The great deceiver: a case series of 'double fire' atrioventricular nodal response.

Background: The 'double fire' (DF) atrioventricular (AV) nodal response is a rare mechanism of two ventricular electrical activations following a single atrial beat due to dual AV node physiology. DF AV nodal response is often misdiagnosed and may lead to unnecessary invasive procedures. Case summary: We describe a series of three cases with distinct clinical manifestations of DF AV nodal response: Patient 1 remained symptomatic after slow pathway modification for common AV nodal re-entry tachycardia. Patient 2 was misdiagnosed as having junctional bigeminy and developed heart failure with reduced left ventricle ejection fraction. Patient 3 was misdiagnosed as having atrial fibrillation (AF) and underwent two pulmonary vein isolation (PVI) procedures, without clinical improvement. All patients underwent an electrophysiological study (EPS) during which DF AV nodal response was confirmed and treated with radiofrequency ablation of the slow pathway. All patients were afterwards relieved from their symptoms. Discussion and conclusion: DF AV nodal response is a rare electrophysiological phenomenon which can be clinically misinterpreted as other common arrhythmias, such as premature junctional bigeminy or AF and can contribute to tachycardia induced cardiomyopathy. Typical electrocardiogram- and EPS-derived findings can be indicative for DF AV nodal response. DF AV nodal response can be easily and effectively treated by slow pathway ablation.