The correct answer is increasing the wavelength will terminate the tachycardia. This raises the concept of wavelength and the wavelength and its properties. The observation here is that the activation map shows a macro re-entrant arrhythmia in the left atrium with a scar in the posterior wall around which this activation wave revolves. The relationship between the wavelength, which is a product of the conduction velocity and the refractory period, and the path length is as follows. In order to sustain a re-entrant tachycardia, the path length has to be greater larger than the wavelength. If the path length is near to or shorter or larger than the path length, the wave head will bump into the wave tail and sustained re-entry will no longer be possible. In considering the answers, decreasing conduction velocity will reduce the wavelength of the tachycardia, and may slow the rate of the SVT, but will not necessarily create the circumstances for termination. Modulation of conduction velocity is, in fact, a therapeutic strategy, but most often involves creating bidirectional block in a re-entrant circuit for termination. Exaggerated dispersion of repolarization is a factor that predisposes to the generation of functional arrhythmias like polymorphic VT, and in some cases, ventricular fibrillation and atrial fibrillation. So again, not the best answer here. Increasing the wavelength to exceed the path length will not permit the arrhythmia to continue, that is, wave head will collide with wave tail, and the arrhythmia will no longer be sustainable. An increase in the refractory period will increase the wavelength, not the path length, and is a strategy to treat the arrhythmia, and may be associated in and of itself with a different type of arrhythmia functional re-entry. So again, the correct answer here is increasing the wavelength.

macro re-entrant tachycardia

left atrium

wavelength

refractory period

arrhythmia termination