A rare combination of undiagnosed hypertrophic cardiomyopathy revealed by intraoperative anaphylaxis resulting in acute left ventricular outflow obstruction and cardiac arrest.

A 75-year-old female presented for left total hip reimplantation and suffered pulseless electrical activity arrest upon lateral positioning and administering vancomycin. Resuscitation was achieved according to Advanced Cardiac Life Support protocol. Post-event echocardiography showed hypertrophic cardiomyopathy with asymmetrical septal thickening, an under-filled left ventricle, dynamic left ventricular outflow obstruction, and severe mitral regurgitation related to systolic anterior motion of the mitral valve. Laboratory analysis showed a tryptase level of 209 ng/mL. After multispecialty evaluation, it was concluded that the patient's arrest was due to vancomycin anaphylaxis in the setting of previously undiagnosed hypertrophic cardiomyopathy leading to acute left ventricular outflow tract obstruction. After medical optimization of the patient's cardiomyopathy and an evaluation of potential intraoperative allergic triggers, the patient underwent a successful hip reimplantation without incident. This case presents a novel combination of events leading to intraoperative cardiac arrest. Rapid identification and an understanding of the cause(s) of cardiac arrest in this setting are critical for effective perioperative care.