Background: The hearts of pregnant women and rodents undergo physiological hypertrophy with preserved function. Recently, we have demonstrated that the hearts of late pregnant (LP) rodents are more prone to ischemia reperfusion injury compared to non-pregnant (NP) rodents. Currently, measurements such as ejection fraction (EF) are not sensitive enough to determine subclinical myocardial dysfunction. However, speckle-tracking echocardiography (STE), a novel imaging tool, has been demonstrated to assess myocardial function with greater sensitivity. Tumor Necrosis Factor Receptor 2 (TNFR2), a membrane receptor that has been implicated in cardioprotection and has been demonstrated as marker for subclinical myocardial dysfunction in patients. Thus, we hypothesized that global circumferential strain (GCS) measured by STE can detect subclinical myocardial dysfunction in pregnancy that is associated with a decrease in TNFR2 in rats.
Methods: LP (20 days pregnant) and NP female Sprague-Dawley rats were used for the study (n=14). Left ventricular EF (LVEF, %), fractional shortening (FS, %), heart rate (HR, bpm), and GCS (%) were obtained using echocardiography (Visualsonics, Vevo 2100) (n=7/group). GCS was obtained with STE and was measured in triplicates. Total ventricular weight (VW) was recorded and LV was isolated to measure LV hypertrophy (LV/VW) (n=6/group). TNFR2 expression was measured using qPCR.
Results: LP rats showed slightly reduced but insignificant LVEF (LP: 67.65+/-1.41% vs. NP: 71.35+/-1.52%, P=0.10) and FS (39.07+/-0.90 % vs. 42.643+/-1.76 %, P=0.09) compared to NP rats. Additionally, no difference in HR between LP and NP rats were found (352.50+/-16.36 bpm vs. 333.75+/-4.78 bpm, respectively, p=0.314).However, hearts from LP rats had evidence of hypertrophy evident by an increase in LV/VW compared to NP (0.57+/-0.03 g vs. 0.48+/-0.02 g). LP rats had a significantly reduced GCS compared to NP rats (-27.50+/-1.40 % vs. -34.375+/-1.95 %, p<0.01) and reduced TNFR2 expression compared to NP.
Conclusions: Our results demonstrate that late pregnancy is associated with a decrease in GCS with no significant change in EF and a decrease in TNFR2, which may be a subclinical marker for myocardial dysfunction.