Hemodynamic effect of fetal supraventricular tachycardia on the unaffected twin.

Fetal arrhythmias are diagnosed in 1 to 3% of pregnancies, of which supraventricular tachycardia (SVT) constitutes 10% (Reed, 1989). Sustained fetal SVT with a heart rate more than 220 beats per minute (bpm) can result in congestive heart failure and nonimmune hydrops, which is associated with a poor outcome (Simpson and Sharland, 1998). SVT in twin pregnancy is infrequently reported and poses a therapeutic and ethical dilemma in regard to the effect of treatment on the unaffected twin. To date, there is no evidence that fetal SVT in one twin affects hemodynamics of the other twin who is in normal rhythm. We report for the first time, a case in which fetal SVT in one twin was associated with early signs of congestive heart failure, in the other twin, with subsequent echocardiographic improvement following control of the SVT in the first twin. A 26-year-old gravida 2, para 0 African-American woman with a twin pregnancy at 27 (3/7) weeks of gestation was referred to us for evaluation of fetal tachycardia in one of the twins. The course of pregnancy was uneventful until then. Specifically, there was no history of hypertension, diabetes or infections. She was a nonsmoker and denied use of alcohol or drugs. She was not on any medications. During a regular prenatal visit, auscultation revealed audible arrhythmia in twin A with heart rate in the range of 200 bpm. Ultrasound revealed monochorionic diamniotic twins of similar size (estimated fetal weight of twin A, 992 g and twin B, 959 g). There were no other congenital defects. A fetal echocardiogram utilizing M mode and Doppler techniques revealed that Twin A had SVT at a rate of 230 bpm with 1 : 1 conduction to ventricles. Cardiac anatomy was normal. The size and contractile function of the ventricles were normal and there was no mitral or tricuspid regurgitation. There was no evidence of pericardial effusion or congestive heart failure as assessed by the cardiovascular profile (Huhta, 2004). Fetal echocardiography of Twin B revealed normal cardiac structural anatomy. There was mild cardiomegaly with a cardiothoracic circumference ratio of