Pietro Delise, Aldo Bonso*, Leonardo Coro, Mauro Fantinel, Gianni Gasparini*, Antonio Raviele*.
Operative Units of Cardiology, Hospitals of Feltre and *Mestre, Italy
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The rationale of the pacemapping of the Koch’s triangle is to localize
the site of the fast pathway on the basis of the shortest St-H interval. Indeed, on stimulating the site where fast
pathway is present, a short St-H interval is recorded and, conversely, the greater the distance between the
mapping catheter and the anterograde conducting fast pathway the longer the St-H interval (Figs. 1 and 2 A-C).
Fig. 1: Schematic representation of the AV node and His bundle. Dual AV nodal pathways can
be recognized: fast pathway anteriorly located and slow pathway posteriorly located in front of the
coronary sinus (CS). A catheter is depicted stimulating in the anteroseptal (AS), midseptal (MS) and
posteroseptal (PS) regions. A second catheter is located in the His bundle region which records A
and H deflections. The shortest St-H interval is recorded when stimulating in the AS region, where
the fast pathway is located. The greater the distance between the mapping catheter and the
anterogradely conducting fast pathway, the longer the St-H interval. The longer St-H intervals
obtained when stimulating in the MS and PS areas are related to longer ST-A intervals, while AH
intervals are constant.
Fig. 2: Pacemapping of Koch's triangle. St-H interval is calculated stimulating in anteroseptal
(A), midseptal (B) and posteroseptal areas. The shortest St-H interval is recorded stimulating in the
anteroseptal area, where the anterogradely conducting fast pathway is located.
The triangle of Koch can be easily identified in the right anterior oblique view by using the apex of its virtual
three angles as reference points: the catheter positioned on the His bundle (which represents the apex of the
triangle), the proximal electrodes of the catheter introduced in the coronary sinus (which represents the apex
of the second angle of the triangle) and the atrial insertion of the tricuspid valve in the area surrounding the
ostium of the coronary sinus (identified on the basis of the electrophysiologic recordings by the mapping
catheter). At least three main regions of the Koch’s triangle should be mapped: the anteroseptal (AS), mid-septal
(MS) and posteroseptal (PS). Pacemapping is performed stimulating at a rate sligtly faster than the sinus one
(generally 100/min) with an output twice than diastolic threshold. The stimulation of the AS aspect of the triangle
of Koch is obtained by first placing the catheter where the highest His deflecion is recorded. By stimulating at
this site, the right ventricle or His bundle is generally captured. During continuous stimulation, the catheter is
then slowly withdrawn until the atrium is captured. The first 2-3 beats are used for calculations. During this
manouvre particular attention must be paied to avoid to stimulate the right septum posteriorly to the tendon of
Todaro. Consequently, when necessary, the manouvre must be repeated more than one time and the shortest
St-H should be chosen. Stimulation of the posterior aspect of the triangle of Koch is obtained by placing the
catheter in front of the ostium of the coronary sinus. Finally, the MS aspect of the triangle of Koch is stimulated
by placing the catheter in an intermediate position between AS and PS regions.
When stimulating from AS, MS and PS regions the St-H and AH intervals are calculated in the catheter positioned
on the His bundle.
Retrograde atrial activation (V-A) was recorded during ventricular pacing at 100/m in AS, MS and PS regions of
the Koch’s triangle in the same sites where pacemapping was performed.
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