Myocardial integrated ultrasound backscatter in patients with Duchenne's progressive muscular dystrophy

Assessment of left ventricular regional function in affected and carrier dogs with Duchenne muscular dystrophy using speckle tracking echocardiography

Background

Two-dimensional speckle tracking echocardiography (STE) is a relatively new method to detect regional myocardial dysfunction. To assess left ventricular (LV) regional myocardial dysfunction using STE in Duchenne muscular dystrophy model dogs (CXMD_J) without overt clinical signs of heart failure.

Methods

Six affected dogs, 8 carrier dogs with CXMD_J, and 8 control dogs were used. Conventional echocardiography, systolic and diastolic function by Doppler echocardiography, tissue Doppler imaging (TDI), and strain indices using STE, were assessed and compared among the 3 groups.

Results

Significant differences were seen in body weight, transmitral E wave and E' wave derived from TDI among the 3 groups. Although no significant difference was observed in any global strain indices, in segmental analysis, the peak radial strain rate during early diastole in posterior segment at chordae the tendineae level showed significant differences among the 3 groups.

Conclusions

The myocardial strain rate by STE served to detect the impaired cardiac diastolic function in CXMD_J without any obvious LV dilation or clinical signs. The radial strain rate may be a useful parameter to detect early myocardial impairment in CXMD_J.

Circumferential strain analysis identifies strata of cardiomyopathy in Duchenne muscular dystrophy: a cardiac magnetic resonance tagging study

OBJECTIVES

This study sought to evaluate the natural history of occult cardiac dysfunction in Duchenne muscular dystrophy (DMD).

BACKGROUND

Duchenne muscular dystrophy is characterized by progressive cardiac dysfunction and myocardial fibrosis late in the disease process. We hypothesized that left ventricular myocardial peak circumferential strain (epsilon(cc)) would decrease in DMD before global systolic functional abnormalities regardless of age or ventricular ejection fraction (EF).

METHODS

We evaluated cardiac magnetic resonance image (MRI) data from 70 DMD patients and 16 aged-matched control subjects. Standard imaging data included steady-state free precession short-axis cine stack images, cine myocardial tagged images, and myocardial delayed enhancement (MDE) (an indicator of myocardial fibrosis) sequences. Analysis was performed with QMASS (Medis Medical Imaging Systems, Leiden, the Netherlands) and HARP (Diagnosoft, Palo Alto, California) software. The DMD patient data were subdivided by age (<10 or >10 years), EF (>55% or <55%), and the presence or absence of MDE.

RESULTS

The DMD patients with normal EF had reduced epsilon(cc) at an early age (<10 years) compared with control subjects (p < 0.01). The DMD patients age >10 years with normal EF had further decline in epsilon(cc) compared with younger DMD patients (p < 0.01). There was further decline in epsilon(cc) with age in patients with reduced EF (p < 0.01) without MDE. The oldest patients, with both reduced EF and positive MDE, exhibited the lowest epsilon(cc). None of the patients had ventricular hypertrophy.

CONCLUSIONS

Myocardial strain abnormalities are prevalent in young DMD patients despite normal EF, and these strain values continue to decline with advancing age. Strain analysis in combination with standard MRI and MDE imaging provides a means to stratify DMD cardiomyopathy.