RSNA: Cardiac MR should be performed in lateral position for pregnant women
CHICAGO--Positional changes affect cardiovascular performance, especially at later periods of gestation. Therefore, a cardiac MRI should be performed in the lateral position to correctly investigate the cardiac workload in pregnant women with congenital heart disease particularly in the second and third trimesters, based on a prospective study presented today at the 96th annual Radiological Society of North America (RSNA) conference.

There are physiological reasons for the effects of positioning on hemodynamic variables and cardiac dimensions, related to altered intra-abdominal and intra-thoracic pressures. According to the study’s presenter, Alexia Rossi, MD, from the department of cardiology at Erasmus University Medical Center in Rotterdam, the Netherlands, this problem is “especially evident” in pregnant women due to the additional aorto-caval compression by the enlarged uterus.

"While cardiac MR is considered the gold standard for assessing cardiac function in patients with congenital heart disease, but currently, there are very few studies that have evaluated affect of positioning on pregnant women," she said. Therefore, Rossi and her colleagues sought to investigate the effect of postural changes on cardiac dimensions and function during the second and third trimester of pregnancy using MRI.

The researchers enrolled 14 healthy pregnant women during the second trimester (week 20 of gestation; six patients) and third trimester of pregnancy (week 32 of gestation; eight patients), along with 10 volunteers who were not pregnant women with no history of cardiac disease underwent a cardiac MRI in supine and left lateral positions.

They compared heart rate, ejection fraction, end-diastolic volume, end-systolic volume, stroke volume and cardiac output in both positions. Lateral and supero-inferior left atrial diameters were measured at the end of ventricular systole on a four-chamber view. The researchers used a 1.5 MRI scanner (Signa Discovery 450, GE Healthcare).

Rossi reported that heart rate was 81 bpm in the supine position and it decreased to 74 in the left lateral position. The end-diastolic volume, ejection fraction, stroke volume and cardiac output increased significantly from supine position to left lateral position: 10 percent, 19 percent, 31 percent and 14 percent, respectively. The cardiac left atrium dimensions increased significantly from supine position to left lateral position.

However, the end-systolic volume did not change significantly between the two recumbent positions.

During the third trimester of pregnancy, the researchers found that the left ventricle cardiac output significantly increased between supine and left lateral position; the percentage of increment at 32 weeks was 24.3 percent. No changes between the two recumbent positions were present at 20 gestational weeks.

Conversely, in the women who were not pregnant, there were no significant differences found between supine and left lateral position.

Rossi acknowledged the limitations of their study, including its small sample size. Also, she noted that all the pregnant women were healthy, and therefore, the researchers cannot be certain that the results would translate to unhealthy pregnant women.

She concluded that positional changes affect cardiovascular performance, and the left lateral position should be preferred starting at 20 weeks of pregnancy. Rossi advocated for a larger randomized clinical trial to assess this positioning consideration in pregnant women.