Published Online
on November 1, 2004

A more recent version of this article appeared on November 16, 2004

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Submitted on February 6, 2004
Revised on June 8, 2004
Accepted on June 10, 2004

Value of Noncontact Mapping for Identifying Left Ventricular Scar in an Ovine Model

Aravinda Thiagalingam FRACP, Elisabeth M. Wallace BSc, Craig R. Campbell BSc(Hons), Anita C. Boyd BMedSci(Hons), Vicki E. Eipper , Karen Byth PhD, David L. Ross FRACP, and Pramesh Kovoor PhD^*

From the Cardiology Department, Westmead Hospital, Westmead, Sydney, Australia.

^* To whom correspondence should be addressed. E-mail: kovoor{at}westgate.wh.usyd.edu.au.

Background--We assessed the hypothesis that "virtual electrograms" from a noncontact mapping system (EnSite 3000) could be used to localize myocardial scar.

Methods and Results--Myocardial infarctions were induced in sheep by inflating an angioplasty balloon in the left anterior descending coronary artery for 3 hours. Scar mapping was performed on 8 sheep without inducible ventricular tachycardia by use of the noncontact mapping system and a 256-channel contact mapping system. Transmural mapping needles were inserted into myocardial regions that were (1) scarred, (2) peripheral to the scar, and (3) distant from the scar. Unipolar electrograms were exported from both systems and analyzed on a personal computer workstation. The percentage of myocardial scarring at each needle site was assessed histologically. Pearson’s correlation was used to assess the degree of association between various electrogram characteristics and the presence of myocardial scarring. The only noncontact electrogram characteristic that showed any association with the presence of myocardial scarring was the negative slope duration (contact, r=0.62, P<0.001; noncontact, r=0.23, P=0.004). The other electrogram characteristics studied were electrogram maximal deflection (contact, r=0.38, P<0.001; noncontact, r=0.03, P=0.75) and minimal slope (contact, r=0.42, P<0.001; noncontact, r=0.05, P=0.54).

Conclusions--Noncontact electrograms do not reliably identify ventricular scar. Alternative strategies such as importing computed tomography images into the geometry should be used when scar localization is important.

Key words: electrophysiology • mapping • ablation • myocardial infarction • arrhythmia

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