Supraventricular tachycardia (SVT) is the most common arrhythmia in children. Isolated SVT inducing cardiogenic shock is rare and factors leading to cardiac dysfunction are unknown. We aim to determine the predictive factors of cardiogenic shock in children with SVT.

In total, 109 children under the age of 1 [median age 10 days (1d; 30d)], who were referred for SVT to our pediatric cardiologic intensive care unit were included. Cardiogenic shock was defined as a systemic ventricular ejection fraction under 50% and the need for inotropes use. Types of SVT, antenatal diagnosis of arrhythmia, demographic data, clinical and biological characteristics and the therapeutic management were reviewed.

Seventeen percent of patients had cardiogenic shock [median age 12 days (3.5d; 17.5d)]. Heart failure was significantly more frequent in case of flutter (54.5% in flutter; 13.3% in other SVT; P<0.01). When the heart rate was high, the risk of failure was greater [median heart rate flutter/other SVT: 280bpm (235; 300)/230bpm (210; 280); P=0.04]. Abortive therapy by adenosine worked for 60% of other types of SVT with or without cardiogenic shock but was ineffective for patients with flutter in our sample. On the other hand, almost all cases of flutter were reduced by electrical cardioversion. Twenty-nine percent of patients had experienced fetal tachycardia without any additional risk of cardiogenic shock (on all cardiogenic shock 42.1% with antenatal arrhythmia and 57.9% without antenatal tachycardia). Associated congenital heart diseases were not a risk factor of cardiogenic shock.

The occurrence of cardiogenic shock is not uncommon in children with SVT and concerns mainly patients with flutter. Faster heart rate and the ineffectiveness of adenosine are associated with potentially severe outcomes. These predictive factors of shock will help identify higher risk patients and improve the therapeutic management.