Electrophysiology study (EPS) tracings used in the determination of the corrected sinus node recovery time (SNRT)

This tracing is from a 76-year-old male with paroxysmal atrial fibrillation and recurrent near syncope associated with palpitations. Surface leads represented are I, II, III, V1, and V6. Intracardiac tracings shown are the high right atrium (HRA d), the proximal His bundle electrogram (HIS p), the mid His bundle electrogram (HIS m), the distal His bundle electrogram (HIS d), and the right ventricular apex (RVa d). High right atrial pacing at 400 milliseconds (150 beats per minute) is performed for 30 seconds. Upon termination of pacing, a sinus node recovery time of 2150 milliseconds is observed (arrow). The basal sinus cycle length was 1200 milliseconds, giving a corrected sinus node recovery time of 950 milliseconds, consistent with severe sinus node dysfunction. Note the significant secondary pause extending beyond the end of the tracing providing additional evidence of sinus node dysfunction.