Cardiac mechano-electric coupling: a role in regulating normal function of the heart?: Figure 1

This editorial refers to ‘Synchronization of repolarization by mechano-electrical coupling in the porcine heart’ by T. Opthof et al ., doi:10.1093/cvr/cvv140. At the most basic level, the heart is an electrically controlled pump. As such, our attention tends to focus on the feed-forward mechanisms by which cardiac excitation, occurring through co-ordinated ion channel activity, leads to the calcium signal necessary for contraction. Yet, it is becoming clear that the heart is intrinsically regulated, including feedback from its mechanical state to ion channel function, electrical conduction, and calcium–myofilament interactions. This essential aspect of intra-cardiac regulation, originally termed Mechano-Electric Feedback, is now more generally known as Mechano-Electric Coupling (MEC).1MEC might seem to be an evolutionary quirk or physiological epiphenomenon. It is now understood, however, to be important in numerous cardiac diseases, for instance contributing to the electrophysiological effects of non-uniform contraction, the reduced arrhythmia threshold accompanying atrial or ventricular enlargement, and the impact of pulmonary vein loading on atrial fibrillation.2 Yet this says nothing about its importance in the healthy heart. Does MEC play a role in regulating normal cardiac function?The first evidence that MEC may be important for cardiac auto-regulation came 100 years ago, with Francis Arthur Bainbridge's observation that right-atrial distension in anaesthetized dogs results in an acute increase in heart rate. …