Supraventricular tachycardia with QRS and cycle length alternans. What is the diagnosis?

Supraventricular tachycardia with QRS and cycle length alternans. What is the diagnosis?
Hellenic J Cardiol. 2019 Jan 22;:
Authors: Varvarousis D, Polytarchou K, Margos P, Psychari SN, Paravolidakis K, Tsoukalas D, Kotsakis A
PMID: 30682421 [PubMed - as supplied by publisher]

Source: Hellenic Journal of Cardiology - January 28, 2019 Category: Cardiology Tags: Hellenic J Cardiol Source Type: research