Supraventricular tachycardia-ventricular tachycardia discrimination algorithms in implantable cardioverter defibrillators: state-of-the-art review

To reduce inappropriate therapy of supraventricular tachycardia (SVT), implantable cardioverter defibrillators (ICDs) include algorithms to discriminate ventricular tachycardia (VT) from SVT. Dual-chamber algorithms analyze atrial and ventricular rates or AV relationship. They provide advantages over single-chamber algorithms, but introduce new ways to detect SVT as VT inappropriately and to underdetect VT. Unlike pacemakers, dual-chamber ICDs require accurate atrial sensing during high ventricular rates. A postventricular atrial blanking period prevents oversensing of far-field R waves as atrial electrograms, but causes underdetection of atrial fibrillation during high ventricular rates. Tachycardias with 1:1 AV relationship and VT during atrial tachyarrhythmias present specific SVT-VT discrimination problems. The first dual-chamber algorithms performed comparably to single-chamber algorithms. Present dual-chamber algorithms correct some limitations of earlier versions.