A 36-year-old woman, gravida 2 para 1, at 30 weeks gestation comes to the office for a prenatal visit. The patient has noticed some ankle swelling at the end of the day that is relieved with elevating her legs, but she has no other concerns. The pregnancy has been uncomplicated, and her only medications are a prenatal vitamin and iron supplement. The patient has no chronic medical conditions. She does not use tobacco or alcohol. Blood pressure is 118/78 mm Hg and pulse is 72/min. BMI is 30 kg/m². Fetal heart tones are normal. There is trace bilateral pedal edema to the shins. Physical examination is otherwise unremarkable. Urinalysis shows no protein. Compared to a nonpregnant state, which of the following cardiac changes are most likely to be found in this patient?

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11ec160b_3a80_97eb_9249_03c2b2fd6323_MD0001_00 During pregnancy, the increased metabolic demand required for fetal growth and development leads to multiple physiologic maternal adaptations, particularly cardiovascular changes. These changes both benefit the fetus and protect the patient against the risks of delivery (eg, hemorrhage). The driving force behind maternal hemodynamic changes is a significant decrease in systemic vascular resistance (SVR) due to both increased release of peripheral vasodilators (eg, nitric oxide, prostacyclin) and formation of a high-flow, low-resistance uteroplacental circuit (increases blood flow to the placenta and fetus). There is also significantly increased blood volume. These changes have the following effects on cardiac preload and afterload: Both increased blood volume and decreased SVR (which allows blood to return to the heart more quickly and easily) contribute to increased cardiac venous return (ie, increased preload). The marked reduction in SVR leads to decreased blood pressure (ie, reduced afterload). Both the increased preload and decreased afterload facilitate an increase in stroke volume, which is the primary cause of increased cardiac output (ie, stroke volume x heart rate) in early pregnancy. As the pregnancy progresses, the stroke volume decreases but maternal heart rate gradually increases, contributing to an overall increase in cardiac output of up to 30%-50% during pregnancy. Educational objective: During pregnancy, increased metabolic demands lead to multiple physiologic cardiovascular changes, including decreased systemic vascular resistance and increased blood volume. These changes cause increased preload and decreased afterload, resulting in increased stroke volume and cardiac output. Heart rate also gradually increases during pregnancy and is the major contributor to increased cardiac output in late pregnancy. __________ References: Cardiovascular physiology of pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/25223771)

A 36-Year-Old Woman, Gravida 2 Para 1, at 30 Weeks