Monophasic Action Potential Amplitude for Substrate Mapping.

While radiofrequency ablation has revolutionized the management of tachyarrhythmias, the rate of arrhythmia recurrence is a large drawback. Successful substrate identification is paramount to abolishing arrhythmia and bipolar voltage electrogram's narrow field of view can be further reduced for increased sensitivity. In this report, we perform cardiac mapping with monophasic action potential (MAP) amplitude. We hypothesize that MAP amplitude (MAPA) will provide more accurate infarct sizes than other mapping modalities via increased sensitivity to distinguish healthy myocardium from scar tissue. Using the left-coronary artery ligation Sprague Dawley rat model of ischemic heart failure, we investigate the accuracy of ventricular epicardial maps derived from MAPA, MAP duration to 90% repolarization (MAPD), unipolar voltage amplitude (UVA), and bipolar voltage amplitude (BVA) when compared to gold-standard histopathological measurement of infarct size. Numerical analysis reveals discrimination of healthy myocardium versus scar tissue using MAPD (p=0.0158) and UVA (p<0.001) (n=21). MAPA and BVA decreased between healthy and border tissue (p=0.0218, p=0.0015 respectively) and border and scar tissue (p=0.0037, 0.0094 respectively). Contrary to our hypothesis, BVA mapping performed most accurately regarding quantifying infarct size. MAPA mapping may have high spatial resolution for myocardial tissue characterization but was quantitatively less accurate than other mapping methods at determining infarct size. BVA mapping's superior utility has been reinforced, supporting its use in translational research and clinical EP labs. MAPA may hold potential value for precisely distinguishing healthy myocardium, border zone, and scar tissue in diseases of disseminated fibrosis such as atrial fibrillation.