A case of hypertrophic cardiomyopathy presenting with high-degree atrioventricular block.

RATIONALE: Hypertrophic cardiomyopathy (HCM) with high-degree atrioventricular (AV) block is rarely reported in China. This case is unique for a 35-year-old female with progressive high-degree AV block and dual heterozygous variants (MYH7 c.748A > T, DES c.553G > A), supplementing HCM's clinical-genetic spectrum. PATIENT CONCERNS: The patient had 11-year post-exertional chest pain (aggravated recently), family history of sudden cardiac death, hypotension (87/46 mm Hg), bradycardia (50 bpm). ECG progressed to complete heart block; echocardiography showed left atrial enlargement, septal thickening, apical trabecular hyperplasia; cardiac MRI revealed septal fibrosis. Pro-BNP (846 ng/L) and troponin T (12 ng/L) were elevated. Genetic testing found MYH7 (highly suspected pathogenic) and DES (suspected pathogenic) variants; family screening identified 2 affected individuals. DIAGNOSES: HCM, high-degree AV block, left atrial enlargement. INTERVENTIONS: Dual-chamber pacemaker implantation, metoprolol + spironolactone. OUTCOMES: Symptom relief, no perioperative complications; long-term follow-up initiated. LESSONS: HCM with high-degree AV block needs genetic testing; pacemaker implantation and long-term monitoring are key for preventing sudden cardiac death. Family screening is vital for risk stratification.