Evaluation of the use of unipolar voltage amplitudes for detection of myocardial scar assessed by cardiac magnetic resonance imaging in heart failure patients

Fig 1. Study workflow. DE-CMR = delayed enhancement cardiac magnetic resonance imaging, EAM = electro-anatomic mapping, HF = heart failure.

Fig 2. A. Unipolar voltage (UnipV) distribution grouped according to DE-CMR defined scar extent (red) and compared with non-scar (blue). Dashed blue lines represent optimal thresholds: 8.3 mV for the endocardial measurements, and 7.6 mV for the epicardial measurements. The tops and bottoms of each "box" represent the 25th and 75th percentiles of the subgroups, respectively. Distances between the tops and bottoms of each box represent the interquartile ranges. The horizontal middle line in the box represents the median value. The whiskers (vertical lines) above and below each box are drawn from the ends of the interquartile ranges to the furthest observations within the whisker length. B. ROC curves for UnipV in identifying DE-CMR defined segments with any-scar (1–100% scar) and segments with several severities of scar (>25%, >50%, and >75%). Note that the endocardial measurements are superior in detecting scar, independent of scar burden, although only segments with >75% scar can be properly detected (AUC 0.76) using endocardial measurements.

Fig 3. Endocardial and epicardial box-plots of the unipolar voltage (UnipV) distribution per individual patient in non-scar (0%, blue) and any-scar (1–100%, red). P-values per individual patient are based on Mann-Whitney U tests; a p-value of ≤0.05 is considered as significant (*), while p-values >0.05 are regarded as not significant (NS). Note that significantly lower UnipV in scar compared to non-scar were only present in the minority of patients. Patients without scar on delayed enhancement cardiac magnetic resonance imaging (DE-CMR) are plotted on the right. Dashed blue lines represent optimal voltage thresholds. Note the large variation in voltages from non-scar between individual patients.

Fig 4. Representative patient (endocardial no.26) from without scar on delayed enhancement cardiac magnetic resonance imaging (DE-CMR). All unipolar electrograms were in non-scar, but still low unipolar voltage amplitudes (UnipV) were measured, demonstrating a lack of correlation between normal UnipV and non-scar. EAM = electro-anatomic mapping, LAO = left anterior oblique, RAO = right anterior oblique.

Fig 5. Representative patient (epicardial no.19) with extensive scar on delayed enhancement cardiac magnetic resonance imaging (DE-CMR). All unipolar electrograms were in extensive scar, but normal unipolar voltage amplitudes (UnipV) were still present demonstrating a lack of correlation between low UnipV and scar. EAM = electro-anatomic mapping, LAO = left anterior oblique, RAO = right anterior oblique.