Fetal tachycardia : diagnosis and treatment

Abstract

Part I: Fetal tachyarrhythmias

Diagnosis Fetal tachycardia is a serious condition warranting specialized evaluation. In chapter 2, methods of diagnosis of fetal tachycardia are described, including doppler and M-mode echocardiography and fetal magnetocardiography. The study presented in chapter 3 describes a method for further delineation in the classification of fetal SVT in short and long VA tachyarrhythmias.

Consequences Tachyarrhythmia is associated with fetal hydrops. As outlined in chapter 4 and 5, predisposing factors for the development of hydrops seem to be the percentage of time that the tachycardia is present, the gestational age at which the tachycardia occurs, the ventricular rate and the site of origin of the tachycardia. In fetal hydrops, the fetus is at risk for neurological morbidity. In chapter 4, the outcome of 11 fetuses with hydrops as a result of tachyarrhythmia is presented.

Treatment In the chapters 3, 4 and 7, it is outlined that transplacental treatment is to be preferred above expectant management. The issue of direct fetal therapy is described in chapter 5 and a review of the literature on the various regimens of drugs used in the transplacental treatment of fetal tachycardia is presented. Chapter 6 describes the pharmacokinetics and pharmacodynamics of sotalol in pregnancy. The overall success rate of sotalol as a single therapy in the treatment of atrial flutter in the studies presented in chapters 6 and 7, was 63 %, and reached 79 % after the addition of digoxin. The success rates in fetal SVT were 53 % and 74 %, respectively. In the SVT group, there were however, four deaths. Low initiation dosages of sotalol, stepwise dosage increases and close monitoring, especially during the initiation phase are recommended.

Protocol in the treatment of fetal tachycardia In fetal AF, sotalol, with digoxin as a second line drug, should be the treatment of choice (Figure 1). In nonhydropic fetal SVT, a definite clinical advantage of sotalol over other drugs could not be proved. The treatment protocol (Figure 2) therefore shows 2 options. In fetal SVT complicated by hydrops, two options are proposed: flecainide, or a combination of intravenous digoxin and amiodarone (Figure 3). In conclusion, as a result of the studies of this thesis and of the latest international literature, new treatment protocols are proposed and presented.

Part II: Fetal ECG in labour, aspects of the intrapartum QT interval

In chapter 9, observations on the intrapartum fetal QT interval in three premature sheep fetuses and one human fetus at term, all being exposed to acute and severe asphyxia, are presented. A shortening of the QT interval is present, shortly after the fetus is exposed to asphyxia, in association with a rise in T/QRS ratio and an increase in blood pressure. In chapter 10, the QT interval in 68 fetuses with signs of severe intrapartum hypoxia also showed a significant shortening of the QT interval. The fetal QT interval during labour may therefore provide additional information on the condition of the fetus.