Abnormal QT intervals, long QT or short QT, have been epidemiologically linked with sudden cardiac death due to ventricular fibrillation (VF). Consequently, Food and Drug Administration (FDA) recommends testing all pharmacological agents for “QT toxicity” as a risk factor for cardiac toxicity. Such tests assess QT/QTc interval, which represents ventricular depolarization and repolarization. However, the current QT toxicity analysis does not account for the well-known anisotropy in cardiac tissue conductivity. Mines demonstrated in 1913 that cardiac wavelength λ determines inducibility of reentrant arrhythmia, where both repolarization time or action potential duration (APD) and conduction velocity (CV) determine λ=APDxCV. We seek to determine the role of anisotropic wavelength λ in inducibility of VF in explanted human left ventricular (LV) preparations in presence of parasympathetic and sympathetic stimulation.