The purpose of this article is to analyze a clinical case of pacemaker-mediated tachycardia. It can develop only in patients with dual-chamber or biventricular pacemakers and preserved ventriculoatrial conduction. The mechanism of pacemaker-mediated tachycardia is re-entry between pacemaker and conduction system. https://hollandscountryclothinges.shop/product-category/dog-collars/