A rare case of myotonic dystrophy (MD) with congestive heart failure, assoc
iated with QT prolongation and torsade de pointes (TdP) is reported. A 53-y
ear-old woman was admitted to the hospital because of congestive heart fail
ure. Electrocardiograph (ECG) showed first-degree atrioventricular block an
d QT prolongation. During hospitalization, TdP appeared but returned to sin
us rhythm spontaneously. As the patient had quadriplegia, a myopathic face,
cataracts, diabetes mellitus, and an increased number of cytosine-thymine-
guanine (CTG) repeats (760 repeats), she was diagnosed as having MD. Electr
ocardiographic analysis of her family also revealed abnormal QT(U) prolonga
tion in her daughter and brother who both had MD, while ECG findings of oth
er family members without MD were normal. Thus, the presence of QT(U) prolo
ngation was associated with MD in this family.