Show notes
CardioNerd Amit Goyal, cardioobstetrics series co-chair Dr. Natalie Stokes, and episode lead Dr. Daniela Crousillat discuss normal cardiovascular physiology in pregnancy with Dr. Garima Sharma, Director of the Cardio-Obstetrics Program and the Ciccarone Center ‘s Associate Director of Preventive Cardiology Education in the Division of Cardiology. They discuss physiology from conception to post-partum, including the key hemodynamic, hormonal, and structural changes associated with normal pregnancy in the absence of pre-existing cardiovascular disease. Series introduction by Dr. Sharonne N. Hayes.
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Abstract • Pearls • Quotables • Notes • References • Guest Profiles • Production Team
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Episode Abstract
Join us for a thrilling ride with our expert as we dive into the normal cardiovascular physiology of women through pregnancy. We discuss physiology from conception to post-partum, including the key hemodynamic, hormonal, and structural changes associated with normal pregnancy in the absence of pre-existing cardiovascular disease. We discuss how these physiologic changes manifest the history, physical exam, and key diagnostic testing (ECG, laboratory markers, and echocardiogram). Armed with these basic principles, we join Dr. Garima Sharma on patient consults to learn about potential signs and symptoms of cardiovascular disease in pregnancy and appropriate ways to risk stratify women with pre-existing or acquired cardiovascular disease in pregnancy. Importantly, we delve deeper into the importance of the growing field of cardio-obstetrics in the context of rising maternal mortality and staggering racial disparities in the care and outcomes of women in pregnancy.
Pearls
In normal pregnancy, plasma volume increases by up to 50% resulting in an adaptive decrease in systemic vascular resistance (SVR) by 25% and an increase in cardiac output (CO) by ~50% by the 2nd trimester.Brisk carotid upstrokes, an S3 gallop, soft systolic ejection murmurs, pedal edema, and a mildly elevated jugular venous pressure (JVP) can all be normal physiologic findings in pregnancy in the context of no other signs/symptoms to suggest heart failure.A normal NT-proBNP among pregnant patients with pre-existing cardiovascular disease has a high negative predictive value for predicting adverse maternal cardiac outcomes.Pregnancy risk predictor tools (mWHO, CARPREG II, ZAHARA) are a crucial component of pre-conception counseling to help predict which women with existing cardiovascular disease are at highest risk for adverse maternal outcomes.The U.S. ranks 1st in the world for maternal mortality among developed nations and cardiovascular disease is the leading cause of pregnancy-associated mortality in the U.S. Non-Hispanic Black are 3.5 times more likely to die from pregnancy as compared to White women.
Quotables
“You don’t know where you are going until you know where you have been” - Dr. Garima Sharma on the importance of holding on to hope when encountering difficult situations in our training and career pathways.
“Do not fear the pregnant patient! The pregnant patient is going through a normal physiologic process in her life, and the more we are familiar with it, the less we fear it” - Dr. Garima Sharma on taking care of pregnant patients.
“If you are going to move the needle on maternal mortality and in making a long-term sustainable change in the lives of these women, you have to focus on prevention” - Dr. Garima Sharma on the importance of prevention in reducing maternal mortality.
“Be empathetic. For most women, pregnancy is a normal state. These women need your help!” - Dr. Garima Sharma on the importance of taking care of women in pregnancy.
Show notes
What are the normal hemodynamic changes that occur in pregnancy? Let’s talk physiology!
Pregnancy, nature’s most grueling stress test, is a dynamic process associated with significant hemodynamic and physiological adaptations in the cardiovascular system which have evolved to support the needs of a developing fetus.Predictable and expected hemodynamic changes occur during pregnancy for all women. Healthy women can adapt without significant consequences, whereas in women with underlying cardiac conditions, these changes may unmask a previously unknown condition or exacerbate existing abnormal hemodynamics.
Adaptive Physiologic Changes of the Cardiovascular System (1)
Source: Me Mehta LS, Warnes CA, Bradley E et al. Cardiovascular Considerations in Caring for Pregnant Patients: A Scientific Statement From the American Heart Association. Circulation 2020;141:e884-e903. Supplemental Table 1: Physiologic Changes Throughout Normal Pregnancy Compared to Pre Pregnancy State (2)
Plasma volumeIncreases by about 50-75% by the 2nd trimester of pregnancy to meet greater circulatory needs of placenta and maternal organsErythropoietin causes an increase in red cell mass by 20-30% leading to relative dilution and “physiologic” anemia of pregnancy
Systemic vascular resistance (SVR)To accommodate the increase in plasma volume, vasodilatation and vascular remodeling occur with a reduction in SVRSVR decreases starting early in the 1st trimester and falls by 25-30% in the 2nd trimester potentiated by progesterone and estrogen-induced vasodilatationDecreased SVR results in activation of the renal angiotensin-aldosterone system (RAAS) to maintain blood pressure and salt/water balance
Cardiac output (CO)Increases by ~ 50% during pregnancy (up to 75% for a twin gestation!), starting at 5 weeks of gestation, and peaks at about 18-24 weeks in the 2nd trimesterCO (stroke volume (SV) x heart rate (HR)) increases predominantly via an increase in SV, but also an increase in HR by about 10-15 bpm by the 3rd trimester due to activation of the sympathetic system
There are a multitude of other physiological changes that allow our cardiovascular systems to adapt to the normal hemodynamics of pregnancy.
Respiratory: Increase in metabolic rate & O2 consumption, minute ventilation and tidal volume resulting in a mild compensatory respiratory alkalosis.Renal: Systemic vasodilation results in 50% increase in renal plasma flow and glomerular filtration rate (GFR), activation of RAAS to maintain fluid and electrolyte balance.Hematologic: “Physiologic” anemia of pregnancy due to increase in plasma volume red blood cell mass, increased production of coagulation factors with promotion of a pro-thrombotic state.Endocrine: Increase in total cholesterol, triglycerides, LDL (by 50%) and decrease in HDL; mild insulin resistance.
Labor & Delivery and Post-Partum Period:
Labor:
The maximum CO associated with pregnancy occurs during labor and immediately post-partum.Repeated Valsalva maneuvers with a doubling of CO (up to 10L!) in active laborEach uterine contraction displaces about 300-500 mL of blood back into the maternal systemic circulation
Post-partum:
Immediate: Caval decompression from evacuation of gravid uterus leads to marked increase in venous return (“auto transfusion”) back into the maternal systemic circulationTwo weeks post-partum: Maternal hemodynamics largely return to the pre-pregnancy state!
2. How are the normal physiological changes of pregnancy reflected in the physical exam and diagnostic cardiac testing? When should we worry?
Physical Exam (2)Heart rate: Increases by 10-15 bpm by 3rd trimester, mild sinus tachycardiaBlood pressure: Decrease of 10-15 mm Hg in both SBP and DBP, nadiring in 2nd trimester, improving to pre-pregnancy state in 3rd trimesterWeight: 25-35 lbs considered normal total gestational weight gain in patients who are normal weight pre-partumCardiac exam: Mildly elevated jugular venous pressure with more prominent x and y descents, brisk carotid upstrokes, soft, systolic ejection murmur (flow murmur), S3 gallop, mild pedal edema, varicose veins, mammary flow murmurECG:Mild sinus tachycardiaInfrequent premature atrial and ventricular atrial contractionsLeftward axis deviationQ waves in inferior (II, III, aVF) and/or lateral (V4-V6) leads due to heart’s spatial shift left, anterior, and in the transverse plane to accommodate the gravid uterusCardiac BiomarkersNT-proBNPIncrease up to two-fold in pregnancy but should remain within normal rangeImportant clinical utility in patients with pre-existing cardiac disease to serially assess changes throughout pregnancyBNP