Mechanical and Electrophysiological Substrate for Recurrent Atrial Flutter Detected by Right Atrial Speckle Tracking Echocardiography and Electroanatomic Mapping in Myotonic Dystrophy Type 1

A 48-year-old patient with myotonic dystrophy (MD) type 1, recurrent typical atrial flutter (AF), and otherwise unremarkable history was hospitalized for an electrophysiological study. The diagnosis of MD type 1 had been made 25 years earlier and was based on typical clinical features and confirmation by genetic analysis. The ECG pattern of AF was characterized by negative waves in the inferior leads and positive waves in V1, a cycle length of 280 milliseconds, and 2:1 atrioventricular conduction. At the time of the study, the patient was asymptomatic and showed normal findings at the cardiac physical examination, ECG, and standard echocardiography. Preablation ECG showed sinus rhythm at 60 bpm with a normal PR interval (180 milliseconds), regular QRS duration and morphology, and normal ventricular repolarization. Average septal-lateral mitral annulus velocities (s′, 9.5 cm/s; e′, 10.3 cm/s; a′, 7.4 cm/s), the E/e′ ratio (7.3), and left ventricular global longitudinal and circumferential strain (−21.5% and −23.2%, respectively) were all normal, as well as right ventricular systolic function (tricuspid annulus systolic excursion and peak systolic velocity, 25 mm and 18.5 cm/s, respectively). Analysis of longitudinal right atrial deformation by speckle tracking showed impaired strain mechanics in the inferior segment of the atrial …