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(Circulation. 1998;98:671-677.)
© 1998 American Heart Association, Inc.

Clinical Investigation and Reports

First Postpacing Interval Variability During Right Ventricular Stimulation

A Single Algorithm for the Differential Diagnosis of Regular Tachycardias

Angel Arenal, MD; Jesus Almendral, MD; Julian Villacastin, MD; Raimundo Morris, MD; Eduardo Castellanos, MD; ; Juan Luis Delcan, MD

From the Department of Cardiology, Hospital General Universitario Gregorio Marañon, Madrid, Spain.

Correspondence to Angel Arenal, MD, Laboratorio de Electrofisiologia, Departamento de Cardiologia, Hospital General Universitario Gregorio Marañon, C/Dr Esquerdo 46, 28007 Madrid, Spain.

Background—Failure to differentiate supraventricular from ventricular arrhythmias is the most frequent cause of inappropriate implantable cardioverter-defibrillator therapies. Although a sudden-onset criterion is available to differentiate sustained monomorphic ventricular tachycardias (SMVTs) and sinus tachycardias (STs), SMVTs arising during ST and SMVTs gradually accelerating above the cutoff rate can remain undetected. Regular paroxysmal atrial tachycardias (ATs) also can be undetected by onset and stability algorithms. We hypothesized that the first postpacing interval (FPPI) variability after overdrive right ventricular pacing may differentiate SMVTs from STs and ATs.

Methods and Results—FPPI variability was measured in 23 SMVTs (cycle length [CL] 366±50 ms [VT group]), 27 supraventricular tachycardias, 15 episodes of induced or simulated ATs (CL 376±29 ms [AT group]), and 12 exercise-related STs (CL 381±24 [ST group]). Sequences of trains of 5, 10, and 15 beats were delivered with a CL 40 ms shorter than the tachycardia CL. An FPPI absolute mean difference between consecutive trains of 5 and 10 beats (FPPI) 25 ms identified all VTs (mean difference 5±7 ms). In the AT group, the FPPI was >25 ms in all sequences (mean difference 129±60 ms, P<0.01). In the ST group, the FPPI was >50 ms in all STs (mean difference 118±47 ms, P<0.01).

Conclusions—FPPI variability may differentiate SMVT from AT and ST. This criterion is potentially useful in implantable devices that use a single ventricular lead.

Key Words: diagnosis • tachycardia • pacing