Early Left Ventricular Structural Myocardial Alterations and Their Relationship with Functional and Electrical Properties of the Heart in Myotonic Dystrophy Type 1

Background: Conduction disturbances and arrhythmias characterize the cardiac feature of myotonic dystrophy type 1 (MD1), and a myocardial involvement has been suggested as part of the cardiac disease. The aim of the study was to investigate the role of novel ultrasonic techniques, such as integrated backscatter (IBS) and color Doppler myocardial imaging (CDMI), in the assessment of the subclinical functional and structural myocardial involvement in patients with MD1. Methods: Thirty-one patients with MD1 (MD1 group) without known heart failure were evaluated and compared with 31 healthy, age-matched controls. In all patients, 19 conventional and 28 new echocardiographic parameters (14 tissue Doppler, 10 CDMI, and 4 IBS indexes) were analyzed. Results: In regard to ultrastructural left ventricular (LV) properties, a significantly higher IBS echointensity was found at the septum level in the MD1 group, with a statistically significant correlation with MPI (myocardial performance index) (r = 0.34; P = .05) and PR interval duration (r = 0.40; P = .05). In regard to LV systolic function, the MD1 group showed an early alteration of systolic function compared with controls, evidenced by a significant higher MPI and lower peak strain, strain rate, and cyclic variation index (CVI). In regard to LV diastolic function, the MD1 group showed an early alteration of diastolic function compared with controls, evidenced by lower tissue Doppler imaging, E/A, and E/A strain rate, with a statistically significant inverse correlation to the muscular disability rating scale. On receiver operating characteristic curve analysis, MPI and CVI showed the highest discriminating ability to differentiate the hearts of patients with MD1 from healthy subjects. Conclusion: Highly sensitive ultrasonic techniques can detect early functional and structural alterations of the LV myocardium in patients with MD1. (J Am Soc Echocardiogr 2009; 22: 1173-9.