Nifekalant for Atrial Tachycardia-Induced Cardiogenic Shock in a Patient With Severe Left Ventricular Systolic Dysfunction.

BACKGROUND: Atrial tachycardia (AT) during acute heart failure with reduced left ventricular ejection fraction (LVEF) can worsen hemodynamics. Antiarrhythmic drugs are limited by negative inotropic effects. CASE SUMMARY: A 55-year-old man with idiopathic dilated cardiomyopathy was admitted with worsening heart failure under sustained AT. His LVEF had declined to 12%. Multiple ATs caused resistance to inotropes and diuretics. Repeated electrical cardioversion with intravenous amiodarone failed owing to recurrent ATs triggered by premature atrial contractions, leading to cardiogenic shock. Intravenous nifekalant and digoxin were administered for rhythm and rate control. After electrical cardioversion, premature atrial contractions no longer induced AT. Continuous nifekalant maintained sinus rhythm, allowing recovery from shock without mechanical support. Catheter ablation, cardiac resynchronization therapy, and oral sotalol achieved long-term rhythm control. The patient was discharged on day 96. DISCUSSION: Nifekalant, a selective delayed rectifier potassium current blocker, prolongs refractoriness with minimal inotropic effect, stabilizing rhythm and bridging to definitive therapy. TAKE-HOME MESSAGE: Nifekalant may be effective for refractory AT in patients with severely reduced LVEF and hemodynamic instability.