A new way to control cardiac chaos

Ordinary heart contractions are triggered by regular waves of electric depolarization of the cardiac cellular membrane. If, however, some portions of heart tissue are electrically anomalous, high-frequency rotating spiral waves can arise and propagate, inducing the overall activity of the heart to become chaotic and perhaps deadly. The usual treatment is either to administer a massive electrical shock—defibrillation, up to 4000 volts and 15 amps—to disrupt the waves, or to deliver trains of low-amplitude pulses. The former treatment is very traumatic and the latter cannot terminate high-frequency waves. Alain Pumir and Valentin Krinsky of the CNRS Nonlinear Institute in Nice, France, and their colleagues try to undo the threat not by jolting the whole heart but by aiming countermeasures just at the spirals’ origins. Their scheme, called wave emission from heterogeneities (WEH), paces the heart using virtual electrodes. An electric field pulse creates virtual electrodes by altering the membrane potential of cardiac cells near conductivity anomalies. Changing the electric field affects different anomalies and thus changes the number and positions of the electrodes, which emit their own waves that can terminate the spirals. Operating at energies far below those needed for defibrillation, WEH can selectively target high-frequency rotating waves and thereby overcome the disadvantages of both current treatments. Initial simulations and experiments on heart tissue from rats were encouraging, and the method is now being tested at Cornell University and the Max Planck Institute in Göttingen, Germany. (A. Pumir et al., Phys. Rev. Lett., in press.)