Cardiac disease in pregnancy and acute myocardial infarction
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In general, women of childbearing age are at relatively low risk for coronary artery disease. While rare, the risk of acute myocardial infarction (AMI) is 3-4 times higher during pregnancy, and negative fetal and maternal outcomes are associated with this condition.
The first case was reported in the literature in 1922.
Acute myocardial infarction can occur at all stages of pregnancy, and is more common in multi-gravid patients.
The etiology of coronary dissection in pregnant patients is thought to be related to an excess of progesterone, which causes changes in the vessel wall, including loss of normal corrugation elastin fibers, fragmentation of reticular fibers, and decreases in the amount of acid mucopolysaccharides. The increase in blood volume and cardiac output that occurs with pregnancy magnifies shear forces of the blood column in large vessels, which in combination with the vessel wall changes leaves these patients predisposed to coronary dissection.
In a review performed in 2008, myocardial infarction (MI) location was mostly (78%) in the anterior wall and involved the left anterior descending artery; the most common cause was coronary artery dissection.
The angiographic findings on cardiac catheterization in series of pregnant women are as follows:
- Family history of coronary artery disease
- Low HDL
- High LDL
- Previous oral contraceptive use
- MI patients tend to be older (>35 years old)
- Non-hispanic white or african american
- Chronic hypertension
- History of eclampsia / pre-eclampsia
Epidemiology and Demographics
- Incidence ~1/10,000 to 1/37,500 deliveries
- Ages range 16-45
Natural History, Complications, Prognosis
- Outcomes better if MI early in pregnancy
- Maternal mortality rate is 7%-11% (most at time of MI or within 2 weeks- usually with labor and delivery) and a fetal mortality rate is 9%.
The following should be considered in diagnosis and treatment of this condition:
- Criteria for diagnosis of AMI in pregnant women are in general the same as in non pregnant patients (symptoms, exam, ECG, biomarkers, +/- imaging/angiography). 37% of patients undergoing elective C-section have EKG changes suggestive of MI or ischemia. Echocardiography to assess regional wall motion abnormalities can be useful.
- Note that creatine kinase and its MB fraction can increase nearly 2-fold within 30 minutes after delivery, as can troponin levels.
- If exercise stress testing is indicated, a submaximal protocol (<70% of maximal predicted heart rate) with fetal monitoring is preferred.
- Radionuclide imaging using 99m technetium-labeled sestamibi or 201 thallium, as well as cardiac catheterization or interventional procedure, are expected to yield<11 rad of radiation to the conceptus, which is generally considered safe; termination of pregnancy is generally recommended at a level of 10 rads.
The treatment of pregnant women with AMI and its complications should follow the usual standard of care; a cardiologist should work in tandem with an obstetrician in order to tailor therapy to both the mother and the fetus. Initial therapy generally consists of unfractionated heparin, low dose aspirin after a loading dose of non-enteric coated aspirin, and nitrates. Care should be exercised with nitrates as they are excreted in breast milk and may cause fetal methemoglobinemia.
Common Drugs used in Patients with CAD and their Pregnancy Categories
- Morphine Sulfate (Risk Category C)
- Organic Nitrates (Risk Category B: Nitroglycerin; Risk Category C: Isosorbide dinitrate)
- Beta-Adrenergic Blocking Agents (Risk Category B: Metoprolol; Risk Category C: Atenolol)
- Calcium Channel Blockers (CCBs) (Risk Category C: Nifedipine, Diltiazem, Verapamil)
- Angiotensin Converting Enzyme Inhibitors and Angiotensin Receptor Antagonists Teratogenic and should not be used
- Eplerenone (Risk Category B)
- HMG-CoA Reductase Inhibitors (Statins) (Risk Category X). These agents may be teratogenic and are not recommended.
- Unfractionated (UFH) and Low Molecular Weight Heparin (LMWH) (Risk Category B: LMWH; Risk Category C: UFH)
- Aspirin (Risk Category C) Low dose aspirin should be administered.
- Thienopyridine derivatives (Risk Category B)
- Glycoprotein IIb/IIIa inhibitors (Risk Category B: eptifibatide, tirofiban; Risk Category C: abciximab)
Drugs to be Avoided
- Greatest experience in massive pulmonary embolism
- Streptokinase does not cross placental membrane in animals, but Ab found in neonatal spinal cord fluid
- Urokinase not teratogenic in mice/rats
- Risk for maternal hemorrhage (1 case of placental abruption reported); increased risk when given at time of delivery
- Delivery best delayed at least 2-3 weeks
Primary PCI with intracoronary bare metal stent placement is the preferred treatment particularly in cases of spontaneous coronary dissection. Thrombolytic therapy can be considered if PCI is not available.
- Manalo-Estrella P, Barker AE (1967). "Histopathologic findings in human aortic media associated with pregnancy". Arch Pathol. 83 (4): 336–41. PMID 4225694.
- Bonnet J, Aumailley M, Thomas D, Grosgogeat Y, Broustet JP, Bricaud H (1986). "Spontaneous coronary artery dissection: case report and evidence for a defect in collagen metabolism". Eur Heart J. 7 (10): 904–9. PMID 3792352.
- Roth A, Elkayam U (2008). "Acute myocardial infarction associated with pregnancy". J Am Coll Cardiol. 52 (3): 171–80. doi:10.1016/j.jacc.2008.03.049. PMID 18617065.
- Ladner et al:Ostet Gynecol, 2005
- Shivvers SA, Wians FH, Keffer JH, Ramin SM (1999). "Maternal cardiac troponin I levels during normal labor and delivery". Am J Obstet Gynecol. 180 (1 Pt 1): 122. PMID 9914590.
- Kleinman B (1993). "Electrocardiographic changes during cesarean section". Anesthesiology. 78 (5): 997–8. PMID 8489079.
- Elkayam U, Gleicher N (1984). "Cardiac problems in pregnancy. I. Maternal aspects: the approach to the pregnant patient with heart disease". JAMA. 251 (21): 2838–9. PMID 6716610.