Disclosed herein are systems and methods for assessing electrically active cell cultures. Optionally, the data can be collected using a microelectrode array (MEA). For example, electrically active cells, such as cardiomyocytes, are cultured such that they are in electrical communication with at least a portion of the electrodes of a well of the MEA. The assessments derived from the disclosed methods may be used to reduce the effects of confounding variables in data obtained from an electrically active cell culture. The methods may also be used to determine a quantitative measure of arrhythmia burden. The methods may also be used to decide if a particular culture or set of data is suitable for inclusion in scientific and characterization studies. Also disclosed is a method of finding the global conduction velocity of an electrically active cell culture.