Functional Ventricular Undersensing After Ventricular Ectopic Beats Due to ICD Dynamic Sensitivity.

An 80-year-old patient, previously implanted for idiopathic sustained ventricular tachycardia with a Rivacor VR-T DX implantable cardioverter defibrillator (ICD Biotronik, Berlin, Germany), came to our pacemaker clinic for palpitations. Electrocardiogram (ECG) showed sinus bradycardia with interpolated ventricular ectopic beats. A ventricular-paced event occurred with a coupling interval shorter than the expected one suggesting ventricular undersensing. The phenomenon can be explained by the default ICD sensitivity setting proposed by the manufacturer.