Propranolol has been used for different indications for many years. Propranolol is accepted for use in infants with hemangiomas and supraventricular tachycardia. Hemangeol was approved by the FDA for use in infants with hemangiomas. However, βAR antagonists are not without potential adverse effects, including hypotension, bradycardia, hypoglycemia, bronchospasms, and sleep disturbances. FDA-approved dose range for treating hemangiomas in infants (>5 weeks old, >2kg) ranged from 1-3mg/kg/day in divided doses. Propranolol doses of up to 4mg/kg/day has been used for pediatric supraventricular tachycardia. Therefore, the investigator's experience with propranolol use in LM patients have been at the low end of most accepted clinical indications. The investigators propose to escalate propranolol dosages up to 3mg/kg/day in this study, well below the dose ranges currently used in clinical settings.