Cardiovascular Changes in Pregnancy

Key Points

Pregnancy causes several physiologic changes in the cardiovascular system.
Maternal cardiac output increases during the first and second trimesters.^1,2
An increase in heart rate contributes to most of the increase in cardiac output during the first trimester, whereas an increase in stroke volume contributes to most of the increase in cardiac output during the second trimester.²
There are structural changes to the heart that occur to accommodate the changes in cardiac physiology. These changes are reflected in certain physical exam findings.
Blood pressure (BP) and systemic vascular resistance (SVR) decrease during the first and second trimesters. BP goes back to prepregnancy values towards the end of the third trimester, but SVR remains approximately 20% below prepregnancy values at the end of pregnancy.^1,2

Introduction

Pregnancy involves complex physiological changes to adapt the body to carry a growing fetus. One of the most important systems affected by these physiological changes is the cardiovascular system.
The changes that occur through the first, second, and third trimesters are important for an anesthesiologist to know, as some of these hemodynamic changes affect anesthetic management.
This summary will cover the normal and abnormal changes of cardiovascular physiology in a pregnant patient.

Physiological Changes

Normal Changes

Higher blood volume: Estrogen raises renin levels and leads to sodium and water retention through the renin-angiotensin aldosterone system.³
Cardiac output (CO): Both heart rate and stroke volume increase throughout pregnancy. The initial increase in cardiac output in the first trimester is due to an increase in heart rate, whereas most of the increase in cardiac output in the second trimester is due to an increase in stroke volume.^1,2
The changes in CO, heart rate (HR), blood pressure (BP), and stroke volume (SV) in pregnancy are listed in Tables 1, 2, and 3.^1,2

Abbreviations: CO, cardiac output; HR, heart rate; BP, blood pressure; SV, stroke volume

Abbreviations: BP, blood pressure; SVR, systemic vascular resistance

Figure 1. Structural changes of the heart during normal pregnancy. Abbreviations: LA, left atrium; LV, left ventricle. Adapted from ArtFavor. Medical illustration of a human heart. Public Domain. Link

Normal and abnormal physical exam and electrocardiogram (ECG) changes are listed in Tables 4 and 5.^4-6

Abbreviations: ECG, electrocardiogram

Laboratory Testing

Plasma lipid concentration increase
Total serum cholesterol, triglycerides, LDL cholesterol concentrations all increase due to insulin resistance and increase in estrogen levels.⁷
B-type natriuretic peptide (BNP)⁸
- Normal pregnancy has double the nonpregnant levels of BNP.
- The BNP levels does not change between trimesters.
Cardiac enzymes
- Cardiac enzymes are not elevated above the upper limits of normal during normal pregnancy.⁹
- Troponin levels may be elevated in gestational hypertension or preeclampsia.¹⁰
- CK-MB levels can be elevated up 2-4 times due to the presence of these enzymes in uterus and placenta.11

Echocardiography Changes

• Echocardiographic changes during pregnancy are listed in Table 6.¹²

Indications for echocardiography in pregnant patients are listed in Table 7.¹²

References

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Fleming SM, O'Gorman T, Finn J, et al. Cardiac troponin I in pre-eclampsia and gestational hypertension. BJOG. 2000;107(11):1417-20. PubMed
Abramov Y, Abramov D, Abrahamov A, et al. Elevation of serum creatine phosphokinase and its MB isoenzyme during normal labor and early puerperium. Acta Obstet Gynecol Scand. 1996;75(3):255-20. PubMed
Afari HA, Davis EF, Sarma AA. Echocardiography for the Pregnant Heart. Curr Treat Options Cardiovasc Med. 2021;23(8):55. PubMed

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