Scar voltage threshold determination using ex vivo magnetic resonance imaging integration in a porcine infarct model: Influence of interelectrode distances and three-dimensional spatial effects of scar

Roderick Tung; Steve Kim; Daigo Yagishita; Marmar Vaseghi; Daniel B Ennis; Sarah Ouadah; Olujimi A Ajijola; Jason S Bradfield; Srijoy Mahapatra; Paul Finn; Kalyanam Shivkumar

doi:10.1016/j.hrthm.2016.07.003

Scar voltage threshold determination using ex vivo magnetic resonance imaging integration in a porcine infarct model: Influence of interelectrode distances and three-dimensional spatial effects of scar

Heart Rhythm. 2016 Oct;13(10):1993-2002. doi: 10.1016/j.hrthm.2016.07.003. Epub 2016 Jul 5.

Authors

Affiliations

¹ UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, California. Electronic address: rodericktung@uchicago.edu.
² St. Jude Medical, Minneapolis, Minnesota.
³ UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, California.
⁴ Department of Radiological Sciences, University of California, Los Angeles, California,; Department of Bioengineering, University of California, Los Angeles, California.
⁵ Department of Bioengineering, University of California, Los Angeles, California.
⁶ Department of Radiological Sciences, University of California, Los Angeles, California.
⁷ UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, California; Department of Radiological Sciences, University of California, Los Angeles, California,; Department of Bioengineering, University of California, Los Angeles, California.

PMID: 27392944
DOI: 10.1016/j.hrthm.2016.07.003

Abstract

Background: Studies analyzing optimal voltage thresholds for scar detection with electroanatomic mapping frequently lack a gold standard for comparison.

Objective: The purpose of this study was to use a porcine infarct model with ex vivo magnetic resonance imaging (MRI) integration to characterize the relationship between interelectrode spacing and bipolar voltage thresholds and examine the influence of 3-dimensional scar on unipolar voltages.

Methods: Thirty-two combined endocardial-epicardial electroanatomic maps were created in 8 postinfarct porcine subjects (bipolar 2-mm, 5-mm, and 8-mm interelectrode spacing and unipolar) for comparison with ex vivo MRI. Two thresholds were compared: (1) 95% normal distribution and (2) best fit to MRI. Direct electrogram analysis was performed in regions across from MRI-defined scar and adjacent to scar border zone.

Results: A linear increase in optimal thresholds was observed with wider bipole spacing. The 95% thresholds for scar were lower than MRI-matched thresholds with moderate sensitivity for nontransmural scar (54% endo, 63% epi). Unipolar endocardial scar area exceeded MRI-defined scar, resulting in mismatched false scar in 5 of 8 (63%). Endocardial and epicardial unipolar voltages were lower than normal in regions adjacent and across from scar.

Conclusion: Variations in interelectrode spacing necessitate tailored bipolar voltage thresholds to optimize scar detection. Statistical 95% thresholds appear to be conservative and not fully sensitive for the detection of scar defined by high-resolution ex vivo MRI. In the presence of endocardial scar, unipolar mapping to quantitatively characterize epicardial scar may be overly sensitive due to 3-dimensional spatial averaging.

Keywords: Bipolar; Electroanatomic mapping; Infarct; Magnetic resonance imaging; Porcine; Unipolar; Ventricular scar; Voltage threshold.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Cicatrix / diagnostic imaging*
Cicatrix / etiology
Cicatrix / physiopathology
Disease Models, Animal
Electrophysiologic Techniques, Cardiac / methods*
Imaging, Three-Dimensional / methods
Magnetic Resonance Imaging / methods*
Myocardial Infarction / complications*
Myocardium / pathology*
Swine
Tachycardia, Ventricular / etiology
Tachycardia, Ventricular / prevention & control