EFFECT OF RECORDING SITE ON POSTPACING INTERVAL MEASUREMENT DURING CATHETER MAPPING AND ENTRAINMENT OF POSTINFARCTION VENTRICULAR-TACHYCARDIA

Postpacing Interval and VTCL. Introduction: During entrainment of reen trant ventricular tachycardia (VT), the difference between the postpac ing interval (PPI) and the VT cycle length (VTCL) measured at the paci ng site is an indication of the conduction time from the pacing site t o the reentry circuit, The difference is usually less than or equal to 30 msec at successful ablation sites, However, electrical noise durin g pacing sometimes obscures the electrograms recorded directly from th e pacing site, The objective of this study is to determine if the PPI- VTCL difference measured at the mapping catheter electrodes proximal t o the stimulating electrode accurately predicts the PPI-VTCL differenc e at the stimulating electrode. Methods and Results: Endocardial cathe ter mapping was performed in 26 patients with infarct-related VT, At 1 91 sites during 56 VTs, unipolar pacing from the distal electrode entr ained VT and electrograms recorded from the mapping catheter were disc ernable following pacing in both the bipolar recordings from the dista l electrode pair (BI 1-2) and the electrode pair 6 mm proximal to the distal electrode (BI 3-4), The PPI-VTCL difference at BI 1-2 correlate d well with that measured at BI 3-4 (r = 0.88, P = 0.001), A PPI-VTCL difference at BI 3-4 : 30 msec predicted a PPI-VTCL difference at BI 1 -2 less than or equal to 30 msec with a sensitivity of 95%, specificit y of 87 %, and predictive accuracy of 91 %. Conclusions: Measurement o f the PPI from electrodes proximal to the stimulating electrode is a r easonable alternative when the PPI cannot be assessed from the pacing electrode.