1386 JACC Vol 7. No 6 June 19X6 I3Xh-91

Doppler Echocardiography in the Diagnosis and Management of Persistent Fetal Arrhythmias

JANETTE F. STRASBURGER, MD, JAMES C. HUHTA, MD, FACC,

ROBERT J. CARPENTER, JR., MD, ARTHUR GARSON, JR., MD, FACC,

DAN G. McNAMARA, MD, FACC

Houston, Texas

Thirteen fetuses with persistent arrhythmias underwent combined noninvasive echocardiographic evaluation uti­lizing M-mode, two-dimensional and pulsed Doppler echocardiography. This group (Group A) was compared with 14 fetuses in which only two-dimensional and M­mode echocardiogtaphic evaluations were performed (Group B). In both groups correct prenatal interpre­tation of the arrhythmia was confirmed by postnatal electrocardiograms in all surviving fetuses. Although Doppler echocardiography was not more sensitive than M-mode echocardiography in the interpretations of the arrhythmia, Doppler tracings of sufficient quality to ana-

Persistent fetal arrhythmias are rare, life-threatening and potentially treatable. Persistent arrhythmias that have been detected prenatally include atrial premature contractions, ventricular premature contractions, ventricular bigeminy, atrial flutter, supraventricular tachycardia, complete atrio­ventricular (A V) block, sinus bradycardia and complex atrial arrhythmias (1-5), Persistent arrhythmias have been asso­ciated with an increased incidence of fetal and perinatal mortality, nonimmunologic hydrops fetalis and structural congenital heart disease. The purpose of this study was to determine how Doppler echocardiography contributes to the

From The LiJlie Frank Abercrombie Section of CardIOlogy, Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital and Department of Obstetric5 and Gynecology, DiVision of Perinatal Med­icine, Baylor College of Medicine and SI. Luke's Episcopal Hospital, Houston, Texas. This study was supported in part by Grant RR-OOI88 from the General ClImcal Research Branch, National Institutes of Health, Bethesda, Maryland and Grant RR-05425 from the National Institutes of Health, United States Public Health Service, Bethesda. Dr. Huhta was supported in part by New Investigator Research Award HL31153 from the National Heart, Lung, and Blood Institute, Umted States Public Health Service. This paper was presented In part to the Amencan Academy of Pediatrics, Section of Cardiology, Chicago, I\linois, September 1984.

Manuscript received August 13, 1985; revised manuscript received December 18, 1985, accepted January 13, 1986.

Address forreprints: James C. Huhta, MD, Pediatric Cardiology, Texas Children's Hospital, 6621 Fannin Street, Houston, Texas 77030.

© 1986 by the AmerIcan College of Cardiology

Iyze rate and rhythm were easier to obtain in all cases and provided additional information about valvular in­competence and the functional state of the fetal heart. Cardiac malformations and hydrops fetalis were com­monly associated with persistent arrhythmias. Congen­ital heart disease occurred frequently (6 of 11) with com­plete atrioventricular (A V) block. Pulsed Doppler echocardiography defined the A V contraction sequ~nce, atrial and ventricular rates and A V valve insufficiency, allowing rapid interpretation of fetal arrhythmias.

(J Am Coli CardioI1986;7:1386-91)

diagnosis and management of fetuses with persistent ar­rhythmias.

Methods Definition of persistent fetal arrhythmias. A persistent

fetal arrhythmia was defined as an abnormality in fetal car­diac rhythm in which the ventricular rate was greater than 180/min, less than 100/min or irregular. The arrhythmia was detected on one or more examinations before the onset of labor. To be included in the study the fetal arrhythmia must have persisted after delivery or disappeared as the result of postnatal medical treatment. This definition ex­cluded fetuses with commonly observed transient intrauter­ine heart rate abnormalities, which may be present in up to 10% of normal fetuses, including normal beat to beat var­iability and arrhythmias occurring only during labor.

Study group. Between January 1978 and June 1985, 27 fetuses with persistent arrhythmias underwent combined evaluation by members of the Obstetrical Perinatoiogy and Pediatric Cardiology divisions of our hospitals. The fetal gestational age at diagnosis ranged from 18 to 39 weeks (mean 32). These patients represented 20% of fetal cardiac evaluations. Obstetric ultrasound was obtained for assess­ment of fetal and placental growth and extracardiac mal-

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formations. All fetuses had combined two-dimensional and M-mode echocardiograms using ATL 600 MK or Acuson-128 ultrasound/Doppler equipment and previously described methods of segmental examination (6-10).

Doppler echocardiograpltic evaluation. Since 1983, 13 of the 27 fetuses with persistent arrhythmias have had pulsed Doppler echocardiographic evaluation using a 3 or 5 MHz transducer and limiting energy output and exposure time (Group A). Doppler sample volume size ranged from 2 to 5 mm2 • Doppler tracings were recorded at 100 mmls paper speed with standard 1 second calibration lines. The heart rates were measured from the baseline at the onset of flow or at peak flow velocity when minimal upstroke var­iability was present. Two views were routinely obtained for rhythm assessment (Fig. 1). The ventricular rate and A V contraction sequence were determined by sampling in the area of fibrous continuity between the aortic and mitral valves in an apical four chamber view equivalent. From this position (position A), ventricular inflow and outflow could be recorded simultaneously, and the A V contraction se­quence could be determined, allowing the identification of atrial flutter and complete A V dissociation, as well as atrial and ventricular extrasystoles. A normal A V Doppler flow velocity consisted of rapid diastolic filling and atrial systole followed by ventricular systole (Fig. 2). We compared each surviving patient's fetal records with that patient's neonatal and infant records of simultaneous Doppler echocardio-

Figure 1. Illustration of Doppler sample volume positIOns. A. Area of mitral-aortic (Ao) fibrous continuity for recording ven­tricular rate and atrial-ventricular contraction ~equence. B, Area of the foramen ovale for determining atrial rate. LA = left atrium; LV = left ventricle; RA = right atrium.

A

B

STRASBURGER ET AL DOPPLER ECHOCARDIOGRAPH) IN FErAl. ARRHYTHMIAS

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gram~ and electrocardiograms taken during SinUS rhythm. During systole, ventricular flow is in the direction opposite to the mitral valve inflow velocity. Atrial systole is more prominent in the fetus than in the newborn.

The atrial rate was confirmed by Doppler sampling at the fossa oval is to record the flow velocity from the right to the left atrium (position B) (Fig. 1). In Figure 3, normal sinus rhythm and supraventricular tachycardia in a 28 week fetus are demonstrated. Comparable views in the neonate do not demonstrate right to left atrial shunting during systole in sinus rhythm.

Limited Doppler echocardiograms were repeated in six patients to assess the continued presence of tricuspid in­sufficiency. Doppler study was performed in four patients in the neonatal period during the persistent arrhythmia to confirm the flow patterns detected prenatally, and electro­cardiograms were obtained postnatally during the arrhyth­mia in all 19 surviving infants.

Before 1983, 14 of the 27 fetuses were evaluated using standard methods of noninvasive rhythm diagnosis combin­ing imaging and two-dimensional-directed M-mode echo­cardiography (12). No blinded M-mode echocardiographic evaluations were attempted. Fetuses were evaluated at 2 week intervals unless hydrops fetalis or transplacental phar­macologic therapy necessitated more frequent follow-up.

Results Arrhythmias in the 27 fetuses were A V block in 11,

tachycardia in 10 and atrial premature contractions in 6. Rhythm diagnosis. The prenatal rhythm diagnosis was

confirmed electrocardiographically in 18 surviving infants who continued to have tachycardia postnatally; I infant has not had recurrence of supraventricular tachycardia while receiving postnatal digoxin therapy. Four had postnatal Doppler echocardiographic confirmation of the in utero flow patterns during arrhythmias, further supporting the cardiac rhythm diagnosis by Doppler techniques.

Doppler echocardiography (Group A). Doppler echo­cardiography allowed correct antenatal arrhythmia interpre­tation in all 13 cases. Doppler study was not more sensitive than M-mode recording in the same fetus in the interpre­tation of the arrhythmia, but interpretation was more rapid. Doppler examination also allowed detection of A V valve regurgitation and diastolic regurgitation in complete heart block (12).

Atrial premature contractions characteristically showed an early atrial systolic flow pattern followed by prolonged mitral inflow. The Doppler velocity findings of noncon­ducted atrial premature contractions are shown in Figure 4. No ventricular systolic flow pattern follows the early atrial premature contraction. Very early atrial premature contrac­tions such as these may not produce a visible atrial flow velocity.

1388 STRASBURGER ET AL DOPPLER ECHOCARDIOGRAPHY IN FETAL ARRHYTHMIAS

Figure 2. A, Normal atrioventricular (A V) con­traction sequence recorded from the area of mitral­aortic continuity. A prominent atrial systolic ve­locity (A) as seen here is a normal finding in the fetus. The normal A V activation sequence is seen when the atrial deflection (A) immediately precedes left ventricular (LV) ejection (V). B, Doppler sam­pling in position A in the area of mitral-aortic con­tinuity in an infant after birth with simultaneous echocardiography showing the timing of the P and R waves with respect to the Doppler correlates of atrial systole (A) and ventricular systole (V). Ao = aorta.

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Figure 3. Atrial rates recorded from the foramen ovale position (position B in Fig. 1) during normal rhythm (left) and during supraventricular tachycardia (SVT) (right) in a 28 week fetus. BPM = beats/min; other abbreviations as in Figure I.

JACC Vol 7. No 6 June 1986 1386-91

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During atrial flutter, variable degrees of A V block were present. Atrial flutter with 1 : 1 A V conduction could not be differentiated by Doppler or M-mode echocardiography from supraventricular tachycardia. No diagnosis could be con­firmed in two fetuses dying in utero from hydrops fetalis and tachycardia with 1: 1 A V conduction.

The Doppler evaluation of six fetuses with AV block dem­onstrated AV valve regurgitation in four and absent AV conduction in five (Fig. 5). Second degree A V block was present in one patient (Fig. 6).

M-mode echocardiography (Group B). The limita­tions of M-mode echocardiographic technique included 1) inability to record simultaneous atrial and ventricular con­tractions in 2 of the 14 patients, 2) poor quality tracings as the result of maternal obesity, polyhydramnios or fetal movement in 2 patients, and 3) dilated cardiac chambers resulting in limited atrial wall motion in 1 patient with complete heart block and a massively dilated common atrium.

Figure S. Pulsed Doppler sampling in a 24 week fetus with left isomerism, atrioventricular (A V) canal defect and complete A V block. Upper panel, The pulsed Doppler sampling volume (top white arrow) is placed in the common atrium (CA) superior to the common A V valve orifice (CA YO) in a four chamber view equivalent where the apex of the heart and the nght ventricle (RV) are seen. Lower panel, The Doppler velocity pattern IS typical of complete heart block with A V valve insufficiency (A VVI). Atrial contractions produce velocity deflections (A) at a rate of 120 beats/min (BPM). Ventricular contractions (V) are marked by a high velocity jet of atrioventricular valve insufficiency at a rate of 35 beats/min with no relation between atrial and ventricular velocity deflections.

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Figure 4. Nonconducted premature atrial contrac­tion (PAC-NC) recorded from the mitral valve (MV)

A at position A in Figure I. During the pause, ven­tncular filling (LV IN) continues until the next atrial contraction (A). LV OUT = left ventricular out­flow.

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1390 STRASBURGER ET AL DOPPLER ECHOCARDIOGRAPHY IN FETAL ARRHYTHMIAS

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Figure 6. Doppler recording from a 32 week fetus with 2: 1 atrioventricular block obtained at position A in Figure I. Upper panel, Left ventricular inflow (LV In) and outflow (LV Out) velocities are in opposite directions. Note the constant relation of the diastolic rapid filling, atrial systole (A) and ventricular sys­tole (V). Lower panel, Nonsimultaneous M­mode recording of the right atrium (RA) and left ventricle (LV) shows a 2: I atrial to ven­tricular relation. mls = meters per second; s = second.

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Prognosis of persistent fetal arrhythmias. Atrial pre­mature contractions were benign and not associated with morbidity or mortality. The mortality in fetuses with com­plete A V block and tachycardia was 9 of 21. Two deaths were attributable to structural cardiac defects. Six of seven fetal patients dying of an arrhythmia had associated hydrops fetalis. Two fetuses with hydrops fetalis treated in utero for supraventricular tachycardia survived. Persistent arrhyth­mias presenting in the second trimester had a poor prognosis. Hydrops fetalis was present at the initial evaluation in four of five fetuses of less than 28 weeks' gestational age, and all four died in utero.

Discussion Appropriate management of the fetus with a persistent

arrhythmia requires thorough prenatal echocardiographic evaluation. It is necessary to determine the type of arrhyth­mia, the presence of associated structural cardiac malfor­mations, and the degree of hemodynamic compromise. Dop­pler echocardiography allowed rapid and correct assessment of atrial and ventricular rates and A V contraction sequences necessary to identify the type of fetal arrhythmia. Patients with ventricular tachycardia were not encountered in this

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study and data on the Doppler findings of this group are not yet available using a logical approach to rhythm (12).

Doppler versus M-mode echocardiography. Unlike M­mode and two-dimensional echocardiography, which detect only mechanical cardiac events, Doppler echocardiography is sensitive in detecting even low blood flow velocities. Until electrocardiographic diagnosis of arrhythmias is possible in the fetus, Doppler echocardiography appears to be a highly sensitive tool to assess myocardial flow patterns that can be used to infer the rhythm. Although M-mode echocardiog­raphy allows correct rhythm diagnosis in most cases, Dop­pler echocardiography may be necessary when M-mode tracings are technically inferior or inconclusive or when severe myocardial dysfunction compromises wall motion. Doppler rhythm interpretation is rapid and high quality two­dimensional images are not requisite for obtaining quality Doppler tracings.

Prognosis. The prognosis of the fetus with a persistent arrhythmia depends on the gestational age of the fetus, the type and duration of the arrhythmia, the degree of hemo­dynamic compromise, the presence of structural cardiac de­fects, the ability to treat the arrhythmia in utero and the fetal and neonatal response to therapy. Hydrops fetalis ap­pears to be a late, nonspecific manifestation of severe fetal

JACC Vol 7, No 6 June 1986,1386-91

cardiac decompensation, Its presence may be due to the arrhythmia, the structural cardiac defect, the A V valve in­sufficiency or a combination of factors. Doppler detection of A V valve insufficiency suggested significant fetal cardiac decompensation associated with cardiac dilation and struc­tural cardiac defects (13).

Experienced perinatologists and cardiologists should care for these patients with persistent fetal arrhythmia. Thorough structural and functional prenatal echocardiographic and Doppler evaluation before and during treatment may de­crease the mortality associated with these arrhythmias. Al­though Doppler echocardiography can be used to estimate transvalvular indexes, cardiac blood flows and right ven­tricular pressures in children after birth, experience with quantitation of Doppler recordings in the fetus is limited and requires further investigation.

References I, Kleinman CE, Donnerstein RL, laffe CC, et al. Fetal echocardiog­

raphy: a tool for evaluation of in utero cardIac arrhythmias and mon­itoring of in utero therapy: analysis of 71 patients. Am 1 Cardiol 1983;51 :237-43.

2. Allan LD, Anderson RH, SullIvan 10, et al. Evaluation of fetal ar­rhythmias by echocardiography. Br Heart 1 1983;50:240-5.

3. Shenker L. Fetal cardiac arrhythmias (review). Obstet Gynecol Surv 1979;34:561-72.

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4 Newburger lW, Keane IF. Intrautenne supraventricular tachycardia. 1 Pediatr 1979;95:780-6.

5 DeVore GR, Siassi B, Platt CD. Fetal echocardiography. III. The dIagnosis of cardiac arrhythmIas usmg real-time-directed M-mode ultrasound. Am 1 Obstet Gynecol 1983;146:792-7.

6. DeVore GR, Donnerstein RL, Kleinman CS, Platt LD, Hobbins lC. Fetal echocardiography. I. Normal anatomy using real-time-directed M-mode ultrasound. Am 1 Obstet Gynecol 1982;144:249-60.

7. Huhta lC, Hagler DJ, Hill LM, Two-dimensional echocardiographic assessment of normal fetal cardiac anatomy. J Reprod Med 1984;29:162-7.

8. Kleinman CS, Donnerstein RL, DeVore GR, et al. Fetal echocardi­ography for evaluation of in utero congestive heart failure: a technique for study of non-immune hydrops. N Engl J Med 1982;306:568-75.

9. Sahn OJ, Lange LW, Allen HD, et al. Quantitative real-time cross­sectional echocardiography in the developing normal human fetus and newborn. Circulation 1980;62:588-97.

10. Huhta lC, Strasburger lF, Carpenter RJ, Reiter A, Abinader E. Pulsed Doppler fetal echocardlOgraphy. J Clin Ultrasound 1985;13:247-54.

II. Silverman NH, Enderlem MA, Stanger P, Teitel DF, Heymann MA, Golbus MS. Recognition of fetal arrhythmias by echocardiography. 1 Clin Ultrasound 1985;13:255-63.

12. Rokey R, Murphy Dl, Nielsen AP, Abmader EC, HuhtalC, Quinones MA. Detection of diastolic atrioventricular valvular regurgitation by pulsed-Doppler echocardiography and its association with complete heart block. Am 1 Cardiol 1986 (in press).

13. Silverman NH, Kleinman CS, Rudolph AM, et al. Fetal atrioventric­ular valve insufficiency associated WIth nonimmune hydrops: a two­dimensional echocardiographic and pulsed Doppler ultrasound study. Circulation 1985;72:825-32.