen, buttheirconnectionsare notclear. Middle,Amid-
lineview(note Spine to the right) showsthe inferiorvena cava
(IVC) and hepatic veins (HV) connecting to the right atrium
(RA), and the rightvenous valve oreustachian valve (EV). The Figure5.-Long-axis imagesallowimaging oftheventriculoarte-
leftatrium (LA), with itsfingerlikeappendage (LAA), and theas- rial anatomy (see Figure 6). Top, A standard long-axis image
cending (Ao) and descending (DAo) aorta and right ventricle shows the entire left system. The left atrium (LA) drains to the
(RV) are also visualized. Bottom, Furthest to the right can be ventricle(LV),whichgivesrisetotheascendingaorta(AAo).The
seen boththesuperior(SVC)andinferior(IVC)venacavaedrain- innominate vein (IV) and descending aorta (DAo) are seen in
ing into the right atrium (RA), with its broad atrial appendage cross-section, as isa portion oftherightventricle (RV). Bottom,
(RAA). A cross-section of the right pulmonary artery (RPA) is Amoreleftward imageshowstherightventricle(RV)connecting
seen posteriortotheSVC(from Schmidtetal, reprintedwith per- to the pulmonary artery (PA) inferior to the aortic arch (AA)
mission50). St=stomach (from Schmidteta150).
THEWESTERN JOURNALOF MEDICINE * SEPTEMBER 1993 * 159 * 3 289
When toPerform aFetalEchocardiogram average), and Doppler interrogation should be limitedto
as shortatimeaspossible.4344
Weprefertodoanelectiveevaluationbetween 18and
22 weeks' gestation because the valves are well devel-
Examination Technique
oped, the heartis ofadequate size forstudy, andthe fetal
size and position usually allow the best access to the Cross-sectionalScanning
heart. Although the incidence of successful imaging is Todefine the cardiac position and site, thecross-sec-
lessthan at 18to22 weeks, successful echocardiographic tional image mustbeoriented to the fetal bodyby noting
examination oftheheartcan be done as early as the 16th the position ofthe head, body, and limbs. An estimated
week. Intravaginal ultrasound transducers may provide fetalage,usingbiparietaldiameterorfemorallengthmea-
excellent imaging evenearlier. Ifthe mothermust termi- surements, is also importantbecause cardiac dimensions
nate the pregnancy because ofamajor abnormality, this relatetogestationalageandfetalweight.5'4547 Imagingthe
information needs tobeimpartedbeforethe24thweekof heart through the fetal abdomen usually provides the
thepregnancy. highestresolution(Figures 1 through8 5o); however, this
imaging can be done through the back and rib cage be-
Equipment causethe fetal lungs arefilledwith fluid andthus donot
The cornerstone offetal echocardiography is a high- generateechoreflections astheydopostnatally.
resolution ultrasound imaging systemequipped with M-
mode, pulsed Doppler, continuous wave, andcolorflow DopplerColorFlowMapping
Doppler ultrasound. Dopplerultrasonic energy should be
Recentlytheuseofcolorflowmappinghasaddedan-
keptatorbelow 100mWpercm2 (spatial peak-temporal
otherdimensiontocardiacevaluation,3 allowingtherapid
detection of stenotic or regurgitantjets and thereby di-
minishing the time required for Doppler interrogation.
Differenttechniquesfrompostnatalechocardiographyare
usedtodefine the low-velocity signals foundin manyof
thefetal chambers andvessels, as the amountand veloc-
ityoffloware substantially less.
DopplerEchocardiography
Pulsed Doppler echocardiography is obtained from
thereal-time scan with superimposed Dopplercolorflow
imaging. Dopplerinterrogation withinvascularstructures
Figure 7.-Amagnifiedfetal sagittal viewat 36weeks'gestation
shows the continuation of the main pulmonary artery (MPA),
ductus arteriosus (PDA), and descending aorta (DAo), the so-
Figure 6.-The top frame shows the entire aortic arch and de- calledductusarch.Theascending aorta (Ao) isseen incross-sec-
scending aorta (DAo) lying anteriortothespine (S). Thevessels tion; theorigin ofthe left pulmonary artery branch isseen, but
tothe head and neck(HNA)can beseen arisingfrom thesupe- themaincontinuation oftheductuscontinuesasanarchintothe
riorsurface. The bottom frame shows a largerviewofthearch. descending aorta. Notethattheductusatthisstageofgestation
Thethreearteriestotheheadand neckareclearlyvisualized. The appearsto be narrowerthan thecaliberof pulmonaryarteryor
leftatrium (LA) and right pulmonary artery(PA) can beseen in thedescending aorta. Theotherstructures identified inthisview
theconcavityofthearch. Notethatthe "ductusarch" cannotbe arethe rightventricle (RV) anda small portion ofthe leftatrium
seen inthisview.Ao=ascending aorta (LA).
'|'.i''''.''.;t78X
290 CARDIACULTRASONOGRAPHY
identifies arterial orvenous flow (Figures 9 and 10) and andthe semilunarvalves.51-57 As afterbirth, whenthe ve-
defines thedirection ofbloodflow incomplex cardiovas- locity ofthe pulsed-mode Doppler is exceeded, we use
cularmalformations. Normal flow velocity profiles have continuous-mode Dopplertodefinethepeakvelocity for
been defined in the fetus across both the atrioventricular assessing pressure drops across stenotic or regurgitant
valves.
PRF
Wi.FLT
2013
2B:gJw 's : t1: 'GAIN
POWER
31-W1t*.1| :.9!3REJ9E*C'T
s¢ -vBe F :. I '! |~049 Ms SH
-07 -sE NORMAL
Figure 9.-A pulsed Doppler evaluation of the atrioventricular
(left) andsemilunar(right)valves. Left,Thetop portion shows
a4-chamberviewwiththesamplevolume (box) belowthetri-
cuspidvalveintherightventricle(RV).Thespectraldisplay(bot-
tom) showsa normal Dopplersignal.Thesignal is biphasicwith
a largeawave (arrows) duetoatrial contraction preceded bya
smallervwave dueto rapidfilling. The mirrorimage belowthe
baselineisan artifact. Right, Pulmonaryartery(PA)evaluation is
donefromtheshortaxis, whichalsoshowstheaorta (Ao), right
atrium (RA), and rightventricle (RV).Thesamplevolume(box)
is always distal to the valve and here is in the main pulmonary
artery.Thespectraldisplayshowsaclassicarterial Dopplersignal-
pulsatileflowwithasmallamountofdiastolicflow(fromSchmidt
and Silverman48).
Figure 8.-Top, Short-axis views atthe base ofthe heartshow
-la- -
tcahteiaoonrtiinctorotohte(rAiOgh)ta(nRd)tahnedpluefltm(oLn)arpyulamrotenrayr(yPaAr)tewriietsh.iTtshebifduer-- SRvE1J.EESCITZE1-i1tP' SRIE1J.ESSCi
scending aorta (DAO) isseen in cross-section behind the bifur- Figure 10.-Apulsed Dopplerinterrogation oftheumbilicalcord
cating pulmonary branches. Middle, This image is similar to a also provides important hemodynamic information. Left, The
postnatal short-axisviewand showsthe rightventricularoutflow Dopplersamplevolume lieswithin the umbilical artery (UA, ar-
tract (RVO) surrounding theaorta (Ao), with the rightcoronary row). In the lowerpanel, acharacteristic umbilicalarterial signal
artery(RCA) inthenormal position. Bottom,Aftermagnification isdisplayed abovethe baseline showingflowtoward the trans-
(3x),thisframeshowsfocusontheheart,whichliesbetween2.5 ducer. Right,TheDopplersamplevolumeiswithintheumbilical
and4.5 cmawayfromthetransducer. Thecardiacstructures are vein (UV, arrow); thefetal bodyand head arealsoseen. In the
betterdemonstrated than above; the leftventricle (LV), the mi- lowerpanel, a Dopplersignal ofuniformlylowvelocitythrough-
tralvalveorifice(MVO), andtherightventricle (RV)canbeiden- outsystoleanddiastole isdemonstrated belowthebaseline.The
tified (from Schmidteta150). LA=leftatrium, RA= rightatrium, blankspacebetweenthe baselineand Dopplersignal istheresult
A=anterior, I=inferior, P=posterior, S=superior ofa highwall-filtersetting (from Schmidtand Silverman¶8).
THEWESTERN JOURNALOF MEDICINE * SEPTEMBER 1993 * 159 * 3 291
M-ModeEchocardiography ter examination in utero or afterbirth as in some ofour
M-modeechocardiography in the fetus isparticularly observations.
usefulfordefiningcardiac arrhythmias andformeasuring Several forms ofcomplexcardiac defectsthatinvolve
cardiac dimensions and wall thicknesses'8-'4546 (Figure a single functioning ventricle have been detected. Most
11). Itis done using areal-time-directed beam toensure commonly thisisin ahypoplastic leftheartcomplexwith
theaccurate assessmentofwall andvalve motion. aortic ormitral atresia(Figure 14).59Although the classic
case ofthe absent left ventricle is usually an uncompli-
Findings
cateddiagnosis, variants ofthis lesion maypresentdiag-
Detection ofFetalHeartAbnormalities nostic andmanagementdilemmas. These include fetuses
We found a structural cardiac abnormality in 135 with a smallleftventricle, endocardial fibroelastosis, and
(9%) cases among more than 1,500 fetal examinations
(Table 1). Isolated cardiac rhythm disturbances were
presentin 17%.
Atrioventricular septal defect (atrioventricular canal
defect)wasthecommonestseriousstructuralabnormality
we found (Figure 12). This defect often was part of a
complexcardiac lesionthatincludedleftatrialisomerism,
complete heartblock, and nonimmune hydrops orin as-
sociation with chromosomal abnormalities. In all, 85%
diedeitherinuteroorduring theneonatalperiod.
Ventricular septal defects were found as isolatedphe-
nomena as frequently as were atrioventricular septal de- -TV 4.
fects (Figure 13) (Table 1). We have observed apparent -kiv
spontaneous closure ofaventricularseptal defectontwo Ao
follow-up examinations when the lesion was an isolated
phenomenon. An isolated ventricular septal defect may
be difficult to detectbecause interventricular shunting is Figure 11.-Real-time-directed M-mode ultrasonogram allows
an assessmentofthetiming ofatrial andventricularevents. Left,
minimal andbidirectional as aresultofsimilarventricu-
In thetopframe, the M-mode cursor has been passed through
larpressures (Figure 13). the fetal thorax, the pulmonary artery (PA) and its valve, the
We have encountered nine cases ofcardiomyopathy, aorta (Ao) and itsvalve(arrows), andthe leftatrium posteriorly.
moreoftenwithdilated,poorly contracting ventricles and The bottomframeshowstheopening oftheaorticvalve (AoV)
atrioventricular valve regurgitation associated with fetal and the pulmonaryvalve(PV)within theirrespectiveventricles.
The leftatrium and thecorresponding atrial contraction can be
hydrops.58 One fetus presenting with hypertrophic car-
seen bythechanging sizeoftheleftatrium ascontributed to by
diomyopathy was identified to have the Noonan syn- the left atrial wall contraction. Right, In the top frame the M-
drome atbirth. Twofetuses appearedtohavenormal car- mode cursor line crosses the right (RV) and leftventricle (LV)
diac function at 20 weeks' gestational age, but were seen in long axis. In the bottom frame, the M-mode recording
shows normal movementofbothventricularwallsinsystole. Tri-
foundtohave dilatedcardiomyopathy shortly afterbirth,
cuspid (TV) and mitralvalve (MV) motion isalsoseen.Theven-
suggesting thatitis adifficultdiseasetodiagnose prena- tricularseptum(S)and bothventricularfreewallshaveaboutthe
tallyandthatmyocardialdysfunctionmayoccureitheraf- samethickness(from Schmidtand Silverman48).
TABLE1.-CardiacStructuralAbnormalitiesandSurvivorsAfterFetalUltrasonography(N> 1,500)*t
Abnormality PercentofTotal Survivors,%ofDefects
Atrioventricularseptaldefect,induding4withleftatrialisomerismandCHB......... 1.5 18.2
.........................
Ventricularseptaldefect(VSD),including1 withleftatrialisomerismandCHB................................. 1.5 45.5
Cardiomyopathy,including3withfamilialdisease 0.9 28.6t
........................................................
PulmonaryatresiaorstenosiswithoutVSD................................................................ 0.8 33.3
Double-outletrightventricle,including1 withpulmonarystenosis........................................... 0.7 0
Hypoplasticleftheartsyndrome...................................................................... 0.7 0
Univentricularatrioventricularconnection,3left-sided, 1 right-sided.......... 0.5 0
...............................
Ebstein'sanomaly...................................................................... 0.4 0
AortopulmonarytranspositionwithVSD................................................................. 0.3 0
TruncusarteriosustetralogyofFallot.................................................................... 0.3 0
Multplerhabdomyoma...................................................................... 0.3 50.0
Thoracopagus...................................................................... 0.4 0
Others...................................................................... 1.1 37.5
Total 9.4
......................................................................
CHB=completeheartblock
*FromSilverman." tBasedondataavailablein1988. tOneafterhearttransplantat6monthsofage.
292 CARDIACULTRASONOGRAPHY
Figure 12.-Thisexampleofa4-chamberviewofafetuswithan
atrioventricularseptal defectshowsthecommon atrioventricular
valve (CV) straddling theleftand rightatria(LA, RA)andtheleft
and rightventricle(LV, RV).Thefetuswas18weeks'gestationat
the time the image was made (from Schmidtand Silverman48).
DAo=descendingaorta
Figure 14.-Aviewofa hypoplastic leftheartwastaken ina pa-
tientat30weeks'gestation and referred becausetheobstetrician
had noted an enlarged leftatrium.Thetopframe, taken in a4-
chamberview, shows a minute leftventricle (LV) with a thick-
enedendocardium.Theotherchambers, rightatrium (RA), right
ventricle (RV), and leftatrium (LA), can beidentified. Inthebot-
tomframe, inanequivalenttoa parasternal long-axisview, the
minute leftventricularoutflowtractand hypoplasticventricleare
identified. Thereappearsto benocontinuity betweentheaorta
(Ao)andtheleftventricle(from Schmidtand Silverman49).
Figure 13.-A 4-chamber view of a ventricular septal defect is
shown. The right atrium (RA), right ventricle (RV), left atrium anomalies, whereasonehadanabsentrightatrioventricu-
(LA),andleftventricle(LV)canbeseen lyingwithinthefetaltho- lar connection and transposition. None of these infants
rax. The Dopplercolorflow information is represented in black survivedbeyondthe firstmonthoflife.
andwhite, butclearlyshowsflowbetween thetwoventricles re- Various forms ofrightheartabnormalities canbe di-
latedtoaventricular septaldefect.
agnosed. We have seen eight patients with severe pul-
adysplastic, immobile aortic valve orwith anearly nor- monary valvarobstruction, eithercritical stenosis oratre-
mal leftventricle butwithpoorventricularfunction, mi- sia (Figure 15) (Table 1). Although postnatally these
tral regurgitation, and severe endocardial fibroelastosis. patients frequently haveasmall rightventricle, itmaybe
Wehave seen threecasesofmitral valve stenosis oratre- larger than normal during early gestation.60'61 Tricuspid
sia and one with Shone's complex (parachute mitral regurgitation is always seen in these patients. Ebstein's
valve, a single leftventricularpapillary muscle, bicuspid anomalyofthetricuspidvalvehasbeen seen in sevenpa-
aortic valve, and atrial and ventricular septal defects). tients (Figure 16). None survived the first week oflife,
Onefetus died prenatally, and anotherwas born withthe with two dying in utero.6263 Significantriskfactors have
CHARGE* association anddiedat3 months. In addition, been seenfrequently. Onewasthechildofawomanwith
we have seen five fetuses with a single atrioventricular Ebstein's anomaly, oneofawomanreceivinglargedoses
connection. Threehad an absentleftatrioventricular con- oflithium," andone ofawomanwith diabetes mellitus;
nection, with a double-outlet right ventricle and arch thelastfetusalsohad skeletalanomalies.
Defects in the ventriculoarterial connection are not
*The CHARGE association is acomplex ofdefects including Coloboma, unusual. Wehave seen fourfetuses withtransposition of
Heartdefects,choanalAtresia,mentalRetardation, andGenitalandEaranom-
alies. the great arteries and ventricular septal defect. Two had
THEWESTERN JOURNALOF MEDICINE * SEPTEMBER 1993 * 159 * 3 293
associated systemic malformations, namely omphalocele survival. The one woman who refused termination re-
anddiaphragmatic hernia. Truncus arteriosus was seen in quired acesarean section fordelivery oftwins, whodied
threefetuses. One ofthese also hadtrisomy 13.65 Onehas shortly afterbirth.
survived to undergo surgical correction afterdelivery. A Three cases of rhabdomyoma as an expression of
total of 13 fetuses with forms oftetralogy ofFallothave tuberous sclerosis were encountered (Figure 18). Hy-
been seen,including 7 withadouble-outletrightventricle drops, occasionally found in these cases, may be related
and2withanabsentpulmonary valvecomplex. Thesele- to hamartomas obstructing venous return or ventricular
sionshaveahigherrateofrecurrencewithinfamiliesthan inflow." A lesion in the ventricular septum in one fetus
otherlesions; threeoffourfetuses with standardtetralogy produced left ventricular outflow obstruction and left
ofFallot had immediate relatives with the same abnor- ventricular endocardial fibroelastosis. These lesions are
mality. They are also frequent in fetuses with midline theonly prenatal expression oftuberous sclerosis; there-
anomalies, including diaphragmatic hernia, omphalocele, fore, detectionprovidesanimportantbasisforthegenetic
cleft lip andpalate, holoprosencephaly, orectopiacordis counseling ofparents whocarry thisgene.
(Figure 17).
Valvar stenosis can be readily identified in utero.
Ineach ofthree fetuses we have seen with thoracopa-
Flow disturbance imaged with color flow mapping and
gus, wecouldidentify themajorbutnotcomplete aspects
ofthe disorder.Y"67 All have hadmajorabnormalities and
fusion atthe ventricularlevel inconsistent withpostnatal
Figure 16.-Ebstein's anomaly is shown in a fetus at 30weeks'
gestation. The 4-chamberviewshows a characteristic displace-
ment of the septal leaflet of the fetal tricuspid valve (TV) and
largesail-likeanteriorleaflet.The rightventricle (RV)appearsdi-
minishedinsizebythedisplacementoftheenlarged rightatrium
(RA) (from Silverman, reprinted with permission'5). DAo=de-
scending aorta, LA=leftatrium, LV=leftventricle
Figure 15.-In thetopframe, taken in a4-chamberview, thein-
tense hypertrophy ofthe rightventricle (RV) and the rightven-
tricular myocardium can be identified. The pericardial effusion
highlights the limits ofthe muscle. The rightatrium (RA) is en-
larged and the rightventricularcavitysmall. In a craniallyangu-
lated 4-chamberview (bottom frame), bright echoes in the re- Figure 17.-A fetus is shown with ectopia cordis seen at 33
gion of the pulmonary valve annulus can be identified. No weeks'gestation. Theentireheartisoutsidethechestwall in the
forwardflowwas identified acrossthestructure. The pulmonary amnioticcavity. All4cardiacchambersareseen nexttothe um-
artery (PA) bifurcation isshown. Theendocardium oftheventri- bilical cord. Inaddition,thereisalargesuperiorventricularseptal
cleappears bright(fibroelastosis) and the rightventricle appears defectbetween the right(RV) and left(LV) ventricles(from Sil-
hypertrophied (from Schmidtand Silverman49). LA=leftatrium verman15). Ao=aorta, LA=leftatrium, RA=rightatrium
294 CARDIACULTRASONOGRAPHY
substantiatedby continuous wave Dopplerultrasonogra- They can be difficult to diagnose because electrical
phy allows the gradientto bemeasured, even though the events cannotbemeasured, only themechanical resultof
velocity is slow becauseofthe lowbloodpressure in the these events. Therefore, the construction of ladder dia-
fetus. grams (Figure 19) is crucial to analyzing andunderstand-
ing arrhythmias. Ladderdiagrams, which allow adeter-
DiagnosisandTreatmentof mination of the temporal sequence of atrial and
Fetal CardiacArrhythmias ventricular contraction, are generally derived from M-
Fetal arrhythmias are a common occurrence, with a modeorDopplerultrasonography. Normallytheatrialac-
frequency ofapproximately 15% in ourseries (Table 2). tivity is followed by that of the atrioventricular node,
whichinturn isfollowedbycontractionoftheventricle.
The most common arrhythmia seen in fetuses is iso-
lated premature atrial contractions, accounting for two
thirds ofthearrhythmias inourseries (Table2). M-mode
(Figure 20) or Doppler ultrasonograms (Figure 21) can
easilyseetheseprematurebeats.Prematureatrialcontrac-
tions are benign, usually transient, and do not require
treatment.'8-24 Because caffeine, nicotine, chocolate, and
other pharmacologically active substances can increase
theirfrequency, abstinence fromtheseis usually recom-
mended. Isolated premature atrial contractions rarely
progress to supraventriculartachycardia. Therefore, peri-
odic monitoring of the fetal heart rate by the primary
physician is essential, butrepeatfetal echocardiography
israrely indicated.
Isolated premature ventricular contractions were
muchrarerthan atrial contractions inourexperience, but
othershavefoundthemmorefrequently.23Differentiating
atrial fromventricularpremature beats canbedifficultin
afetus. Themostreliable methodinvolves measuring the
compensatory pause. The compensatory pause is a phe-
nomenon seen in electrocardiography, caused by the re-
setting, orlackofresetting, ofthesinusnode.Acomplete
compensatory pause occurs when the interval from the
beatbeforetheprematurebeattotheoneaftertheprema-
ture beat is equal to the interval between two normal
beats. A complete pause is more commonly associated
with premature ventricular contractions (Figure 22),
whereas premature atrial contractions generally have an
incomplete compensatory pause; that is, the interval is
lessthantwo normalbeats.
Fetal tachyarrhythmias are common, accounting for
15% ofall arrhythmias in our series. Most common is a
supraventricular tachycardia (Figure 23). Though this
maybe toleratedforextendedperiods, itcanleadtocar-
TABLE2.-FetalArrhythmiasDetectedbyUltrasonography*
Fetuses, Treated, Neonatal
Arrhythmia No. No. Survivors
Figure 18.-Two ultrasonogramstakenfrom afetuswith a rhab-
domyomashowapattern consistentwithadiagnosisoftuberous Prematureatrialcontraction 190 -- 189
sclerosis. In the topframe, the masses (m) appearto be in the Prematureventricularcontraction... 3 -- 3
apex,thefreewalloftherightventricle(RV),andprotrudinginto Supraventriculartachycardia 17 16t 16
therightatrium.Thebottomframeshowsalargetumormass(T) Atrialflutter. 5 5t 5
within theventricularseptum and narrowing the leftventricular Completeheartblock. 19 2§ 11
(LV) outflow tract. Note the brightness ofthe endocardium of
the left ventricle, indicating endocardial fibrosis. The mass en- *FromSilverman."
croaches on the left ventricular outflow tract situated between digotxEifnfeacntidveprtorceaatimneanmti:dedihgyodxrionchalloorniedeini1n11,.digoxinandverapamilin2,flecainidein2,and
theleftventricle andaorta (Ao).Thisfetuswasfoundtohaveen- tEffectivetreatmentwithdigoxinaloneinallexcept1 fetus,controlledwithdigoxin,
doouctafrldoiwaltrafcitbroobesltarsutocstiisonasatabicrothns(efqruomenSccehmoifdtthaenldefStivlevnetrrmainc¶u8l)a.r tqiumien§,iIdaninn1edfsteuhtluefsaftweeit,utashndhdieeavdretrdaubplraoimcnikgl,.tfhetealoppelraactieomne.ntofapacemakerwasonlysuccessfulforashort
LA-leftatrium, LV leftventricle, RV rightventricle
= =
THEWESTERNJOURNALOF MEDICINE * SEPTEMBER 1993 9 159 9 3 229955
diac failure, fetal hydrops, and fetal demise. Stroke vol- ofthe fetus. The preferred course is to deliver the fetus
ume is usually decreased during tachycardia; thiscanbe because treatment is much safer and more reliable after
seen by examining the Doppler signal in the umbilical birth. Ifdelivery is notindicatedbecauseofotherfactors,
cord(Figure24). Atrialflutterusuallypresents withvary- intrauterine treatment may be required. Medication ad-
ingdegrees ofatrioventricularblock (Figure 25) and also ministeredtothe fetusby givingitto the motherusually
withhydrops duetocardiac failure. is effective18"926'69-71 andtherefore is thetreatment modal-
Thetreatmentoftachyarrhythmias dependsontheage ity ofchoice. Direct administration to the fetus is rarely
indicated.
Digoxin has been the drug offirst choice.1819'7072Ifit
A
failstoconvertthefetalheartratetosinusrhythm,wead-
ditionally use flecainide acetate, verapamil, propranolol
E
A
Ventricle
EA
;~~~~LRA 7.7> 4
krial Contractioin
(Activation)
\ AVConduction
I
VentrcularContraction I
(Activation)
T .~~~~~~~~~~~~~~~.~~~~~.~~~~~~.~~~~~.~~~~~.~~~~~~.~.
I
Figure 19.-Theschematic representation showsthe motion of .c-..-_z.
cardiacstructures that may beseen byM-modeechocardiogra-
phyandladderdiagramsobtainedfromtheserecordings.A,This
depictsthe ultrasound beam passing through aventricleand an
atrioventricular (AV) valve within it. The atrioventricular valve
leafletscan beseen opening in earlydiastole(D-Eportion), mov- Is
ingtowards each otherin mid-diastole (E-F), and moving away
fromeachotheragain in latediastoleduringatrialcontraction (F-
A). Thebeginning ofthissecond opening (F point) indicatesthe
onset of atrial contraction. The closure of the valve leaflets (C
point)orthe beginning offorward motion ofthe posteriorven- Figure 20.-An M-modeevaluation isshown in afetuswith pre-
tricularwall (VW) indicates theonsetoftheventricularcontrac- mature atrial contractions. A, In the top frame, the ultrasound
tion.The ladderdiagram (below) markstheseevents; thedelay beam passes obliquely through the heart and shows the right
between atrial and ventricular activation is the atrioventricular atrium (RA)and leftventricle(LV). Normalatrial beats(whitear-
conduction time. B, This shows the ultrasound beam passing rows) are followed by ventricular contraction (black arrows),
through the rootofa greatartery(A), in thiscasetheaorta and buttheectopic beats (open arrows) do not resultin ventricular
thesemilunarvalvewithin it,thenthroughanatrium behindthat contraction. The bottom frame confirms that the ectopic beats
vessel. The M-mode recording shows the onsetofforward mo- are blocked. Normal atrial contractions (white arrows) arefol-
tion oftheatrial wall (AW; lowerarrow), which definesthe be- lowed by aortic valve opening (black arrows), butthe ectopic
ginning ofatrial contraction. Theopening ofthesemilunarvalve beatsare not. B,The ladderdiagram showstheschematic repre-
(SV,curvedarrow)definesthebeginningoftheventricularcon- sentationofblocked prematureatrial contractions.Thetoplineis
traction. The ladderdiagram (below) demonstratestheseevents theatrium, the middletheatrioventricularnode, andthebottom
asinA(from Schmidtand Silverman48). theventricle(from Schmidtand Silverman49).