Abbreviation
PVC premature ventricular contraction
We wish to thank Dr. Anderson and colleagues for their thoughtful
comments about our findings and congratulate them for their own
contribution towards improved interpretation of complex intracardiac
electrograms in the outflow tract and left ventricular summit
regions1.
As our study2 was a retrospective review of
electroanatomic maps collected in clinical practice, intraprocedural
approaches to selecting ablation targets were not standardized across
operators. Our recommended approach to mapping outflow tract PVCs
suspected to be of epicardial left ventricular summit or deep
mid-myocardial origin involves mapping all 3 surrounding surfaces (right
ventricular endocardium, left ventricular endocardium, and coronary
sinus). We routinely incorporate both standard activation mapping and
Ripple visualization, as well as manual annotation of the earliest
bi-polar deflection regardless of whether it represents far-field or
consists of a multi-component signal, into the decision regarding the
initial site of ablation. We do not routinely perform empiric ablation
at an alternative site if PVC suppression is achieved. However, in cases
in which the putative site of origin is not reachable with a standard
ablation catheter (e.g., when the earliest signal is mapped to a narrow
coronary sinus branch), we perform ablation at the endocardial site(s)
anatomically closest to that site.
We agree with the assessment of Dr. Anderson and colleagues that deep
intramural foci may certainly be manifest as broad or multiple
endocardial breakout sites using Ripple visualization. We used strict
criteria, using frame-by-frame analysis, to define the earliest Ripple
signal: the earliest point at which 3 grouped simultaneous Ripple bars
appeared in late diastole. We believe that this definition minimizes the
contribution of noise to interpretation of the earliest Ripple signal
and increases the likelihood that any discrepant signal observed is
clinically relevant. For the purposes of this study, only the earliest
Ripple signal and earliest activation point were annotated, therefore we
are unable to report whether multiple Ripple breakout sites preceded the
earliest activation point in the cases included in this study.
We look forward to future discussions regarding optimizing
electroanatomic mapping techniques in challenging anatomic locations and
again wish to thank Dr. Anderson and colleagues for their contributions.
Funding: None
References:
Anderson RD, Bhaskaran A, Ha ACT, Nanthakumar K. Two Ripples in a
Pond: The Subtleties of Mapping Observations in Localizing PVC sites.
Journal of Electrophysiology. In Press.
Arps K, Barnett AS, Koontz JI, Pokorney SD, Jackson KP, Bahnson TD,
Piccini JP, Sun AY. Use of Ripple mapping to enhance localization and
ablation of outflow tract premature ventricular contractions. Journal
of Electrophysiology. In Press.