Electrocardiographic criteria for diagnosis of irregular broad complex tachycardia with a high sensitivity for preexcited atrial fibrillation

AF may appear as an irregular broad complex tachycardia (BCT) if atrioventricular conduction occurs via an accessory pathway (preexcited AF) or if bundle branch block (BBB), preexistent or rate related, exists in the His-Purkinje system (BBB-AF). While BBB-AF is relatively benign, preexcited AF may herald sudden cardiac death. Hence it is important that the two conditions can be reliably distinguished. Yet, there is no preexistent algorithms for this purpose. Griffith et al. previously proposed a simple algorithm for a similar problem, that of distinguishing the two differential diagnoses for regular BCT: VT and SVT with BBB, on the basis that unless the QRS morphologies in V1 and V6 are absolutely typical of BBB, VT will be diagnosed. The authors propose an extrapolation of this principle to irregular BCT by stating that, unless the QRS morphologies in V1 and V6 are absolutely typical of BBB, preexcited AF will be diagnosed. Seventy-five ECGs showing irregular BCT (41 preexcited AF and 34 BBB-AF) were shown to two fellows in electrophysiology who were given no other information and were instructed to diagnose preexcited AF unless the QRS morphology pattern was typical of BBB. Observer 1 achieved a sensitivity of 100% (41/41) and a specificity of 79% (27/34), while observer 2 achieved a sensitivity of 100% and a specificity of 85% (29/34). By QRS morphology pattern, an average sensitivity of 100% and specificity of 82% were achieved for the diagnosis of irregular BCT. The algorithm is simple and easy to implement and recommended for clinical use.