Propranolol Therapy in Tetralogy of Fallot: Treating the Echocardiogram or Treating the Patient

Hypercyanotic spells are one of the defining clinical features of Tetralogy of Fallot (TOF). Limited data exist on peak Doppler right ventricular outflow tract (RVOT) gradient as a risk factor for the development of hypercyanotic spells, frequency of prophylactic use of propranolol based on peak RVOT gradient, and its impact on preventing the occurrence of hypercyanotic spells. We aimed to quantify peak RVOT gradients as measured on transthoracic echocardiography in infants with unrepaired TOF and assess for correlation with clinical symptoms of hypercyanotic spells. We also assessed the frequency of pre-operative use of propranolol, indication for medication initiation, and occurrence of hypercyanotic spells with or without propranolol use. Retrospective analysis was performed on patients at our institution who were born between February 1, 2011 and May 31, 2023. Patients were excluded if they were maintained on prostaglandin infusion or underwent palliative shunt placement or balloon valvuloplasty prior to complete surgical repair. Demographics, occurrence of hypercyanotic spells, propranolol use, peripheral oxygen saturation, age at surgical repair, and peak RVOT gradient at the time of propranolol initiation were collected from the electronic medical record. If no propranolol use was recorded, the single highest maximum RVOT gradient prior to surgery was collected. 203 patients were identified, of which 92 patients were included in analysis. Thirty-six (39%) patients received propranolol and 19% of patients developed hypercyanotic spells prior to surgery. Patients with higher peak RVOT gradients were more likely to be started on propranolol even in the absence of overt symptoms, and they also demonstrated more systemic desaturation. Additionally, peak RVOT gradient was found to be a poor predictor for the development of hypercyanotic spells. Wide clinical variation exists in the prophylactic use of propranolol for prevention of hypercyanotic spells. Peak RVOT gradient is not a reliable tool for prophylactic propranolol initiation to prevent hypercyanotic spells.