The report was ethically approved by the institutional review board (Faculty of Medicine, Chiang Mai University) and written informed consent has been obtained from the patient(s) to publish this paper.
Case 1
A 33-year-old pregnant woman, G2 P1001, attended the scheduled antenatal care at 35 weeks of gestation at a community hospital. On physical examination, fetal tachycardia with heart rate greater than 200 bpm was detected. The pregnancy was referred to our center for further management. Her history of prenatal course was uneventful. Fetal anomaly screening at 20 weeks of gestation showed normal and chromosome study result was low-risk for aneuploidy. At our center, at 35 weeks, detailed ultrasound showed a normally formed female fetus with normal growth and fetal biometry, occasional PAC, alternate with occasional atrial flutter (AF) (Fig. 1A, 1B) and with normal rhythm. However, the fetal heart had atrial septal aneurysm (ASA), with abnormally wide excursion of the foramen ovale flap (approximately 80% of left atrial diameter: Fig. 1C) with turbulent reversed flow in the septum back to the right atrium (Fig. 1D), instead of crossing the foramen. The patient was admitted for close follow-up with ultrasound and expectantly treated. The dysrhythmias were more progressive, turning to be persistent AF. During surveillance, at 36+ 5 weeks ultrasound showed fetal atrial rate was 505 bpm and ventricular rate was 245 bpm. AF with 2:1 AV block was diagnosed. AF was persistent after observation over a period of four hours. The cardiac size was within normal limit. No hydropic sign was detected. The last fetal heart rate 2 weeks before this admission was normal (150 bpm), recorded by Doppler device.
Because the AF was persistent, without alternate normal rhythm, early treatment was needed. Since the gestational age was nearly term, rather than in utero treatment, cesarean delivery was performed for early treatment after birth. The female newborn had birthweight of 2,750 g, no gross structural anomaly, and Apgar score 10 at 5 min. Just immediately after birth, the heart rate was firstly detected to be approximately 240 bpm. Ten minutes later, the heart rate was suddenly reduced to 124 bpm, no longer tachycardia. Neonatal echocardiography, the heart was otherwise normal except the small size of atrial septal aneurysm with minimal redundant the atrial septum, bulging predominantly into the right atrium, no significant turbulent flow in the septum as previously shown in utero. The AF completely disappeared without recurrence.
Case 2
A 20-year-old pregnant woman, G0 P0, attended routine antenatal care at 33+ 4 weeks of gestation at a private hospital. On physical examination, fetal tachycardia with heart rate of approximately 230 bpm was detected. The pregnancy was referred to our center because of fetal tachycardia. The pregnancy was low-risk and prenatal course was unremarkable. Fetal anomaly screening and fetal biometry at 21 weeks of gestation revealed normal. Fetal Down syndrome screening was low-risk. At our center, fetal heart rate was sometime irregular and sometime very fast (approximately 240 bpm). The detailed ultrasound examination at 33+ 4 weeks revealed a normally formed male fetus with proper growth. Nevertheless, the fetal tachycardia was the fetal heart had tortious ductus arteriosus and ASA (abnormally wide excursion of the foramen ovale flap: approximately 80% of left atrial diameter) with turbulent reversed flow in the septum, circulating back to the right atrium. The fetal atrial rate was varied, occasional bigeminy of PAC with conduction with the rate of about 150 bpm (Fig. 2a), occasional normal rate of 140–150 bpm, but mostly tachycardia with atrial rate of 480 bpm and ventricular rate was 240 bpm (Fig. 2b). AF with 2:1 AV block was diagnosed and the AF took most of the time. Because AF was not persistent and no any hydropic signs, other than mild cardiomegaly (cardio-thoaracic diameter ratio of 65%), expectant management with close follow-up was given. Fetal well-being was assessed by biophysical profile. At 36 weeks of gestation AF was persistent. We decided to have cesarean delivery for postnatal treatment, giving birth to a 2,540-g male newborn, Apgar scores 10 at 5 min. Just immediately after birth, the heart rate was regular, 120 bpm and no longer tachycardia. Neonatal echocardiography revealed normal cardiac structures except the atrial septal aneurysm with the redundant atrial septum, no flow crossing the foramen ovale. The AF and hydropic signs completely disappeared without any treatment.
Case 3
A 25-year-old pregnant woman, G2 P1001, attended our antenatal care at 37+ 4 weeks of gestation with incidental findings atrial septal aneurysm with fetal tachycardia, the heart rate of approximately 220 bpm. She attended her first antenatal visit at 12+ 4 weeks of gestation. The antenatal course was low-risk and uneventful. Fetal anomaly screening at 20+ 5 weeks of gestation was unremarkable. The second trimester serum screening was low-risk. At 33+ 4 weeks of gestation the fetus developed occasional PACs with conduction and also ASA was firstly noted, with the maximal excursion of about 80% of the left atrial width. Fetal heart rate was relatively normal, though sometime irregular. Expectant management and close follow-up as out-patient care was provided. At 34+ 4 weeks, the fetus developed persistent SVT, atrial rate to ventricular rate ratio of 1:1 (220 bpm) (Fig. 3a). Also, hydropic signs including pleural effusion and ascites were observed. Because SVT was persistent during preterm period, intrauterine treatment with flecainide via maternal circulation was instituted. Drug administration and dosage flecainide of dosage described elsewhere (7). Approximately 24 hours after treatment, cardioversion to normal sinus rhythm was successful. However, four days after the initiation of intrauterine treatment, AF developed in spite of intrauterine treatment (Fig. 3b). Then the combination of digoxin (0.5 mg/d) and flecainide were administered instead. Nevertheless, cardioversion was not successful. We decided to have delivery for early postnatal treatment. Cesarean delivery was performed at 35+ 6 weeks of gestation, giving birth to a normally-formed male newborn, birthweight of 2,550 g., and Apgar score of 9 at 5 min. The neonatal heart (ventricular) rate at the delivery room was 240 bpm. Shortly after that, at the NICU, the heart rate was suddenly lowered to 130 bpm, no need of any anti-arrhythmic medication. Neonatal echocardiography showed a markedly decrease in the maximal excursion of the foramen ovale flap, no significant turbulent flow in the septum as previously shown in utero. There was a trivial low velocity left to right shunt across the patent foramen ovale. The AF and hydropic signs completely disappeared without recurrence.
The summary of characteristics of the three cases with AF associated with ASA is presented in Table 1.
Table 1
Characteristics of the three cases with atrial flutter associated with septal aneurysms
Case no. | Maternal age | GA of diagnosis | Intrauterine treatment | GA of delivery | Hydrops fetalis | Preceding arhythmia | Birth weight |
1 | 33 | 35 | No | 36+ 5 | No | Bigeminy | 2750 |
2 | 20 | 33+ 4 | No | 36 | No | PACs, Bigeminy | 2540 |
3 | 25 | 34+ 4 | Yes | 35+ 6 | Yes | PACs, SVT | 2550 |