Differential sequential septal pacing: a simple maneuver to differentiate nodal versus extranodal ventriculoatrial conduction.

BACKGROUND

Distinguishing retrograde nodal conduction from extranodal conduction using an accessory pathway (AP) can sometimes be challenging.

OBJECTIVE

To distinguish nodal from extranodal ventriculoatrial (VA) conduction regardless of AP location by proposing a simple method. This method is based on the principle that moving the pacing site progressively from the basal region toward the entrance of the His-Purkinje system should shorten VA time for nodal but not for AP conduction.

METHODS

Sixty-seven patients with supraventricular tachycardia were prospectively recruited. Quadripolar catheters were placed at the right ventricular (RV) apex, right atrium, and His and coronary sinus. The RV septum was sequentially paced at 4 sites: (1) basal, (2) high midventricle, (3) low midventricle, and (4) apex at a cycle length 100 ms shorter than the resting cycle length. The stimulus-to-atrial (SA) interval was measured by using the proximal coronary sinus atrial electrogram.

RESULTS

Group 1 (n = 33) had nodal VA conduction; all patients had typical atrioventricular nodal reentrant tachycardia. Group 2 (n = 34) had extranodal VA conduction via an AP: 19 left-sided, 6 right-sided, and 9 posteroseptal. In group 1, the SA interval decreased significantly as pacing site moved closer toward the apex (site 1: 166 ± 35 ms, site 2: 153 ± 32 ms, site 3: 149 ± 32 ms, site 4: 154 ± 33 ms, P < .001, respectively, at sites 2-4 compared with site 1). In contrast, in group 2, the SA interval increased significantly toward the apex (site 1: 149 ± 45 ms, site 2: 158 ± 43 ms, site 3: 161 ± 43 ms, and site 4: 163 ± 40 ms, P < .001, respectively, at sites 2-4 compared with site 1). The SA interval at the high midventricular site (site 2) - SA interval at the base (site 1) ≤ 0 ms for nodal and > 0 ms for extranodal conduction had optimal sensitivity and specificity (nodal: selectivity = 97.0% and specificity = 85.3%; extranodal: selectivity = 85.3% and specificity = 97.0%).

CONCLUSIONS

Differential sequential pacing of the RV septum reliably distinguishes retrograde atrioventricular nodal conduction from AP conduction.