Coronary Heart Disease During Pregnancy

Modern medical care has reduced maternal mortality -the amount of deaths of women during pregnancy and childbirth- to the point at which it is extremely rare, whereas it used to be very common. The main reason for this is improved understanding and management of various pregnancy complications, such as preeclampsia and eclampsia, but there are certain categories of conditions that always have made pregnancy particularly dangerous and still do. Heart disease falls into this category. It is rare in women of reproductive age, present in 0.4 percent to 4 percent of pregnancies. But, it currently is the leading cause of maternal mortality.

In many cases, heart disease can be managed during pregnancy to minimize dangers. There are levels of conditions that can make pregnancy either very difficult or deadly. Coronary heart disease (CHD) is also called coronary artery disease (CAD). It is a condition in which one or more arteries supplying the muscular layer of the heart, called the myocardium, cannot deliver adequate quantities of blood and oxygen. This situation can be due to obstruction related to atherosclerosis, a condition characterized by the formation of plaques in the lining of the artery. Consequently, the lumen of the artery (the hollow middle through which blood flows) is too narrow and the wall of the artery hard. There are earlier stages in which the lumen is not so narrowed, but the plaque is interfering with the ability of the blood vessel wall to stretch, there person experiences symptoms.

Such changes in coronary arteries and their branches can take a long time and be mostly silent, but there are changes in the cardiovascular system during pregnancy that can add stresses, causing serious problems to appear. CAD can develop during pregnancy, causing what doctors called spontaneous coronary artery dissection, meaning that a major artery supplying the heart tears within a short period of time, which often can be followed by atherosclerosis. Although not classified as CAD, also can happen in the big artery that comes off the heart, the aorta. This is very rare, but the risk is higher in pregnant women than for those who are not pregnant.

Severity of heart conditions during pregnancy can range from inability to support activity that would be normal outside of pregnancy, such as mild exercise, to a severe, immediately life threatening condition, such as ST elevation myocardial infarction (STEMI), a heart attack resulting from a portion of the heart muscle losing ability to function, due to an inadequate oxygen supply.

Clues that you may have a coronary condition are symptoms such as dyspnea and chest pain or a feeling of pressure of heaviness on the chest, along with pain in other sites, such as shoulder, arm, or neck. You may also feel fatigue when you try to increase your activity, such as walking fast or climbing stairs, and you may feel palpitations, sensations that your heart is skipping a beat, or is making extra beats. For diagnosis, the physical examination can provide important clues but your doctor will need more information from blood tests and other procedures such as electrocardiography (ECG) and echocardiography. Your doctor may refer you to a specialist, such as a cardiologist and a specialist in high-risk pregnancies, or more likely to both. In addition to determining whether you have a heart problem, doctors will evaluate physiological values of your heart. These values include the ejection fraction (the fraction of blood that enters a heart chamber and is pumped out in each beat) and the stroke volume (volume of blood pumped with each beat). These values normally change during pregnancy to meet the needs of supporting the fetus in the growing womb, but your cardiovascular function can worsen, if you have an underlying problem. In evaluating you, doctors will rate your heart function based on the New York Heart Association (NYHA) Functional Classification, which defines four classes. In Class I, you have heart disease, but no symptoms that would limit your normal activity. In Class II, there are mild symptoms, such as dyspnea or angina (chest pain that comes and goes). If you have Class III heart disease, you are comfortable only when you rest, so your activity is limited. In Class IV, you suffer symptoms, even when resting and so activity is extremely limited and you must remain in bed. Additionally, the World Health Organization (WHO) rates risk during pregnancy from cardiovascular disease.

Most cases of CAD in pregnant women put the woman into an NYHA Class I or Class II category, so the risk of problems isn’t excessive. However, CAD can put you in Class III or IV, in which case pregnancy threatens your life, meaning that you should seriously consider never getting pregnant. If your condition is severe enough (Class III or IV), the baby is also at risk for problems that include distress and poor growth, caused by inadequate blood circulation into the placenta. This also can lead to fetal death.

Numerous medications are given to people with CAD, some of which are safe during pregnancy and others should be avoided. Notably, if you are taking an angiotensin-converting enzyme (ACE) inhibitor, it must be stopped before the second trimester because it can damage your developing baby’s kidneys. In such case, your cardiologist will replace the ACE inhibitor with a different type of drug and/or adjust your other drugs. Certain cholesterol lowering drugs called statins, are thought to be harmful to the baby too, so they must be stopped. People with CAD also are treated with aspirin, which thins the blood by interfering with platelets and with beta blockers, which slow the heart while increasing the power of each contraction.

Often, the treatment of choice for a pregnant woman with CAD is to deliver the baby as early as possible but the timing depends, in part, on medications given to prevent coagulation (the formation of blood clots). This is because there is a risk of birth defects from an anticoagulation drug called warfarin, if given during the first trimester. That risk goes down in the second trimester, but if given within a few weeks before birth, it increases your baby’s risk of hemorrhage (severe bleeding). As a substitute for warfarin, pregnant women can be given low-molecular-weight heparin (LMWH), generally for short-term therapy, but it doesn’t work as well as warfarin, so it is a matter of balancing the risk to the mother against the risk to the fetus. There is often debate as to whether a woman should be switched from warfarin to LMWH for the entire pregnancy, whether she should be switched to LMWH for the first trimester, then put back on warfarin for the second trimester, then back to LMWH for the last few weeks of pregnancy, plus there is an idea to use what is called unfractionated heparin (UH) as a kind of compromise. There is a lot of controversy, because heart disease makes everything more difficult, including pregnancy. On the other hand, both warfarin and LMWH are considered fairly safe during breastfeeding.

In extreme cases, a pregnant woman may have such severe CAD that termination of pregnancy will be the only recourse.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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