Ventriculo-atrial time interval measured on M mode echocardiography: a determining element in diagnosis, treatment, and prognosis of fetal supraventricular tachycardia

Abstract

Objective: To determine whether M mode echocardiography can differentiate fetal supraventricular tachycardia according to the ventriculo-atrial (VA) time interval, and if the resulting division into short and long VA intervals holds any relation with clinical presentation, management, and fetal outcome.

Design: Retrospective case series.

Subjects: 23 fetuses with supraventricular tachycardia.

Main outcome measures: A systematic review of the M mode echocardiograms (for VA and atrioventricular (AV) interval measurements), clinical profile, and final outcome.

Results: 19 fetuses (82.6%) had supraventricular tachycardia of the short VA type (mean (SD) VA/AV ratio 0.34 (0.16); heart rate 231 (29) beats/min). Tachycardia was sustained in six and intermittent in 13. Hydrops was present in three (15.7%). Digoxin, the first drug given in 14, failed to control tachycardia in five. Three of these then received sotalol and converted to sinus rhythm. All fetuses of this group survived. Postnatally, supraventricular tachycardia recurred in three, two having Wolff-Parkinson-White syndrome. Four fetuses (17.4%) had long VA tachycardia (VA/AV ratio 3.89 (0.82); heart rate 226 (10) beats/min). Initial treatment with digoxin was ineffective in all, but sotalol was effective in two. Heart failure caused fetal death in one and premature delivery in one. All three surviving fetuses had recurrences of supraventricular tachycardia after birth: two had the permanent form of junctional reciprocating tachycardia and one had atrial ectopic tachycardia.

Conclusions: Careful measurement of ventriculo-atrial intervals on fetal M mode echocardiography can be used to distinguish short from long VA supraventricular tachycardia and may be helpful in optimising management. Digoxin, when indicated, may remain the drug of choice in the short VA type but appears ineffective in the long VA type.

Figure 1

Measurement of ventriculo-atrial time interval on M mode echocardiography during fetal supraventricular tachycardia. Examples of a long (panel A) and short (panel B) ventriculo-atrial time intervals are shown. A, atrium; V, ventricle.

Figure 2

(A) Example of simultaneous M mode echocardiogram and ECG recordings during a neonatal reentry supraventricular tachycardia. Arrows mark peaks of P waves. Vertical lines mark mechanical ventricular and atrial events. The ECG shows a short RP supraventricular tachycardia of 260 beats/min with 1:1 AV conduction, an RP interval of 95 ms, and a PR interval of 135 ms, leading to an electrical RP/PR ratio of 0.7. The M mode echocardiogram indicates a corresponding short VA tachycardia with a VA interval of 80 ms, an AV interval of 150 ms, and a mechanical VA/AV ratio of 0.53. (B) Electrocardio- graphic demonstration of pre-excitation (Wolff-Parkinson-White syndrome) after termination of the supraventricular tachycardia in the same neonate (case 19). IVS, interventricular septum; LA, left atrium; MV, mitral valve; RV, right ventricle.

Figure 3

(A) Electrocardiogram of one of the neonates with permanent form of junctional reciprocating tachycardia: limb leads I, II, III, aVR, aVL, aVF in full standardisation; narrow QRS tachycardia at 180 beats/min with l:l AV relation; long RP, short PR; negative P waves in II, III, and aVF. (B) Atrial ectopic tachycardia: limb leads I, II, III, aVR, aVL, aVF in full standardisation, narrow QRS tachycardia at 180 beats/min with l:l AV relation; long RP, short PR; abnormal P wave morphology and axis.