Subclinical cardiac involvement in myotonic dystrophy manifesting as decreased myocardial Doppler velocities.

To assess subendocardial (long-axis) and mid-wall (short-axis) left ventricular (LV) function in patients with type 1 myotonic dystrophy (MD1), with no symptoms or clinical signs of heart disease, to investigate if they have subclinical cardiac involvement, 28 subjects (14 with MD1, and 14 age- and sex-matched normals) had conventional and tissue Doppler echocardiography. Myocardial velocities and timings to peak systolic contractions were measured. LV wall thickness, diameters, and ejection fraction were not different between the groups. 4/14 of the MD1 patients (29%) had global diastolic dysfunction. Both long-axis and short-axis systolic and early diastolic myocardial velocities were lower in patients with MD1, whereas time-to-peak myocardial contraction was longer; mean longitudinal systolic velocity was 5.5+/-1.7 cm/s in patients with MD1, compared with 7.8+/-1.3 cm/s in normal subjects (P<0.001) 10/14 of the patients (71%) had reduced longitudinal systolic function. Longitudinal systolic and diastolic velocities were inversely related to the duration of the QRS complex ( r=-0.86 and r=-0.63 respectively, both P<0.01), but they did not correlate with the CTG-repeat size. Patients with MD1 have subclinical cardiac impairment revealed by measurement of myocardial velocities using tissue Doppler echocardiography.