Effectiveness of Metoprolol Versus Propranolol for Prevention of Hypercyanotic (Tet) Spells in Children with Unrepaired Tetralogy of Fallot

Background: Hypercyanotic spells are acute episodes of severe hypoxemia in patients with tetralogy of Fallot (TOF), potentially causing neurological injury and cardiovascular collapse. Beta-blockers are used to prevent recurrent spells by reducing dynamic right ventricular outflow tract obstruction. This study compared metoprolol and propranolol for preventing hypercyanotic spells in patients awaiting definitive surgery. Objective: To compare the effectiveness and safety of metoprolol versus propranolol in preventing hypercyanotic spells in patients with unrepaired TOF. Methods: This quasi-experimental study was conducted at the Department of Pediatric Cardiac Surgery, National Institute of Cardiovascular Diseases (NICVD), Dhaka, Bangladesh. Sixty patients aged 3–12 years were allocated to two groups. Group A received oral propranolol (1–2 mg/kg/day) in three divided doses, while Group B received oral metoprolol (1–2 mg/kg/day) in two divided doses. Outcomes included hypercyanotic spells, oxygen saturation (SpO₂), hemodynamic parameters, severe spells, emergency interventions, intensive care admission, and adverse events. Results: Mean age was 6.85 ± 1.64 years in Group A and 6.79 ± 1.62 years in Group B. Mean heart rate, mean arterial pressure, and SpO₂ were comparable between groups (86.7 versus 92.5 beats/min, 72.4 versus 75.1 mmHg, and 85.8% versus 86.3%, respectively). No between-group differences were statistically significant. One patient (3.3%) in each group experienced a hypercyanotic spell, with no severe spells reported. In the propranolol group, hypoxia and bronchospasm occurred in two (6.7%) and one (3.3%) patient, respectively. Conclusion: Metoprolol and propranolol demonstrated similar outcomes in this study. Metoprolol may be a potential alternative for preventing hypercyanotic spells in patients with unrepaired TOF; however, larger studies are required to establish comparative efficacy and safety.