Neth Heart J (2011) 19:305–306 DOI 10.1007/s12471-011-0126-0 RHYTHM PUZZLE - QUESTION A simple broad complex tachycardia? C. Liesting & M. J. M. Kofflard Published online: 19 May 2011 # Springer Media / Bohn Stafleu van Loghum 2011 A 74-year-old man was referred to our hospital with a 2-week history of progressive shortness of breath. The patient’s medical history reported hypothyroidism and depression, for which he was treated with levothyroxine and mianserine, respectively. Physical examination revealed that the patient was afebrile, blood pressure was 168/112 mmHg, pulse 150 beats/min and heart sounds were normal without murmurs. Pulmonary rales were present on auscultation. Laboratory tests were normal except for a raised creatinine of 123 μmol/l (normal <100 μmol/l). The chest X-ray C. Liesting : M. J. M. Kofflard (*) Department of Cardiology, Albert Schweitzer Hospital, P.O. Box 306, 3300 AH Dordrecht, the Netherlands e-mail: m.j.m.kofflard@asz.nl showed marked cardiomegaly and signs of venous pulmonary congestion. The ECG on admission showed a broad complex tachycardia (Fig. 1). Adenosine was administered intravenously without any effect. Subsequently the arrhythmia was ended after cardioversion with 10 Watt. The ECG after cardioversion is shown in Fig. 2. What is your diagnosis with respect to Fig. 1? Answer You will find the answer elsewhere in this issue. 306 Fig. 1 ECG on admission Fig. 2 ECG after cardioversion Neth Heart J (2011) 19:305–306