Roderick Tung1, Steve Kim2, Daigo Yagishita3, Marmar Vaseghi3, Daniel B Ennis4, Sarah Ouadah5, Olujimi A Ajijola3, Jason S Bradfield3, Srijoy Mahapatra2, Paul Finn6, Kalyanam Shivkumar7. 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.
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.
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.
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