An apparatus comprises a first implantable sensor produces a first electrical sensor signal representative of cardiac depolarization events of a heart of a subject, a second implantable sensor that produces a second electrical sensor signal representative of hemodynamic function of the heart, a signal analyzer circuit, and an arrhythmia discrimination circuit. The signal analyzer circuit detects an arrhythmic event from the first sensor signal and calculates hemodynamic stability in response to the arrhythmic event detection using the second sensor signal. The arrhythmia discrimination circuit selects, according to a calculated hemodynamic stability produced by the signal analyzer circuit, an arrhythmia discrimination algorithm from among a plurality of candidate arrhythmia discrimination algorithms that are implementable by the arrhythmia discrimination circuit, classifies the detected arrhythmia using the selected arrhythmia discrimination algorithm, and provides the arrhythmia classification to a user or process.