What is myocardial infarction during pregnancy?
Myocardial infarction is commonly called a heart attack. The term infarction refers to the death of tissue (necrosis) in a particular region, due to the blood supply being inadequate in supplying the affected region with oxygen and other consumables. In the heart, most of the needed blood flow is to supply whats called the myocardium. Thickest of the layers of tissue that form the heart, the myocardium consists of muscle cells called cardiomyocytes. Most cardiomyocytes contract and relax in order to pump blood, plus there is a system of specialized muscle cells, which penetrate through the myocardium and other heart layers and serve to conduct electrical signals that control the heartbeat. The term myocardial infarction (MI) applies to any infarction occurring partway (non-transmural) or all the way through the myocardial layer (transmural).
Classically, MI is divided into two categories based on a particular feature that occurs when a person is tested with electrocardiography (ECG). One category, called ST elevation myocardial infarction (STEMI), tends to be transmural (infarct penetrates entirely through the myocardium), while the other category, non-ST elevation myocardial infarction (NSTEMI), tends to be non-transmural, but there is plenty of overlap between the categories. The vocabulary connected with MI can be a little confusing because both MI categories belong to a bigger category, known as acute coronary syndrome (ACS). ACS is categorized either as STEMI, or as nonST elevation acute coronary syndrome (NSTE-ACS), but NSTE includes both NSTEMI and another condition called unstable angina, which is not a type of MI.
Most MIs occur because an artery supplying part of the heart is obstructed by a clot (thrombus) that has formed in connection with plaque building up in the wall of the artery (atherosclerosis), and a small percentage of MIs are due to embolism, a clot that started from something that traveled from another location. Since atherosclerosis tends to strike women who are too old to get pregnant, MI traditionally has been rare in pregnancy. However, it is seen increasingly, due to the rising age of mothers, and especially due to the rising prevalence of obesity. On the other hand, increased demand for blood supply during pregnancy often leads to anemia. Usually, anemia is mild, but if severe, anemia can cause an MI more often an NSTEMI2 by making it difficult for the blood system to meet the needs of the heart, even if none of the coronary arteries are obstructed.
How common is myocardial infarction during pregnancy?
Although MI classically has been rare during pregnancy, MI has been on the rise in recent years, due to increasing numbers of older women getting pregnant, and due to the increasing prevalence of obesity and type 2 diabetes among women of reproductive age.
How is myocardial infarction during pregnancy diagnosed?
Doctors can get an initial clue that you may be suffering from an MI if you experience classic symptoms, namely feelings of pressure or pain in the chest and dyspnea (breathing difficulty). This will trigger a diagnostic workup that includes blood tests for looking for high levels of what are called cardiac biomarkers (cardiac muscle enzymes), particularly troponin (a group of proteins), the myocardial fraction of creatine kinase (CK-MB), and myoglobin, and also includes ECG. In ECG, the change in the voltage (electrical potential) over time that occurs across the heart is measured from different directions. By finding various subtle abnormalities in the signals that the heart sends out in the different directions, cardiologists can determine, not only if you have suffered an MI, but also learn about the nature and location of the infarction. Subsequently, there are more specialized procedures that can be performed to locate the problem and to determine its severity and whether it requires immediate invasive treatment, such as percutaneous coronary intervention (PCI), or, in severe cases, open-heart surgery.
Does myocardial infarction cause problems during pregnancy?
MI can lead to a range of heart dysfunctions that can compromise the ability of the heart to pump blood where it needs to go, including to the heart itself, leading to progressively worsening heart disease. Generally, a STEMI is worse than an NSTEMI.
Does myocardial infarction during pregnancy cause problems for the baby?
Yes, complications of MI can be fatal to the mother, thereby killing the fetus. However, even when the mother survives, compromise of the hearts ability to pump blood can lead to inadequate circulation through the placenta and fetus, leading to a range of outcomes from reduced fetal growth to fetal death.
What to consider about taking medications when you are pregnant or breastfeeding:
- The risks to yourself and your baby if you do not treat the MI
- The risks and benefits of each medication you use when you are pregnant
- The risks and benefits of each medication you use when you are breastfeeding
What should I know about using medication to treat MI during pregnancy?
Medications include aspirin to prevent blood clots from forming, and drugs of a category called fibrinolytic (or thrombolytic) agents, which are given to break up clots if it is determined that one or more clots are present in the coronary blood vessels. Aspirin at doses appropriate for MI has been used in many pregnancies without harm, while the use of thrombolytics in pregnancy is generally thought to be safe. However, more studies are needed to be sure of this, although, if you need these agents to unclog a vessel in your heart, there is no rationale for refusing them, since a living, healthy mother is the best way to deliver a live, healthy baby. If you require PCI, additional anti-clot medications will be given, notably heparin. Types of heparin that are given during pregnancy include low molecular weight heparin (LMWH) and unfractionated heparin (UFH). LMWH is given frequently in pregnancy when there is some risk of clotting, but not a severe risk because it does not put the baby at high risk of birth defects or bleeding. In PCI, however, cardiologists prefer to use unfractionated heparin (UFH), because of increased bleeding risk during the procedure for those who receive LMWH. Now, UFH is considered less pregnancy-safe than LMWH, so there is a tradeoff between minimizing the risk to the mother versus the risk to the fetus, and generally, clinicians lean in favor of the mother. Normally, when there is an MI, depending on the persons condition, doctors also may give various other drugs, including nitroglycerin, intravenous morphine (an opioid), beta-blockers, angiotensin-converting enzyme (ACE) inhibitors, and statins. Some of these drugs, notably ACE inhibitors, are contraindicated in pregnancy, so your doctors will avoid them. With others, such as statins, there is concern about harmful effects on the fetus, but not a clear answer on whether they are harmful.
Who should NOT stop taking medication
for an MI during pregnancy?
An MI is life-threatening, so nobody who is offered medication should stop taking it, until the end of the treatment period.
What should I know about choosing a medication for my MI during pregnancy?
It is important to stay in communication with your health care provider as the release of new studies over time can change the outlook on the role of specific medications during pregnancy.
You may find Pregistrys expert reports about the medications to treat this condition here. Additional information can also be found in the sources listed below.
What should I know about taking a medication for my MI when I am breastfeeding?
There is some concern about aspirin because it enters breastmilk, but it enters in very tiny amounts. Neither UFH nor LMWH is thought to be harmful in breastfeeding, but after a heart attack, you are likely to be on various medications, some of which may require you to avoid breastfeeding.
What alternative therapies besides medications can I use to treat my MI during pregnancy?
If an artery is obstructed such that a section of the myocardium is not getting adequate blood flow, PCI is the treatment of choice, but in some cases, this will not be adequate, and an open-heart procedure called coronary artery bypass surgery (CABG) will be performed.
What can I do for myself and my baby when I have a myocardial infarction during pregnancy?
It is very important to follow the instructions of your physicians.
Resources for MI in pregnancy:
For more information about myocardial infarction during and after pregnancy, contact http://www.womenshealth.gov/ (800-994-9662 [TDD: 888-220-5446]) or contact the following organizations: