Most cases (61-73%) of infant SVT occur by age 4 months [9, 17, 18], and almost all occur before the age of 12 months [1, 2, 5, 6, 9, 13, 17-19]. In 1981, Garson et al. reported data from one of the largest retrospective series, encompassing 217 SVT referrals over 25 years [6]. Infants who presented with SVT before 4 months of age had faster tachycardia rates and a greater risk of presenting with congestive heart failure (CHF) (24%) than did older infants or children. Although infants can tolerate SVT for >24 hours before signs of CHF ensue [1], CHF is seen in a significant number of patients (24-54%) when they come to medical attention. Infants with CHF can progress to cardiovascular collapse, accounting for the mortality of 1-4% in infants with SVT [2, 5, 6, 20].