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We would like to make a few comments on the interesting observations made by Drs.
Michaud and Morady. First, in our opinion, an easier detection of clear entrainment
is obtained with a pacing cycle length 20 to 40 ms shorter than the TCL. In addition,
based on our experience from 22 consecutive patients with atypical AVNRT and 36 consecutive
patients with ORT through a septal concealed accessory pathway, a PPI-TCL difference
<115 ms without correction for AV nodal delay would result in a decrease of sensitivity
for the diagnosis of the latter tachycardia mechanism (78% vs 100% with the appropriate
correction; Figure 1). Therefore, the corrected PPI-TCL interval permits the correct diagnosis of septal
ORT using a single parameter. Second, this simple maneuver would also rule out an
atrial tachycardia in patients with typical AVNRT if a V-A-V response is observed
after ventricular entrainment. Third, the technique is proposed as a simple, initial
maneuver through which a free-wall accessory pathway could be suggested using only
two right-sided catheters, thus avoiding the initial placement of a catheter in the
coronary sinus after induction of a long VA interval tachycardia. In fact, according
to our experience, even the highest corrected PPI-TCL value in ORT patients was out
of the range of values we observed in atypical AVNRT patients (135 ms). We greatly
appreciate the seminal contribution and the interest in our article shown by Drs.
Michaud and Morady.
Figure 1Scatterplot showing the individual values and mean ± SD of the postpacing interval–tachycardia
cycle length (PPI-TCL) difference (ms) without correction for AV nodal delay for patients with atypical atrioventricular nodal reentrant tachycardias (AVNRT)
and orthodromic reciprocating tachycardias (ORT) using a septal bypass.
We read with great interest the article by González-Torrecilla et al1 in the June 2006 issue of Heart Rhythm. This is an excellent refinement of the postpacing interval—tachycardia cycle length (PPI-TCL) and stimulus-atrial—ventriculoatrial (SA-VA) criteria we first proposed for differentiating septal orthodromic reciprocating tachycardia (ORT) from atypical atrioventricular nodal reentrant tachycardia (AVNRT).2 We would like to make a few comments. First, the authors report 5of 31 patients with septal ORT who had a PPI-TCL >115 ms (our original criteria), but they used right ventricular (RV) pacing cycle lengths 20 to 40 ms below the TCL.
