Synonyms for Cardiograph (same or very similar meaning)
WordNet sense 1 (medical instrument that records electric currents associated with contractions of the heart):
electrocardiographWordNet sense 2 (a medical instrument that measures the mechanical force of cardiac contractions and the amount of blood passing through the heart during a specified period by measuring the recoil of the body as blood is pumped from the ventricles):
ballistocardiographFrom the ODE community, based on WordNetadd/edit