Functional and Molecular Changes of the Maternal Heart During the Late Pregnancy: A Two-Dimensional Speckle-Tracking Echocardiography Study
Background: During pregnancy, the hearts of pregnant women undergo several changes that effect its structure and function, which is necessary for the progression of a successful pregnancy. Currently, many publications have shown highly variable reporting in the systolic function pregnant women when compared to non-pregnant (NP) controls. Here we investigated whether two-dimensional speckle tracking echocardiography (STE), a highly sensitive load independent modality that is intended to measure cardiac function, can detect changes in the myocardium in late pregnant (LP) female rats. Moreover, we believe that STE can detect subtle changes that may be attributed to hypertrophy process and/or subclinical myocardial dysfunction.
Methods: Adult female Sprague-Dawley rats were used in NP, LP, and post-partum (PP; day 3, 7, and 14) stages. The hearts and the left ventricles were isolated to measure LV hypertrophy and total RNA was isolated using the Trizol RNA isolation protocol. RNA was then reverse transcribed with a gene-specific primer. Standard western blot analysis was performed using in-vivo whole heart lysates. Transthoracic echocardiography was acquired to monitor cardiac function by conventional parameters (LVEF, FS, and heart rate) and with STE.
Results: As expected LP rats had significantly increased hypertrophy and this was reversed by day 14 after delivery. LP rats showed no statistically significant change in LVEF and FS compared to NP rats. LP rats had significantly reduced global circumferential and radial strain compared to NP rats. Changes were transient as both strain values were reversed by day 14 in the circumferential plane and after 1 day in the radial plane after delivery. Finally, Western Blot analysis showed that phosphorylated Akt/Akt protein levels were decreased 7 fold at the end of pregnancy compared to NP. Additionally, phosphorylated STAT3/STAT3 was also significantly lower ( 4 fold) at the end of pregnancy.
Conclusions: The hearts of LP rats have significantly different strain changes compared to NP when using STE. This study provides reference data on the normal range of maternal cardiac motion with STE and changes in LV systolic function during normal pregnancy. However, whether these changes are an adaptive response or are a response to sub-clinical myocardial dysfunction has yet to be elucidated. In the future, use of STE for early detection of pregnancy-associated cardiovascular complications.