MR study of postnatal development of myocardial structure and left ventricular function

Area of Science:

• Cardiovascular research
• Developmental biology
• Medical imaging

Background:

• Understanding postnatal cardiac development is crucial for identifying congenital heart abnormalities.
• Early life cardiac function and myocardial structure undergo significant changes.
• Non-invasive imaging techniques are essential for studying these developmental processes.

Purpose of the Study:

• To investigate the postnatal development of left ventricular (LV) cardiac function and myocardium structure in Sprague-Dawley rats.
• To establish baseline imaging data for normal postnatal heart development.
• To assess the utility of cardiac MRI and diffusion tensor imaging (DTI) in characterizing these changes.

Main Methods:

• Cardiac magnetic resonance (MR) imaging and ex vivo diffusion tensor imaging (DTI) were performed on Sprague-Dawley rats at multiple postnatal time points (days 2, 4, 7, 14, 21, 28, and 56).
• Measurements included LV size, stroke volume, cardiac output, heart rate, and ejection fraction.
• DTI parameters such as fractional anisotropy, mean apparent diffusion coefficient, axial diffusivity, and radial diffusivity were analyzed to assess myocardial microstructure.

Main Results:

• Left ventricular size and cardiac output increased with age, while heart rate stabilized after day 14.
• Ejection fraction showed dynamic changes, increasing early, decreasing at day 7, and stabilizing by day 21.
• A double-helical myocardial structure was observed from day 2, with distinct patterns in DTI parameters reflecting hyperplasia and hypertrophy stages.

Conclusions:

• Cardiac MRI and DTI successfully documented postnatal heart development in rats.
• DTI findings correlate with the known stages of early postnatal cardiac growth (hyperplasia and hypertrophy).
• These results provide essential baseline data for studying developmental abnormalities and highlight DTI's capability in detecting microstructural myocardial changes.