Cardiomyopathy and Pregnancy

Note: The Pregistry website includes expert reports on more than 2000 medications, 300 diseases, and 150 common exposures during pregnancy and lactation. For the topic Cardiomyopathy, go here. These expert reports are free of charge and can be saved and shared.

Cardiomyopathy is a set of diseases in which the myocardium, the muscular layer of the heart, has difficulty contracting with enough force to pump blood through the body, when the difficulty cannot be explained by an underlying condition, such as heart valve problems or high resistance to blood flow in arteries. In many cases, this causes what doctors call a low ejection fraction, meaning that an abnormally low amount of blood is pumped from the ventricles compared to how much blood is in the ventricles prior to the contraction. Normally, the ejection fraction ranges from 55 to 75 percent (it can be higher than 75 percent in trained athletes). If your ejection fraction is 75 percent, for example, this means that 75 percent of the blood present in the left ventricle prior to systole —the part of the heart cycle when the ventricles contract— passes through the aortic valve into the aorta and does not flow backward through the valve into the ventricle. Cardiologists —doctors who specialize in conditions of the heart— also consider ejection fraction of blood moving from the right ventricle into the pulmonary artery and ejection fractions for the blood from each of the heart’s upper chambers, the atria. In certain types of cardiomyopathy, ejection fraction remains close to normal, yet the pumping of blood is nevertheless inadequate, because the total amount of blood in the ventricle prior to systole is below normal. What you should remember, however, is that all cases of cardiomyopathy involve inadequate pumping of blood, due to some problem with the muscle of the heart. As the situation gets progressively worse, it results in heart failure, meaning that the heart cannot meet the body’s circulatory needs.

Outside of pregnancy, cardiomyopathy can happen for a variety of reasons, leading to various subtypes of cardiomyopathy. The main subtypes are dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), and restrictive cardiomyopathy (RCM). All of these subtypes of cardiomyopathy could complicate pregnancy, but there is also a cardiomyopathy specific to pregnancy. This is a type of DCM called peripartum cardiomyopathy (PPCM), also called postpartum cardiomyopathy, which can develop during the final weeks of pregnancy, or up to approximately five months after you give birth.

The incidence of PPCM varies depending on geographic location and socioeconomic status, with rates higher than 1 case per 100 births reported in Nigeria and 1 case per 20,000 births occurring in Japan. Rates reported for HCM vary from as high as 1 per 500 people (whether pregnant or not) down to 1 per 3,000, while the other main subtypes of cardiomyopathy mentioned above are more rare, especially RCM. Although PPCM is rare, being above the age of 30 when you are pregnant puts you at higher risk of developing PPCM compared with younger women.

Since PPCM is a type of dilated cardiomyopathy, we need to discuss what dilated cardiomyopathy actually means. It is a situation in which the heart gets larger as it gets weaker. This is something that can be seen on a simple chest X-ray (CXR), which is one test that will be performed, and you should not worry about radiation exposure to the fetus, because it is a very low radiation dose and modern X-ray are very narrowly focused and aimed. To assess PPCM, you will also be given an electrocardiogram (ECG, which measures electrical activity in the heart from different directions), an echocardiogram (ultrasound of the heart), a stress test on a treadmill, and a range of other tests. Such other tests may include cardiac magnetic resonance imaging (MRI), cardiac catheterization in which instruments are passed into your heart through a tube inserted through a vein in your leg, and various blood tests and genetic tests. A diagnosis of PPCM can be made if you meet three criteria: Heart failure beginning any time from a month before delivery until 5 months after delivery; an ejection fraction below 45 percent as measured during echocardiography; your physicians are able to rule out other possible causes of the low ejection fraction and heart failure.

PPCM is a very serious condition, since heart failure can be fatal to mother and fetus, and often the only effective treatment involves heart surgery, either to install a ventricular assist device (a machine that augments the heart’s pumping), or to perform heart transplantation. Such procedures generally are not possible while you are actually pregnant, but can be performed after the baby is delivered.

PPCM can cause a type of heart failure called systolic heart failure, failure of the heart to generate enough force when it contracts to pump blood out. PPCM thus is treated similar to other types of systolic heart failure. This means that you will be admitted to the intensive care unit (ICU) for extensive monitoring and also to receive treatment that will include medications. These include medicines that make you excrete water from the blood to reduce the load that the heart must push. Such medicines are safe during and after pregnancy. Other medications for this type of heart failure include drugs that widen blood vessels, such as nitroglycerin and nitroprusside, which also are okay during pregnancy. If needed, medications that strengthen the heart’s contraction, such as dobutamine or milrinone are also given. If the ejection fraction is very low (less than 35 percent), you also will need low‐molecular‐weight heparin (LMWH, also safe in pregnancy) to thin the blood, because large amounts of blood remaining in the left ventricle after contraction means that thrombi (blood clots) can form in the ventricle. Once you deliver, you can be switched from LMWH to a stronger blood thinner. This can be either an old medication called warfarin, which requires regular monitoring with blood tests, but is covered by all health plans, or newer medications, called DOACs, that are advertised a lot on television in the United States, but are not always affordable.

In very severe cases, cardiologists and surgeons can treat heart failure by implanting various devices that help the heart to pump blood. Additionally, some patients may become candidates for heart transplantation.

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.

Leave a Reply