Download A. Septal B. Anterior C. Free Wall

Radiological and Electrocardiographic Characterization of Right Ventricular
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Outflowtract Pacing. J.C. Balt , N.M. van Hemel , H.J.J. Wellens and W.G. de Voogt
1
Department of Cardiology, St. Antonius Hospital, Nieuwegein, The Netherlands
3 Cardiovascular Research Institute Maastricht, Maastricht, The Netherlands
2
Utrecht University, Heart Lung Center Utrecht, Utrecht, The Netehrlands
4 Department of Cardiology, St Lucas Andreas Hospital, Amsterdam, The Netherlands
Background
A. Septal
B. Anterior
The RVOT is used as an alternative pacing site, but its
superiority to the RV-apex remains to be established. The
aim of the present study is to characterize the RVOT in
terms of fluoroscopic and electrocardiographic
parameters.
C. Free Wall
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Methods
143 patients underwent pacemaker implantation in the
RVOT. Lead position was determined by fluoroscopy. The
RVOT was divided into four areas: Anterior, Posterior,
Septal and Free Wall (figures 1 and 2). During ventricular
pacing, QRS-duration, configuration and amplitude was
determined.
Figure 1. Fluoroscopy images after lead implantation. LAO 45° projection. Septal placement is assumed when the RV-lead points
rightward (A). If the leads points upward, the lead is assumed to be in the Anterior position (B). Free wall placement is assumed
when the RV-lead points leftward (towards the sternum) (B).
Figure 2. Cross-section of the chest, adapted with
permission from Mond et al. The different areas of the
RVOT are schematically outlined.
Results
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Figures 4 and 5. QRS vector and morphology in lead I. A QRScomplex with an amplitude of  0.05 mV is defined as positive.
Regarding QRS vector, differences between pacing sites are
statistically significant (2-test, p<0.05). Regarding QRSmorphology, differences between pacing sites are not
statistically significant (2-test, p=0.07).
Figure 3.
The Transitional Zone
Index (TZI) is used to
quantify precordial
R-transition.
#: p < 0.05 compared with septal. *: p < 0.001 compared with septal
The TZI is defined as the abscissa of the point
at which the R-wave amplitude and S-wave
amplitude are equal. Adated from Shima et al.
Conclusions
We conclude that (1) in patients in whom lead implantation in the RVOT
was performed, in 1/3 of patients, a septal position was achieved and (2)
the paced QRS complexes resulting from different stimulation sites
within the RVOT differ significantly. However, the overlap of QRS patterns
is considerable. Therefore, we could not define clear cut-off point or
devise flow-charts to match ECG and pacing site.