Date Published: July 5, 2017
Publisher: Public Library of Science
Author(s): Uyên Châu Nguyên, Francesco Maffessanti, Masih Mafi-Rad, Giulio Conte, Stef Zeemering, François Regoli, Maria Luce Caputo, Antonius M. W. van Stipdonk, Sebastiaan C. A. M. Bekkers, Daniel Suerder, Tiziano Moccetti, Rolf Krause, Frits W. Prinzen, Kevin Vernooy, Angelo Auricchio, Vincenzo Lionetti.
Validation of voltage-based scar delineation has been limited to small populations using mainly endocardial measurements. The aim of this study is to compare unipolar voltage amplitudes (UnipV) with scar on delayed enhancement cardiac magnetic resonance imaging (DE-CMR).
Heart failure patients who underwent DE-CMR and electro-anatomic mapping were included. Thirty-three endocardial mapped patients and 27 epicardial mapped patients were investigated. UnipV were computed peak-to-peak. Electrograms were matched with scar extent of the corresponding DE-CMR segment using a 16-segment/slice model. Non-scar was defined as 0% scar, while scar was defined as 1–100% scar extent.
UnipVs were moderately lower in scar than in non-scar (endocardial 7.1 [4.6–10.6] vs. 10.3 [7.4–14.2] mV; epicardial 6.7 [3.6–10.5] vs. 7.8 [4.2–12.3] mV; both p<0.001). The correlation between UnipV and scar extent was moderate for endocardial (R = -0.33, p<0.001), and poor for epicardial measurements (R = -0.07, p<0.001). Endocardial UnipV predicted segments with >25%, >50% and >75% scar extent with AUCs of 0.72, 0.73 and 0.76, respectively, while epicardial UnipV were poor scar predictors, independent of scar burden (AUC = 0.47–0.56). UnipV in non-scar varied widely between patients (p<0.001) and were lower in scar compared to non-scar in only 9/22 (41%) endocardial mapped patients and 4/19 (21%) epicardial mapped patients with scar. UnipV are slightly lower in scar compared to non-scar. However, significant UnipV differences between and within patients and large overlap between non-scar and scar limits the reliability of accurate scar assessment, especially in epicardial measurements and in segments with less than 75% scar extent.
The measurement of voltage amplitudes to distinguish scar tissue from viable myocardium is widely employed in invasive cardiology and electrophysiology including ablation therapy, targeted delivery of biological therapy, and cardiac resynchronization therapy (CRT).[1–5] Low voltage amplitudes are considered to be associated with scar, while high voltage amplitudes are regarded as viable myocardium.
In the present study UnipV from either endocardial measurements or epicardial measurements were compared with DE-CMR defined scar in two large cohorts of heterogeneous HF patients, clinically representative for the patients undergoing EAM investigations. The main findings of this study are as follow: (1) UnipV in any-scar are moderately lower than in non-scar, but large overlap exists, particularly for epicardial measurements; (2) UnipV in any-scar were not significantly lower than non-scar in the majority of patients; (3) A large inter-patient variability in non-scar UnipV exists; (4) UnipV are inversely correlated with scar extent, but this was only moderate for endocardial and poor for epicardial measurements; and finally (5) only scar segments with >75% can be properly identified (AUC = 0.76) by endocardial UnipV.
UnipV in scar defined by DE-CMR are moderately lower than in non-scar, but large overlap in UnipV between non-scar and scar and high inter-patient variability exists, particularly in patients undergoing epicardial measurements and segments with lower scar extent. The only reasonably scar assessment can be expected when using endocardial UnipV measurements for the detection of segments with >75% scar. Based on the current results, the use of low UnipV for identification of myocardial scar should be done with caution.