Hemodynamic effect of rapid atrial pacing in fetal lambs

Fetal cardiac interventions

The present article aims to highlight fetal cardiac interventions (FCIs) in terms of indications, strategies, and fetal prognoses. FCIs of the early years were predominantly pharmacological therapies for fetal arrhythmia or heart block. A transplacental transmission of therapeutic agents has now become the main route of pharmacological FCIs. There have been various FCI strategies, which can be categorized into three types: pharmacological, open FCIs, and closed FCIs. Rather than as a routine management for materno-fetal cardiac disorders, however, FCIs are only applied in those fetal cardiac disorders that are at an increased risk of mortality and morbidity and warrant an interventional therapy. Pharmacological FCIs have been well applied in fetal arrhythmias but require further investigations for novel therapeutic agents. The development of open FCI in humans is an issue for the long run. Closed FCIs may largely rely on advanced imaging techniques. Hybrid FCIs might be the future goal in the treatment of fetal heart diseases.

Optimal ventricular pacing rate in fetal lambs with complete atrioventricular block

OBJECTIVE

This study was undertaken to determine the optimum ventricular pacing rate at which the optimal cardiac function can be attained in fetal lambs with complete atrioventricular block.

STUDY DESIGN

Complete atrioventricular block was created by cryosurgery in 12 fetal lambs, and the ventricle was paced randomly at rates of 60, 90, 120, 150, 180, 210, 240, and 270 beats/min. The aortic pressure, central venous pressure, and right ventricular cardiac output were measured before cryosurgery and during ventricular pacing.

RESULTS

Complete atrioventricular block was created in 9 of 12 fetal lambs. Systolic aortic pressure significantly decreased at pacing rates of 60, 90 and 240 beats/min (P <.01), and central venous pressure was increased significantly at a pacing rate of 60 beats/min (P <.01) compared with the control. Right ventricular cardiac output significantly decreased at pacing rates of 60, 90, 120, 180, 210, 240, and 270 beats/min (P <.01), although no significant difference was found at the pacing rate of 150 beats/min compared with control.

CONCLUSION

Ventricular pacing at a rate of 150 beats/min gave the highest aortic pressure, the lowest central venous pressure, and the highest right ventricular cardiac output in fetal lambs with complete atrioventricular block.

Fetal supraventricular tachycardias: diagnosis and management

In the majority of cases, the diagnosis of an isolated fetal tachyarrhythmia results in a favorable perinatal outcome. Although there is general consensus on the management of fetal extrasystoles, refractory supraventricular tachycardia, and atrial flutter and fibrillation, the optimal approach to supraventricular tachycardia without hemodynamic compromise remains uncertain. The benefits of conservative management without antiarrhythmic therapy must be weighed carefully against the lack of reliable predictors for the development of fetal hydrops and associated neurologic complications.