Controlling reentrant arrhythmias in cardiac tissue

Ekaterina Zhuchkova* and Harald Engel

Institut für Theoretische Physik, Technische Universität zu Berlin, Berlin, Germany

*ekaterina@physik.tu-berlin.de

Ventricular tachyarrhythmias (tachycardias and fibrillations) caused by rotating waves (reentry) in the heart can lead to highly rapid and uncoordinated contractions, resulting in dysfunction of the blood pumping by the heart. For terminating these pathologies devices surgically implanted in high-risk cardiac patients are used. Modern implantable cardioverter defibrillators possess pacing, cardioversion and defibrillation capabilities, and in the case of ventricular tachycardia may try to pace the heart faster than its intrinsic rate in order to break it before the latter proceeds to fibrillation. This local forcing is known as anti-tachycardia pacing (ATP). It locally applies one or more series of low-power stimuli to return a racing heart to its normal rhythm. So far, ATP is the only low-energy therapy for both types of ventricular tachyarrhythmias and it would be desirable since it prevents destruction of the cardiac and surrounding tissues and adverse side effects.

However, we have systematically analyzed and have shown that the low-voltage non-feedback local forcing is not a robust method to terminate reentrant arrhythmias. Even in homogeneous isotropic tissue simulated by a simplified ionic model it was found that success/failure of the “point” pacing strongly depends on the type of reentry, location of the electrode, phase of stimuli during the rotation period, stimulation frequency and waveform and the size of tissue. Along with elimination of spiral waves, shift of spiral cores closer to unexcitable boundaries or no effect, the local forcing may also cause spiral-wave turbulence (fibrillation) and prolong existence of an otherwise self-terminating single spiral wave (reentrant tachycardia).

Finally we propose feedback-mediated control of reentry as an alternative realistic low-energy defibrillation strategy.