Tachyarrhythmias Bookmark ShareFast heart rhythms on an ECG may be caused by supraventricular or ventricular rhythms, some of which are imminently life threatening and require rapid assessment. Try our ECG QuizOn this page: Narrow Complex TachycardiaWide Complex TachycardiaOtherNarrow Complex TachycardiaApproach to Narrow Complex TachycardiaSinus TachycardiaRegular narrow complex tachycardia with uniform P waves and PR intervalsFocal Atrial TachycardiaRegular narrow complex tachycardia with abnormal yet consistent P wavesMultifocal Atrial TachycardiaIrregular narrow complex tachycardia with multiple P wave morphologies and variable PP intervalsAtrial FlutterRegular narrow complex tachycardia with sawtooth wavesAtrial FibrillationIrregular narrow complex tachycardia with absence of P waves and disorganised atrial activityAV Nodal Reentrant TachycardiaRegular narrow complex tachycardia with P waves hidden within QRSAV Reentrant TachycardiaOrthodromic or antidromicRegular narrow complex tachycardia with P waves visible after QRS (orthodromic)Wide Complex TachycardiaApproach to wide complex tachycardiaVentricular TachycardiaRegular tachycardia with broad QRSSVT with Aberrancy or PreexcitationRegular tachycardia with broad QRS complexesAF with Aberrancy or PreexcitationIrregular tachycardia with broad QRS complexesOtherVentricular FibrillationChaotic electrical activity without PQRST