129 Rev Esp Cardiol 2002;55(10):1093-7 1093 INTRODUCTION Myotonic muscular dystrophy is the most frequent type of muscular dystrophy in adults, with a prevalence of 1 in 8000. 1-3 It is an autosomal dominant hereditary familial disease characterized by unstable ampliation of the cytosine-thymine-guanine trinucleotide in the long arm of chromosome 19. 1,4 It affects the neuromuscular system and can also affect other systems. 1,3 Cardiac involvement is frequent and disturbances in the His-Purkinje conduction system predominate. 2,4,5 In post-mortem studies, fibrosis, fat infiltration, and atrophy of the conduction system are found. 6,7 Myocardial involvement is rare, although echocardiography shows disturbances in the ventricular diastolic function 8,9 and, occasionally, systolic function as well. 10 Atrial and ventricular arrhythmias are present in up to 50% of patients, with sinus bradycardia, atrioventricular block, atrial and ventricular premature beats, atrial fibrillation and flutter, and ventricular tachycardia being reported. 4,11 The frequency of sudden death varies in different series and is caused by complete atrioventricular block and ventricular tachycardia or fibrillation. Exceptionally, sustained ventricular tachycardia is the cardiac form of presentation of this disease 4 and the most likely trigger mechanism is bundle-branch re- entry, as demonstrated in recent publications. 2,13 PRESENTATION OF CLINICAL CASE A 37-year-old man, who had been diagnosed two years earlier as myotonic muscular dystrophy by a genetic study and had a family history of the disease (his mother, brother, and maternal uncles and cousins had died), was seen in the emergency service for chest pain, palpitations, diaphoresis, and dyspnea. The physical examination disclosed an arterial pressure of 120/80 mm Hg and heart rate of 110 beats/min. On auscultation, the heart sounds were arrhythmic and tachycardic, without murmurs. The pulmonary fields were well ventilated. Other typical findings of the B RIEF REPORTS Myotonic Dystrophy and Bundle-Branch Re-Entrant Tachycardia Carlos J. Ramírez, Diego A. Rodríguez, Víctor M. Velasco and Fernando Rosas Departamento de Electrofisiología y Marcapasos. Fundación Clínica A. Shaio. Bogotá. Colombia. Correspondence: Dr. C.J. Ramírez. Departamento de Electrofisiología y Marcapasos. Clínica A. Shaio. Diagonal 110, 53-67. Bogotá. Colombia. E-mail: electrofisio@shaio.com Received 17 October 2001. Accepted for publication 9 May 2002. We report the case of a 37-year-old man diagnosed with myotonic dystrophy who presented atrial fibrillation with high ventricular rate. While being treated with amiodarone, he suffered cardiac arrest. The electrophysiological study disclosed bundle-branch reentrant ventricular tachycardia and ventricular fibrillation. Catheter ablation of the right bundle branch was performed and a bicameral defibrillator was implanted. The mechanisms and treatment of arrhythmias in these patients are discussed. Key words: Dystrophy. Tachycardia. Re-entry. Ablation. Defibrillator. Full English text available at: www.revespcardiol.org Distrofia miotónica y taquicardia ventricular por reentrada rama-rama Presentamos el caso de un varón de 37 años con distrofia muscular miotónica que ingresó por fibrilación auricular con alta respuesta ventricular. Durante la administración de amiodarona presentó un episodio de muerte súbita intrahospitalaria. En el estudio electrofisiológico se evidenció una taquicardia ventricular por reentrada rama-rama y una fibrilación ventricular. Se realizó, con éxito, ablación mediante energía de radiofrecuencia de la rama derecha del haz de His y se implantó un cardiodesfibrilador bicameral. Se discuten los mecanismos y tratamiento de las arritmias en estos pacientes. Palabras clave: Distrofia. Taquicardia. Reentrada. Abla- ción. Desfibrilador. Document downloaded from http://www.revespcardiol.org, day 12/09/2017. This copy is for personal use. Any transmission of this document by any media or format is strictly prohibited.