OBJECTIVES: The aim of this study was to establish an original transapical septal myectomy procedure that can be performed in the beating heart via a minimally invasive approach for the treatment of hypertrophic obstructive cardiomyopathy. METHODS: We designed an original intracardiac septum resection device to conduct off-pump septal myectomy in swine. A subxiphoid minithoracotomy was performed to access the apex of the heart. This resection device was inserted into the left ventricular outflow tract of the heart via the apex. The basal anteroseptal myocardium beneath the right aortic cusp was identified using a combination of transoesophageal and transthoracic echocardiography and then resected and collected by the device. RESULTS: Six consecutive operations were successfully and accurately performed using the custom-made device under echocardiographic guidance. All pigs survived and appeared to be normal until planned euthanasia 1 week after operation. A 300-700mg portion of the septal myocardium was resected from the normal swine heart. Echocardiography and electrocardiogram revealed no abnormalities after resection. One exception was the fifth pig, in which mild annular regurgitation of the aortic valve occurred after repetitive resection. Postmortem necropsy demonstrated that all resections were correctly located at the basal anteroseptal septum beneath the right aortic cusp. CONCLUSIONS: Our study provides the first proof-of-concept evidence for a novel beating heart transapical septal myectomy procedure, which showed promising translational potential for the treatment of hypertrophic obstructive cardiomyopathy. This procedure would probably reduce operative risks and improve outcomes and reduce the demanding expertise required to perform conventional surgical myectomy.