A 32-year-old woman presents with a 3-month history of progressive dyspnea, chest pain on exertion, and syncope. Physical examination reveals a loud systolic ejection murmur at the left sternal border. Chest X-ray shows a boot-shaped heart with right ventricular hypertrophy. ECG demonstrates right axis deviation and right ventricular strain pattern. Which imaging modality is the investigation of choice to confirm the diagnosis and assess the anatomy for surgical planning?