A 72-year-old man presented with exertional chest pain and dyspnea due to severe coronary artery calcification with a total score of 16996, hypertrophic cardiomyopathy, and left ventricular outflow tract obstruction. Percutaneous coronary intervention guided by quantitative flow ratio and intravascular ultrasound was performed on the right coronary artery and left circumflex artery. Lesions of the left anterior descending artery had preserved function but microvascular dysfunction, so no intervention was performed. Magnetic resonance imaging of the heart confirmed hypertrophic cardiomyopathy with segmental fibrosis and outflow tract obstruction. After the intervention, the patient received dual antiplatelet therapy for 6 months, then monotherapy with aspirin and oral mavacam at a dose of 2.5 mg daily. After 4 months, the outflow tract gradient decreased from 51 mmHg to 9–12 mmHg. Treatment alleviated both myocardial ischemia and outflow tract obstruction and brought relief from symptoms.